Opioid and neuroHIV Comorbidity - Current and Future Perspectives

Cognitive impairment in people living with HIV: mechanisms, controversies, and future perspectives

Despite the dramatic decrease in HIV-associated neurocognitive impairment (NCI) in the combined antiretroviral treatment (cART) era, subtler neuropsychological complications remain prevalent. In this review, we discuss the changing pathophysiology of HIV-associated NCI, considering recent evidence of HIV neuropathogenesis, and the pivotal role of cART. Furthermore, we address the multifactorial nature of NCI in people living with HIV, including legacy and ongoing insults to the brain, as well as host-specific factors. We also summarize the ongoing debate about the refinement of diagnostic criteria, exploring the strengths and limitations of these recent approaches. Finally, we present current research in NCI management in people living with HIV and highlight the need for using both pharmacological and nonpharmacological pathways toward a holistic approach.

Examining the effects of the HIV-1 protein Tat and morphine on antiretroviral accumulation and distribution within the brain

Despite combination antiretroviral therapy effectively suppressing HIV within the periphery, neuro-acquired HIV (neuroHIV) remains a significant problem and approximately half of people living with HIV will experience HIV-associated neurocognitive disorders (HAND). Concurrent opioid use exacerbates neuroHIV by promoting neuroinflammation, neuronal injury and synaptodendritic culling, viral replication, and potentially altering antiretroviral concentrations within the brain. The present study examined the effects of HIV and morphine co-exposure on the accumulation and spatial distribution of antiretroviral drugs across multiple regions within the brain in an HIV-1 Tat transgenic mouse model by using infrared-matrix-assisted laser desorption electrospray ionization mass spectrometry imaging (IR-MALDESI MSI). Morphine exposure uniquely decreased antiretroviral concentrations in anterior cerebral (primary motor and somatosensory) cortices, corpus collosum (anterior forceps), caudoputamen, nucleus accumbens, and posterior regions including the hippocampus, corpus callosum (main body), cerebral cortex (somatosensory and auditory cortices), thalamus, and hypothalamus. Interestingly, male mice experienced greater morphine-associated decreases in antiretroviral concentrations than females. The study also assessed whether changes in antiretroviral concentrations were linked with inflammation in astroglia, assessed through the measurement of astroglial activation using glial fibrillary acidic protein (GFAP) as a marker. Alterations in antiretroviral concentrations co-registering with areas of astroglial activation exhibited sex-specific treatment differences. This study highlights the intricate interplay between HIV, opioids, and antiretroviral drugs within the CNS, elucidating distinct regional and sex variations in responsiveness. Our findings emphasize the identification of vulnerabilities within the neural landscape and underscore the necessity of carefully monitoring opioid use to maintain the efficacy of antiretroviral therapies.

Adult Human Brain Tissue Cultures to Study NeuroHIV

HIV-associated neurocognitive disorders (HAND) persist under antiretroviral therapy as a complex pathology that has been difficult to study in cellular and animal models. Therefore, we generated an ex vivo human brain slice model of HIV-1 infection from surgically resected adult brain tissue. Brain slice cultures processed for flow cytometry showed >90% viability of dissociated cells within the first three weeks in vitro, with parallel detection of astrocyte, myeloid, and neuronal populations. Neurons within brain slices showed stable dendritic spine density and mature spine morphologies in the first weeks in culture, and they generated detectable activity in multi-electrode arrays. We infected cultured brain slices using patient-matched CD4+ T-cells or monocyte-derived macrophages (MDMs) that were exposed to a GFP-expressing R5-tropic HIV-1 in vitro. Infected slice cultures expressed viral RNA and developed a spreading infection up to 9 days post-infection, which were significantly decreased by antiretrovirals. We also detected infected myeloid cells and astrocytes within slices and observed minimal effect on cellular viability over time. Overall, this human-centered model offers a promising resource to study the cellular mechanisms contributing to HAND (including antiretroviral toxicity, substance use, and aging), infection of resident brain cells, and new neuroprotective therapeutics.

Antiretroviral drugs from multiple classes induce loss of excitatory synapses between hippocampal neurons in culture

Introduction: Antiretroviral (ARV) drugs have improved prognoses for people living with HIV. However, HIV-associated neurocognitive disorders (HAND) persist despite undetectable viral loads. Some ARVs have been linked to neuropsychiatric effects that may contribute to HAND. Synapse loss correlates with cognitive decline in HAND and synaptic deficits may contribute to the neuropsychiatric effects of ARV drugs. Methods: Using an automated high content assay, rat hippocampal neurons in culture expressing PSD95-eGFP to label glutamatergic synapses and mCherry to fill neuronal structures were imaged before and after treatment with 25 clinically used ARVs. Results and Discussion: At a concentration of 10 μM the protease inhibitors nelfinavir and saquinavir, the non-nucleoside reverse transcriptase inhibitors etravirine and the 8-OH metabolite of efavirenz, the integrase inhibitor bictegravir, and the capsid inhibitor lenacapavir produced synaptic toxicity. Only lenacapavir produced synapse loss at the nanomolar concentrations estimated free in the plasma, although all 4 ARV drugs induced synapse loss at Cmax. Evaluation of combination therapies did not reveal synergistic synaptic toxicity. Synapse loss developed fully by 24 h and persisted for at least 3 days. Bictegravir-induced synapse loss required activation of voltage-gated Ca2+ channels and bictegravir, etravirine, and lenacapavir produced synapse loss by an excitotoxic mechanism. These results indicate that select ARV drugs might contribute to neuropsychiatric effects in combination with drugs that bind serum proteins or in disease states in which synaptic function is altered. The high content imaging assay used here provides an efficient means to evaluate new drugs and drug combinations for potential CNS toxicity.

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.

Is the Central Nervous System Reservoir a Hurdle for an HIV Cure?

There is currently no cure for HIV infection although adherence to effective antiretroviral therapy (ART) suppresses replication of the virus in blood, increases CD4+ T-cell counts, reverses immunodeficiency, and increases life expectancy. Despite these substantial advances, ART is a lifelong treatment for people with HIV (PWH) and upon cessation or interruption, the virus quickly rebounds in plasma and anatomic sites, including the central nervous system (CNS), resulting in disease progression. With recent advances in quantifying viral burden, detection of genetically intact viral genomes, and isolation of replication-competent virus from brain tissues of PWH receiving ART, it has become apparent that the CNS viral reservoir (largely comprised of macrophage type cells) poses a substantial challenge for HIV cure strategies. Other obstacles impacting the curing of HIV include ageing populations, substance use, comorbidities, limited antiretroviral drug efficacy in CNS cells, and ART-associated neurotoxicity. Herein, we review recent findings, including studies of the proviral integration sites, reservoir decay rates, and new treatment/prevention strategies in the context of the CNS, together with highlighting the next steps for investigations of the CNS as a viral reservoir.

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.

Application of infrared matrix-assisted laser desorption electrospray ionization mass spectrometry for morphine imaging in brain tissue

Here, we present a method developed for the analysis of spatial distributions of morphine in mouse brain tissue using infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) coupled to a Q Exactive Plus mass spectrometer. The method is also capable of evaluating spatial distributions of the antiretroviral drug abacavir. To maximize sensitivity to morphine, we analyze various Orbitrap mass spectrometry acquisition modes utilizing signal abundance and frequency of detection as evaluation criteria. We demonstrate detection of morphine in mouse brain and establish that the selected ion monitoring mode provides 2.5 times higher sensitivity than the full-scan mode. We find that distributions of morphine and abacavir are highly correlated with the Pearson correlation coefficient R = 0.87. Calibration showed that instrument response is linear up to 40 pg/mm2 (3.8 μg/g of tissue).

Astrocytes: Role in pathogenesis and effect of commonly misused drugs in the HIV infected brain

The roles of astrocytes as reservoirs and producers of a subset of viral proteins in the HIV infected brain have been studied extensively as a key to understanding HIV-associated neurocognitive disorders (HAND). However, their comprehensive role in the context of intersecting substance use and neurocircuitry of the reward pathway and HAND has yet to be fully explained. Use of methamphetamines, cocaine, or opioids in the context of HIV infection have been shown to lead to a faster progression of HAND. Glutamatergic, dopaminergic, and GABAergic systems are implicated in the development of HAND-induced cognitive impairments. A thorough review of scientific literature exploring the variety of mechanisms in which these drugs exert their effects on the HIV brain and astrocytes has revealed marked areas of convergence in overexcitation leading to increased drug-seeking behavior, inflammation, apoptosis, and irreversible neurotoxicity. The present review investigates astrocytes, the neural pathways, and mechanisms of drug disruption that ultimately play a larger holistic role in terms of HIV progression and drug use. There are opportunities for future research, therapeutic intervention, and preventive strategies to diminish HAND in the subset population of patients with HIV and substance use disorder.

Beyond the Syndemic of Opioid Use Disorders and HIV: The Impact of Opioids on Viral Reservoirs

People with HIV are more likely to have opioid use disorder and to be prescribed opioids for chronic pain than the general population; however, the effects of opioids on the immune system and HIV persistence have not been fully elucidated. Opioids may affect HIV reservoirs during their establishment, maintenance, and reactivation by enhancing HIV infectivity and replication due to upregulation of co-receptors and impairment of innate antiviral responses. Opioids may also modulate immune cell functioning and microbial translocation and can reverse viral latency. In this review, we summarize the current findings for and against the modulating effects of opioids on HIV cellular and anatomical reservoirs, highlighting the current limitations that affect in vitro, ex vivo, and in vivo studies in the field. We propose further research targets and potential strategies to approach this topic.

Human iPSC-derived brain organoids: A 3D mini-brain model for studying HIV infection

The brain is one of the important reservoir sites for HIV persistent/latent infection that often leads to HIV-associated neurocognitive disorders (HAND). However, HIV dynamics in the brain is an understudied area and little is known about mechanisms underlying the development and progression of HAND. This issue is mainly due to the lack of suitable in vitro models that can recapitulate the cellular and molecular complexity of the human brain. Hence, there is an urgent need for such models to study HIV neuropathogenesis and to develop therapeutics for HAND. The emergence of three-dimensional (3D) brain organoids generated from induced pluripotent stem cells (iPSCs) has now provided a clinically relevant in vitro model to study HIV brain infection and neuropathogenesis. Recently, there have been a noticeable number of publications that demonstrate the feasibility and advantages of this model for studies of neurobiology and brain disorders as well as HIV infection. Here, we describe the development of iPSC-derived human microglia-containing brain organoids, including advantages/challenges, and focus on their applicability for modeling HIV brain infection.

Differential Regulation of Tachykinin and Opioid System Gene Expression in Brain and Immune Cells of Chronic Binge Alcohol-Treated Simian Immunodeficiency Virus-Infected Macaques

People living with HIV have a high likelihood of at-risk alcohol use and are at increased risk for neurocognitive decline. The underlying mechanisms involved in HIV-associated neurocognitive disorder (HAND) are not completely understood. Previously, we showed that chronic binge alcohol (CBA) administration produced behavioral deficits in non antiretroviral therapy (ART)-treated simian immunodeficiency virus (SIV)-infected macaques. Moreover, we observed that CBA/SIV enhanced neuroinflammatory gene expression and attenuated growth factor signaling in the frontal cortex (FC) and basal ganglia, effects that were partially ameliorated by ART. We hypothesized that the neuroinflammatory and growth factor changes observed could be associated with alterations in opioid, tachykinin, and endocannabinoid gene expression. Furthermore, we proposed that gene expression patterns in peripheral blood mononuclear cells (PBMCs) could serve as an indicator of expression changes in the brain (FC). We examined gene expression patterns of opioid, tachykinin, and endocannabinoid systems in FC and PBMCs isolated from CBA/SIV macaques. Expression of targeted genes as determined by reverse transcription-quantitative polymerase chain reaction was analyzed in relation to CBA, ART, plasma, and brain viral loads (PVL and BVL, respectively) and compared with baseline (PBMC) or FC from SIV- controls. FC expression of ORM1, POMC, and TACR1 was negatively associated with PVL (p = .03, .002, .05 respectively). FC expression of TAC1 was positively associated with CBA exposure (p = .05). PBMC expression of DAGLA was positively associated with CBA exposure; but negatively associated with combined CBA/ART exposure (p = .03). Our findings reflect the complex interactions of SIV, CBA, and ART in modulating opioid and tachykinin system gene expression. Contrary to our prediction, results did not reveal parallel changes (in magnitude or direction) in PBMC and FC gene expression. Further studies are warranted to determine the relevance of these transcriptional changes in modulating HAND-related behaviors resulting from at-risk alcohol use and HIV/SIV exposure.

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.

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.

Casein Kinase 2 Mediates HIV- and Opioid-Induced Pathologic Phosphorylation of TAR DNA Binding Protein 43 in the Basal Ganglia

SUMMARY STATEMENT

HIV/HIV-1 Tat and morphine independently increase pathologic phosphorylation of TAR DNA binding protein 43 in the striatum. HIV- and opioid-induced pathologic phosphorylation of TAR DNA binding protein 43 may involve enhanced CK2 activity and protein levels.

Morphine suppresses peripheral responses and transforms brain myeloid gene expression to favor neuropathogenesis in SIV infection

The twin pandemics of opioid abuse and HIV infection can have devastating effects on physiological systems, including on the brain. Our previous work found that morphine increased the viral reservoir in the brains of treated SIV-infected macaques. In this study, we investigated the interaction of morphine and SIV to identify novel host-specific targets using a multimodal approach. We probed systemic parameters and performed single-cell examination of the targets for infection in the brain, microglia and macrophages. Morphine treatment created an immunosuppressive environment, blunting initial responses to infection, which persisted during antiretroviral treatment. Antiretroviral drug concentrations and penetration into the cerebrospinal fluid and brain were unchanged by morphine treatment. Interestingly, the transcriptional signature of both microglia and brain macrophages was transformed to one of a neurodegenerative phenotype. Notably, the expression of osteopontin, a pleiotropic cytokine, was significantly elevated in microglia. This was especially notable in the white matter, which is also dually affected by HIV and opioids. Increased osteopontin expression was linked to numerous HIV neuropathogenic mechanisms, including those that can maintain a viral reservoir. The opioid morphine is detrimental to SIV/HIV infection, especially in the brain.

HIV-1 Tat reduces apical dendritic spine density throughout the trisynaptic pathway in the hippocampus of male transgenic mice

Nearly one-third of persons infected with HIV-1 (PWH) develop HIV-associated neurocognitive disorders (HAND), which can be exacerbated by exposure to opioids. The impact of opioids on HIV-induced alterations in neuronal plasticity is less well understood. Both morphine exposure and HIV have been shown to disrupt synaptic growth and stability in the hippocampus suggesting a potential site of convergence for their deleterious effects. In the present study, we examined the density of dendritic spines in CA1 and CA3 pyramidal neurons, and granule neurons within the dentate gyrus representing the hippocampal trisynaptic pathway after short-term exposure to the HIV transactivator of transcription (Tat) protein and morphine. We exposed inducible male, HIV-1 Tat transgenic mice to escalating doses of morphine (10-40 mg/kg, b.i.d.) and examined synaptodendritic structure in Golgi-impregnated hippocampal neurons. HIV-1 Tat, but not morphine, systematically reduced the density of apical, but not basilar, dendrites of CA1 and CA3 pyramidal neurons, and granule neuronal apical dendrites, suggesting the coordinated loss of specific synaptic interconnections throughout the hippocampal trisynaptic pathway.

Comparing Perceptions of Addiction Treatment between Professionals and Individuals in Recovery

Background: The purpose of this qualitative study was to compare and contrast the differing perspectives of service users and professionals regarding the current substance use disorders (SUD) services provided in Summit County, Ohio. Seven focus groups were conducted with 44 participants (52.3% male, mean age 46 years), including 15 individuals in recovery, 16 direct service providers, and 13 executive directors. The participants were asked about three areas: (1) effective treatment for SUD, (2) challenges for persons with SUD, and (3) suggestions for improving SUD treatment outcomes. The data were analyzed and coded according to major themes. Results: While there were numerous emergent themes that were concordant between service use and professionals, several differing themes between the groups were also identified. First, participants disagreed on the effectiveness of medication-assisted treatment/Medications for Opioid Use Disorder. Second, professionals identified trauma, stigma, "one-size-fits-all" approach to treatment, and limitations set by managed care act as barriers to treatment, whereas individuals in recovery reported difficulty dealing with feelings, feeling of being rushed into recovery, and the lack of long-term recovery plans as the most significant barriers. Lastly, in order to improve treatment outcomes, professionals emphasized the importance of education unlike individuals in recovery who identified sober supports as the most important factor. Conclusion: This study identified challenges in SUD recovery and highlights essential areas for consideration when developing and implementing SUD treatment. The findings can be used as guidelines to provide better services to individuals with SUDs.Supplemental data for this article is available online at https://doi.org/10.1080/10826084.2022.2058706 .

Dextromethorphan Dampens Neonatal Astrocyte Activation and Endoplasmic Reticulum Stress Induced by Prenatal Exposure to Buprenorphine

Prenatal exposure to buprenorphine renders offspring vulnerable to cerebral impairments. In this study, our data demonstrate, for the first time, that prenatal exposure to buprenorphine escalates astrocyte activation concurrent with indications of endoplasmic reticulum (ER) stress in the hippocampi of neonates, and this can be prevented by the coadministration of dextromethorphan with buprenorphine. Furthermore, dextromethorphan can inhibit the accumulation of GPR37 in the hippocampus of newborns caused by buprenorphine and is accompanied by the proapoptotic ER stress response that involves the procaspase-3/CHOP pathway. Primary astrocyte cultures derived from the neonates of the buprenorphine group also displayed aberrant ER calcium mobilization and elevated basal levels of cyclooxygenase-2 (COX-2) at 14 days in vitro while showing sensitivity to lipopolysaccharide-activated expression of COX-2. Similarly, these long-lasting defects in the hippocampus and astrocytes were abolished by dextromethorphan. Our findings suggest that prenatal exposure to buprenorphine might instigate long-lasting effects on hippocampal and astrocytic functions. The beneficial effects of prenatal coadministration of dextromethorphan might be, at least in part, attributed to its properties in attenuating astrocyte activation and hippocampal ER stress in neonates.

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.

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.

Unraveling neuroHIV in the Presence of Substance Use Disorders

This special issue contains 10 invited review papers that highlighted and extended the presentations at the NIDA-sponsored workshop "Unraveling NeuroAIDS in the Presence of Substance Use Disorders" at the 25th Society on NeuroImmune Pharmacology conference in 2019. The topics covered by these papers focused on the interactive, additive or synergistic effects of substance use disorders (SUD) with HIV infection on the immune system and on neuropathogenesis. These papers reviewed four categories of substances of abuse (opioids, tobacco, stimulants, and cannabis) and how comorbid HIV infection (including models with HIV proteins, HIV transgenic rodent models and SIV) might further impact the dysregulated dopaminergic and immune systems, and the subsequent neuropathogenesis and behavioral disorders known as HIV-associated neurological disorders (HAND). These reviews provided detailed background knowledge regarding how each of these addictive substances and HIV individually or collectively affected the immune system at the cellular, molecular and system levels, and the subsequent clinical and behavioral outcomes. The authors also identified gaps, confounds or constraints in the current disease models and approaches, and proposed future research directions.

Morphine and HIV-1 Tat interact to cause region-specific hyperphosphorylation of tau in transgenic mice

Opiate abuse is prevalent among HIV-infected individuals and may exacerbate HIV-associated age-related neurocognitive disorders. However, the extent to which HIV and opiates converge to accelerate pathological traits indicative of brain aging remains unknown. The pathological phospho-isotypes of tau (pSer396, pSer404, pThr205, pSer202, and pThr181) and the tau kinases GSK3β and CDK5/p35 were explored in the striatum, hippocampus, and prefrontal cortex of inducible male and female HIV-1 Tat-transgenic mice, with some receiving escalating doses of morphine for 2 weeks. In the striatum of male mice, pSer396 was increased by co-exposure to morphine and Tat as compared to all other groups. Striatal pSer404 and pThr205 were increased by Tat alone, while pSer202 and pThr181 were unchanged. A comparison between Tat-transgenic female and male mice revealed disparate outcomes for pThr205. No other sex-related changes to tau phosphorylation were observed. In the hippocampus, Tat increased pSer396, while other phosphorylation sites were unchanged and pSer202 was not detected. In the prefrontal cortex, morphine increased pSer396 levels, which were unaffected by Tat, while other phosphorylation sites were unaffected. Assessment of tau kinases revealed no changes to striatal GSK3β (phosphorylated or total) or the total CDK5 levels. Striatal levels of phosphorylated CDK5 and p35, the activator of CDK5, were increased by Tat and with morphine co-exposure, respectively. P35 levels positively correlated with those of pSer396 with Tat and morphine co-exposure. The results reveal region-specific hyperphosphorylation of tau induced by exposure to morphine, Tat, and unique morphine and Tat interactions.