Opiate drug use and the pathophysiology of neuroAIDS

A Perfect Storm: The Convergence of Aging, Human Immunodeficiency Virus Infection, and Inflammasome Dysregulation

The emergence of combination antiretroviral therapy (cART) has greatly transformed the life expectancy of people living with HIV (PWH). Today, over 76% of the individuals with HIV have access to this life-saving therapy. However, this progress has come with a new challenge: an increase in age-related non-AIDS conditions among patients with HIV. These conditions manifest earlier in PWH than in uninfected individuals, accelerating the aging process. Like PWH, the uninfected aging population experiences immunosenescence marked by an increased proinflammatory environment. This phenomenon is linked to chronic inflammation, driven in part by cellular structures called inflammasomes. Inflammatory signaling pathways activated by HIV-1 infection play a key role in inflammasome formation, suggesting a crucial link between HIV and a chronic inflammatory state. This review outlines the inflammatory processes triggered by HIV-1 infection and aging, with a focus on the inflammasomes. This review also explores current research regarding inflammasomes and potential strategies for targeting inflammasomes to mitigate inflammation. Further research on inflammasome signaling presents a unique opportunity to develop targeted interventions and innovative therapeutic modalities for combating HIV and aging-associated inflammatory processes.

HIV-1 Tat and morphine interactions dynamically shift striatal monoamine levels and exploratory behaviors over time

Despite the advent of combination anti-retroviral therapy (cART), nearly half of people infected with HIV treated with cART still exhibit HIV-associated neurocognitive disorders (HAND). HAND can be worsened by co-morbid opioid use disorder. The basal ganglia are particularly vulnerable to HIV-1 and exhibit higher viral loads and more severe pathology, which can be exacerbated by co-exposure to opioids. Evidence suggests that dopaminergic neurotransmission is disrupted by HIV exposure, however, little is known about whether co-exposure to opioids may alter neurotransmitter levels in the striatum and if this in turn influences behavior. Therefore, we assayed motor, anxiety-like, novelty-seeking, exploratory, and social behaviors, and levels of monoamines and their metabolites following 2 weeks and 2 months of Tat and/or morphine exposure in transgenic mice. Morphine decreased dopamine levels, but significantly elevated norepinephrine, the dopamine metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), and the serotonin metabolite 5-hydroxyindoleacetic acid, which typically correlated with increased locomotor behavior. The combination of Tat and morphine altered dopamine, DOPAC, and HVA concentrations differently depending on the neurotransmitter/metabolite and duration of exposure but did not affect the numbers of tyrosine hydroxylase-positive neurons in the mesencephalon. Tat exposure increased the latency to interact with novel conspecifics, but not other novel objects, suggesting the viral protein inhibits exploratory behavior initiation in a context-dependent manner. By contrast, and consistent with prior findings that opioid misuse can increase novelty-seeking behavior, morphine exposure increased the time spent exploring a novel environment. Finally, Tat and morphine interacted to affect locomotor activity in a time-dependent manner, while grip strength and rotarod performance were unaffected. Together, our results provide novel insight into the unique effects of HIV-1 Tat and morphine on monoamine neurochemistry that may underlie their divergent effects on motor and exploratory behavior.

Fentanyl dysregulates neuroinflammation and disrupts blood-brain barrier integrity in HIV-1 Tat transgenic mice

Opioid overdose deaths have dramatically increased by 781% from 1999 to 2021. In the setting of HIV, opioid drug abuse exacerbates neurotoxic effects of HIV in the brain, as opioids enhance viral replication, promote neuronal dysfunction and injury, and dysregulate an already compromised inflammatory response. Despite the rise in fentanyl abuse and the close association between opioid abuse and HIV infection, the interactive comorbidity between fentanyl abuse and HIV has yet to be examined in vivo. The HIV-1 Tat-transgenic mouse model was used to understand the interactive effects between fentanyl and HIV. Tat is an essential protein produced during HIV that drives the transcription of new virions and exerts neurotoxic effects within the brain. The Tat-transgenic mouse model uses a glial fibrillary acidic protein (GFAP)-driven tetracycline promoter which limits Tat production to the brain and this model is well used for examining mechanisms related to neuroHIV. After 7 days of fentanyl exposure, brains were harvested. Tight junction proteins, the vascular cell adhesion molecule, and platelet-derived growth factor receptor-β were measured to examine the integrity of the blood brain barrier. The immune response was assessed using a mouse-specific multiplex chemokine assay. For the first time in vivo, we demonstrate that fentanyl by itself can severely disrupt the blood-brain barrier and dysregulate the immune response. In addition, we reveal associations between inflammatory markers and tight junction proteins at the blood-brain barrier.

Progress in Pathological and Therapeutic Research of HIV-Related Neuropathic Pain

HIV-related neuropathic pain (HRNP) is a neurodegeneration that gradually develops during the long-term course of acquired immune deficiency syndrome (AIDS) and manifests as abnormal sock/sleeve-like symmetrical pain and nociceptive hyperalgesia in the extremities, which seriously reduces patient quality of life. To date, the pathogenesis of HRNP is not completely clear. There is a lack of effective clinical treatment for HRNP and it is becoming a challenge and hot spot for medical research. In this study, we conducted a systematic review of the progress of HRNP research in recent years including (1) the etiology, classification and clinical symptoms of HRNP, (2) the establishment of HRNP pathological models, (3) the pathological mechanisms underlying HRNP from three aspects: molecules, signaling pathways and cells, (4) the therapeutic strategies for HRNP, and (5) the limitations of recent HRNP research and the future research directions and prospects of HRNP. This detailed review provides new and systematic insight into the pathological mechanism of HRNP, which establishes a theoretical basis for the future exploitation of novel target drugs. HIV infection, antiretroviral therapy and opioid abuse contribute to the etiology of HRNP with symmetrical pain in both hands and feet, allodynia and hyperalgesia. The pathogenesis involves changes in cytokine expression, activation of signaling pathways and neuronal cell states. The therapy for HRNP should be patient-centered, integrating pharmacologic and nonpharmacologic treatments into multimodal intervention.

Strategies Used to Manage Chronic Pain in HIV-Disease: Comparing Persons Prescribed Opioids Versus Persons not Receiving Opioids

Chronic pain is common in people living with HIV (PLWH), causes substantial disability and is associated with limitations in daily activities. Opioids are commonly prescribed for pain treatment among PLWH, but evidence of sustained efficacy is mixed. There is little information available on how PLWH who have chronic pain use multimodal strategies in pain management. The current cross-sectional study examined background characteristics, self-reported pain, and the use of other pain treatments among 187 PLWH with chronic pain and depressive symptoms who were and were not prescribed opioids. Approximately 20.9% of participants reported using prescription opioids at the time of the study interview. These individuals were significantly more likely to report having engaged in physical therapy or stretching, strengthening or aerobic exercises in the previous 3 months, recent benzodiazepine use, and receiving disability payments. There were no significant differences in pain characteristics (pain-related interference, average pain severity, and worst pain severity) between the two groups. Those not prescribed opioids were more likely to report better concurrent physical functioning and general health, and fewer physical role limitations, but higher depression symptom severity. Our findings suggest that many PLWH with chronic pain and depressive symptoms express high levels of pain with deficits in physical function or quality of life despite their use of opioids. The high rate of co-use of opioids and benzodiazepines (30.8%) is a concern because it may increase risk of overdose. An integrated care approach that includes a variety of effective non-pharmacologic treatment strategies such as physical therapy may be beneficial in reducing the reliance on opioids for pain management.

Progressive Degeneration and Adaptive Excitability in Dopamine D1 and D2 Receptor-Expressing Striatal Neurons Exposed to HIV-1 Tat and Morphine

The striatum is especially vulnerable to HIV-1 infection, with medium spiny neurons (MSNs) exhibiting marked synaptodendritic damage that can be exacerbated by opioid use disorder. Despite known structural defects in MSNs co-exposed to HIV-1 Tat and opioids, the pathophysiological sequelae of sustained HIV-1 exposure and acute comorbid effects of opioids on dopamine D1 and D2 receptor-expressing (D1 and D2) MSNs are unknown. To address this question, Drd1-tdTomato- or Drd2-eGFP-expressing reporter and conditional HIV-1 Tat transgenic mice were interbred. MSNs in ex vivo slices from male mice were assessed by whole-cell patch-clamp electrophysiology and filled with biocytin to explore the functional and structural effects of progressive Tat and acute morphine exposure. Although the excitability of both D1 and D2 MSNs increased following 48 h of Tat exposure, D1 MSN firing rates decreased below control (Tat-) levels following 2 weeks and 1 month of Tat exposure but returned to control levels after 2 months. D2 neurons continued to display Tat-dependent increases in excitability at 2 weeks, but also returned to control levels following 1 and 2 months of Tat induction. Acute morphine exposure increased D1 MSN excitability irrespective of the duration of Tat exposure, while D2 MSNs were variably affected. That D1 and D2 MSN excitability would return to control levels was unexpected since both subpopulations displayed significant synaptodendritic degeneration and pathologic phospho-tau-Thr205 accumulation following 2 months of Tat induction. Thus, despite frank morphologic damage, D1 and D2 MSNs uniquely adapt to sustained Tat and acute morphine insults.

Meaningful cognitive decline is uncommon in virally suppressed HIV, but sustained impairment, subtle decline and abnormal cognitive aging are not

BACKGROUND

High antiretroviral therapy (ART) coverage and viral suppression among people with HIV (PWH) in Australia provide a unique context to study individual cognitive trajectories, cognitive aging and factors associated with longitudinal cognitive function during chronic and stable HIV disease.

METHODS

Participants from the Predictors of Adherence to Antiretroviral Therapy study (n = 457, recruited between September 2013 and November 2015, median age = 52 years, and all with HIV RNA <50 copies mL) completed a cognitive assessment with CogState Computerized Battery (CCB) at baseline, Month-12, and Month-24. Demographics, psycho-social and socioeconomic factors, healthcare seeking behaviors, HIV disease characteristics and comorbidities were assessed. The CCB data were corrected for age, sex and practice effect and averaged into a global z-score (GZS). Cognitive impairment was defined with the global deficit score method (GDS>0.5). Meaningful cognitive change was statistically defined (decline or improvement versus stability, i.e., 90% CI, that is p < 0.05, 2-tailed) using a novel evidence-based change score: the linear mixed-effect regression (LMER)-based GZS change score. A separate LMER model with a top-down variable selection approach identified the independent effects of age and other demographic, HIV disease characteristics, socioeconomic and health-related factors on the demographically corrected GZS. The combined definitions of change and cross-sectional impairment enabled the identification of cognitive trajectories.

FINDINGS

At Month-12 and Month-24, 6% and 7% showed meaningful cognitive decline and 4% and 3% improved respectively. Only 1% showed sustained decline. Incident impairment due to subtle cognitive decline (i.e., below the threshold of meaningful cognitive decline) was 31% and 25% at Month-12 and Month-24, while 14% showed sustained impairment (i.e., cognitively impaired at all study visits). Older age (≥50 years) and time interaction was associated with lower demographically corrected GZS (β = -0.31, p < 0.001). Having a regular relationship, excellent English proficiency, and perceived stigma (avoidance) were associated with higher GZS (all p < 0.05). Relying on government subsidy, severe depression, and lower belief in ART necessity and higher concerns were associated with lower GZS (all p < 0.05). No HIV disease characteristics had a significant effect.

INTERPRETATIONS

Meaningful cognitive decline was not different from normal expectation in chronic stable HIV disease. Despite this, subtle cognitive decline, sustained cognitive impairment, and greater than normative-age cognitive aging were evident.

FUNDING

Funding for the PAART study was provided in part by unrestricted educational grants from Gilead Sciences (www.gilead.com) (Grant Number: IN-AU-264- 0131), the Balnaves Foundation (www.balnavesfoundation.com), the Victorian Department of Health and Human Services (Australia) (www.dhs.vic.gov.au/home), Western Australia Health (www.health.wa.gov.au), the ACT Ministry of Health (Australia) (www.health.act.gov.au), and in-kind support from the Queensland Department of Health (Australia) (www.health.qld.gov.au), and NHMRC Partnership grant APP1058474 (PI: Carr, Andrew).

Accelerated brain aging with opioid misuse and HIV: New insights on the role of glially derived pro-inflammation mediators and neuronal chloride homeostasis

Opioid use disorder (OUD) has become a national crisis and contributes to the spread of human immunodeficiency virus (HIV) infection. Emerging evidence and advances in experimental models, methodology, and our understanding of disease processes at the molecular and cellular levels reveal that opioids per se can directly exacerbate the pathophysiology of neuroHIV. Despite substantial inroads, the impact of OUD on the severity, development, and prognosis of neuroHIV and HIV-associated neurocognitive disorders is not fully understood. In this review, we explore current evidence that OUD and neuroHIV interact to accelerate cognitive deficits and enhance the neurodegenerative changes typically seen with aging, through their effects on neuroinflammation. We suggest new thoughts on the processes that may underlie accelerated brain aging, including dysregulation of neuronal inhibition, and highlight findings suggesting that opioids, through actions at the μ-opioid receptor, interact with HIV in the central nervous system to promote unique structural and functional comorbid deficits not seen in either OUD or neuroHIV alone.

Different Roles of Beclin1 in the Interaction Between Glia and Neurons after Exposure to Morphine and the HIV- Trans-Activator of Transcription (Tat) Protein

Previously we showed that Beclin1 has a regulatory role in the secretion of inflammatory molecules in glia after exposure to morphine and Tat (an HIV protein). Here we show increased secretion of neuronal growth factors and increased neuronal survival in Beclin1-deficient glia. However, without glia co-culture, neurons deficient in Beclin1 showed greater death and enhanced dendritic beading when compared to wild-type neurons, suggesting that glial-secreted growth factors compensate for the damage reduced autophagy causes neurons. To assess if our ex vivo results correlated with in vivo studies, we used a wild-type (Becn1+/+) and Beclin1-deficient (Becn1+/+) mouse model and intracranially infused the mice with Tat and subcutaneously administered morphine pellets. After morphine implantation, significantly impaired locomotor activities were detected in both Becn1+/+ and Becn1+/- mice, irrespective of Tat infusion. After induction of pain, morphine-induced antinociception was detected. Interestingly, co-exposure to morphine and Tat increased sensitivity to pain in Becn1+/+ mice, but not in similarly treated Becn1+/- mice. Brain homogenates from Becn1+/+ mice exposed to Tat, alone and in combination with morphine, showed increased secretion of pro-inflammatory cytokines and reduced expression of growth factors when compared to similarly treated Becn1+/- mice. Likewise, increased neuronal loss was detected when both Tat and morphine were administered to Becn1+/+ mice, but not in similarly treated Becn1+/- mice. Overall, our findings show that there is a Beclin1-driven interaction between Tat and morphine in glia and neurons. Moreover, reduced glial-Beclin1 may provide a layer of protection to neurons under stressful conditions, such as when exposed to morphine and Tat.

Buprenorphine reverses neurocognitive impairment in EcoHIV infected mice: A potential therapy for HIV-NCI

Thirty-eight million people worldwide are living with HIV, PWH, a major public health problem. Antiretroviral therapy (ART) revolutionized HIV treatment and significantly increased the lifespan of PWH. However, approximately 15-50% of PWH develop HIV associated neurocognitive disorders (HIV-NCI), a spectrum of cognitive deficits, that negatively impact quality of life. Many PWH also have opioid use disorder (OUD), and studies in animal models of HIV infection as well as in PWH suggest that OUD can contribute to HIV-NCI. The synthetic opioid agonist, buprenorphine, treats OUD but its effects on HIV-NCI are unclear. We reported that human mature inflammatory monocytes express the opioid receptors MOR and KOR, and that buprenorphine reduces important steps in monocyte transmigration. Monocytes also serve as HIV reservoirs despite effective ART, enter the brain, and contribute to HIV brain disease. Using EcoHIV infected mice, an established model of HIV infection and HIV-NCI, we previously showed that pretreatment of mice prior to EcoHIV infection reduces mouse monocyte entry into the brain and prevents NCI. Here we show that buprenorphine treatment of EcoHIV infected mice with already established chronic NCI completely reverses the disease. Disease reversal was associated with a significant reduction in brain inflammatory monocytes and reversal of dendritic injury in the cortex and hippocampus. These results suggest that HIV-NCI persistence may require a continuing influx of inflammatory monocytes into the brain. Thus, we recommend buprenorphine as a potential therapy for mitigation of HIV brain disease in PWH with or without OUD.

Independent actions by HIV-1 Tat and morphine to increase recruitment of monocyte-derived macrophages into the brain in a region-specific manner

Despite advances in the treatment of human immunodeficiency virus (HIV), approximately one-half of people infected with HIV (PWH) experience neurocognitive impairment. Opioid use disorder (OUD) can exacerbate the cognitive and pathological changes seen in PWH. HIV increases inflammation and immune cell trafficking into the brain; however, less is known about how opioid use disorder affects the recruitment of immune cells. Accordingly, we examined the temporal consequences of HIV-1 Tat and/or morphine on the recruitment of endocytic cells (predominantly perivascular macrophages and microglia) in the dorsal striatum and hippocampus by infusing multi-colored, fluorescently labeled dextrans before and after exposure. To address this question, transgenic mice that conditionally expressed HIV-1 Tat (Tat+), or their control counterparts (Tat-), received three sequential intracerebroventricular (i.c.v.) infusions of Cascade Blue-, Alexa Fluor 488-, and Alexa Fluor 594-labeled dextrans, respectively infused 1 day before, 1-day after, or 13-days after morphine and/or Tat exposure. At the end of the study, the number of cells labeled with each fluorescent dextran were counted. The data demonstrated a significantly higher influx of newly-labeled cells into the perivascular space than into the parenchyma. In the striatum, Tat or morphine exposure increased the number of endocytic cells in the perivascular space, while only morphine increased the recruitment of endocytic cells into the parenchyma. In the hippocampus, morphine (but not Tat) increased the influx of dextran-labeled cells into the perivascular space, but there were too few labeled cells within the hippocampal parenchyma to analyze. Collectively, these data suggest that HIV-1 Tat and morphine act independently to increase the recruitment of endocytic cells into the brain in a region-specific manner.

Monoacylglycerol Lipase Inhibitor MJN110 Reduces Neuronal Hyperexcitability, Restores Dendritic Arborization Complexity, and Regulates Reward-Related Behavior in Presence of HIV-1 Tat

While current therapeutic strategies for people living with human immunodeficiency virus type 1 (HIV-1) suppress virus replication peripherally, viral proteins such as transactivator of transcription (Tat) enter the central nervous system early upon infection and contribute to chronic inflammatory conditions even alongside antiretroviral treatment. As demand grows for supplemental strategies to combat virus-associated pathology presenting frequently as HIV-associated neurocognitive disorders (HAND), the present study aimed to characterize the potential utility of inhibiting monoacylglycerol lipase (MAGL) activity to increase inhibitory activity at cannabinoid receptor-type 1 receptors through upregulation of 2-arachidonoylglycerol (2-AG) and downregulation of its degradation into proinflammatory metabolite arachidonic acid (AA). The MAGL inhibitor MJN110 significantly reduced intracellular calcium and increased dendritic branching complexity in Tat-treated primary frontal cortex neuron cultures. Chronic MJN110 administration in vivo increased 2-AG levels in the prefrontal cortex (PFC) and striatum across Tat(+) and Tat(–) groups and restored PFC N-arachidonoylethanolamine (AEA) levels in Tat(+) subjects. While Tat expression significantly increased rate of reward-related behavioral task acquisition in a novel discriminative stimulus learning and cognitive flexibility assay, MJN110 altered reversal acquisition specifically in Tat(+) mice to rates indistinguishable from Tat(–) controls. Collectively, our results suggest a neuroprotective role of MAGL inhibition in reducing neuronal hyperexcitability, restoring dendritic arborization complexity, and mitigating neurocognitive alterations driven by viral proteins associated with latent HIV-1 infection.

Co-receptor signaling in the pathogenesis of neuroHIV

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.

The effects of anaesthetics and sedatives on brain inflammation

Microglia are involved in many dynamic processes in the central nervous system (CNS) including the development of inflammatory processes and neuromodulation. Several sedative, analgesic or anaesthetic drugs, such as opioids, ∝2-adrenergic agonists, ketamine, benzodiazepines and propofol can cause both neuroprotective and harmful effects on the brain. The purpose of this review is to present the main findings on the use of these drugs and the mechanisms involved in microglial activation. Alpha 2-adrenergic agonists, propofol and benzodiazepines have several pro- or anti-inflammatory effects on microglia. Long-term use of benzodiazepines and propofol causes neuroapoptotic effects and α2-adrenergic agonists may attenuate these effects. Conversely, morphine and fentanyl may have proinflammatory effects, causing behavioural changes in patients and changes in cell viability in vitro. Conversely, chronic administration of morphine induces CCL5 chemokine expression in microglial cells that promotes their survival.

Amyloidogenic, neuroinflammatory and memory dysfunction effects of HIV-1 gp120

Human immunodeficiency virus 1 (HIV-1) infection can cause several HIV-associated neurocognitive disorders a variety of neurological impairments characterized by the loss of cortical and subcortical neurons and decreased cognitive and motor function. HIV-1 gp120, the major envelope glycoprotein on viral particles, acts as a binding protein for viral entry and is known to be an agent of neuronal cell death. To determine the mechanism of HIV-1 gp120-induced memory dysfunction, we performed mouse intracerebroventricular (i.c.v.) infusion with HIV-1 gp120 protein (300 ng per mouse) and investigated memory impairment and amyloidogenesis. Infusion of the HIV-1 gp120 protein induced memory dysfunction, which was evaluated using passive avoidance and water maze tests. Infusion of HIV-1 gp120 induced neuroinflammation, such as the release of iNOS and COX-2 and the activation of astrocytes and microglia and increased the mRNA and protein levels of IL-6, ICAM-1, M-CSF, TIM, and IL-2. In particular, we found that the infusion of HIV-1 gp120 induced the accumulation of amyloid plaques and signs of elevated amyloidogenesis, such as increased expression of amyloid precursor protein and BACE1 and increased β-secretase activity. Therefore, these studies suggest that HIV-1 gp120 may induce memory impairment through Aβ accumulation and neuroinflammation.

Structure-Based Design and Development of Chemical Probes Targeting Putative MOR-CCR5 Heterodimers to Inhibit Opioid Exacerbated HIV-1 Infectivity

Crystal structures of ligand-bound G-protein-coupled receptors provide tangible templates for rationally designing molecular probes. Herein, we report the structure-based design, chemical synthesis, and biological investigations of bivalent ligands targeting putative mu opioid receptor C-C motif chemokine ligand 5 (MOR-CCR5) heterodimers. The bivalent ligand VZMC013 possessed nanomolar level binding affinities for both the MOR and CCR5, inhibited CCL5-stimulated calcium mobilization, and remarkably improved anti-HIV-1BaL activity over previously reported bivalent ligands. VZMC013 inhibited viral infection in TZM-bl cells coexpressing CCR5 and MOR to a greater degree than cells expressing CCR5 alone. Furthermore, VZMC013 blocked human immunodeficiency virus (HIV)-1 entry in peripheral blood mononuclear cells (PBMC) cells in a concentration-dependent manner and inhibited opioid-accelerated HIV-1 entry more effectively in phytohemagglutinin-stimulated PBMC cells than in the absence of opioids. A three-dimensional molecular model of VZMC013 binding to the MOR-CCR5 heterodimer complex is constructed to elucidate its mechanism of action. VZMC013 is a potent chemical probe targeting MOR-CCR5 heterodimers and may serve as a pharmacological agent to inhibit opioid-exacerbated HIV-1 entry.

Dopamine Levels Induced by Substance Abuse Alter Efficacy of Maraviroc and Expression of CCR5 Conformations on Myeloid Cells: Implications for NeuroHIV

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.

HIV-1 Tat and Morphine Differentially Disrupt Pyramidal Cell Structure and Function and Spatial Learning in Hippocampal Area CA1: Continuous versus Interrupted Morphine Exposure

About half the people infected with human immunodeficiency virus (HIV) have neurocognitive deficits that often include memory impairment and hippocampal deficits, which can be exacerbated by opioid abuse. To explore the effects of opioids and HIV on hippocampal CA1 pyramidal neuron structure and function, we induced HIV-1 transactivator of transcription (Tat) expression in transgenic mice for 14 d and co-administered time-release morphine or vehicle subcutaneous implants during the final 5 d (days 9-14) to establish steady-state morphine levels. Morphine was withheld from some ex vivo slices during recordings to begin to assess the initial pharmacokinetic consequences of opioid withdrawal. Tat expression reduced hippocampal CA1 pyramidal neuronal excitability at lower stimulating currents. Pyramidal cell firing rates were unaffected by continuous morphine exposure. Behaviorally, exposure to Tat or high dosages of morphine impaired spatial memory Exposure to Tat and steady-state levels of morphine appeared to have largely independent effects on pyramidal neuron structure and function, a response that is distinct from other vulnerable brain regions such as the striatum. By contrast, acutely withholding morphine (from morphine-tolerant ex vivo slices) revealed unique and selective neuroadaptive shifts in CA1 pyramidal neuronal excitability and dendritic plasticity, including some interactions with Tat. Collectively, the results show that opioid-HIV interactions in hippocampal area CA1 are more nuanced than previously assumed, and appear to vary depending on the outcome assessed and on the pharmacokinetics of morphine exposure.

HIV-1 and drug abuse comorbidity: Lessons learned from the animal models of NeuroHIV

Various research studies that have investigated the association between HIV infection and addiction underpin the role of various drugs of abuse in impairing immunological and non-immunological pathways of the host system, ultimately leading to augmentation of HIV infection and disease progression. These studies have included both in vitro and in vivo animal models wherein investigators have assessed the effects of various drugs on several disease parameters to decipher the impact of drugs on both HIV infection and progression of HIV-associated neurocognitive disorders (HAND). However, given the inherent limitations in the existing animal models of HAND, these investigations only recapitulated specific aspects of the disease but not the complex human syndrome. Despite the inability of HIV to infect rodents over the last 30 years, multiple strategies have been employed to develop several rodent models of HAND. While none of these models can accurately mimic the overall pathophysiology of HAND, they serve the purpose of modeling some unique aspects of HAND. This review provides an overview of various animal models used in the field and a careful evaluation of methodological strengths and limitations inherent in both the model systems and study designs to understand better how the various animal models complement one another.

Chronic morphine administration differentially modulates viral reservoirs in SIVmac251 infected rhesus macaque model

HIV persists in cellular reservoirs despite effective combined antiretroviral therapy (cART) and there is viremia flare up upon therapy interruption. Opioids modulate the immune system and suppress antiviral gene responses, which significantly impact people living with HIV (PLWH). However, the effect of opioids on viral reservoir dynamics remain elusive. Herein, we developed a morphine dependent SIVmac251 infected Rhesus macaque (RM) model to study the impact of opioids on HIV reservoirs. RMs on a morphine (or saline control) regimen were infected with SIVmac251. The cART was initiated in approximately half the animals five weeks post-infection, and morphine/saline administration continued until the end of the study. Among the untreated RM, we did not find any difference in plasma/CSF or in cell-associated DNA/RNA viral load in anatomical tissues. On the other hand, within the cART suppressed macaques, there was a reduction in cell-associated DNA load, intact proviral DNA levels, and in inducible SIV reservoir in lymph nodes (LNs) of morphine administered RMs. In distinction to LNs, in the CNS, the size of latent SIV reservoirs was higher in the CD11b+ microglia/macrophages in morphine dependent RMs. These results suggest that in the proposed model, morphine plays a differential role in SIV reservoirs by reducing the CD4+ T-cell reservoir in lymphoid tissues, while increasing the microglia/reservoir size in CNS tissue. The findings from this pre-clinical model will serve as a tool for screening therapeutic strategies to reduce/eliminate HIV reservoirs in opioid dependent PLWH.IMPORTANCE Identification and clearance of HIV reservoirs is a major challenge in achieving a cure for HIV. This is further complicated by co-morbidities that may alter the size of the reservoirs. There is an overlap between the risk factors for HIV and opioid abuse. Opiates have been recognized as prominent co-morbidities in HIV-infected populations. People infected with HIV also abusing opioids have immune modulatory effects and more severe neurological disease. However, the impact of opioid abuse on HIV reservoirs remains unclear. In this study, we used morphine dependent SIVmac251 infected rhesus macaque (RM) model to study the impact of opioids on HIV reservoirs. Our studies suggested that people with HIV who abuse opioids had higher reservoirs in CNS than the lymphoid system. Extrapolating the macaque findings in humans suggests that such differential modulation of HIV reservoirs among people living with HIV abusing opioids could be considered for future HIV cure research efforts.

Treating viruses in the brain: Perspectives from NeuroAIDS

Aggressive use of antiretroviral therapy has led to excellent viral suppression within the systemic circulation. However, despite these advances, HIV reservoirs still persist. The persistence of HIV within the brain can lead to the development of HIV-associated neurocognitive disorders (HAND). Although the causes of the development of neurocognitive disorders is likely multifactorial, the inability of antiretroviral therapy to achieve adequate concentrations within the brain is likely a major contributing factor. Information about antiretroviral drug exposure within the brain is limited. Clinically, drug concentrations within the cerebrospinal fluid (CSF) are used as markers for central nervous system (CNS) drug exposure. However, significant differences exist; CSF concentration is often a poor predictor of drug exposure within the brain. This article reviews the current information regarding antiretroviral exposure within the brain in humans as well as preclinical animals and discusses the impact of co-morbidities on antiretroviral efficacy within the brain. A more thorough understanding of antiretroviral penetration into the brain is an essential component to the development of better therapeutic strategies for neuroAIDS.

Neuroimaging and Cognitive Evidence for Combined HIV-Alcohol Effects on the Central Nervous System: A Review

Alcohol use disorder (AUD) among people living with HIV (PLWH) is a significant public health concern. Despite the advent of effective antiretroviral therapy, up to 50% of PLWH still experience worsened neurocognition, which comorbid AUD exacerbates. We report converging lines of neuroimaging and neuropsychological evidence linking comorbid HIV/AUD to dysfunction in brain regions linked to executive function, learning and memory, processing speed, and motor control, and consequently to impairment in daily life. The brain shrinkage, functional network alterations, and brain metabolite disruption seen in individuals with HIV/AUD have been attributed to several interacting pathways: viral proteins and EtOH are directly neurotoxic and exacerbate each other's neurotoxic effects; EtOH reduces antiretroviral adherence and increases viral replication; AUD and HIV both increase gut microbial translocation, promoting systemic inflammation and HIV transport into the brain by immune cells; and HIV may compound alcohol's damaging effects on the liver, further increasing inflammation. We additionally review the neurocognitive effects of aging, Hepatitis C coinfection, obesity, and cardiovascular disease, tobacco use, and nutritional deficiencies, all of which have been shown to compound cognitive changes in HIV, AUD, and in their comorbidity. Finally, we examine emerging questions in HIV/AUD research, including genetic and cognitive protective factors, the role of binge drinking in HIV/AUD-linked cognitive decline, and whether neurocognitive and brain functions normalize after drinking cessation.

Alzheimer's disease-like perturbations in HIV-mediated neuronal dysfunctions: understanding mechanisms and developing therapeutic strategies

Excessive exposure to toxic substances or chemicals in the environment and various pathogens, including viruses and bacteria, is associated with the onset of numerous brain abnormalities. Among them, pathogens, specifically viruses, elicit persistent inflammation that plays a major role in Alzheimer's disease (AD) as well as dementia. AD is the most common brain disorder that affects thought, speech, memory and ability to execute daily routines. It is also manifested by progressive synaptic impairment and neurodegeneration, which eventually leads to dementia following the accumulation of Aβ and hyperphosphorylated Tau. Numerous factors contribute to the pathogenesis of AD, including neuroinflammation associated with pathogens, and specifically viruses. The human immunodeficiency virus (HIV) is often linked with HIV-associated neurocognitive disorders (HAND) following permeation through the blood-brain barrier (BBB) and induction of persistent neuroinflammation. Further, HIV infections also exhibited the ability to modulate numerous AD-associated factors such as BBB regulators, members of stress-related pathways as well as the amyloid and Tau pathways that lead to the formation of amyloid plaques or neurofibrillary tangles accumulation. Studies regarding the role of HIV in HAND and AD are still in infancy, and potential link or mechanism between both is not yet established. Thus, in the present article, we attempt to discuss various molecular mechanisms that contribute to the basic understanding of the role of HIV-associated neuroinflammation in AD and HAND. Further, using numerous growth factors and drugs, we also present possible therapeutic strategies to curb the neuroinflammatory changes and its associated sequels.

Neuroimmune communication in infection and pain: Friends or foes?

Clinically, a variety of micro-organisms cause painful infections. Before seen as bystanders in the context of infections, recent studies have demonstrated that, as immune cells, nociceptors can sense pathogen-derived products. Nociceptors and immune cells, therefore, have evolved to communicate with each other to control inflammatory and host responses against pathogens in a complementary way. This interaction is named as neuroimmune communication (or axon-axon immune reflex) and initiates after the release of neuropeptides, such as CGRP and VIP by neurons. By this neurogenic response, nociceptors orchestrate the activity of innate and adaptive immune cells in a context-dependent manner. In this review, we focus on how nociceptors sense pathogen-derived products to shape the host response. We also highlight the new concept involving the resolution of inflammation, which is related to an active and time-dependent biosynthetic shift from pro-inflammatory to pro-resolution mediators, the so-called specialized pro-resolving lipid mediators (SPMs). At very low doses, SPMs act on specific receptors to silence nociceptors, limit pain and neurogenic responses, and resolve infections. Furthermore, stimulation of the vagus nerve induces SPMs production to regulate immune responses in infections. Therefore, harnessing the current understanding of neuro-immune communication and neurogenic responses might provide the bases for reprogramming host responses against infections through well balanced and effective immune response and inflammation resolution.

Cognitive Impairment among People Who Use Heroin and Fentanyl: Findings from the Miami Adult Studies on HIV (MASH) Cohort

Background: Cognitive impairment is common in people living with HIV (PLWH). Opioid drugs exert direct and indirect effects on cognitive processes, which may contribute to cognitive dysfunction among PLWH. This study was designed to determine if opioid use is associated with cognitive impairment and whether the effect differs between PLWH and HIV-uninfected adults. Other neuropsychiatric symptoms, such as depression and apathy, were also examined. We conducted a cross-sectional analysis of 265 PLWH and 284 HIV-uninfected participants from the Miami Adult Studies on HIV (MASH) cohort. The Mini-Mental State Examination (MMSE) was used to assess cognitive impairment. Substance use was self-reported. Overall, 26.8% of PLWH and 15.1% of HIV-uninfected used opioids. Cognitive impairment was more frequent among people who used heroin and/or fentanyl than those who misused prescription opioids (31.6% vs. 10.5%, p = .005). The use of heroin/fentanyl was associated with increased odds for cognitive impairment (adjusted OR: 2.21, 95% CI 1.05-4.64, p = .036). Among PLWH only, the misuse of opioids was associated with a higher frequency of neuropsychiatric symptoms such as depression and apathy. A higher risk for cognitive impairment was seen among people who used heroin and fentanyl. PLWH who misuse opioids may be at an increased risk for neuropathology, but elucidation of mechanisms for opioid-induced cognitive deficits is needed.

Escalating morphine dosing in HIV-1 Tat transgenic mice with sustained Tat exposure reveals an allostatic shift in neuroinflammatory regulation accompanied by increased neuroprotective non-endocannabinoid lipid signaling molecules and amino acids

BACKGROUND

Human immunodeficiency virus type-1 (HIV-1) and opiates cause long-term inflammatory insult to the central nervous system (CNS) and worsen disease progression and HIV-1-related neuropathology. The combination of these proinflammatory factors reflects a devastating problem as opioids have high abuse liability and continue to be prescribed for certain patients experiencing HIV-1-related pain.

METHODS

Here, we examined the impact of chronic (3-month) HIV-1 transactivator of transcription (Tat) exposure to short-term (8-day), escalating morphine in HIV-1 Tat transgenic mice that express the HIV-1 Tat protein in a GFAP promoter-regulated, doxycycline (DOX)-inducible manner. In addition to assessing morphine-induced tolerance in nociceptive responses organized at spinal (i.e., tail-flick) and supraspinal (i.e., hot-plate) levels, we evaluated neuroinflammation via positron emission tomography (PET) imaging using the [18F]-PBR111 ligand, immunohistochemistry, and cytokine analyses. Further, we examined endocannabinoid (eCB) levels, related non-eCB lipids, and amino acids via mass spectrometry.  RESULTS: Tat-expressing [Tat(+)] transgenic mice displayed antinociceptive tolerance in the tail withdrawal and hot-plate assays compared to control mice lacking Tat [Tat(-)]. This tolerance was accompanied by morphine-dependent increases in Iba-1 ± 3-nitrotryosine immunoreactive microglia, and alterations in pro- and anti-inflammatory cytokines, and chemokines in the spinal cord and striatum, while increases in neuroinflammation were absent by PET imaging of [18F]-PBR111 uptake. Tat and morphine exposure differentially affected eCB levels, non-eCB lipids, and specific amino acids in a region-dependent manner. In the striatum, non-eCB lipids were significantly increased by short-term, escalating morphine exposure, including peroxisome proliferator activator receptor alpha (PPAR-α) ligands N-oleoyl ethanolamide (OEA) and N-palmitoyl ethanolamide (PEA), as well as the amino acids phenylalanine and proline. In the spinal cord, Tat exposure increased amino acids leucine and valine, while morphine decreased levels of tyrosine and valine but did not affect eCBs or non-eCB lipids.

CONCLUSION

Overall results demonstrate that 3 months of Tat exposure increased morphine tolerance and potentially innate immune tolerance evidenced by reductions in specific cytokines (e.g., IL-1α, IL-12p40) and microglial reactivity. In contrast, short-term, escalating morphine exposure acted as a secondary stressor revealing an allostatic shift in CNS baseline inflammatory responsiveness from sustained Tat exposure.

Bivalent Ligand Aiming Putative Mu Opioid Receptor and Chemokine Receptor CXCR4 Dimers in Opioid Enhanced HIV-1 Entry

A bivalent compound 1a featuring both a mu opioid receptor (MOR) and a CXCR4 antagonist pharmacophore (naltrexone and IT1t) was designed and synthesized. Further binding and functional studies demonstrated 1a acting as a MOR and a CXCR4 dual antagonist with reasonable binding affinities at both receptors. Furthermore, compound 1a seemed more effective than a combination of IT1t and naltrexone in inhibiting HIV entry at the presence of morphine. Additional molecular modeling results suggested that 1a may bind with the putative MOR-CXCR4 heterodimer to induce its anti-HIV activity. Collectively, bivalent ligand 1a may serve as a promising lead to develop chemical probes targeting the putative MOR-CXCR4 heterodimer in comprehending opioid exacerbated HIV-1 invasion.

Opioid-Mediated HIV-1 Immunopathogenesis

Despite the ability of combination antiretroviral therapy to dramatically suppress viremia, the brain continues to be a reservoir of HIV-1 low-level replication. Adding further complexity to this is the comorbidity of drug abuse with HIV-1 associated neurocognitive disorders and neuroHIV. Among several abused drugs, the use of opiates is highly prevalent in HIV-1 infected individuals, both as an abused drug as well as for pain management. Opioids and their receptors have attained notable attention owing to their ability to modulate immune functions, in turn, impacting disease progression. Various cell culture, animal and human studies have implicated the role of opioids and their receptors in modulating viral replication and virus-mediated pathology both positively and negatively. Further, the combinatorial effects of HIV-1/HIV-1 proteins and morphine have demonstrated activation of inflammatory signaling in the host system. Herein, we summarized the current knowledge on the role of opioids on peripheral immunopathogenesis, viral immunopathogenesis, epigenetic profiles of the host and viral genome, neuropathogenesis of SIV/SHIV-infected non-human primates, blood-brain-barrier, HIV-1 viral latency, and viral rebound. Overall, this review provides recent insights into the role of opioids in HIV-1 immunopathogenesis. Graphical abstract.

Effect of Opioid Use on Immune Activation and HIV Persistence on ART

While there is an emerging consensus that engagement of the Mu opioid receptor by opioids may modulate various stages the HIV life cycle (e.g.: increasing cell susceptibility to infection, promoting viral transcription, and depressing immune responses to virally-infected cells), the overall effect on latency and viral reservoirs remains unclear. Importantly, the hypothesis that the increase in immune activation observed in chronic opioid users by direct or indirect mechanisms (i.e., microbial translocation) would lead to a larger HIV reservoir after ART-suppression has not been supported to date. The potential for a subsequent decrease in reservoirs after ART-suppression has been postulated and is supported by early reports of opioid users having lower latent HIV burden. Here, we review experimental data supporting the link between opioid use and HIV modulation, as well as the scientific premise for expecting differential changes in immune activation and HIV reservoir between different medications for opioid use disorder. A better understanding of potential changes in HIV reservoirs relative to the engagement of the Mu opioid receptor and ART-mediated immune reconstitution will help guide future cure-directed studies in persons living with HIV and opioid use disorder. Graphical Abstract Review. HIV replication, immune activation and dysbiosis: opioids may affect immune reconstitution outcomes despite viral suppression.

Opioid Use Disorders in People Living with HIV/AIDS: A Review of Implications for Patient Outcomes, Drug Interactions, and Neurocognitive Disorders

The opioid epidemic has had a significant, negative impact in the United States, and people living with HIV/AIDS (PLWHA) represent a vulnerable sub-population that is at risk for negative sequela from prolonged opioid use or opioid use disorder (OUD). PLWHA are known to suffer from HIV-related pain and are commonly treated with opioids, leading to subsequent addictive disorders. PLWHA and OUD are at an increased risk for attrition in the HIV care continuum, including suboptimal HIV laboratory testing, delayed entry into HIV care, and initiation or adherence to antiretroviral therapy. Barriers to OUD treatment, such as medication-assisted therapy, are also apparent for PLWHA with OUD, particularly those living in rural areas. Additionally, PLWHA and OUD are at a high risk for serious drug–drug interactions through antiretroviral-opioid metabolic pathway-related inhibition/induction, or via the human ether-a-go-go-related gene potassium ion channel pathways. HIV-associated neurocognitive disorders can also be potentiated by the off-target inflammatory effects of opioid use. PLWHA and OUD might require more intensive, individualized protocols to sustain treatment for the underlying opioid addiction, as well as to provide proactive social support to aid in improving patient outcomes. Advancements in the understanding and management of PLWHA and OUD are needed to improve patient care. This review describes the effects of prescription and non-prescription opioid use in PLWHA.

Opioid and neuroHIV Comorbidity - Current and Future Perspectives

With the current national opioid crisis, it is critical to examine the mechanisms underlying pathophysiologic interactions between human immunodeficiency virus (HIV) and opioids in the central nervous system (CNS). Recent advances in experimental models, methodology, and our understanding of disease processes at the molecular and cellular levels reveal opioid-HIV interactions with increasing clarity. However, despite the substantial new insight, the unique impact of opioids on the severity, progression, and prognosis of neuroHIV and HIV-associated neurocognitive disorders (HAND) are not fully understood. In this review, we explore, in detail, what is currently known about mechanisms underlying opioid interactions with HIV, with emphasis on individual HIV-1-expressed gene products at the molecular, cellular and systems levels. Furthermore, we review preclinical and clinical studies with a focus on key considerations when addressing questions of whether opioid-HIV interactive pathogenesis results in unique structural or functional deficits not seen with either disease alone. These considerations include, understanding the combined consequences of HIV-1 genetic variants, host variants, and μ-opioid receptor (MOR) and HIV chemokine co-receptor interactions on the comorbidity. Lastly, we present topics that need to be considered in the future to better understand the unique contributions of opioids to the pathophysiology of neuroHIV.

Graphical Abstract

Tobacco smoke and morphine alter peripheral and CNS inflammation following HIV infection in a humanized mouse model

Tobacco smoking is common in HIV-infected patients, and is prevalent among intravenous opiate abusers. Conversely, intravenous opiate abusers are more likely HIV-infected, and opiate abuse is associated with more severe neuroinflammation. Given the coincident use of tobacco smoking among HIV-infected intravenous drug users (IVDUs), we set out to study the effects of smoke exposure, chronic morphine administration, and HIV infection using the NSG humanized mouse model. Our results show that smoke, morphine, and the combination promotes the decline in CD4+ T cells in HIV-infected mice. Further, chronic morphine administration increases the numbers of circulating CD8+ T cells which express the inhibitory receptor PD-1, as well as the cytolytic proteins perforin and granzyme B in the infected mice. We also found that the combination of smoke and morphine inhibited the expression of IL-1α, IL-4 and IL-17A. Finally, the combination of smoke and morphine exposure induces microglial activation following infection, as well as in the absence of HIV infection. To our knowledge, this is the first report to assess the combined effects of smoke and chronic morphine exposure on the inflammation associated with HIV infection, and demonstrate that these two insults exert significant neuroinflammatory activity.

Combined HIV-1 Tat and oxycodone activate the hypothalamic-pituitary-adrenal and -gonadal axes and promote psychomotor, affective, and cognitive dysfunction in female mice

The majority of HIV⁺ patients present with neuroendocrine dysfunction and ~50% experience co-morbid neurological symptoms including motor, affective, and cognitive dysfunction, collectively termed neuroHIV. In preclinical models, the neurotoxic HIV-1 regulatory protein, trans-activator of transcription (Tat), promotes neuroHIV pathology that can be exacerbated by opioids. We and others find gonadal steroids, estradiol (E₂) or progesterone (P₄), to rescue Tat-mediated pathology. However, the combined effects of Tat and opioids on neuroendocrine function and the subsequent ameliorative capacity of gonadal steroids are unknown. We found that conditional HIV-1 Tat expression in naturally-cycling transgenic mice dose-dependently potentiated oxycodone-mediated psychomotor behavior. Tat increased depression-like behavior in a tail-suspension test among proestrous mice, but decreased it among diestrous mice (who already demonstrated greater depression-like behavior); oxycodone reversed these effects. Combined Tat and oxycodone produced apparent behavioral disinhibition of anxiety-like responding which was greater on diestrus than on proestrus. These mice made more central entries in an open field, but spent less time there and demonstrated greater circulating corticosterone. Tat increased the E₂:P₄ ratio of circulating steroids on diestrus and acute oxycodone attenuated this effect, but repeated oxycodone exacerbated it. Corticotropin-releasing factor was increased by Tat expression, acute oxycodone exposure, and was greater on diestrus compared to proestrus. In human neuroblastoma cells, Tat exerted neurotoxicity that was ameliorated by E₂ (1 or 10 nM) or P₄ (100, but not 10 nM) independent of oxycodone. Oxycodone decreased gene expression of estrogen and κ-opioid receptors. Thus, neuroendocrine function may be an important target for HIV-1 Tat/opioid interactions.

Pregnane steroidogenesis is altered by HIV-1 Tat and morphine: Physiological allopregnanolone is protective against neurotoxic and psychomotor effects

Pregnane steroids, particularly allopregnanolone (AlloP), are neuroprotective in response to central insult. While unexplored in vivo, AlloP may confer protection against the neurological dysfunction associated with human immunodeficiency virus type 1 (HIV-1). The HIV-1 regulatory protein, trans-activator of transcription (Tat), is neurotoxic and its expression in mice increases anxiety-like behavior; an effect that can be ameliorated by progesterone, but not when 5α-reduction is blocked. Given that Tat's neurotoxic effects involve mitochondrial dysfunction and can be worsened with opioid exposure, we hypothesized that Tat and/or combined morphine would perturb steroidogenesis in mice, promoting neuronal death, and that exogenous AlloP would rescue these effects. Like other models of neural injury, conditionally inducing HIV-1 Tat in transgenic mice significantly increased the central synthesis of pregnenolone and progesterone's 5α-reduced metabolites, including AlloP, while decreasing central deoxycorticosterone (independent of changes in plasma). Morphine significantly increased brain and plasma concentrations of several steroids (including progesterone, deoxycorticosterone, corticosterone, and their metabolites) likely via activation of the hypothalamic-pituitary-adrenal stress axis. Tat, but not morphine, caused glucocorticoid resistance in primary splenocytes. In neurons, Tat depolarized mitochondrial membrane potential and increased cell death. Physiological concentrations of AlloP (0.1, 1, or 10 nM) reversed these effects. High-concentration AlloP (100 nM) was neurotoxic in combination with morphine. Tat induction in transgenic mice potentiated the psychomotor effects of acute morphine, while exogenous AlloP (1.0 mg/kg, but not 0.5 mg/kg) was ameliorative. Data demonstrate that steroidogenesis is altered by HIV-1 Tat or morphine and that physiological AlloP attenuates resulting neurotoxic and psychomotor effects.

The impact of substance abuse on HIV-mediated neuropathogenesis in the current ART era

Approximately 37 million people worldwide are infected with human immunodeficiency virus (HIV). One highly significant complication of HIV infection is the development of HIV-associated neurocognitive disorders (HAND) in 15-55% of people living with HIV (PLWH), that persists even in the antiretroviral therapy (ART) era. The entry of HIV into the central nervous system (CNS) occurs within 4-8 days after peripheral infection. This establishes viral reservoirs that may persist even in the presence of ART. Once in the CNS, HIV infects resident macrophages, microglia, and at low levels, astrocytes. In response to chronic infection and cell activation within the CNS, viral proteins, inflammatory mediators, and host and viral neurotoxic factors produced over extended periods of time result in neuronal injury and loss, cognitive deficits and HAND. Substance abuse is a common comorbidity in PLWH and has been shown to increase neuroinflammation and cognitive disorders. Additionally, it has been associated with poor ART adherence, and increased viral load in the cerebrospinal fluid (CSF), that may also contribute to increased neuroinflammation and neuronal injury. Studies have examined mechanisms that contribute to neuroinflammation and neuronal damage in PLWH, and how substances of abuse exacerbate these effects. This review will focus on how substances of abuse, with an emphasis on methamphetamine (meth), cocaine, and opioids, impact blood brain barrier (BBB) integrity and transmigration of HIV-infected and uninfected monocytes across the BBB, as well as their effects on monocytes/macrophages, microglia, and astrocytes within the CNS. We will also address how these substances of abuse may contribute to HIV-mediated neuropathogenesis in the context of suppressive ART. Additionally, we will review the effects of extracellular dopamine, a neurotransmitter that is increased in the CNS by substances of abuse, on HIV neuropathogenesis and how this may contribute to neuroinflammation, neuronal insult, and HAND in PLWH with active substance use. Lastly, we will discuss some potential therapies to limit CNS inflammation and damage in HIV-infected substance abusers.

Specialized pro-resolving lipid mediators: A new class of non-immunosuppressive and non-opioid analgesic drugs

We now appreciate that the mechanism of resolution depends on an active and time-dependent biosynthetic shift from pro-inflammatory to pro-resolution mediators, the so-called specialized pro-resolving lipid mediators (SPMs). These SPMs are biosynthesized from the omega-3 fatty acids arachidonic acid (AA), eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), or docosahexaenoic acid (DHA). Despite effective for a fraction of patients with rheumatic diseases and neuropathic pain, current analgesic therapies such as biological agents, opioids, corticoids, and gabapentinoids cause unwanted side effects, such as immunosuppression, addiction, or induce analgesic tolerance. A growing body of evidence demonstrates that isolated SPMs show efficacy at very low doses and have been successively used as therapeutic drugs to treat pain and infection in experimental models showing no side effects. Moreover, SPMs work as immunoresolvents and some of them present long-lasting analgesic and anti-inflammatory effects (i.e. block pain without immunosuppressive effects). In this review, we focus on how SPMs block pain, infection and neuro-immune interactions and, therefore, emerge as a new class of non-immunosuppressive and non-opioid analgesic drugs.

The Effects of Opioids on HIV Neuropathogenesis

HIV associated neurocognitive disorders (HAND) are a group of neurological deficits that affect approximately half of people living with HIV (PLWH) despite effective antiretroviral therapy (ART). There are currently no reliable molecular biomarkers or treatments for HAND. Given the national opioid epidemic, as well as illegal and prescription use of opioid drugs among PLWH, it is critical to characterize the molecular interactions between HIV and opioids in cells of the CNS. It is also important to study the role of opioid substitution therapies in the context of HIV and CNS damage in vitro and in vivo. A major mechanism contributing to HIV neuropathogenesis is chronic, low-level inflammation in the CNS. HIV enters the brain within 4–8 days after peripheral infection and establishes CNS reservoirs, even in the context of ART, that are difficult to identify and eliminate. Infected cells, including monocytes, macrophages, and microglia, produce chemokines, cytokines, neurotoxic mediators, and viral proteins that contribute to chronic inflammation and ongoing neuronal damage. Opioids have been shown to impact these immune cells through a variety of molecular mechanisms, including opioid receptor binding and cross desensitization with chemokine receptors. The effects of opioid use on cognitive outcomes in individuals with HAND in clinical studies is variable, and thus multiple biological mechanisms are likely to contribute to the complex relationship between opioids and HIV in the CNS. In this review, we will examine what is known about both HIV and opioid mediated neuropathogenesis, and discuss key molecular processes that may be impacted by HIV and opioids in the context of neuroinflammation and CNS damage. We will also assess what is known about the effects of ART on these processes, and highlight areas of study that should be addressed in the context of ART.

Cell-type specific differences in antiretroviral penetration and the effects of HIV-1 Tat and morphine among primary human brain endothelial cells, astrocytes, pericytes, and microglia

The inability to achieve adequate intracellular antiretroviral concentrations may contribute to HIV persistence within the brain and to neurocognitive deficits in opioid abusers. To investigate, intracellular antiretroviral concentrations were measured in primary human astrocytes, microglia, pericytes, and brain microvascular endothelial cells (BMECs), and in an immortalized brain endothelial cell line (hCMEC/D3). HIV-1 Tat and morphine effects on intracellular antiretroviral concentrations also were evaluated. After pretreatment for 24 h with vehicle, HIV-1 Tat, morphine, or combined Tat and morphine, cells were incubated for 1 h with equal concentrations of a mixture of tenofovir, emtricitabine, and dolutegravir at one of two concentrations (5 μM or 10 μM). Intracellular drug accumulation was measured using LC-MS/MS. Drug penetration differed depending on the drug, the extracellular concentration used for dosing, and cell type. Significant findings included: 1) Dolutegravir (at 5 μM or 10 μM) accumulated more in HBMECs than other cell types. 2) At 5 μM, intracellular emtricitabine levels were higher in microglia than other cell types; while at 10 μM, emtricitabine accumulation was greatest in HBMECs. 3) Tenofovir (5 or 10 μM extracellular dosing) displayed greater accumulation inside HBMECs than in other cell types. 4) After Tat and/or morphine pretreatment, the relative accumulation of antiretroviral drugs was greater in morphine-exposed HBMECs compared to other treatments. The opposite effect was observed in astrocytes in which morphine exposure decreased drug accumulation. In summary, the intracellular accumulation of antiretroviral drugs differed depending on the particular drug involved, the concentration of the applied antiretroviral drug, and the cell type targeted. Moreover, morphine, and to a lesser extent Tat, exposure also had differential effects on antiretroviral accumulation. These data highlight the complexity of optimizing brain-targeted HIV therapeutics, especially in the setting of chronic opioid use or misuse.

Autophagy Induction by HIV-Tat and Methamphetamine in Primary Midbrain Neuronal Cells of Tree Shrews via the mTOR Signaling and ATG5/ATG7 Pathway

Background: Addictive stimulant drugs, such as methamphetamine (METH), increase the risk of exposure to the human immunodeficiency virus-1 (HIV-1) infection and thus predispose individuals to the development of HIV-associated neurocognitive disorders (HANDs). Previous studies have indicated that HIV-Tat (the transactivator of transcription) and METH can synergistically induce autophagy in SH-SY5Y neuroblastoma cells and that autophagy plays a pivotal role in the neuronal dysfunction in HANDs. However, the underlying mechanism of METH-and HIV-Tat-induced neuronal autophagy remains unclear. Methods: We cultured primary midbrain neuronal cells of tree shrews and treated them with METH and HIV-Tat to study the role of METH and HIV-Tat in inducing autophagy. We evaluated the effects of the single or combined treatment of METH and HIV-Tat on the protein expressions of the autophagy-related genes, including Beclin-1 and LC3B, ATG5, and ATG7 in METH and HIV-Tat-induced autophagy. In addition, the presence of autophagosomes in the METH and/or HIV-Tat treatment was revealed using transmission electron microscopy. Results: The results indicated that METH increased the protein levels of LC3B and Beclin-1, and these effects were significantly enhanced by HIV-Tat. Moreover, the results suggested that ATG5 and ATG7 were involved in the METH and HIV-Tat-induced autophagy. In addition, it was found that mTOR inhibition via pharmacological intervention could trigger autophagy and promote METH and HIV-Tat-induced autophagy. Discussion: Overall, this study contributes to the knowledge of the molecular underpinnings of METH and HIV-Tat-induced autophagy in primary midbrain neuronal cells. Our findings may facilitate the development of therapeutic strategies for METH-and HIV-Tat-induced autophagy in HANDs.

Protective Effects of Ginsenoside Rb1 against Blood-Brain Barrier Damage Induced by Human Immunodeficiency Virus-1 Tat Protein and Methamphetamine in Sprague-Dawley Rats

Although antiretroviral therapy has helped to improve the lives of individuals infected with human immunodeficiency virus 1 (HIV-1), these patients are often still afflicted with HIV-1-associated neurocognitive disorders, which can lead to neurocognitive impairment and even dementia, and continue to hamper their quality of life. Methamphetamine abuse in HIV-1 patients poses a potential risk for HIV-associated neurocognitive disorders, because methamphetamine and HIV-1 proteins such as transactivator of transcription can synergistically damage the blood-brain barrier (BBB). In this study, we aimed to examine the effects of methamphetamine and HIV-1 Tat protein on the blood-brain barrier function and to determine whether ginsenoside Rb1 (GsRb1) plays a role in protecting the BBB. Sprague-Dawley rats were divided into four groups. The experimental groups received methamphetamine and HIV-1 Tat protein or both and the control group received saline or GsRb1 pretreatment. Oxidative stress-related factors, tight junction (TJ) proteins, blood-brain barrier permeability, and morphological changes were recorded in each group. The results showed that the group treated with Methamphetamine[Formula: see text]Tat showed a significant change at the ultrastructural level and in the levels of oxidative stress-related factors, TJ proteins, and BBB permeability, suggesting that the BBB function was severely damaged by HIV-1 Tat and methamphetamine synergistically. However, malondialdehyde levels and BBB permeability were lower and the oxidative stress-related factors superoxide dismutase and glutathione were higher in the GsRb1-treated group than in the Methamphetamine[Formula: see text]Tat-treated group, indicating that GsRb1 can protect the BBB against the toxic effects of HIV-1 Tat and methamphetamine. These results show that GsRb1 may offer a potential therapeutic option for patients with HIV-associated neurocognitive disorders or other neurodegenerative diseases.

Critical Role of Beclin1 in HIV Tat and Morphine-Induced Inflammation and Calcium Release in Glial Cells from Autophagy Deficient Mouse

We previously showed that autophagy is an important component in human immunodeficiency virus (HIV) replication and in the combined morphine-induced neuroinflammation in human astrocytes and microglia. Here we further studied the consequences of autophagy using glial cells of mice partially lacking the essential autophagy gene Atg6 (Beclin1) exposed to HIV Tat and morphine. Tat is known to cause an inflammatory response, increase calcium release, and possibly interact with autophagy pathway proteins. Following Tat exposure, autophagy-deficient (Becn1^+/-) glial cells had significantly and consistently reduced levels in the pro-inflammatory cytokine IL-6 and the chemokines RANTES and MCP-1 when compared to Tat-treated cells from control (C57BL/6J) mice, suggesting an association between the inflammatory effects of Tat and Beclin1. Further, differences in RANTES and MCP-1 secretion between C57BL/6J and Becn1^+/- glia treated with Tat and morphine also suggest a role of Beclin1 in the morphine-induced enhancement. Analysis of autophagy maturation by immunoblot suggests that Beclin1 may be necessary for Tat, and to a lesser extent morphine-induced arrest of the pathway as demonstrated by accumulation of the adaptor protein p62/SQSTM1 in C57BL/6J glia. Calcium release induced by Tat alone or in combination with morphine in C57BL/6J glia was significantly reduced in Becn1^+/- glia while minimal interactive effect of Tat with morphine in the production of reactive oxygen or nitrogen species was detected in glia derived from Becn1^+/- or C57BL/6J. Overall, the data establish a role of Beclin1 in Tat and morphine-mediated inflammatory responses and calcium release in glial cells and support the notion that autophagy mediates Tat alone and combined morphine-induced neuropathology.

The role of catecholamines in HIV neuropathogenesis

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.

Morphine-potentiated cognitive deficits correlate to suppressed hippocampal iNOS RNA expression and an absent type 1 interferon response in LP-BM5 murine AIDS

Opioid use accelerates neurocognitive impairment in HIV/AIDS patients. We assessed the effect of chronic morphine treatment and LP-BM5/murine AIDS (MAIDS) infection on cognition, cytokine production, and type 1 interferon (IFN) expression in the murine CNS. Morphine treatment decreased expression of pro-inflammatory factors (CCL5, iNOS) and reduced cognitive performance in LP-BM5-infected mice, correlating to increased hippocampal viral load and a blunted type 1 IFN response. In the striatum, morphine reduced viral load while increasing IFN-α RNA expression. Our results suggest that differentially regulated type 1 IFN responses may contribute to distinct regional outcomes in the hippocampus and striatum in LP-BM5/MAIDS.

Progressive white matter impairment as a predictor of outcome in a cohort of opioid-dependent patient's post-detoxification

White matter impairment is associated with opioid dependence. However, the specific neuropathology related to opioid dependence is still not fully understood. The main aims of this study were to: (1) assess the association between white matter impairment and duration of dependence; (2) examine whether this impairment correlates with treatment outcome measures in opioid-dependent patients post-detoxification. Fifty-eight opioid-dependent patients participated, 20 females and 38 males, across three groups: less than 10 years use (n = 18), 10-15 years use (n = 26) and 16-25+ years use (n = 14). Diffusion tensor imaging was used to assess white matter impairment; whole brain voxel-wise analysis of fractional anisotropy, mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD) were performed by Tract-Based-Spatial-Statistics to pinpoint abnormalities in white matter. The longer the subjects were dependent on opioids, the more widespread and severely the white-matter integrity was disrupted. A general linear model was used to examine patients who relapsed compared to those who were abstinent at follow-up. No statistical difference was found between groups (p > 0.05). Partial correlations were performed to investigate the relationship between clinical outcome measures (physical health, psychological well being and quality of life and hope for the future) and white-matter microstructural differences. Significant correlations were found between AD in the posterior corona radiata (L) and MD in the superior longitudinal fasciculus and a clinical measure for HOPE at 9-month follow-up. Nevertheless, it must be noted that the calculation of numerous correlations raises the possibility of a type I error, namely; to incorrectly conclude the occurrence of a significant correlation. The ability to investigate the structure-clinical relationship may improve our understanding of the pathological abnormalities associated with opioid dependence and has promise for use in evaluating future therapeutic outcomes in this population.

Opioids and Opioid Maintenance Therapies: Their Impact on Monocyte-Mediated HIV Neuropathogenesis

BACKGROUND

HIV-1 enters the CNS within two weeks after peripheral infection and results in chronic neuroinflammation that leads to HIV associated neurocognitive disorders (HAND) in more than 50% of infected people. HIV enters the CNS by transmigration of infected monocytes across the blood brain barrier. Intravenous drug abuse is a major risk factor for HIV-1 infection, and opioids have been shown to alter the progression and severity of HAND. Methadone and buprenorphine are opioid derivates that are used as opioid maintenance therapies. They are commonly used to treat opioid dependency in HIV infected substance abusers, but their effects on monocyte migration relevant to the development of cognitive impairment are not well characterized.

CONCLUSION

Here, we will discuss the effects of opioids and opioid maintenance therapies on the inflammatory functions of monocytes and macrophages that are related to the development of neuroinflammation in the context of HIV infection.

Importance of Autophagy in Mediating Human Immunodeficiency Virus (HIV) and Morphine-Induced Metabolic Dysfunction and Inflammation in Human Astrocytes

Under physiological conditions, the function of astrocytes in providing brain metabolic support is compromised under pathophysiological conditions caused by human immunodeficiency virus (HIV) and opioids. Herein, we examined the role of autophagy, a lysosomal degradation pathway important for cellular homeostasis and survival, as a potential regulatory mechanism during pathophysiological conditions in primary human astrocytes. Blocking autophagy with small interfering RNA (siRNA) targeting BECN1, but not the Autophagy-related 5 (ATG5) gene, caused a significant decrease in HIV and morphine-induced intracellular calcium release. On the contrary, inducing autophagy pharmacologically with rapamycin further enhanced calcium release and significantly reverted HIV and morphine-decreased glutamate uptake. Furthermore, siBeclin1 caused an increase in HIV-induced nitric oxide (NO) release, while viral-induced NO in astrocytes exposed to rapamycin was decreased. HIV replication was significantly attenuated in astrocytes transfected with siRNA while significantly induced in astrocytes exposed to rapamycin. Silencing with siBeclin1, but not siATG5, caused a significant decrease in HIV and morphine-induced interleukin (IL)-8 and tumor necrosis factor alpha (TNF-α) release, while secretion of IL-8 was significantly induced with rapamycin. Mechanistically, the effects of siBeclin1 in decreasing HIV-induced calcium release, viral replication, and viral-induced cytokine secretion were associated with a decrease in activation of the nuclear factor kappa B (NF-κB) pathway.

Long-term morphine delivery via slow release morphine pellets or osmotic pumps: Plasma concentration, analgesia, and naloxone-precipitated withdrawal

AIMS

Slow-release morphine sulfate pellets and osmotic pumps are common routes of chronic morphine delivery in mouse models, but direct comparisons of these drug delivery systems are lacking. In this study, we assessed the efficacy of slow-release pellets versus osmotic pumps in delivering morphine to adult mice.

MAIN METHODS

Male C57BL/6NCr mice (8weeksold) were implanted subcutaneously with slow-release pellets (25mg morphine sulfate) or osmotic pumps (64mg/mL, 1.0μL/h). Plasma morphine concentrations were quantified via LC-MS/MS, analgesic efficacy was determined by tail flick assay, and dependence was assessed with naloxone-precipitated withdrawal behaviors (jumping) and physiological effects (excretion, weight loss).

KEY FINDINGS

Morphine pellets delivered significantly higher plasma drug concentrations compared to osmotic pumps, which were limited by the solubility of the morphine sulfate and pump volume/flow rate. Within 96h post-implantation, plasma morphine concentrations were indistinguishable in pellet vs. pump-treated samples. While osmotic pump did not have an antinociceptive effect in the tail flick assay, pumps and pellets induced comparable dependence symptoms (naloxone-precipitated jumping behavior) from 24-72h post-implantation.

SIGNIFICANCE

In this study, we compared slow-release morphine pellets to osmotic minipumps for morphine delivery in mice. We found that osmotic pumps and subcutaneous morphine sulfate pellets yielded significantly different pharmacokinetics over a 7-day period, and as a result significantly different antinociceptive efficacy. Nonetheless, both delivery methods induced dependence as measured by naloxone-precipitated withdrawal.

Lyme and Dopaminergic Function: Hypothesizing Reduced Reward Deficiency Symptomatology by Regulating Dopamine Transmission

The principal vector of Lyme disease in the United States is Ixodes scapularis: black legged or deer ticks. There is increased evidence that those infected may be plagued by anxiety or depression as well. Researchers have identified transcripts coding for two putative cytosolic sulfotransferases in these ticks, which recognized phenolic monoamines as their substrates. It is hypothesized that protracted Lyme disease sequelae may be due to impairment of dopaminergic function of the brain reward circuitry. The subsequent recombinant proteins exhibited sulfotransferase function against two neurotransmitters: dopamine and octopamine. This, in itself, can reduce dopamine function leading to many Reward Deficiency Syndrome behaviors, including depression and possibly, anxiety. In fact, it was shown that activity of Ixosc Sult 1 and Sult 2 in the Ixodid tick salivary glands might contain inactivation of the salivation signal through sulfonation of either dopamine or octopamine. This infraction results in a number of clinically observed mood changes, such as anxiety and depression. In fact, there are common symptoms observed for both Parkinson and Lyme diseases. The importance of understanding the mechanistic and neurobiological effects of Lyme on the central nervous system (CNS) provides the basis for pro-dopamine regulation as a treatment. WC 195

The Role of HIV Infection in Neurologic Injury

The central nervous system (CNS) is a very challenging HIV-1 sanctuary, in which HIV-1 replication is established early on during acute infection and can persist despite potent antiretroviral treatments. HIV-1 infected macrophages play a pivotal role acting as vehicles for HIV-1 to spread into the brain, and can be the major contributor of an early compartmentalization. HIV-1 infection in CNS may lead to a broad spectrum of neurological syndromes, such as dementia, mild neurocognitive disorders, and asymptomatic impairment. These clinical manifestations are caused by the release of neurotoxins from infected cells (mainly macrophages), and also by several HIV-1 proteins, able to activate cell-signaling involved in the control of cellular survival and apoptosis. This review is aimed at highlighting the virological aspects associated with the onset of neurocognitive disorders and at addressing the novel therapeutic approaches to stop HIV-1 replication in this critical sanctuary.

Chronic distress and the vulnerable host: a new target for HIV treatment and prevention?

Pathologic stress (distress) disturbs immune, cardiovascular, metabolic, and behavioral homeostasis. Individuals living with HIV and those at risk are vulnerable to stress disorders. Corticotropin-releasing hormone (CRH) is critical in neuroendocrine immune regulation. CRH, a neuropeptide, is distributed in the central and peripheral nervous systems and acts principally on CRH receptor type 1 (CRHR1). CRH in the brain modulates neuropsychiatric disorders. CRH and stress modulation of immunity is two-pronged; there is a direct action on hypothalamic-pituitary-adrenal secretion of glucocorticoids and through immune organ sympathetic innervation. CRH is a central and systemic proinflammatory cytokine. Glucocorticoids and their receptors have gene regulatory actions on viral replication and cause central and systemic immune suppression. CRH and stress activation contributes to central nervous system (CNS) viral entry important in HIV-associated neurocognitive disorders and HIV-associated dementia. CNS CRH overproduction short-circuits reward, executive, and emotional control, leading to addiction, cognitive impairment, and psychiatric comorbidity. CRHR1 is an important therapeutic target for medication development. CRHR1 antagonist clinical trials have focused on psychiatric disorders with little attention paid to neuroendocrine immune disorders. Studies of those with HIV and those at risk show that concurrent stress-related disorders contribute to higher morbidity and mortality; stress-related conditions, addiction, immune dysfunction, and comorbid psychiatric illness all increase HIV transmission. Neuropsychiatric disease, chronic inflammation, and substance abuse are endemic, and chronic distress is a pathologic factor. It is being understood that stress and CRH are fundamental to neuroendocrine immunity; therapeutic interventions with existing and novel agents hold promise for restoring homeostasis, reducing morbidity and mortality for those with HIV and possibly reducing future disease transmission.