Expression of the mannose receptor CD206 in HIV and SIV encephalitis: a phenotypic switch of brain perivascular macrophages with virus infection

Perivascular macrophages in cerebrovascular diseases

Cerebrovascular diseases are a major cause of stroke and dementia, both requiring long-term care. These diseases involve multiple pathophysiologies, with mitochondrial dysfunction being a crucial contributor to the initiation of inflammation, apoptosis, and oxidative stress, resulting in injuries to neurovascular units that include neuronal cell death, endothelial cell death, glial activation, and blood-brain barrier disruption. To maintain brain homeostasis against these pathogenic conditions, brain immune cells, including border-associated macrophages and microglia, play significant roles as brain innate immunity cells in the pathophysiology of cerebrovascular injury. Although microglia have long been recognized as significant contributors to neuroinflammation, attention has recently shifted to border-associated macrophages, such as perivascular macrophages (PVMs), which have been studied based on their crucial roles in the brain. These cells are strategically positioned around the walls of brain vessels, where they mainly perform critical functions, such as perivascular drainage, cerebrovascular flexibility, phagocytic activity, antigen presentation, activation of inflammatory responses, and preservation of blood-brain barrier integrity. Although PVMs act as scavenger and surveillant cells under normal conditions, these cells exert harmful effects under pathological conditions. PVMs detect mitochondrial dysfunction in injured cells and implement pathological changes to regulate brain homeostasis. Therefore, PVMs are promising as they play a significant role in mitochondrial dysfunction and, in turn, disrupt the homeostatic condition. Herein, we summarize the significant roles of PVMs in cerebrovascular diseases, especially ischemic and hemorrhagic stroke and dementia, mainly in correlation with inflammation. A better understanding of the biology and pathobiology of PVMs may lead to new insights on and therapeutic strategies for cerebrovascular diseases.

Arresting the bad seed: HDAC3 regulates proliferation of different microglia after ischemic stroke

The accumulation of self-renewed polarized microglia in the penumbra is a critical neuroinflammatory process after ischemic stroke, leading to secondary demyelination and neuronal loss. Although known to regulate tumor cell proliferation and neuroinflammation, HDAC3's role in microgliosis and microglial polarization remains unclear. We demonstrated that microglial HDAC3 knockout (HDAC3-miKO) ameliorated poststroke long-term functional and histological outcomes. RNA-seq analysis revealed mitosis as the primary process affected in HDAC3-deficent microglia following stroke. Notably, HDAC3-miKO specifically inhibited proliferation of proinflammatory microglia without affecting anti-inflammatory microglia, preventing microglial transition to a proinflammatory state. Moreover, ATAC-seq showed that HDAC3-miKO induced closing of accessible regions enriched with PU.1 motifs. Overexpressing microglial PU.1 via an AAV approach reversed HDAC3-miKO-induced proliferation inhibition and protective effects on ischemic stroke, indicating PU.1 as a downstream molecule that mediates HDAC3's effects on stroke. These findings uncovered that HDAC3/PU.1 axis, which mediated differential proliferation-related reprogramming in different microglia populations, drove poststroke inflammatory state transition, and contributed to pathophysiology of ischemic stroke.

Mural cells interact with macrophages in the dura mater to regulate CNS immune surveillance

The central nervous system (CNS) tightly regulates access of circulating immune cells. Immunosurveillance is therefore managed in the meninges at the borders of the CNS. Here, we demonstrated that mural cells, which include pericytes and smooth muscle cells, decreased coverage around blood vessels in the dura, the outermost layer of the meninges, and upregulated gene pathways involved in leukocyte migration in presymptomatic experimental autoimmune encephalomyelitis (EAE). Partially depleting mural cells promoted the trafficking of CNS antigen-specific T cells to the dura in a process that depended on resident antigen-presenting cells, thereby increasing susceptibility to passive EAE. Mechanistically, mural cells physically contacted macrophages in the dura and transferred cytoplasmic components, including processing bodies (RNA granules shown to reprogram transcriptomes), which were critical to suppress antigen-dependent T helper (TH) cell activation and TH17 differentiation. Our study revealed a mechanism by which mural cell-macrophage interactions regulate the trafficking of CNS antigen-specific T cells to the dura.

Simian immunodeficiency virus-infected rhesus macaques with AIDS co-develop cardiovascular pathology and encephalitis

Despite effective antiretroviral therapy, HIV co-morbidities remain where central nervous system (CNS) neurocognitive disorders and cardiovascular disease (CVD)-pathology that are linked with myeloid activation are most prevalent. Comorbidities such as neurocogntive dysfunction and cardiovascular disease (CVD) remain prevalent among people living with HIV. We sought to investigate if cardiac pathology (inflammation, fibrosis, cardiomyocyte damage) and CNS pathology (encephalitis) develop together during simian immunodeficiency virus (SIV) infection and if their co-development is linked with monocyte/macrophage activation. We used a cohort of SIV-infected rhesus macaques with rapid AIDS and demonstrated that SIV encephalitis (SIVE) and CVD pathology occur together more frequently than SIVE or CVD pathology alone. Their co-development correlated more strongly with activated myeloid cells, increased numbers of CD14+CD16+ monocytes, plasma CD163 and interleukin-18 (IL-18) than did SIVE or CVD pathology alone, or no pathology. Animals with both SIVE and CVD pathology had greater numbers of cardiac macrophages and increased collagen and monocyte/macrophage accumulation, which were better correlates of CVD-pathology than SIV-RNA. Animals with SIVE alone had higher levels of activated macrophage biomarkers and cardiac macrophage accumulation than SIVnoE animals. These observations were confirmed in HIV infected individuals with HIV encephalitis (HIVE) that had greater numbers of cardiac macrophages and fibrosis than HIV-infected controls without HIVE. These results underscore the notion that CNS and CVD pathologies frequently occur together in HIV and SIV infection, and demonstrate an unmet need for adjunctive therapies targeting macrophages.

Monocytes in the Characterization of Pain in Palliative Patients with Severe Dementia-A Pilot Study

In assessing and managing pain, when obtaining a self-report is impossible, therapeutic decision-making becomes more challenging. This study aimed to investigate whether monocytes and some membrane monocyte proteins, identified as a cluster of differentiation (CD), could be potential non-invasive peripheral biomarkers in identifying and characterizing pain in patients with severe dementia. We used 53 blood samples from non-oncological palliative patients, 44 patients with pain (38 of whom had dementia) and 0 without pain or dementia (controls). We evaluated the levels of monocytes and their subtypes, including classic, intermediate, and non-classic, and characterized the levels of specific phenotypic markers, namely CD11c, CD86, CD163, and CD206. We found that the relative concentrations of monocytes, particularly the percentage of classic monocytes, may be a helpful pain biomarker. Furthermore, the CD11c expression levels were significantly higher in patients with mixed pain, while CD163 and CD206 expression levels were significantly higher in patients with nociceptive pain. These findings suggest that the levels of monocytes, particularly the classic subtype, and their phenotype markers CD11c, CD163, and CD206 could serve as pain biomarkers in patients with severe dementia.

Heterogeneity and developmental dynamics of LYVE-1 perivascular macrophages distribution in the mouse brain

Brain perivascular macrophages (PVMs) are border-associated macrophages situated along blood vessels in the Virchow-Robin space and are thus found at a unique anatomical position between the endothelium and the parenchyma. Owing to their location and phagocytic capabilities, PVMs are regarded as important components that regulate various aspects of brain physiology in health and pathophysiological states. Here, we used LYVE-1 to identify PVMs in the mouse brain using brain-tissue sections and cleared whole-brains to learn about how they are distributed within the brain and across different developmental postnatal stages. We find that LYVE-1⁺ PVMs associate with the vasculature in different patterns and proportions depending on vessel diameter or arterio-venous differentiation. LYVE-1⁺ PVMs relate to blood vessels in a brain-region-dependent manner. We show that their postnatal distribution is developmentally dynamic and peaks at P10-P20 depending on the brain region. We further demonstrate that their density is reduced in the APP/PS1 mouse model of Alzheimer's Disease proportionally to beta-amyloid deposits. In conclusion, our results reveal unexpected heterogeneity and dynamics of LYVE-1⁺ PVMs, with selective coverage of brain vasculature, compatible with potential unexplored roles for this population of PVMs in postnatal development, and in regulating brain functions in steady-state and disease conditions.

Influence of Galectin-3 on the Innate Immune Response during Experimental Cryptococcosis

Cryptococcus neoformans, the causative agent of cryptococcosis, is the primary fungal pathogen that affects the immunocompromised individuals. Galectin-3 (Gal-3) is an animal lectin involved in both innate and adaptive immune responses. The present study aimed to evaluate the influence of Gal-3 on the C. neoformans infection. We performed histopathological and gene profile analysis of the innate antifungal immunity markers in the lungs, spleen, and brain of the wild-type (WT) and Gal-3 knockout (KO) mice during cryptococcosis. These findings suggest that Gal-3 absence does not cause significant histopathological alterations in the analyzed tissues. The expression profile of the genes related to innate antifungal immunity showed that the presence of cryptococcosis in the WT and Gal-3 KO animals, compared to their respective controls, promoted the upregulation of the pattern recognition receptor (PRR) responsive to mannose/chitin (mrc1) and a gene involved in inflammation (ccr5), as well as the downregulation of the genes related to signal transduction (card9, fos, ikbkb, jun) and PRRs (cd209a, colec12, nptx1). The absence of Gal-3, in fungal infection, a positively modulated gene involved in phagocytosis (sftpd) and negatively genes involved in signal transduction (syk and myd88), proinflammatory cytokines il-1β and il-12b and cd209a receptor. Therefore, our results suggest that Gal-3 may play an essential role in the development of antifungal immune responses against cryptococcosis.

The structural basis of accelerated host cell entry by SARS-CoV-2†

Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) is the causative agent of the pandemic coronavirus disease 2019 (COVID‐19) that exhibits an overwhelming contagious capacity over other human coronaviruses (HCoVs). This structural snapshot describes the structural bases underlying the pandemic capacity of SARS‐CoV‐2 and explains its fast motion over respiratory epithelia that allow its rapid cellular entry. Based on notable viral spike (S) protein features, we propose that the flat sialic acid‐binding domain at the N‐terminal domain (NTD) of the S1 subunit leads to more effective first contact and interaction with the sialic acid layer over the epithelium, and this, in turn, allows faster viral ‘surfing’ of the epithelium and receptor scanning by SARS‐CoV‐2. Angiotensin‐converting enzyme 2 (ACE‐2) protein on the epithelial surface is the primary entry receptor for SARS‐CoV‐2, and protein–protein interaction assays demonstrate high‐affinity binding of the spike protein (S protein) to ACE‐2. To date, no high‐frequency mutations were detected at the C‐terminal domain of the S1 subunit in the S protein, where the receptor‐binding domain (RBD) is located. Tight binding to ACE‐2 by a conserved viral RBD suggests the ACE2‐RBD interaction is likely optimal. Moreover, the viral S subunit contains a cleavage site for furin and other proteases, which accelerates cell entry by SARS‐CoV‐2. The model proposed here describes a structural basis for the accelerated host cell entry by SARS‐CoV‐2 relative to other HCoVs and also discusses emerging hypotheses that are likely to contribute to the development of antiviral strategies to combat the pandemic capacity of SARS‐CoV‐2.

TMEM119 as a specific marker of microglia reaction in traumatic brain injury in postmortem examination

The aim of the present study was a refined analysis of neuroinflammation including TMEM119 as a useful microglia-specific marker in forensic assessments of traumatic causes of death, e.g., traumatic brain injury (TBI). Human brain tissue samples were obtained from autopsies and divided into cases with lethal TBI (n = 25) and subdivided into three groups according to their trauma survival time and compared with an age-, gender-, and postmortem interval-matched cohort of sudden cardiovascular fatalities as controls (n = 23). Brain tissue samples next to cortex contusions and surrounding white matter as well as samples of the ipsilateral uninjured brain stem and cerebellum were collected and stained immunohistochemically with antibodies against TMEM119, CD206, and CCR2. We could document the highest number of TMEM119-positive cells in acute TBI death with highly significant differences to the control numbers. CCR2-positive monocytes showed a significantly higher cell count in the cortex samples of TBI cases than in the controls with an increasing number of immunopositive cells over time. The number of CD206-positive M2 microglial cells increased survival time-dependent. After 3 days of survival, the cell number increased significantly in all four regions investigated compared with controls. In sum, we validate a specific and robustly expressed as well as fast reacting microglia marker, TMEM119, which distinguishes microglia from resident and infiltrating macrophages and thus offers a great potential for the estimation of the minimum survival time after TBI.

Chikungunya virus infection induces differential inflammatory and antiviral responses in human monocytes and monocyte-derived macrophages

Chikungunya virus (CHIKV) is a zoonotic arthropod-borne virus that has caused several outbreaks in tropical and subtropical areas worldwide during the last 50 years. The virus is known to target different human cell types throughout the course of infection including epithelial and endothelial cells, fibroblasts, primary monocytes and monocyte-derived macrophages (MDMs). The two latter are phagocytic cell populations of the innate immune system which are involved in some aspects of CHIKV pathogenesis. However, monocytes and macrophages also potentially contribute to the control of viral replication through the expression of different pattern recognition receptors sensing viral pathogens and subsequently, inducing an type I interferone (IFN-I)-dependent antiviral immune response. The aim of this study was to determine the modulation of the expression of Toll-like receptors (TLRs), cytokine secretion capabilities and antiviral factor production in monocytes and MDMs following infection with CHIKV. Moreover, we sought to determine the replication kinetics of CHIKV in these two cell populations. We found that the maximum peak of CHIKV replication was observed between 18- and 24-hours post-infection (hpi), while after that the is strongly reduced. Furthermore, CHIKV infection induced the pro-inflammatory cytokine production starting from the first 6 hpi in both monocytes and MDMs, with similar kinetics but different protein levels. In contrast, the kinetics of transcriptional expression of some TLRs were different between both cell types. In addition, IFN-I, 2',5'-oligoadenylate synthetase 1 (OAS1), and double-stranded RNA-activated protein kinase R (PKR) mRNA levels were detected in response to CHIKV infection of monocytes and MDMs, resulting the highest expression levels at 48 hpi. In conclusion, our data provides evidence that CHIKV infection activates the TLR pathways in primary monocytes and MDMs, which play a crucial role in CHIKV pathogenesis and/or host defense, differentially. However, additional studies are required to determine the functional role of TLRs in monocytes and MDMs.

Vpr Is a VIP: HIV Vpr and Infected Macrophages Promote Viral Pathogenesis

HIV infects several cell types in the body, including CD4+ T cells and macrophages. Here we review the role of macrophages in HIV infection and describe complex interactions between viral proteins and host defenses in these cells. Macrophages exist in many forms throughout the body, where they play numerous roles in healthy and diseased states. They express pattern-recognition receptors (PRRs) that bind viral, bacterial, fungal, and parasitic pathogens, making them both a key player in innate immunity and a potential target of infection by pathogens, including HIV. Among these PRRs is mannose receptor, a macrophage-specific protein that binds oligosaccharides, restricts HIV replication, and is downregulated by the HIV accessory protein Vpr. Vpr significantly enhances infection in vivo, but the mechanism by which this occurs is controversial. It is well established that Vpr alters the expression of numerous host proteins by using its co-factor DCAF1, a component of the DCAF1-DDB1-CUL4 ubiquitin ligase complex. The host proteins targeted by Vpr and their role in viral replication are described in detail. We also discuss the structure and function of the viral protein Env, which is stabilized by Vpr in macrophages. Overall, this literature review provides an updated understanding of the contributions of macrophages and Vpr to HIV pathogenesis.

Quantitative immunohistochemical analysis of myeloid cell marker expression in human cortex captures microglia heterogeneity with anatomical context

Current immunohistochemical methods of studying microglia in the post-mortem human brain do not capture the heterogeneity of microglial function in response to damage and disease. We therefore investigated the expression of eight myeloid cell proteins associated with changes in function alongside Iba1. To study the myeloid cells we used immunohistochemistry on post-mortem human middle temporal gyrus sections from neurologically normal individuals. First we investigated co-labelling between the classical 'activation' marker, HLA-DR and each of the other markers of interest. Significant co-labelling between HLA-DR with CD206, CD32, CD163, or L-Ferritin was observed, although complete overlap of expression of HLA-DR with aforementioned markers was not observed. A qualitative assessment also demonstrated that perivascular macrophages expressed higher levels of the markers of interest we investigated than microglia, suggesting perivascular macrophages show a more phagocytic and antigen presentation state in the human brain. To determine whether the markers of interest were expressed in different functional states, the immunoreactivity for each marker was qualitatively assessed on microglial morphologies. Degenerating marker, L-Ferritin, was specific for dystrophic microglia. We demonstrate that microglial heterogeneity can be investigated in immunohistochemically stain post-mortem human tissue by integrating the single-cell abundance of proteins and cell morphology to infer function.

Myeloid C-Type Lectin Receptors in Tuberculosis and HIV Immunity: Insights Into Co-infection?

C-type lectin receptors (CLRs) are carbohydrate binding pattern recognition receptors (PRRs) which play a central role in host recognition of pathogenic microorganisms. Signaling through CLRs displayed on antigen presenting cells dictates important innate and adaptive immune responses. Several pathogens have evolved mechanisms to exploit the receptors or signaling pathways of the CLR system to gain entry or propagate in host cells. CLR responses to high priority pathogens such as Mycobacterium tuberculosis (Mtb), HIV, Ebola, and others are described and considered potential avenues for therapeutic intervention. Mtb and HIV are the leading causes of death due to infectious disease and have a synergistic relationship that further promotes aggressive disease in co-infected persons. Immune recognition through CLRs and other PRRs are important determinants of disease outcomes for both TB and HIV. Investigations of CLR responses to Mtb and HIV, to date, have primarily focused on single infection outcomes and do not account for the potential effects of co-infection. This review will focus on CLRs recognition of Mtb and HIV motifs. We will describe their respective roles in protective immunity and immune evasion or exploitation, as well as their potential as genetic determinants of disease susceptibility, and as avenues for development of therapeutic interventions. The potential convergence of CLR-driven responses of the innate and adaptive immune systems in the setting of Mtb and HIV co-infection will further be discussed relevant to disease pathogenesis and development of clinical interventions.

Mannose receptor is an HIV restriction factor counteracted by Vpr in macrophages

HIV-1 Vpr is necessary for maximal HIV infection and spread in macrophages. Evolutionary conservation of Vpr suggests an important yet poorly understood role for macrophages in HIV pathogenesis. Vpr counteracts a previously unknown macrophage-specific restriction factor that targets and reduces the expression of HIV Env. Here, we report that the macrophage mannose receptor (MR), is a restriction factor targeting Env in primary human monocyte-derived macrophages. Vpr acts synergistically with HIV Nef to target distinct stages of the MR biosynthetic pathway and dramatically reduce MR expression. Silencing MR or deleting mannose residues on Env rescues Env expression in HIV-1-infected macrophages lacking Vpr. However, we also show that disrupting interactions between Env and MR reduces initial infection of macrophages by cell-free virus. Together these results reveal a Vpr-Nef-Env axis that hijacks a host mannose-MR response system to facilitate infection while evading MR's normal role, which is to trap and destroy mannose-expressing pathogens.

Co-Administration of Curcumin and Artepillin C Induces Development of Brown-Like Adipocytes in Association with Local Norepinephrine Production by Alternatively Activated Macrophages in Mice

Classical brown adipocytes, characterized by interscapular depots, have multilocular fat depots and are known to release excess energy. Recent studies have shown that induction of brown-like adipocytes, also referred to as beige or brite cells, in white adipose tissue (WAT) results in the release of excess energy through mitochondrial heat production via uncoupling protein 1. This has potential a therapeutic strategy for obesity and related diseases as well as classical brown adipocytes. In our previous studies, we found that artepillin C (ArtC, 10 mg/kg body weight), a characteristic constituent of Brazilian propolis, significantly induced the development of brown-like adipocytes in inguinal WAT (iWAT) of mice. Furthermore, we recently demonstrated that curcumin (Cur, 4.5 mg/kg) also significantly induced the development of brown-like adipocytes in mice. The combined administration of several food-derived factors can enhance their bioactivity and reduce their required functional doses. In this study, we showed that co-administration of Cur and ArtC at lower doses (Cur, 1.5 mg/kg; ArtC, 5 mg/kg) additively induce brown-like adipocyte development in mouse iWAT. Moreover, this induction is associated with the localized production of norepinephrine following accumulation of alternatively activated macrophages in iWAT. These findings suggest that co-administration of Cur and ArtC is significantly effective to reduce the dose and enhance the formation of brown-like adipocyte via a unique molecular mechanism.

Perivascular macrophages in the neonatal macaque brain undergo massive necroptosis after simian immunodeficiency virus infection

We previously showed that rhesus macaques neonatally infected with simian immunodeficiency virus (SIV) do not develop SIV encephalitis (SIVE) and maintain low brain viral loads despite having similar plasma viral loads compared to SIV-infected adults. We hypothesize that differences in myeloid cell populations that are the known target of SIV and HIV in the brain contribute to the lack of neonatal susceptibility to lentivirus-induced encephalitis. Using immunohistochemistry and immunofluorescence microscopy, we examined the frontal cortices from uninfected and SIV-infected infant and adult macaques (n = 8/ea) as well as adults with SIVE (n = 4) to determine differences in myeloid cell populations. The number of CD206+ brain perivascular macrophages (PVMs) was significantly greater in uninfected infants than in uninfected adults and was markedly lower in SIV-infected infants while microglia numbers were unchanged across groups. CD206+ PVMs, which proliferate after infection in SIV-infected adults, did not undergo proliferation in infants. While virtually all CD206+ cells in adults are also CD163+, infants have a distinct CD206 single-positive population in addition to the double-positive population commonly seen in adults. Notably, we found that more than 60% of these unique CD206+CD163- PVMs in SIV-infected infants were positive for cleaved caspase-3, an indicator of apoptosis, and that nearly 100% of this subset were concomitantly positive for the necroptosis marker receptor-interacting protein kinase-3 (RIP3). These findings show that distinct subpopulations of PVMs found in infants undergo programmed cell death instead of proliferation following SIV infection, which may lead to the absence of PVM-dependent SIVE and the limited size of the virus reservoir in the infant brain.

Vessel-Associated Immune Cells in Cerebrovascular Diseases: From Perivascular Macrophages to Vessel-Associated Microglia

Cerebral small vessels feed and protect the brain parenchyma thanks to the unique features of the blood-brain barrier. Cerebrovascular dysfunction is therefore seen as a detrimental factor for the initiation of several central nervous system (CNS) disorders, such as stroke, cerebral small vessel disease (cSVD), and Alzheimer's disease. The main working hypothesis linking cerebrovascular dysfunction to brain disorders includes the contribution of neuroinflammation. While our knowledge on microglia cells - the brain-resident immune cells - has been increasing in the last decades, the specific populations of microglia and macrophages surrounding brain vessels, vessel-associated microglia (VAM), and perivascular macrophages (PVMs), respectively, have been overlooked. This review aims to summarize the knowledge gathered on VAM and PVMs, to discuss existing knowledge gaps of importance for later studies and to summarize evidences for their contribution to cerebrovascular dysfunction.

Amphiphilic Polypeptoids Rupture Vesicle Bilayers To Form Peptoid-Lipid Fragments Effective in Enhancing Hydrophobic Drug Delivery

Peptoids are highly biocompatible pseudopeptidic polyglycines with designable substituents on the nitrogen atoms. The therapeutic and drug-carrying potential of these materials requires a fundamental understanding of their interactions with lipid bilayers. In this work, we use amphiphilic polypeptoids with up to 100 monomeric units where a significant fraction (26%) of the nitrogen atoms are functionalized with decyl groups (hydrophobes) that insert into the lipid bilayer through the hydrophobic effect. These hydrophobically modified polypeptoids (HMPs) insert their hydrophobes into lipid bilayers creating instabilities that lead to the rupture of vesicles. At low HMP concentrations, such rupture leads to the creation of large fragments which remarkably anchor to intact vesicles through the hydrophobic effect. At high HMP concentrations, all vesicles rupture to smaller HMP-lipid fragments of the order of 10 nm. We show that the technique for such nanoscale polymer-lipid fragments can be exploited to sustain highly hydrophobic drug species in solution. Using the kinase inhibitor, Sorafenib as a model drug, it is shown that HMP-lipid fragments containing the drug can efficiently enter a hepatocellular carcinoma cell line (Huh 7.5), indicating the use of such fragments as drug delivery nanocarriers.

Soluble Macrophage Mannose Receptor (sCD206/sMR) as a Biomarker in Human Immunodeficiency Virus Infection

Macrophages play important roles during human immunodeficiency virus (HIV) infection, reflected by changes in macrophage-activation biomarker soluble CD163 (sCD163). Here, we present data on the novel macrophage-activation biomarker soluble mannose receptor/CD206 (sCD206) in HIV infection. We investigated sCD206 blood levels at baseline and follow-up with/without antiretroviral therapy (ART), in 212 patients with HIV type 1 (HIV-1), HIV type 2 (HIV-2), or dual infection. At baseline, there was no difference in sCD206 level between HIV types, and sCD206 was unchanged at follow-up without ART. However, in contrast to sCD163, sCD206 levels decreased significantly for both HIV-1 and HIV-2, but not for HIV-1/2 patients, during ART. Further investigations are needed to establish sCD206 as a biomarker in HIV infection.

Increased CD68/TGFβ Co-expressing Microglia/ Macrophages after Transient Middle Cerebral Artery Occlusion in Rhesus Monkeys

The function of microglia/macrophages after ischemic stroke is poorly understood. This study examines the role of microglia/macrophages in the focal infarct area after transient middle cerebral artery occlusion (MCAO) in rhesus monkeys. We measured infarct volume and neurological function by magnetic resonance imaging (MRI) and non-human primate stroke scale (NHPSS), respectively, to assess temporal changes following MCAO. Activated phagocytic microglia/macrophages were examined by immunohistochemistry in post-mortem brains (n=6 MCAO, n=2 controls) at 3 and 24 hours (acute stage), 2 and 4 weeks (subacute stage), and 4, and 20 months (chronic stage) following MCAO. We found that the infarct volume progressively decreased between 1 and 4 weeks following MCAO, in parallel with the neurological recovery. Greater presence of cluster of differentiation 68 (CD68)-expressing microglia/macrophages was detected in the infarct lesion in the subacute and chronic stage, compared to the acute stage. Surprisingly, 98~99% of transforming growth factor beta (TGFβ) was found colocalized with CD68-expressing cells. CD68-expressing microglia/macrophages, rather than CD206⁺ cells, may exert anti-inflammatory effects by secreting TGFβ after the subacute stage of ischemic stroke. CD68⁺ microglia/macrophages can therefore be used as a potential therapeutic target.

Dysregulation of sonic hedgehog pathway and pericytes in the brain after lentiviral infection

BACKGROUND

Impairment of the blood-brain barrier (BBB) has been associated with cognitive decline in many CNS diseases, including HIV-associated neurocognitive disorders (HAND). Recent research suggests an important role for the Sonic hedgehog (Shh) signaling pathway in the maintenance of BBB integrity under both physiological and pathological conditions.

METHODS

In the present study, we sought to examine the expression of Shh and its downstream effectors in relation to brain pericytes and BBB integrity in HIV-infected humans and rhesus macaques infected with simian immunodeficiency virus (SIV), an animal model of HIV infection and CNS disease. Cortical brain tissues from uninfected (n = 4) and SIV-infected macaques with (SIVE, n = 6) or without encephalitis (SIVnoE, n = 4) were examined using multi-label, semi-quantitative immunofluorescence microscopy of Shh, netrin-1, tight junction protein zona occludens 1 (ZO1), glial fibrillary acidic protein, CD163, platelet-derived growth factor receptor b (PDGFRB), glucose transporter 1, fibrinogen, and SIV Gag p28.

RESULTS

While Shh presence in the brain persisted during HIV/SIV infection, both netrin-1 immunoreactivity and the size of PDGFRB+ pericytes, a cellular source of netrin-1, were increased around non-lesion-associated vessels in encephalitis compared to uninfected brain or brain without encephalitis, but were completely absent in encephalitic lesions. Hypertrophied pericytes were strongly localized in areas of fibrinogen extravasation and showed the presence of intracellular SIVp28 and HIVp24 by immunofluorescence in all SIV and HIV encephalitis cases examined, respectively.

CONCLUSIONS

The lack of pericytes and netrin-1 in encephalitic lesions, in line with downregulation of ZO1 on the fenestrated endothelium, suggests that pericyte loss, despite the strong presence of Shh, contributes to HIV/SIV-induced BBB disruption and neuropathogenesis in HAND.

Clusters of Nanoscale Liposomes Modulate the Release of Encapsulated Species and Mimic the Compartmentalization Intrinsic in Cell Structures

We report the ability to place a high concentration of liposomes in a confined volume as a multicompartment cluster that mimics biological cells and allows for the modulation of release of encapsulated species. The formation of these coated multicompartmental structures is achieved by first binding liposomes into clusters before encapsulating them within a two-dimensional metal-organic framework composed of tannic acid coordinated with a metal ion. The essential feature is a molecularly thin skin over a ssystem of clustered liposomes in a pouch. The structural features of these pouches are revealed by small-angle scattering and electron microscopy. Through cryogenic electron microscopy, clusters with intact liposomes are observed that appear to be encapsulated within a pouch. Small-angle X-ray scattering shows the emergence of a relatively weak Bragg peak at q = 0.125 Å^-1, possibly indicating the attachment of the bilayers of adjacent liposomes. The metal-phenolic network (MPN) forms a nanosized conformal coating around liposome clusters, resulting in the reduced release rate of the encapsulated rhodamine B dye. We further show the possibility of communication between the adjacent nanocompartments in the cluster by demonstrating enhanced energy transfer using fluorescence resonance energy transfer (FRET) experiments where the lipophilic donor dye 3,3'-dioctadecyloxacarbocyanine perchlorate (DiO) incorporated within one liposomal compartment transfers energy upon excitation to the lipophilic acceptor dye 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) in a neighboring liposomal compartment due to their close proximity within the multicompartmental cluster. These observations have significance in adapting these multicompartmental structures that mimic biological cells for cascade reactions and as new depot drug delivery systems.

Chronic Viral Neuroinflammation: Speculation on Underlying Mechanisms

Viral infection in the brain can be acute or chronic, with the responses often producing foci of increasingly cytotoxic inflammation. This can lead to effects beyond the central nervous system (CNS). To stimulate discussion, this commentary addresses four questions: What drives the development of human immunodeficiency virus (HIV)-associated neurocognitive disorders, does the phenotype of macrophages in the CNS spur development of HIV encephalitis (HIVE), does continual activation of astrocytes drive the development of HIV-associated neurocognitive disorders/subclinical disease, and neuroinflammation: friend or foe? A unifying theory that connects each question is the issue of continued activation of glial cells, even in the apparent absence of simian immunodeficiency virus/HIV in the CNS. As the CNS innate immune system is distinct from the rest of the body, it is likely there could be a number of activation profiles not observed elsewhere.

Macrophages but not Astrocytes Harbor HIV DNA in the Brains of HIV-1-Infected Aviremic Individuals on Suppressive Antiretroviral Therapy

The question of whether the human brain is an anatomical site of persistent HIV-1 infection during suppressive antiretroviral therapy (ART) is critical, but remains unanswered. The presence of virus in the brains of HIV patients whose viral load is effectively suppressed would demonstrate not only the potential for CNS to act as an anatomical HIV reservoir, but also the urgent need to understand the factors contributing to persistent HIV behind the blood-brain barrier. Here, we investigated for the first time the presence of cells harboring HIV DNA and RNA in the brains from subjects with undetectable plasma viral load and sustained viral suppression, as identified by the National NeuroAIDS Tissue Consortium. Using new, highly sensitive in situ hybridization techniques, RNAscope and DNAscope, in combination with immunohistochemistry, we were able to detect HIV-1 in the brains of all virally suppressed cases and found that brain macrophages and microglia, but not astrocytes, were the cells harboring HIV DNA in the brain. This study demonstrated that HIV reservoirs persist in brain macrophages/microglia during suppressive ART, which cure/treatment strategies will need to focus on targeting.

Lentiviral infection of proliferating brain macrophages in HIV and simian immunodeficiency virus encephalitis despite sterile alpha motif and histidine-aspartate domain-containing protein 1 expression

Objective:

HIV-1 infection of the brain and related cognitive impairment remain prevalent in HIV-1-infected individuals despite combination antiretroviral therapy. Sterile alpha motif and histidine-aspartate domain-containing protein 1 (SAMHD1) is a newly identified host restriction factor that blocks the replication of HIV-1 and other retroviruses in myeloid cells. Cell cycle-regulated phosphorylation at residue Thr592 and viral protein X (Vpx)-mediated degradation of SAMHD1 have been shown to bypass SAMHD1 restriction in vitro. Herein, we investigated expression and phosphorylation of SAMHD1 in vivo in relation to macrophage infection and proliferation during the neuropathogenesis of HIV-1 and simian immunodeficiency virus (SIV) encephalitis.

Methods:

Using brain and other tissues from uninfected and SIV-infected macaques with or without encephalitis, we performed immunohistochemistry, multilabel fluorescence microscopy and western blot to examine the expression, localization and phosphorylation of SAMHD1.

Results:

The number of SAMHD1⁺ nuclei increased in encephalitic brains despite the presence of Vpx. Many of these cells were perivascular macrophages, although subsets of SAMHD1⁺ microglia and endothelial cells were also observed. The SAMHD1⁺ macrophages were shown to be both infected and proliferating. Moreover, the presence of cycling SAMHD1⁺ brain macrophages was confirmed in the tissue of HIV-1-infected patients with encephalitis. Finally, western blot analysis of brain-protein extracts from SIV-infected macaques showed that SAMHD1 protein exists in the brain mainly as an inactive Thr592-phosphorylated form.

Conclusion:

The ability of SAMHD1 to act as a restriction factor for SIV/HIV in the brain is likely bypassed in proliferating brain macrophages through the phosphorylation-mediated inactivation, not Vpx-mediated degradation of SAMHD1.

Highly Dispersible and Bioavailable Curcumin but not Native Curcumin Induces Brown-Like Adipocyte Formation in Mice

SCOPE

The induction of brown-like adipocytes in white adipose tissue (WAT) is a potential therapeutic target for the treatment of obesity and metabolic disorders via the ability of these cells to release excess energy as heat in association with uncoupling protein 1. Some experimental trials suggest that curcumin (a yellow pigment from turmeric) has a suppressive effect on the accumulation of body fat. However, there is little evidence to show that curcumin induces the formation of brown-like adipocytes and the molecular mechanisms involved remain elusive. In addition, in most experimental trials, high doses of curcumin are administered.

METHODS AND RESULTS

Highly dispersible and bioavailable curcumin (HC, i.e., 4.5 mg native curcumin kg^-1 ) but not the same dose of native curcumin induces the formation of brown-like adipocytes in mouse inguinal WAT. Moreover, the formation of brown-like adipocytes induced by HC in inguinal WAT may be mediated by the production of local norepinephrine from accumulated alternatively activated macrophages.

CONCLUSION

These novel findings suggest that curcumin increases energy expenditure by inducing the formation of brown-like adipocytes via a unique molecular mechanism. Importantly, they show that HC has significant bioactive effects in vivo at lower doses of curcumin.

Animal models of HIV-associated disease of the central nervous system

It is difficult to study the pathogenesis of human immunodeficiency virus (HIV)-associated neurocognitive disorder (HAND) in living patients because central nervous system (CNS) tissues are only available post mortem. Rodent and nonhuman primate (NHP) models of HAND allow for longitudinal analysis of HIV-associated CNS pathology and efficacy studies of novel therapeutics. Rodent models of HAND allow for studies with large sample sizes, short duration, and relatively low cost. These models include humanized mice used to study HIV-associated neuropathogenesis and transgenic mice used to study neurotoxic effects of viral proteins without infection. Simian immunodeficiency virus (SIV)-infected NHP are the premier model of neuroAIDS; SIV-associated CNS pathology is similar to HIV-associated CNS pathology with HAND. Additionally, the size, lifespan of NHP, and time to acquired immune deficiency syndrome (AIDS) progression make SIV-infected NHP models optimal for studies of viral latency and reservoirs, and assessing novel therapeutics for neuroAIDS. NHP models of neuroAIDS generally include conventional progressors (AIDS within 2-3 years) and those that have rapid disease (AIDS within 150 days). Rapid AIDS models are achieved by immune modulation and/or infection with neurovirulent and neurosuppressive viral strains and result in a high incidence of SIV-associated encephalitis. In this chapter, we briefly review rodent and NHP models of neuroAIDS, including contributions made using these models to our understanding of HIV-associated CNS disease.

Critical Role for Monocytes/Macrophages in Rapid Progression to AIDS in Pediatric Simian Immunodeficiency Virus-Infected Rhesus Macaques

Infant humans and rhesus macaques infected with the human or simian immunodeficiency virus (HIV or SIV), respectively, express higher viral loads and progress more rapidly to AIDS than infected adults. Activated memory CD4+ T cells in intestinal tissues are major primary target cells for SIV/HIV infection, and massive depletion of these cells is considered a major cause of immunodeficiency. Monocytes and macrophages are important cells of innate immunity and also are targets of HIV/SIV infection. We reported previously that a high peripheral blood monocyte turnover rate was predictive for the onset of disease progression to AIDS in SIV-infected adult macaques. The purpose of this study was to determine if earlier or higher infection of monocytes/macrophages contributes to the more rapid progression to AIDS in infants. We observed that uninfected infant rhesus macaques exhibited higher physiologic baseline monocyte turnover than adults. Early after SIV infection, the monocyte turnover further increased, and it remained high during progression to AIDS. A high percentage of terminal deoxynucleotidyltransferase dUTP nick end label (TUNEL)-positive macrophages in the lymph nodes (LNs) and intestine corresponded with an increasing number of macrophages derived from circulating monocytes (bromodeoxyuridine positive [BrdU+] CD163+), suggesting that the increased blood monocyte turnover was required to rapidly replenish destroyed tissue macrophages. Immunofluorescence analysis further demonstrated that macrophages were a significant portion of the virus-producing cells found in LNs, intestinal tissues, and lungs. The higher baseline monocyte turnover in infant macaques and subsequent macrophage damage by SIV infection may help explain the basis of more rapid disease progression to AIDS in infants.IMPORTANCE HIV infection progresses much more rapidly in pediatric cases than in adults; however, the mechanism for this difference is unclear. Using the rhesus macaque model, this work was performed to address why infants infected with SIV progress more quickly to AIDS than do adults. Earlier we reported that in adult rhesus macaques, increasing monocyte turnover reflected tissue macrophage damage by SIV and was predictive of terminal disease progression to AIDS. Here we report that uninfected infant rhesus macaques exhibited a higher physiological baseline monocyte turnover rate than adults. Furthermore, once infected with SIV, infants displayed further increased monocyte turnover that may have facilitated the accelerated progression to AIDS. These results support a role for monocytes and macrophages in the pathogenesis of SIV/HIV and begin to explain why infants are more prone to rapid disease progression.

Brain perivascular macrophages: characterization and functional roles in health and disease

Perivascular macrophages (PVM) are a distinct population of resident brain macrophages characterized by a close association with the cerebral vasculature. PVM migrate from the yolk sac into the brain early in development and, like microglia, are likely to be a self-renewing cell population that, in the normal state, is not replenished by circulating monocytes. Increasing evidence implicates PVM in several disease processes, ranging from brain infections and immune activation to regulation of the hypothalamic-adrenal axis and neurovascular-neurocognitive dysfunction in the setting of hypertension, Alzheimer disease pathology, or obesity. These effects involve crosstalk between PVM and cerebral endothelial cells, interaction with circulating immune cells, and/or production of reactive oxygen species. Overall, the available evidence supports the idea that PVM are a key component of the brain-resident immune system with broad implications for the pathogenesis of major brain diseases. A better understanding of the biology and pathobiology of PVM may lead to new insights and therapeutic strategies for a wide variety of brain diseases.

Mannose receptor as a potential biomarker for gastric cancer: a pilot study

BACKGROUND

The mannose receptor is an immune adhesion molecule mainly expressed on the surface of antigen-presenting cells such as nonmature dendritic cells and macrophages. This study aimed to investigate mannose receptor expression and its predictive role in papillary gastric cancer patients.

METHODS

The expression of the mannose receptor was measured in 120 samples of gastric cancer tissues and corresponding paracarcinoma tissues, by immunohistochemical and quantitative real-time PCR analysis. The relationships between mannose receptor expression and clinicopathological features of gastric cancer patients were analyzed.

RESULTS

The expression rate of the mannose receptor in gastric cancer cells was 45.8% (54/120), significantly higher than that in the paracarcinoma tissue (20.0%, 36/120) (χ2 = 6.286, p = 0.012). High expression of the mannose receptor was closely related to tumor size, T stage, N stage and Union for International Cancer Control (UICC) stage of gastric cancer (p<0.05). A Kaplan-Meier survival model indicated that the survival of patients in the high-expression mannose receptor group was significantly shorter than in the low-expression mannose receptor group (p<0.05). Cox regression analysis showed that high mannose receptor expression was an independent predictor for the prognosis of patients with gastric cancer.

CONCLUSIONS

High mannose receptor expression indicates poor prognosis for gastric cancer patients. The mannose receptor may be an important molecular marker for gastric cancer prognosis.

Amphiphilic Polypeptoids Serve as the Connective Glue to Transform Liposomes into Multilamellar Structures with Closely Spaced Bilayers

We report the ability of hydrophobically modified polypeptoids (HMPs), which are amphiphilic pseudopeptidic macromolecules, to connect across lipid bilayers and thus form layered structures on liposomes. The HMPs are obtained by attaching hydrophobic decyl groups at random points along the polypeptoid backbone. Although native polypeptoids (with no hydrophobes) have no effect on liposomal structure, the HMPs remodel the unilamellar liposomes into structures with comparable diameters but with multiple concentric bilayers. The transition from single-bilayer to multiple-bilayer structures is revealed by small-angle neutron scattering (SANS) and cryo-transmission electron microscopy (cryo-TEM). The spacing between bilayers is found to be relatively uniform at ∼6.7 nm. We suggest that the amphiphilic nature of the HMPs explains the formation of multibilayered liposomes; i.e., the HMPs insert their hydrophobic tails into adjacent bilayers and thereby serve as the connective glue between bilayers. At higher HMP concentrations, the liposomes are entirely disrupted into much smaller micellelike structures through extensive hydrophobe insertion. Interestingly, these small structures can reattach to fresh unilamellar liposomes and self-assemble to form new two-bilayer liposomes. The two-bilayer liposomes in our study are reminiscent of two-bilayer organelles such as the nucleus in eukaryotic cells. The observations have significance in designing new nanoscale drug delivery carriers with multiple drugs on separate lipid bilayers and extending liposome circulation times with entirely biocompatible materials.

The Correlation of CD206, CD209, and Disease Severity in Behçet's Disease with Arthritis

The purpose of this study was to clarify the role of pattern recognition receptors in Behçet's disease (BD). The frequencies of several pattern recognition receptors (CD11b, CD11c, CD32, CD206, CD209, and dectin-1) were analyzed in patients with BD by flow cytometry, and cytokine levels, interleukin- (IL-) 18, IL-23, and IL-17A, were compared in plasma. The analysis was performed in active (n = 13) and inactive (n = 13) stages of BD patients. Rheumatoid arthritis patients (n = 19), as a disease control, and healthy control (HC) (n = 19) were enrolled. The frequencies of CD11b+ and CD32+ cells were significantly increased in active BD patients compared to HC. Disease severity score was correlated to CD11c+, CD206+, and CD209+ in whole leukocytes and CD11b+, CD11c+, CD206+, CD209+, and Dectin-1+ in granulocytes. The plasma levels of IL-17A were significantly different between HC and active BD. IL-18 showed significant difference between active and inactive BD patients. From this study, we concluded the expressions of several pattern recognition receptors were correlated to the joint symptoms of BD.

Proliferation of Perivascular Macrophages Contributes to the Development of Encephalitic Lesions in HIV-Infected Humans and in SIV-Infected Macaques

The aim of the present study was to investigate if macrophage proliferation occurs in the brain during simian immunodeficiency virus (SIV) infection of adult macaques. We examined the expression of the Ki-67 proliferation marker in the brains of uninfected and SIV-infected macaques with or without encephalitis. Double-label immunohistochemistry using antibodies against the pan-macrophage marker CD68 and Ki-67 showed that there was a significant increase in CD68+Ki-67+ cells in macaques with SIV encephalitis (SIVE) compared to uninfected and SIV-infected animals without encephalitis, a trend that was also confirmed in brain samples from patients with HIV encephalitis. Multi-label immunofluorescence for CD163 and Ki-67 confirmed that the vast majority of Ki-67+ nuclei were localized to CD163+ macrophages in perivascular cuffs and lesions. The proliferative capacity of Ki-67+ perivascular macrophages (PVM) was confirmed by their nuclear incorporation of bromodeoxyuridine. Examining SIVE lesions, using double-label immunofluorescence with antibodies against SIV-Gag-p28 and Ki-67, showed that the population of Ki-67+ cells were productively infected and expanded proportionally with lesions. Altogether, this study shows that there are subpopulations of resident PVM that express Ki-67 and are SIV-infected, suggesting a mechanism of macrophage accumulation in the brain via PVM proliferation.

Do not judge a cell by its cover--diversity of CNS resident, adjoining and infiltrating myeloid cells in inflammation

Specialized populations of tissue-resident myeloid cells inhabit every organ of the body. While many of these populations appear similar morphologically and phenotypically, they exhibit great functional diversity. The central nervous system (CNS), as an immune privileged organ, possesses a unique tissue-resident macrophage population, the microglia, as well as numerous myeloid cell subsets at its boarders and barriers in CNS-adjoining tissues, namely the meninges, the perivascular space, and the choroid plexus. Recent research has added much to our knowledge about microglia, whereas the populations of CNS-surrounding phagocytes are just starting to be appreciated. As guardians of CNS homeostasis, these myeloid cells perform immune surveillance and immune modulatory tasks in health and disease. As such, microglia and CNS-surrounding antigen-presenting cells have been shown to be crucially involved not only in the initiation and progression but also resolution of multiple sclerosis (MS). MS and its rodent model, experimental autoimmune encephalomyelitis, are autoimmune inflammatory demyelinating CNS pathologies. While some crucial aspects of the disease pathogenesis have been solved, much of the complex involvement and interplay of the innate immune compartment remains yet to be clarified. Here, we will discuss the current understanding of the scope of phenotypes and functions of myeloid cells involved in CNS neuroinflammation.

Enhanced methamphetamine metabolism in rhesus macaque as compared with human: an analysis using a novel method of liquid chromatography with tandem mass spectrometry, kinetic study, and substrate docking

Methamphetamine (MA), which remains one of the widely used drugs of abuse, is metabolized by the cytochrome P450 (P450) family of enzymes in humans. However, metabolism of methamphetamine in macaques is poorly understood. Therefore, we first developed and validated a very sensitive liquid chromatography with tandem mass spectrometry (LC-MS/MS) method using solid phase extraction of rhesus plasma with a lower limit of quantitation at 1.09 ng/ml for MA and its metabolites, 4-hydroxy methamphetamine (4-OH MA), amphetamine (AM), 4-OH amphetamine (4-OH AM), and norephedrine. We then analyzed plasma samples of MA-treated rhesus, which showed >10-fold higher concentrations of AM (∼29 ng/ml) and 4-OH AM (∼28 ng/ml) than MA (∼2 ng/ml). Because the plasma levels of MA metabolites in rhesus were much higher than in human samples, we examined MA metabolism in human and rhesus microsomes. Interestingly, the results showed that AM and 4-OH AM were formed more rapidly and that the catalytic efficiency (Vmax/Km) for the formation of AM was ∼8-fold higher in rhesus than in human microsomes. We further examined the differences in these kinetic characteristics using three selective inhibitors of each human CYP2D6 and CYP3A4 enzymes. The results showed that each of these inhibitors inhibited both d- and l-MA metabolism by 20%-60% in human microsomes but not in rhesus microsomes. The differences between human and rhesus CYP2D6 and CYP3A4 enzymes were further assessed by docking studies for both d and l-MA. In conclusion, our results demonstrated an enhanced MA metabolism in rhesus compared with humans, which is likely to be caused by differences in MA-metabolizing P450 enzymes between these species.