Induction of monocyte chemoattractant protein-1 (MCP-1/CCL2) gene expression by human immunodeficiency virus-1 Tat in human astrocytes is CDK9 dependent

Immune Dysregulation Is Associated with Neurodevelopment and Neurocognitive Performance in HIV Pediatric Populations-A Scoping Review

HIV-1 is known for its complex interaction with the dysregulated immune system and is responsible for the development of neurocognitive deficits and neurodevelopmental delays in pediatric HIV populations. Considering that HIV-1-induced immune dysregulation and its association with neurodevelopmental and neurocognitive impairments in pediatric populations are not well understood, we conducted a scoping review on this topic. The study aimed to systematically review the association of blood and cerebrospinal fluid (CSF) immune markers with neurocognitive deficits and neurodevelopmental delays in pediatric HIV populations. PubMed, Scopus, and Web of Science databases were searched using a search protocol designed specifically for this study. Studies were selected based on a set eligibility criterion. Titles, abstracts, and full texts were assessed by two independent reviewers. Data from the selected studies were extracted and analyzed by two independent reviewers. Seven studies were considered eligible for use in this context, which included four cross-sectional and three longitudinal studies. An average of 130 (±70.61) children living with HIV, 138 (±65.37) children exposed to HIV but uninfected and 90 (±86.66) HIV-negative participants were included across the seven studies. Results indicate that blood and CSF immune markers are associated with neurocognitive development/performance in pediatric HIV populations. Only seven studies met the inclusion criteria, therefore, these limited the number of significant conclusions which could have been made by using such an approach. All considered, the evidence suggests that immune dysregulation, as in the case of adult HIV populations, also has a significant association with neurocognitive performance in pediatric HIV populations.

Effect of miR-506-3p on Proliferation and Apoptosis of Airway Smooth Muscle Cells in Asthmatic Mice by Regulating CCL2 Gene Expression and Mediating TLR4/NF-κB Signaling Pathway Activation

We aimed to investigate the effect of miR-506-3p on the proliferation and apoptosis of airway smooth muscle cells (ASMCS) in asthmatic mice by regulating the activation of TLR4/NF-κB signaling pathway through targeted regulation of C-C Motif Chemokine Ligand 2 (CCL2) expression. Twenty-four BALB/c mice of specific pathogen-free grade were selected to establish asthmatic mouse model, which were randomly divided into normal control group and asthma model group (n = 12 for each group). HE and IHC staining, bioinformatics and dual luciferase reporter assay, RT-PCR MTT, flow cytometry and Western blot were used in this research. HE staining showed airway epithelium thickening, submucosal inflammatory cell infiltration and airway smooth muscle thickening, and the positive expression rate of CCL2 was significantly increased in asthma model group (all P < 0.05). CCL2 was the target gene of miR-506-3p. Moreover, the expression of miR-506-3p in asthma model group was significantly decreased, the mRNA and protein expression levels of CCL2, TLR4, NF-κB (p65) and Bcl-2 were significantly increased, while those of Bax were decreased (all P < 0.05). In miR-506-3p mimic group or siRNA-CCL2 group, the expression of CCL2, TLR4, NF-κB (p65) and Bcl-2 decreased obviously, while that of Bax increased, cell proliferation decreased, G1 phase prolonged, G2 & S phases shortened, and apoptosis rate increased significantly (all P < 0.05), whereas the opposite trends were found in miR-506-3p inhibitor group (all P < 0.05). However, there was no statistical difference in the above-mentioned indexes in miR-506-3p inhibitor + siRNA-CCL2 group (all P > 0.05). Overexpression of miR-506-3p can inhibit ASMCS proliferation and promote apoptosis via inhibiting CCL2 expression and suppressing the activation of TLR4/NF-κB signaling pathway. Inhibited expression of miR-506-3p can reverse the positive role of CCL2 gene silencing. Our study is the first to prove the beneficial role of miR-506-3p-CCL2-TLR4/NF-κB regulatory axis in the development of asthma.

Altered expression of fractalkine in HIV-1-infected astrocytes and consequences for the virus-related neurotoxicity

HIV-1 infection in the central nervous system (CNS) causes the release of neurotoxic products from infected cells which trigger extensive neuronal loss. Clinically, this results in HIV-1-associated neurocognitive disorders (HAND). However, the effects on neuroprotective factors in the brain remain poorly understood and understudied in this situation. HAND is a multifactorial process involving several players, and the complex cellular mechanisms have not been fully elucidated yet. In this study, we reported that HIV-1 infection of astrocytes limits their potential to express the protective chemokine fractalkine in response to an inflammatory environment. We next confirmed that this effect was not due to a default in its shedding from the cell surface. We then investigated the biological mechanism responsible for this reduced fractalkine expression and found that HIV-1 infection specifically blocks the interaction of transcription factor NF-κB on its promoter with no effect on other cytokines. Moreover, we demonstrated that fractalkine production in astrocytes is regulated in response to immune factors secreted by infected/activated microglia and macrophages. In contrast, we observed that conditioned media from these infected cells also trigger neuronal apoptosis. At last, we demonstrated a strong neuroprotective action of fractalkine on human neurons by reducing neuronal damages. Taken together, our results indicate new relevant interactions between HIV-1 and fractalkine signaling in the CNS. This study provides new information to broaden the understanding of HAND and possibly foresee new therapeutic strategies. Considering its neuro-protective functions, reducing its production from astrocytes could have important outcomes in chronic neuroinflammation and in HIV-1 neuropathogenesis.

HIV Tat-mediated induction of autophagy regulates the disruption of ZO-1 in brain endothelial cells

The blood-brain barrier (BBB) is a tight barrier that is critical for preventing the entry of pathogens and small molecules into the brain. HIV protein Tat (Tat) is known to disrupt the tight junctions of the BBB. Autophagy is an intracellular process that involves degradation and recycling of damaged organelles to the lysosome and has recently been implicated in the BBB disruption. The role of autophagy in Tat-mediated BBB disruption, however, remains elusive. Herein we hypothesized that Tat induces endothelial autophagy resulting in decreased expression of the tight junction protein ZO-1 leading to breach of the BBB. In this study, we demonstrated that exposure of human brain microvessel endothelial cells (HBMECs) to Tat resulted in induction of autophagy in a dose- and time-dependent manner, with upregulation of BECN1/Beclin 1, ATG5 and MAP1LC3B proteins and a concomitant downregulation of the tight junction protein ZO-1 ultimately leading to increased endothelial cell monolayer paracellular permeability in an in vitro BBB model. Pharmacological and genetic inhibition of autophagy resulted in the abrogation of Tat-mediated induction of MAP1LC3B with a concomitant restoration of tight junction proteins, thereby underscoring the role of autophagy in Tat-mediated breach of the BBB. Additionally, our data also demonstrated that Tat-mediated induction of autophagy involved PELI1/K63-linked ubiquitination of BECN1. Increased autophagy and decreased ZO-1 was further recapitulated in microvessels isolated from the brains of HIV Tg26 mice as well as the frontal cortex of HIV-infected autopsied brains. Overall, our findings identify autophagy as an important mechanism underlying Tat-mediated disruption of the BBB.

Nef-induced CCL2 Expression Contributes to HIV/SIV Brain Invasion and Neuronal Dysfunction

C-C motif chemokine ligand 2 (CCL2) is a chemoattractant for leukocytes including monocytes, T cells, and natural killer cells and it plays an important role in maintaining the integrity and function of the brain. However, there is accumulating evidence that many neurological diseases are attributable to a dysregulation of CCL2 expression. Acquired immune deficiency syndrome (AIDS) encephalopathy is a severe and frequent complication in individuals infected with the human immunodeficiency virus (HIV) or the simian immunodeficiency virus (SIV). The HIV and SIV Nef protein, a progression factor in AIDS pathology, can be transferred by microvesicles including exosomes and tunneling nanotubes (TNT) within the host even to uninfected cells, and Nef can induce CCL2 expression. This review focuses on findings which collectively add new insights on how Nef-induced CCL2 expression contributes to neurotropism and neurovirulence of HIV and SIV and elucidates why adjuvant targeting of CCL2 could be a therapeutic option for HIV-infected persons.

Β-funaltrexamine inhibits chemokine (CXCL10) expression in normal human astrocytes

Neuroinflammation is an integral component of neurodegenerative disorders, CNS infection and trauma. Astroglial chemokines, such as CXCL10, are instrumental in neuroinflammatory signaling as well as neurotoxicity. We have utilized proinflammatory-induced CXCL10 expression in normal human astrocytes (NHA) as a model in which to assess the anti-inflammatory actions of the selective, mu-opioid receptor (MOR) antagonist, β-funaltrexamine (β-FNA). Interferon (IFN)γ+HIV-1 Tat-induced CXCL10 expression (secreted protein and mRNA) was inhibited by co-treatment with β-FNA. Neither the MOR-selective antagonist, D-Phe-Cys-Tyr-D-Trp-Arg-Pen-Thr-NH2 (CTAP) nor the nonselective opioid receptor antagonist, naltrexone inhibited IFNγ+HIV-1 Tat-induced CXCL10 expression. Furthermore, co-treatment with excess CTAP or naltrexone did not prevent β-FNA mediated inhibition of IFNγ+HIV-1 Tat-induced CXCL10 expression. Additionally, we utilized an inhibitor of NF-κB activation (SN50) to demonstrate that IFNγ+HIV-1 Tat-induced CXCL10 expression is NF-κB-dependent in NHA. Subsequent experiments revealed that β-FNA did not significantly affect NF-κB activation. Interestingly, we discovered that β-FNA inhibited p38 activation as indicated by decreased expression of phospho-p38. Together, these findings suggest that the inhibitory actions of β-FNA are MOR-independent and mediated, in part, via a transcriptional mechanism. These findings add to our understanding of the mechanism by which chemokine expression is inhibited by β-FNA. In conjunction with future investigations, these novel findings are expected to provide insights into the development of safe and effective treatments for neuroinflammation.

p53 is an important regulator of CCL2 gene expression

The p53 protein is a sequence-specific DNA-binding factor that regulates inflammatory genes such as CCL2/MCP-1 that may play a role in various diseases. A recent study has indicated that the knockdown of human p53 leads to a strong negative regulation of CCL2 induction. We are therefore interested in how p53 regulates CCL2 gene expression. In the following study, our findings indicate that UV-induced p53 accumulation in mouse macrophages significantly decreases LPS-induced CCL2 production, and that p53 binds to CCL2 5'UTR in the region (16-35). We also found that a p53 domain (p53pep170) mimics full length p53 to down-regulate CCL2 promoter activity. Treatment of p53-deficient mouse primary macrophages with synthetic p53pep170 was found to decrease LPS-induced production of CCL2 without association with cellular endogenous p53. CCL2 production induced by lentiCLG in human monocytes or mouse primary macrophages was blocked in the presence of p53pep170. Overall, these results demonstrate that p53 or its derived peptide (p53pep170) is an important regulator of CCL2 gene expression via its binding activity, and acts as a novel model for future studies linking p53 and its short peptide to pave the way to possible pharmaceutical intervention of CCL2-mediated inflammatory and cancer diseases.

15-deoxy-Δ¹²,¹⁴ -prostaglandin J₂ inhibits human immunodeficiency virus-1 tat-induced monocyte chemoattractant protein-1/CCL2 production by blocking the extracellular signal-regulated kinase-1/2 signaling pathway independently of peroxisome proliferator-activated receptor-γ and heme oxygenase-1 in rat hippocampal slices

Human immunodeficiency virus (HIV)-induced inflammation, and its consequences within the central nervous system (CNS), must be countered by multiple pharmacologic agents, and 15-deoxy-Δ(12,14) -prostaglandin J(2) (15d-PGJ2) may hold promise in the treatment of pathologies associated with this inflammatory response. 15d-PGJ2 can repress the inflammatory response by means of peroxisome proliferator-activated receptor-γ (PPARγ)-dependent and -independent mechanisms. However, its precise role and antiinflammatory mechanism in the hippocampus remain poorly understood. In the present study, rat hippocampal slices were stimulated with full-length HIV-1 Tat protein to investigate the role of 15d-PGJ2 8in the hippocampal inflammatory response. Pretreatment of slices with 15d-PGJ2 markedly reduced Tat-induced monocyte chemoattractant protein-1 (MCP-1/CCL2) production. Interestingly, the PPARγ antagonist GW9662 did not inhibit action of 15d-PGJ2, confirming the latter's PPARγ-independent mechanism of mediating antiinflammatory effects. Despite 15d-PGJ2's increasing the expression of heme oxygenase-1 (HO-1), its action was not abrogated by the HO-1 inhibitor zinc protoporphyrin IX (ZnPPIX), nor was it recapitulated by HO-1 inducers such as cobalt protoporphyrin (CoPP). Moreover, short interfering RNA (siRNA)-directed knockdown of HO-1 did not abolish the antiinflammatory action of 15d-PGJ2 against Tat-induced MCP-1 production in human microglia-like THP-1 cells. Conversely, 15d-PGJ2 suppressed Tat-induced ERK1/2 activation, decreasing MCP-1 production upon Tat stimulation. The NADPH oxidase inhibitors DPI and apocynin also abrogated Tat-stimulated ERK1/2 activation, reducing MCP-1 production. Collectively, these data demonstrate that the antiinflammatory effects of 15d-PGJ2 on the hippocampus are exerted through inhibition of Tat-mediated ERK1/2 activation, coupled with that of a redox-sensitive pathway, independent of PPARγ and HO-1.

Microvesicles in health and disease

Microvesicles (or MVs) are plasma membrane-derived vesicles released from most eukaryotic cells constitutively during early apoptosis or at higher levels after chemical or physical stress conditions. This review looks at some of the functions of MVs in terms of intercellular communication and ensuant signal transduction, including the transport of proteins (unconventional protein export) as well as of mRNA and microRNA. MVs also have roles in membrane repair, the removal of misfolded proteins, and in the control of apoptosis. We also discuss the role MVs have been shown to have in invasive growth and metastasis as well as in hypoxia in tumours and cerebral ischaemia. The association of MVs in infectious and autoimmune disease is also summarised together with their possible use as therapeutic agents.

HIV-1 Tat-induced microgliosis and synaptic damage via interactions between peripheral and central myeloid cells

Despite the ability of combination antiretroviral treatment (cART) to reduce viral burden to nearly undetectable levels in cerebrospinal fluid and serum, HIV-1 associated neurocognitive disorders (HAND) continue to persist in as many as half the patients living with this disease. There is growing consensus that the actual substrate for HAND is destruction of normal synaptic architecture but the sequence of cellular events that leads to this outcome has never been resolved. To address whether central vs. peripheral myeloid lineage cells contribute to synaptic damage during acute neuroinflammation we injected a single dose of the HIV-1 transactivator of transcription protein (Tat) or control vehicle into hippocampus of wild-type or chimeric C57Bl/6 mice genetically marked to distinguish infiltrating and resident immune cells. Between 8–24 hr after injection of Tat, invading CD11b⁺ and/or myeloperoxidase-positive leukocytes with granulocyte characteristics were found to engulf both microglia and synaptic structures, and microglia reciprocally engulfed invading leukocytes. By 24 hr, microglial processes were also seen ensheathing dendrites, followed by inclusion of synaptic elements in microglia 7 d after Tat injection, with a durable microgliosis lasting at least 28 d. Thus, central nervous system (CNS) exposure to Tat induces early activation of peripheral myeloid lineage cells with phagocytosis of synaptic elements and reciprocal microglial engulfment of peripheral leukocytes, and enduring microgliosis. Our data suggest that a single exposure to a foreign antigen such as HIV-1 Tat can lead to long-lasting disruption of normal neuroimmune homeostasis with deleterious consequences for synaptic architecture, and further suggest a possible mechanism for enduring neuroinflammation in the absence of productive viral replication in the CNS.

Extracellular HIV-1 Tat upregulates TNF-α dependent MCP-1/CCL2 production via activation of ERK1/2 pathway in rat hippocampal slice cultures: inhibition by resveratrol, a polyphenolic phytostilbene

Human immunodeficiency virus-1 (HIV-1) associated dementia (HAD) has been attributed to an encephalitis resulting from intense infiltration of monocytes. Evidence suggests that the viral protein Tat, which is released actively from HIV-1 infected cells, can contribute significantly to this process. Therefore, the principal objective of this study was to evaluate the potential molecular basis for the role of extracellular HIV-1 Tat in the induction of monocyte chemotactic protein-1 (MCP-1/CCL2) in the hippocampus, which is primarily linked to cognitive function and most commonly damaged in HAD. We also attempted to identify the mechanism by which resveratrol (trans-3,5,4'-trihydroxystilbene) modulates MCP-1 release in hippocampal tissues exposed to Tat. An ex vivo study using rat hippocampal slices demonstrated a time- and dose-dependent increase in MCP-1 production from Tat-treated hippocampal tissues. This increase was accompanied by the activation of the MEK/ERK pathway and TNF-α production. Tat-induced MCP-1 release was abrogated by inhibitors of tyrosine kinases (TK), herbimycin A or genistein, a finding that supports the MAPK signaling mechanism. The inhibition of the ERK1/2 pathway with SL327 induced a near-complete abolition of the observed Tat-induced effects. Furthermore, anti-TNF-α antibodies suppressed Tat-induced MCP-1 release. Resveratrol, to a level similar to that of SL327, downregulated Tat-induced proinflammatory responses via the inactivation of ERK1/2. These results indicate that the activation of the ERK1/2 pathway and TK are critical factors in the production of TNF-α and MCP-1 in the Tat-exposed hippocampus. Additionally, the inhibition of Tat-induced production of MCP-1 and TNF-α via the inactivation of the ERK1/2 pathway may represent the anti-inflammatory mechanism of resveratrol in the hippocampus.