HIV-1 Tat-mediated induction of CCL5 in astrocytes involves NF-κB, AP-1, C/EBPα and C/EBPγ transcription factors and JAK, PI3K/Akt and p38 MAPK signaling pathways

Molecular Role of HIV-1 Human Receptors (CCL5-CCR5 Axis) in neuroAIDS: A Systematic Review

Chronic HIV-1 infection can cause neurological illness, also known as HIV-associated neurocognitive disorders (HAND). The elevated level of pro-inflammatory cytokines and chemokines, such as C-C Chemokine Ligand 5 (CCL5/RANTES), is one of the ways of causing HIV-1-mediated neuroinflammation. C-C Chemokine Receptor 5 (CCR5) is the main coreceptor for viral entry into host cells and for mediating induction of CCL5/RANTES. CCR5 and CCL5 are part of a correlated axis of immune pathways used for effective protection against the HIV-1 virus. The purpose of this paper was to review the literary knowledge about the immunopathological relationship between this immune complex and neuroAIDS. A systematic review of the literature was conducted based on the selection and search of articles, available in English, Spanish, or Portuguese in the time frame of 1990-2022, of primary and secondary types in the PUBMED, Science Direct, SciELO, and LILACS databases through descriptors (MeSH) together with "AND": "CCR5"; "CCL5"; "neurological manifestations"; or "HIV". The methodological quality of the articles was assessed using the JBI Checklists and the PRISMA 2020 writing guidelines were followed. A total of 36 articles were included in the final composition of the review. The main cells of the CNS affected by neuroAIDS are: neurons; microglia; astrocytes; and oligodendrocytes. Molecular devices and their associations with cellular injuries have been described from the entry of the virus into the host's CNS cell to the generation of mental disorders. Furthermore, divergent results were found about the levels of CCL5/RANTES secretion and the generation of immunopathogenesis, while all condensed research for CCR5 indicated that elevation of this receptor causes more neurodegenerative manifestations. Therefore, new therapeutic and interventional strategies can be conditioned on the immunological direction proposed in this review for the disease.

Viral protein R (Vpr)-induced neuroinflammation and its potential contribution to neuronal dysfunction: a scoping review

HIV-associated neurocognitive disorders (HAND) are the result of the activity of HIV-1 within the central nervous system (CNS). While the introduction of antiretroviral therapy (ART) has significantly reduced the occurrence of severe cases of HAND, milder cases still persist. The persistence of HAND in the modern ART era has been linked to a chronic dysregulated inflammatory profile. There is increasing evidence suggesting a potential role of Viral protein R (Vpr) in dysregulating the neuroinflammatory processes in people living with HIV (PLHIV), which may contribute to the development of HAND. Since the role of Vpr in neuroinflammatory mechanisms has not been clearly defined, we conducted a scoping review of fundamental research studies on this topic. The review aimed to assess the size and scope of available research literature on this topic and provide commentary on whether Vpr contributes to neuroinflammation, as highlighted in fundamental studies. Based on the specified selection criteria, 10 studies (6 of which were cell culture-based and 4 that included both animal and cell culture experiments) were eligible for inclusion. The main findings were that (1) Vpr can increase neuroinflammatory markers, with studies consistently reporting higher levels of TNF-α and IL-8, (2) Vpr induces (neuro)inflammation via specific pathways, including the PI3K/AKT, p38-MAPk, JNK-SAPK and Sur1-Trpm4 channels in astrocytes and the p38 and JNK-SAPK in myeloid cells, and (3) Vpr-specific protein amino acid signatures (73R, 77R and 80A) may play an important role in exacerbating neuroinflammation and the neuropathophysiology of HAND. Therefore, Vpr should be investigated for its potential contribution to neuroinflammation in the development of HAND.

Disruption of the ADAM17/NF-κB feedback loop in astrocytes ameliorates HIV-1 Tat-induced inflammatory response and neuronal death

A disintegrin and metalloproteinases (ADAMs) are involved in multiple neurodegenerative diseases. However, the roles and mechanisms of ADAMs in HIV-associated neurocognitive disorder (HAND) remain unclear. Transactivator of transcription (Tat) induces inflammatory response in astrocytes, thereby leading to neuronal apoptosis in the central nervous system. In this study, we determined that ADAM17 expression was upregulated during soluble Tat stimulus in HEB astroglial cells. Inhibition of ADAM17 suppressed Tat-induced pro-inflammatory cytokines production and rescued the astrocytes-derived conditioned media (ACM)-mediated SH-SY5Y neural cells apoptosis. Moreover, ADAM17 mediated Tat-triggered inflammatory response in a NF-κB-dependent manner. Conversely, Tat induced ADAM17 expression via NF-κB signaling pathway. In addition, pharmacological inhibition of NF-κB signaling inhibited Tat-induced inflammatory response, which could be rescued by overexpression of ADAM17. Taken together, our study clarifies the potential role of the ADAM17/NF-κB feedback loop in Tat-induced inflammatory response in astrocytes and the ACM-mediated neuronal death, which could be a novel therapeutic target for relief of HAND.

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

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

CCAAT enhancer binding protein gamma (C/EBP-γ): An understudied transcription factor

The CCAAT enhancer binding protein (C/EBP) family of transcription factors are important transcriptional mediators of a wide range of physiologic processes. C/EBP-γ is the shortest C/EBP protein and lacks a canonical activation domain for the recruitment of transcriptional machinery. Despite its ubiquitous expression and ability to dimerize with other C/EBP proteins, C/EBP-γ has been studied far less than other C/EBP proteins, and, to our knowledge, no review of its functions has been written. This review seeks to integrate the current knowledge about C/EBP-γ and its physiologic roles, especially in cell proliferation, the integrated stress response, oncogenesis, hematopoietic and nervous system development, and metabolism, as well as to identify areas for future research.

Functional impact of HIV-1 Tat on cells of the CNS and its role in HAND

Human immunodeficiency virus type 1 (HIV-1) transactivator of transcription (Tat) is a potent mediator involved in the development of HIV-1-associated neurocognitive disorders (HAND). Tat is expressed even in the presence of antiretroviral therapy (ART) and is able to enter the central nervous system (CNS) through a variety of ways, where Tat can interact with microglia, astrocytes, brain microvascular endothelial cells, and neurons. The presence of low concentrations of extracellular Tat alone has been shown to lead to dysregulated gene expression, chronic cell activation, inflammation, neurotoxicity, and structural damage in the brain. The reported effects of Tat are dependent in part on the specific HIV-1 subtype and amino acid length of Tat used. HIV-1 subtype B Tat is the most common subtype in North American and therefore, most studies have been focused on subtype B Tat; however, studies have shown many genetic, biologic, and pathologic differences between HIV subtype B and subtype C Tat. This review will focus primarily on subtype B Tat where the full-length protein is 101 amino acids, but will also consider variants of Tat, such as Tat 72 and Tat 86, that have been reported to exhibit a number of distinctive activities with respect to mediating CNS damage and neurotoxicity.

Methamphetamine Activates Trace Amine Associated Receptor 1 to Regulate Astrocyte Excitatory Amino Acid Transporter-2 via Differential CREB Phosphorylation During HIV-Associated Neurocognitive Disorders

Methamphetamine (METH) use, referred to as methamphetamine use disorder (MUD), results in neurocognitive decline, a characteristic shared with HIV-associated neurocognitive disorders (HAND). MUD exacerbates HAND partly through glutamate dysregulation. Astrocyte excitatory amino acid transporter (EAAT)-2 is responsible for >90% of glutamate uptake from the synaptic environment and is significantly decreased with METH and HIV-1. Our previous work demonstrated astrocyte trace amine associated receptor (TAAR) 1 to be involved in EAAT-2 regulation. Astrocyte EAAT-2 is regulated at the transcriptional level by cAMP responsive element binding (CREB) protein and NF-κB, transcription factors activated by cAMP, calcium and IL-1β. Second messengers, cAMP and calcium, are triggered by TAAR1 activation, which is upregulated by IL-1β METH-mediated increases in these second messengers and signal transduction pathways have not been shown to directly decrease astrocyte EAAT-2. We propose CREB activation serves as a master regulator of EAAT-2 transcription, downstream of METH-induced TAAR1 activation. To investigate the temporal order of events culminating in CREB activation, genetically encoded calcium indicators, GCaMP6s, were used to visualize METH-induced calcium signaling in primary human astrocytes. RNA interference and pharmacological inhibitors targeting or blocking cAMP-dependent protein kinase A and calcium/calmodulin kinase II confirmed METH-induced regulation of EAAT-2 and resultant glutamate clearance. Furthermore, we investigated METH-mediated CREB phosphorylation at both serine 133 and 142, the co-activator and co-repressor forms, respectively. Overall, this work revealed METH-induced differential CREB phosphorylation is a critical regulator for EAAT-2 function and may thus serve as a mechanistic target for the attenuation of METH-induced excitotoxicity in the context of HAND.

Effect of bovine leukemia virus (BLV) infection on bovine mammary epithelial cells RNA-seq transcriptome profile

Bovine leukemia virus (BLV) is a δ-retrovirus responsible for Enzootic Bovine Leukosis (EBL), a lymphoproliferative disease that affects cattle. The virus causes immune system deregulation, favoring the development of secondary infections. In that context, mastitis incidence is believed to be increased in BLV infected cattle. The aim of this study was to analyze the transcriptome profile of a BLV infected mammary epithelial cell line (MAC-T). Our results show that BLV infected MAC-T cells have an altered expression of IFN I signal pathway and genes involved in defense response to virus, as well as a collagen catabolic process and some protooncogenes and tumor suppressor genes. Our results provide evidence to better understand the effect of BLV on bovine mammary epithelial cell's immune response.

Naringin provides neuroprotection in CCL2-induced cognition impairment by attenuating neuronal apoptosis in the hippocampus

Background

Chemokine C–C motif ligand 2 (CCL2) is one of the most widely recognised proinflammatory chemokines in cognitive disorders. Currently, CCL2-targeting drugs are extremely limited. Thus, this study aimed to explore the neuroprotection afforded by naringin in CCL2-induced cognitive impairment in rats.

Methods

Before the CCL2 intra-hippocampal injection, rats were treated with naringin for 3 consecutive days via intraperitoneal injection. Two days post-surgery, the Morris water maze (MWM) and novel object recognition (NORT) tests were performed to detect spatial learning and memory and object cognition, respectively. Nissl staining and dUTP nick-end labelling (TUNEL) staining were performed to assess histopathological changes in the hippocampus. Commercial kits were used to measure the activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) and the content of malondialdehyde (MDA). Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to examine the relative mRNA expression of interleukin 1β, (IL-1β), interleukin 6 (IL-6), glutamate/aspartate transporter (GLAST), glutamate transporter-1 (GLT-1), phosphate-activated glutaminase (PAG), cysteine aspartic acid-specific protease 8 (caspase-8), cysteine aspartic acid-specific protease 3 (caspase-3), cell lymphoma/leukaemia-2 (Bcl-2), and Bcl-2 associated X protein (Bax).

Results

In the MWM, the average escape latency and average swimming distance were significantly reduced and the crossing times were increased in the naringin-treated groups, compared with the CCL2 group. The NORT results revealed that, compared with the CCL2 rats, the discrimination index in the naringin-treated rats increased significantly. Nissl and TUNEL staining revealed that naringin protected the structure and survival of the neurons in the CA1 zone of the hippocampus. In the naringin-treated groups, the SOD and GSH-Px activities were increased, whereas the MDA levels were decreased. Furthermore, in the naringin-treated groups, the relative mRNA expression of IL-1β and IL-6 was significantly decreased; GLAST and GLT-1 mRNA expression levels were increased, whereas PAG was decreased. In the naringin-treated groups, the relative mRNA expression levels of caspase-8, caspase-3, and Bax were decreased, whereas that of Bcl-2 was increased.

Conclusion

Collectively, these data indicated that naringin alleviated the CCL2-induced cognitive impairment. The underlying mechanisms could be associated with the inhibition of neuroinflammation, oxidative stress, apoptosis, and the regulation of glutamate metabolism.

Region-specific effects of HIV-1 Tat on intrinsic electrophysiological properties of pyramidal neurons in mouse prefrontal cortex and hippocampus

Human immunodeficiency virus (HIV)-1 transactivator of transcription protein (Tat) is a viral protein that promotes transcription of the HIV genome and possesses cell-signaling properties. Long-term exposure of central nervous system (CNS) tissue to HIV-1 Tat is theorized to contribute to HIV-associated neurodegenerative disorder (HAND). In the current study, we sought to directly evaluate the effect of HIV-1 Tat expression on the intrinsic electrophysiological properties of pyramidal neurons located in layer 2/3 of the medial prefrontal cortex and in area CA1 of the hippocampus. Toward that end, we drove Tat expression with doxycycline (100 mg·kg^-1·day^-1 ip) in inducible Tat (iTat) transgenic mice for 7 days and then performed single-cell electrophysiological studies in acute tissue slices made through the prefrontal cortex and hippocampus. Control experiments were performed in doxycycline-treated G-tg mice, which retain the tetracycline-sensitive promoter but do not express Tat. Our results indicated that the predominant effects of HIV-1 Tat expression are excitatory in medial prefrontal cortical pyramidal neurons yet inhibitory in hippocampal pyramidal neurons. Notably, in these two populations, HIV-1 Tat expression produced differential effects on neuronal gain, membrane time constant, resting membrane potential, and rheobase. Similarly, we also observed distinct effects on action potential kinetics and afterhyperpolarization, as well as on the current-voltage relationship in subthreshold voltage ranges. Collectively, these data provide mechanistic evidence of complex and region-specific changes in neuronal physiology by which HIV-1 Tat protein may promote cognitive deficits associated with HAND.NEW & NOTEWORTHY We drove expression of human immunodeficiency virus (HIV)-1 transactivator of transcription protein (Tat) protein in inducible Tat (iTat) transgenic mice for 7 days and then examined the effects on the intrinsic electrophysiological properties of pyramidal neurons located in the medial prefrontal cortex (mPFC) and in the hippocampus. Our results reveal a variety of specific changes that promote increased intrinsic excitability of layer II/III mPFC pyramidal neurons and decreased intrinsic excitability of hippocampal CA1 pyramidal neurons, highlighting both cell type and region-specific effects.

Differential Contribution of HIV-1 Subtypes B and C to Neurological Disorders: Mechanisms and Possible Treatments

With the introduction of combinatory antiretroviral therapy, patients infected with human immunodeficiency virus type 1 (HIV-1) can live much longer than before. However, the identification of HIV-associated neurocognitive disorder (HAND), especially HIV-associated dementia in 15-20% of patients infected with HIV-1, indicates additional complexity. These disorders turn out to be subtype dependent. Recently, many studies are ongoing trying to understand how the virus induces neuronal injury which could lead to neurological dysfunction. Most of these studies are focusing on the HIV-1 release of proteins such as Tat. However, the exact role of these proteins and their involvement in neuronal degeneration remains unidentified; this is especially true since viral proteins from different HIV-1 subtypes differ in their ability to cause neuronal damage. This review describes the role of different HIV-1 subtypes, identifies probable pathways involved in neuronal damage, the contribution of different HIV-1 subtypes to the progression of HAND, and potential treatments for HAND.

IL-33 stimulates human mast cell release of CCL5 and CCL2 via MAPK and NF-κB, inhibited by methoxyluteolin

Mast Cells (MCs) are critical for allergic reactions but also play important roles in inflammation, following stimulation by non-allergic triggers such as cytokines. Upon stimulation, MCs secrete numerous newly synthesized mediators, but the mechanism of the release of chemokines, which are important in the pathogenesis of allergic and inflammatory diseases, remains unknown. IL-33 is an "alarmin", known to augment allergic stimulation of MCs, but its effect on the release of chemokines is not known. The present work investigated the action of IL-33 on the release of the chemokines CCL5 and CCL2 from human MCs, as well as the inhibitory effect of the flavonoid 3',4',5,7-tetramethoxyflavone (methoxyluteolin). Stimulation of cultured human MCs (LAD2) and primary MCs (hCBMCs) by IL-33 (1-100 ng/ml) increased the gene expression and the release of CCL5 (P < 0.0001) and CCL2 (P < 0.01). Stimulation with IL-33 (10 ng/ml) activated MAPK components, as shown by phosphorylation of p38α MAPK, JNK, and c-Jun using Western blot analysis. Inhibition of these responses by known inhibitors confirmed that CCL5 and CCL2 are stimulated by the activation of p38α MAPK, JNK, and IκB-α. The gene expression and the release of CCL5 and CCL2 stimulated by IL-33 were significantly inhibited by 2 h pre-treatment with methoxyluteolin (10, 50, 100  μM). The inhibition by methoxyluteolin (50 μM) was not mediated via MAPK inhibition as phosphorylated p38α MAPK and JNK expression were not affected. In conclusion, IL-33 plays an important role in chemokine release from human MCs and that is by activation of more than one signaling pathway. The inhibitory effect of methoxyluteolin may indicate that it can be developed as a novel treatment for inflammatory diseases.

Friends Turn Foe-Astrocytes Contribute to Neuronal Damage in NeuroAIDS

Astrocytes play a wide variety of roles in the central nervous system (CNS). Various facets of astrocyte-neuron interplay, investigated for the past few decades, have placed these most abundant and important glial cell types to be of supreme importance for the maintenance of the healthy CNS. Interestingly, glial dysfunctions have proven to be the major contributor to neuronal loss in several CNS disorders and pathologies. Specifically, in the field of neuroAIDS, glial dysfunction-mediated neuronal stress is a major factor contributing to the HIV-1 neuropathogenesis. As there is increasing evidence that astrocytes harbor HIV-1 and serve as "safe haven" for the dormant virus in the brain, the indirect pathway of neuronal damage has taken over the direct neuronal damage in its contribution to HIV-1 neuropathogenesis. In this review, we provide a brief insight into the astrocyte functions and dysfunctions in different CNS conditions with an elaborated insight into neuroAIDS. Detailed understanding of the role of astrocytes in neuroAIDS will help in the better therapeutic management of the neurological problems associated with HIV-1 patients.

Silibinin inhibits in vitro ketosis by regulating HMGCS2 and NF-kB: elucidation of signaling molecule relationship under ketotic conditions

Ketosis is a condition where ketone bodies are produced as an alternative energy source, due to insufficient glucose for energy production so that the body switches from carbohydrate metabolism to mostly fat metabolism. In this study, we examined the anti-ketosis effects of silibinin, a major active component of silymarin. We induced ketosis in FL83B mouse hepatocytes in vitro by culturing in low glucose media and compared results to hepatocytes maintained in high-glucose conditions. We quantified β-hydroxybutyrate (BHB) levels with a colorimetric assay. In low-glucose conditions, silibinin reduced the amount of BHB produced, compared to high-glucose conditions; thus, silibinin exhibited an anti-ketotic effect. Ketone body formation during beta oxidation is mediated by 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2). The nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) regulates the transcription of HMGCS2, and plays a vital role in BHB levels. We showed that silibinin inhibited the expression of HMGCS2 and NF-kB at transcriptional and translational levels. Silibinin also inhibited the nuclear translocation of NF-kB and its DNA binding activity. To elucidate the relationship between HMGCS2 and NF-kB, we tested inhibited and over-expressed NF-kB. We found that NF-kB acted as a positive regulator for HMGCS2 under ketosis treatment conditions.

HIV-1 Tat enhances purinergic P2Y4 receptor signaling to mediate inflammatory cytokine production and neuronal damage via PI3K/Akt and ERK MAPK pathways

Background

HIV-associated neurocognitive disorders (HANDs) afflict more than half of HIV-1-positive individuals. The transactivator of transcription (Tat) produced by HIV virus elicits inflammatory process and is a major neurotoxic mediator that induce neuron damage during HAND pathogenesis. Activated astrocytes are important cells involved in neuroinflammation and neuronal damage. Purinergic receptors expressed in astrocytes participate in a positive feedback loop in virus-induced neurotoxicity. Here, we investigated that whether P2Y4R, a P2Y receptor subtype, that expressed in astrocyte participates in Tat-induced neuronal death in vitro and in vivo.

Methods

Soluble Tat protein was performed to determine the expression of P2Y4R and proinflammatory cytokines in astrocytes using siRNA technique via real-time PCR, Western blot, and immunofluorescence assays. Cytometric bead array was used to measure proinflammatory cytokine release. The TUNEL staining and MTT cell viability assay were analyzed for HT22 cell apoptosis and viability, and the ApopTag® peroxidase in situ apoptosis detection kit and cresyl violet staining for apoptosis and death of hippocampal neuron in vivo.

Results

We found that Tat challenge increased the expression of P2Y4R in astrocytes. P2Y4R signaling in astrocytes was involved in Tat-induced inflammatory cytokine production via PI3K/Akt- and ERK1/2-dependent pathways. Knockdown of P2Y4R expression significantly reduced inflammatory cytokine production and relieved Tat-mediated neuronal apoptosis in vitro. Furthermore, in vivo challenged with Tat, P2Y4R knockdown mice showed decreased inflammation and neuronal damage, especially in hippocampal CA1 region.

Conclusions

Our data provide novel insights into astrocyte-mediated neuron damage during HIV-1 infection and suggest a potential therapeutic target for HANDs.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1466-8) contains supplementary material, which is available to authorized users.

Benzo(a)pyrene in Cigarette Smoke Enhances HIV-1 Replication through NF-κB Activation via CYP-Mediated Oxidative Stress Pathway

Smoking aggravates HIV-1 pathogenesis and leads to decreased responses to antiretroviral therapy. In this study, we aim to find a molecular mechanism that would explain smoking-induced HIV-1 replication. Benzo(a)pyrene (BaP), a major carcinogen in cigarette, requires metabolic activation through cytochrome P450s (CYPs) to exert its toxic effects. We hypothesized that CYP-mediated BaP metabolism generates reactive oxygen species (ROS), and the resultant oxidative stress aggravates HIV-1 replication. As expected, we observed ~3 to 4-fold increase in HIV-1 replication in U1 cells and human primary macrophages after chronic BaP exposure. We also observed ~30-fold increase in the expression of CYP1A1 at mRNA level, ~2.5-fold increase in its enzymatic activity as well as elevated ROS and cytotoxicity in U1 cells. The knock-down of the CYP1A1 gene using siRNA and treatment with selective CYP inhibitors and antioxidants significantly reduced HIV-1 replication. Further, we observed a nuclear translocation of NF-κB subunits (p50 and p65) after chronic BaP exposure, which was reduced by treatment with siRNA and antioxidants/CYP inhibitors. Suppression of NF-κB pathway using specific NF-κB inhibitors also significantly reduced HIV-1 replication. Altogether, our results suggest that BaP enhances HIV-1 replication in macrophages by a CYP-mediated oxidative stress pathway followed by the NF-κB pathway.

HIV-1-Induced miR-146a Attenuates Monocyte Migration by Targeting CCL5 in Human Primary Macrophages

MicroRNAs (miRNAs) are widely involved in immune regulation during virus infection. Several studies showed that the expression of miR-146a was increased in human immunodeficiency virus type I (HIV-1)-infected cells, but the definitive function of miR-146a in HIV-1 infection remains obscure. The production of chemokine (C-C motif) ligand 5 (CCL5) in macrophages has been reported to play an important role in HIV/AIDS-associated pathogenesis. In this study, we examined the effects of miR-146a on CCL5 regulation in HIV-1-infected macrophages. Gain and loss of function studies showed that CCL5 might be one of the miR-146a targets, as miR-146a mimic reduced, while miR-146a inhibitor increased CCL5 production in HIV-1-infected macrophages. In addition, we demonstrated that miR-146a reduced CCL5-induced monocyte migration. Our study provided evidence that miR-146a targets CCL5 3' untranslated regions, downregulates its release from macrophages, and affects monocyte migration consequently. These findings drew a novel layer of posttranscriptional control of the chemokine CCL5 by miR-146a during HIV infection, which might contribute to HIV pathogenesis.

Tick-Borne Encephalitis Virus Nonstructural Protein NS5 Induces RANTES Expression Dependent on the RNA-Dependent RNA Polymerase Activity

Tick-borne encephalitis virus (TBEV) is one of the flaviviruses that targets the CNS and causes encephalitis in humans. The mechanism of TBEV that causes CNS destruction remains unclear. It has been reported that RANTES-mediated migration of human blood monocytes and T lymphocytes is specifically induced in the brain of mice infected with TBEV, which causes ensuing neuroinflammation and may contribute to brain destruction. However, the viral components responsible for RANTES induction and the underlying mechanisms remain to be fully addressed. In this study, we demonstrate that the NS5, but not other viral proteins of TBEV, induces RANTES production in human glioblastoma cell lines and primary astrocytes. TBEV NS5 appears to activate the IFN regulatory factor 3 (IRF-3) signaling pathway in a manner dependent on RIG-I/MDA5, which leads to the nuclear translocation of IRF-3 to bind with RANTES promoter. Further studies reveal that the activity of RNA-dependent RNA polymerase (RdRP) but not the RNA cap methyltransferase is critical for TBEV NS5-induced RANTES expression, and this is likely due to RdRP-mediated synthesis of dsRNA. Additional data indicate that the residues at K359, D361, and D664 of TBEV NS5 are critical for RdRP activity and RANTES induction. Of note, NS5s from other flaviviruses, including Japanese encephalitis virus, West Nile virus, Zika virus, and dengue virus, can also induce RANTES expression, suggesting the significance of NS5-induced RANTES expression in flavivirus pathogenesis. Our findings provide a foundation for further understanding how flaviviruses cause neuroinflammation and a potential viral target for intervention.

Methamphetamine augment HIV-1 Tat mediated memory deficits by altering the expression of synaptic proteins and neurotrophic factors

Methamphetamine (METH) abuse is common among individuals infected with HIV-1 and has been shown to affect HIV replication and pathogenesis. These HIV-1 infected individuals also exhibit greater neuronal injury and higher cognitive decline. HIV-1 proteins, specifically gp120 and HIV-1 Tat, have been earlier shown to affect neurocognition. HIV-1 Tat, a viral protein released early during HIV-1 replication, contributes to HIV-associated neurotoxicity through various mechanisms including production of pro-inflammatory cytokines, reactive oxygen species and dysregulation of neuroplasticity. However, the combined effect of METH and HIV-1 Tat on neurocognition and its potential effect on neuroplasticity mechanisms remains largely unknown. Therefore, the present study was undertaken to investigate the combined effect of METH and HIV-1 Tat on behavior and on the expression of neuroplasticity markers by utilizing Doxycycline (DOX)-inducible HIV-1 Tat (1-86) transgenic mice. Expression of Tat in various brain regions of these mice was confirmed by RT-PCR. The mice were administered with an escalating dose of METH (0.1 mg/kg to 6 mg/kg, i.p) over a 7-day period, followed by 6 mg/kg, i.p METH twice a day for four weeks. After three weeks of METH administration, Y maze and Morris water maze assays were performed to determine the effect of Tat and METH on working and spatial memory, respectively. Compared with controls, working memory was significantly decreased in Tat mice that were administered METH. Moreover, significant deficits in spatial memory were also observed in Tat-Tg mice that were administered METH. A significant reduction in the protein expressions of synapsin 1, synaptophysin, Arg3.1, PSD-95, and BDNF in different brain regions were also observed. Expression levels of Calmodulin kinase II (CaMKII), a marker of synaptodendritic integrity, were also significantly decreased in HIV-1 Tat mice that were treated with METH. Together, this data suggests that METH enhances HIV-1 Tat-induced memory deficits by reducing the expression of pre- and postsynaptic proteins and neuroplasticity markers, thus providing novel insights into the molecular mechanisms behind neurocognitive impairments in HIV-infected amphetamine users.

Methamphetamine potentiates HIV-1 gp120-mediated autophagy via Beclin-1 and Atg5/7 as a pro-survival response in astrocytes

Methamphetamine (METH), a commonly used controlled substance, is known to exacerbate neuropathological dysfunction in HIV-infected individuals. The neuropathological manifestation results from cell death or dysfunction in the central nervous system (CNS) wherein autophagy is expected to have an important role. Autophagy is generally considered protective during deprivation/stress. However, excessive autophagy can be destructive, leading to autophagic cell death. This study was designed to investigate if METH and HIV-1 gp120 interact to induce autophagy in SVGA astrocytes, and whether autophagy is epiphenomenal or it has a role in METH- and gp120-induced cytotoxicity. We found that METH and gp120 IIIb caused an increase in LC3II level in astrocytes in a dose- and time-dependent manner, and the level of LC3II was further increased when the cells were treated with METH and gp120 IIIb in combination. Next, we sought to explore the mechanism by which METH and gp120 induce the autophagic response. We found that METH induces autophagy via opioid and metabotropic glutamate receptor type 5 (mGluR5) receptors. Other than that, signaling proteins Akt, mammalian target of rapamycin (mTOR), Beclin-1, Atg5 and Atg7 were involved in METH and gp120-mediated autophagy. In addition, long-term treatment of METH and gp120 IIIb resulted in cell death, which was exacerbated by inhibition of autophagy. This suggests that autophagy functions as a protective response against apoptosis caused by METH and gp120. This study is novel and clinically relevant because METH abuse among HIV-infected populations is highly prevalent and is known to cause exacerbated neuroAIDS.

HIV-1 gp120 induces type-1 programmed cell death through ER stress employing IRE1α, JNK and AP-1 pathway

The ER stress-mediated apoptosis has been implicated in several neurodegenerative diseases; however, its role in HIV/neuroAIDS remains largely unexplored. The present study was undertaken to assess the involvement and detailed mechanism of IRE1α pathway in HIV-1 gp120-mediated ER stress and its possible involvement in cell death. Various signaling molecules for IRE1α pathway were assessed using SVGA cells, primary astrocytes and gp120 transgenic mice, which demonstrated gp120-mediated increase in phosphorylated JNK, XBP-1 and AP-1 leading to upregulation of CHOP. Furthermore, HIV-1 gp120-mediated activation of IRE1α also increased XBP-1 splicing. The functional consequence of gp120-mediated ER stress was determined via assessment of gp120-mediated cell death using PI staining and MTT assay. The gp120-mediated cell death also involved caspase-9/caspase-3-mediated apoptosis. These findings were confirmed with the help of specific siRNA for IRE1α, JNK, AP-1, BiP and CHOP showing significant reduction in gp120-mediated CHOP expression. Additionally, silencing all the intermediates also reduced the gp120-mediated cell death and caspase-9/caspase-3 activation at differential levels. This study provides ER-stress as a novel therapeutic target in the management of gp120-mediated cell death and possibly in the treatment of neuroAIDS.

Haemophilus parasuis infection activates chemokine RANTES in PK-15 cells

RANTES is a member of the CC chemokine involved in inflammation and immune response during pathogen infection. In our previous study, Haemophilus parasuis (H. parasuis), which is responsible for the great economic losses in the pig industry worldwide, has been shown to enhance RANTES expression in PK-15 cells. However, the mechanisms behind this biological phenomenon have remained unclear. In this study, we showed that H. parasuis infection significantly upregulated RANTES gene transcription in a time- and dose-dependent manner. Promoter analysis by site-directed mutagenesis indicated that the nuclear factor NF-κB binding site was the most important cis-regulatory element controlling H. parasuis-induced RANTES transcription. Inhibition of NF-κB and JNK activity also significantly reduced H. parasuis-induced RANTES production. In addition, TLRs signaling pathway was found to be involved in H. parasuis induced-RANTES expression. These results represent an important molecular mechanism whereby H. parasuis induced RANTES in the inflammatory response.

Differential signaling mechanism for HIV-1 Nef-mediated production of IL-6 and IL-8 in human astrocytes

Variety of HIV-1 viral proteins including HIV-1 Nef are known to activate astrocytes and microglia in the brain and cause the release of pro-inflammatory cytokines, which is thought to be one of the mechanisms leading to HIV-1- mediated neurotoxicity. IL-6 and IL-8 have been found in the CSF of patients with HIV-1 associated dementia (HAD), suggesting that they might play important roles in HIV-1 neuropathology. In the present study we examined the effects of HIV-1 Nef on IL-6 and IL-8 induction in astrocytes. The results demonstrate that both IL-6 and IL-8 are significantly induced in HIV-1 Nef-transfected SVGA astrocytes and HIV-1 Nef-treated primary fetal astrocytes. We also determined the molecular mechanisms responsible for the HIV-1 Nef-induced increased IL-6 and IL-8 by using chemical inhibitors and siRNAs against PI3K/Akt/PKC, p38 MAPK, NF-κB, CEBP and AP-1. Our results clearly demonstrate that the PI3K/PKC, p38 MAPK, NF-κB and AP-1 pathways are involved in HIV-1 Nef-induced IL-6 production in astrocytes, while PI3K/PKC and NF-κB pathways are involved in HIV-1 Nef-induced IL-8 production. These results offer new potential targets to develop therapeutic strategy for treatment of HIV-1 associated neurological disorders, prevalent in > 40% of individuals infected with HIV-1.

HDAC6 mediates HIV-1 tat-induced proinflammatory responses by regulating MAPK-NF-kappaB/AP-1 pathways in astrocytes

Human immunodeficiency virus (HIV)-1 transactivator of transcription (Tat) is a viral protein that induces extensive neuroinflammation by up-regulating proinflammatory mediators, including cytokines, chemokines, and adhesion molecules. Histone deacetylase 6 (HDAC6) has been implicated in the transcriptional regulation of inflammatory genes. In this study, we investigated the possible role of HDAC6 in HIV-1 Tat-induced up-regulation of proinflammatory mediators in astrocytes. HIV-1 Tat augmented HDAC6 expression, which was correlated with a reduction in acetylated α-tubulin in CRT-MG human astroglioma cells and primary mouse astrocytes. Knockdown and pharmacological inhibition of HDAC6 significantly inhibited HIV-1 Tat-induced expression of CCL2, CXCL8, and CXCL10 chemokines; adhesion molecules; and subsequent adhesion of monocytes to astrocytes. HDAC6 knockdown attenuated HIV-1 Tat-induced activation of mitogen-activated protein kinase species, including ERK, JNK, and p38. Furthermore, HDAC6 knockdown suppressed HIV-1 Tat-induced activation of NF-κB and AP-1. Thus, HDAC6 is involved in HIV-1 Tat-induced expression of proinflammatory genes by regulating mitogen-activated protein kinase-NF-κB/AP-1 pathways and serves as a molecular target for HIV-1 Tat-mediated neuroinflammation GLIA 2015;63:1953-1965.

Differential immune mechanism to HIV-1 Tat variants and its regulation by AEA [corrected]

In the retina, Müller glia is a dominant player of immune response. The HIV-1 transactivator viral protein (Tat) induces production of several neurotoxic cytokines in retinal cells. We show that HIV-1 clades Tat B and C act differentially on Müller glia, which is reflected in apoptosis, activation of cell death pathway components and pro-inflammatory cytokines. The harsher immune-mediated pathology of Tat B, as opposed to milder effects of Tat C, manifests at several signal transduction pathways, notably, MAPK, STAT, SOCS, the NFκB signalosome, and TTP. In activated cells, anandamide (AEA), acting as an immune-modulator, suppresses Tat B effect through MKP-1 but Tat C action via MEK-1. AEA lowers nuclear NF-κB and TAB2 for both variants while elevating IRAK1BP1 in activated Müller glia. Müller glia exposed to Tat shows enhanced PBMC attachment. Tat-induced increase in leukocyte adhesion to Müller cells can be mitigated by AEA, involving both CB receptors. This study identifies multiple signalling components that drive immune-mediated pathology and contribute to disease severity in HIV clades. We show that the protective effects of AEA occur at various stages in cytokine generation and are clade-dependant.

Molecular mechanisms involved in HIV-1 Tat-mediated induction of IL-6 and IL-8 in astrocytes

Background

HIV-associated neurocognitive disorders (HAND) exist in approximately 50% of infected individuals even after the introduction of highly active antiretroviral therapy. HIV-1 Tat has been implicated in HIV-associated neurotoxicity mediated through production of pro-inflammatory cytokines like IL-6 and IL-8 by astrocytes among others as well as oxidative stress. However, the underlying mechanism(s) in the up-regulation of IL-6 and IL-8 are not clearly understood. The present study was designed to determine the mechanism(s) responsible for IL-6 and IL-8 up-regulation by HIV-1 Tat.

Methods

SVG astrocytes were transiently transfected with a plasmid encoding HIV-1 Tat. The HIV-1 Tat-mediated mRNA and protein expression levels of both IL-6 and IL-8 in SVG astrocytes were quantified using real time RT-PCR and multiplex cytokine assay respectively. We also employed immunocytochemistry for staining of IL-6 and IL-8. The underlying signaling mechanism(s) were identified using pharmacological inhibitors and siRNA for different intermediate steps involved in PI3K/Akt, p38 MAPK and JNK MAPK pathways. Appropriate controls were used in the experiments and the effect of pharmacological antagonists and siRNA were observed on both mRNA expression and protein levels.

Results

Both IL-6/IL-8 mRNA and protein showed peak expressions at 6 hours and 96 hours post-transfection, respectively. Elevated levels of IL-6/IL-8 were also confirmed by immunocytochemistry. Our studies indicated that both NF-kB and AP-1 transcription factors were involved in IL-6 and IL-8 expression mediated by HIV-1 Tat; however, AP-1 was differentially activated for either cytokine. In the case of IL-6, p38δ activated AP-1 whereas JNK but not p38 MAPK was involved in AP-1 activation for IL-8 production. On the other hand both PI3K/Akt and p38 MAPK (β subunit) were found to be involved in activation of NF-κB that led to IL-6 and IL-8 production.

Conclusion

Our results demonstrate HIV-1 Tat-mediated induction of both IL-6 and IL-8 in a time-dependent manner in SVG astrocytes. Furthermore, we also showed the involvement of NF-κB and AP-1 transcription factors regulated by PI3/Akt, p38 MAPK and JNK MAPK upstream signaling molecules. These results present new therapeutic targets that could be used in management of HAND.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-014-0214-3) contains supplementary material, which is available to authorized users.

Application of quantitative trait locus mapping and transcriptomics to studies of the senescence-accelerated phenotype in rats

Background

Etiology of complex disorders, such as cataract and neurodegenerative diseases including age-related macular degeneration (AMD), remains poorly understood due to the paucity of animal models, fully replicating the human disease. Previously, two quantitative trait loci (QTLs) associated with early cataract, AMD-like retinopathy, and some behavioral aberrations in senescence-accelerated OXYS rats were uncovered on chromosome 1 in a cross between OXYS and WAG rats. To confirm the findings, we generated interval-specific congenic strains, WAG/OXYS-1.1 and WAG/OXYS-1.2, carrying OXYS-derived loci of chromosome 1 in the WAG strain. Both congenic strains displayed early cataract and retinopathy but differed clinically from OXYS rats. Here we applied a high-throughput RNA sequencing (RNA-Seq) strategy to facilitate nomination of the candidate genes and functional pathways that may be responsible for these differences and can contribute to the development of the senescence-accelerated phenotype of OXYS rats.

Results

First, the size and map position of QTL-derived congenic segments were determined by comparative analysis of coding single-nucleotide polymorphisms (SNPs), which were identified for OXYS, WAG, and congenic retinal RNAs after sequencing. The transferred locus was not what we expected in WAG/OXYS-1.1 rats. In rat retina, 15442 genes were expressed. Coherent sets of differentially expressed genes were identified when we compared RNA-Seq retinal profiles of 20-day-old WAG/OXYS-1.1, WAG/OXYS-1.2, and OXYS rats. The genes most different in the average expression level between the congenic strains included those generally associated with the Wnt, integrin, and TGF-β signaling pathways, widely involved in neurodegenerative processes. Several candidate genes (including Arhgap33, Cebpg, Gtf3c1, Snurf, Tnfaip3, Yme1l1, Cbs, Car9 and Fn1) were found to be either polymorphic in the congenic loci or differentially expressed between the strains. These genes may contribute to the development of cataract and retinopathy.

Conclusions

This study is the first RNA-Seq analysis of the rat retinal transcriptome generated with 40 mln sequencing read depth. The integration of QTL and transcriptomic analyses in our study forms the basis of future research into the relationship between the candidate genes within the congenic regions and specific changes in the retinal transcriptome as possible causal mechanisms that underlie age-associated disorders.

Celastrol ameliorates HIV-1 Tat-induced inflammatory responses via NF-kappaB and AP-1 inhibition and heme oxygenase-1 induction in astrocytes

HIV-1 Tat causes extensive neuroinflammation that may progress to AIDS-related encephalitis and dementia. Celastrol possesses various biological activities such as anti-oxidant, anti-tumor, and anti-inflammatory activities. In this study, we investigated the modulatory effects of celastrol on HIV-1 Tat-induced inflammatory responses and the molecular mechanisms underlying its action in astrocytes. Pre-treatment of CRT-MG human astroglioma cells with celastrol significantly inhibited HIV-1 Tat-induced expression of ICAM-1/VCAM-1 and subsequent monocyte adhesiveness in CRT-MG cells. In addition, celastrol suppressed HIV-1 Tat-induced expression of pro-inflammatory chemokines, such as CXCL10, IL-8, and MCP-1. Celastrol decreased HIV-1 Tat-induced activation of JNK MAPK, AP-1, and NF-κB. Furthermore, celastrol induced mRNA and protein expression of HO-1 as well as Nrf2 activation. Blockage of HO-1 expression using siRNA reversed the inhibitory effect of celastrol on HIV-1 Tat-induced inflammatory responses. These results suggest that celastrol has regulatory effects on HIV-1 Tat-induced inflammatory responses by blocking the JNK MAPK-AP-1/NF-κB signaling pathways and inducing HO-1 expression in astrocytes.

Oxidative Stress Is Associated with Neuroinflammation in Animal Models of HIV-1 Tat Neurotoxicity

HIV-1 trans-acting protein Tat, an essential protein for viral replication, is a key mediator of neurotoxicity. If Tat oxidant injury and neurotoxicity have been described, consequent neuroinflammation is less understood. Rat caudate-putamens (CPs) were challenged with Tat, with or without prior rSV40-delivered superoxide dismutase or glutathione peroxidase. Tat injection caused oxidative stress. Administration of Tat in the CP induced an increase in numbers of Iba-1- and CD68-positive cells, as well as an infiltration of astrocytes. We also tested the effect of more protracted Tat exposure on neuroinflammation using an experimental model of chronic Tat exposure. SV(Tat): a recombinant SV40-derived gene transfer vector was inoculated into the rat CP, leading to chronic expression of Tat, oxidative stress, and ongoing apoptosis, mainly located in neurons. Intra-CP SV(Tat) injection induced an increase in microglia and astrocytes, suggesting that protracted Tat production increased neuroinflammation. SV(SOD1) or SV(GPx1) significantly reduced neuroinflammation following Tat administration into the CP. Thus, Tat-induced oxidative stress, CNS injury, neuron loss and inflammation may be mitigated by antioxidant gene delivery.

HIV-1 Nef induces CCL5 production in astrocytes through p38-MAPK and PI3K/Akt pathway and utilizes NF-kB, CEBP and AP-1 transcription factors

The prevalence of HIV-associated neurocognitive disorders (HAND) remains high in patients infected with HIV-1. The production of pro-inflammatory cytokines by astrocytes/microglia exposed to viral proteins is thought to be one of the mechanisms leading to HIV-1- mediated neurotoxicity. In the present study we examined the effects of Nef on CCL5 induction in astrocytes. The results demonstrate that CCL5 is significantly induced in Nef-transfected SVGA astrocytes. To determine the mechanisms responsible for the increased CCL5 caused by Nef, we employed siRNA and chemical antagonists. Antagonists of NF-κB, PI3K, and p38 significantly reduced the expression levels of CCL5 induced by Nef transfection. Furthermore, specific siRNAs demonstrated that the Akt, p38MAPK, NF-κB, CEBP, and AP-1 pathways play a role in Nef-mediated CCL5 expression. The results demonstrated that the PI3K/Akt and p38 MAPK pathways, along with the transcription factors NF-κB, CEBP, and AP-1, are involved in Nef-induced CCL5 production in astrocytes.