Pygo2 has been discovered as an important Wnt signaling component contributing to the activation of Wnt-target gene transcription. In the present study, we discovered tha... More
Pygo2 has been discovered as an important Wnt signaling component contributing to the activation of Wnt-target gene transcription. In the present study, we discovered that Pygo2 mRNA and protein levels were up-regulated in the majority of (152/209) human brain glioma tissues and five glioma cell lines, and significantly correlated with the age, the WHO tumor classification and poor patient survival. The histone methyltransferase complex components (WDR5, Ash2, and menin, but not CXCC1 or NCOA6) were down-regulated at the promoter loci of Wnt target genes after Pygo2 knockdown, and this was accompanied by the down-regulation of Wnt/β-catenin pathway activity. Further, we demonstrated that the involvement of Pygo2 in the activation of the Wnt pathway in human glioma progression is through up-regulation of the H3K4me3 (but not H3K4me2) by promoting the recruitment of the histone methyltransferase MLL1/MLL2 complex to Wnt target gene promoters. Thus, our study provided evidence that Pygo2 functions as a novel prognostic marker and represents a potential therapeutic target. Less
Microglia are the predominant resident central nervous system (CNS) cell type productively infected by HIV-1 and play a key role in the progression of HIV-associated deme... More
Microglia are the predominant resident central nervous system (CNS) cell type productively infected by HIV-1 and play a key role in the progression of HIV-associated dementia (HAD). Moreover, neural dysfunction and progression to HAD are accelerated in opiate drug abusers. In the present study, we examined the role of the autophagy pathway in the neuropathogenesis of HIV-1 using primary human microglial cells and determined whether opiates converge at this point. Infection of microglia with the HIV-1SF162 macrophage-tropic strain resulted in increased Beclin1 expression, accompanied by an increase in LC3 protein levels and accumulation of LC3 reporter RFP GFP (yellow) puncta, suggesting that HIV-1 infection triggers autophagosome formation without promoting protein degradation by the lysosome. Conversely, coexposure with HIV-1 and morphine significantly decreased virus-induced Beclin1 expression and autophagosome formation. Exploration of the possible mechanisms used by morphine to disrupt the autophagic process unveiled a significant increase in intracellular pH, which coincided with a reduction in the formation of acidic vesicular organelles and autophagolysosome formation. Small interfering RNA targeting BECN1, a gene critical for autophagosome formation, significantly reduced viral replication and the virus-induced inflammatory responses. Conversely, morphine-enhanced viral replication and inflammatory responses were not affected by gene silencing with siBeclin1, suggesting that the interactive effect of morphine in HIV-1 pathogenesis is mediated through a Beclin1-independent mechanism. These novel findings may have important implications for the connections between autophagy and HIV-1 pathogenesis mediated by microglial cells in opioid-abusing individuals. Less
The relationship between cancer-initiating cells and cancer-related inflammation is unclear. Exploring the interaction between glioma-initiating cells (GICs) and tumor-as... More
The relationship between cancer-initiating cells and cancer-related inflammation is unclear. Exploring the interaction between glioma-initiating cells (GICs) and tumor-associated microglia/macrophages (TAM/Ms) may offer us an opportunity to further understand the inflammatory response in glioma and the cellular/molecular features of the GIC niche. Here，we reported a positive correlation between the infiltration of TAM/Ms and the density of GICs. The capacity of GICs to recruit TAM/Ms was stronger than that of adhesive glioma cells (AGCs) in vitro. In vivo experiments suggested that implantations formed by GICs had a higher level of TAM/M infiltration than those formed by AGCs. Our studies indicate a predominant role of GICs in microglia/macrophages tropism to glioma and a close positive correlation between the distribution of GICs and TAM/Ms. As an important part of cancer-related inflammation, TAM/Ms may participate in the architecture of the GIC niche. Copyright © 2010 Elsevier B.V. All rights reserved. Less
Recent reports have described reduced immunological responsiveness and stimulatory capacity among monocytes/microglia that infiltrate malignant human gliomas. Herein, we ... More
Recent reports have described reduced immunological responsiveness and stimulatory capacity among monocytes/microglia that infiltrate malignant human gliomas. Herein, we demonstrate that culture of ex vivo human monocytes or primary human microglia with tumor cells isolated from glioblastoma multiforme (GBM) specimens renders them tolerogenic, capable of suppressing the function of ex vivo monocytes in the absence of tumor cells or their soluble factors. We demonstrate that the tolerance induced in monocytes/microglia by GBM tumor cells is not associated with interference with the signaling cascade associated with TLR- or CD40-induced monocyte activation. Rather, these tumor cells appear to up-regulate pathways that antagonize positive signaling pathways, including but not limited to STAT3 and STAT5. Finally, we demonstrate that the tolerogenic properties of GBM tumor cells amplify properties inherent to nontransformed astrocytes. Future studies that identify all of the molecular mechanisms by which astrocytes and malignant gliomas suppress monocyte/microglial function will have dual therapeutic benefits: suppressing these pathways may benefit patients with astrocytic tumors, while enhancing them may benefit patients with autoimmune processes within the CNS, such as multiple sclerosis. Less
Neurokinin-1 receptor (NK-1R) antagonists suppress HIV-1 infection of macrophages in vitro. We have further investigated the anti-HIV-1 activity of aprepitant, a Food and... More
Neurokinin-1 receptor (NK-1R) antagonists suppress HIV-1 infection of macrophages in vitro. We have further investigated the anti-HIV-1 activity of aprepitant, a Food and Drug Administration-approved NK-1R antagonist, and its cytotoxic effect in the macrophage/microglia system. Aprepitant inhibited infection of macrophages with primary HIV-1 R5 strains (subtypes A, D, and H; UG275, BZ163, and BCF-KITA), while it had little effect on primary HIV-1 X4 strains (subtypes B and D, BZ167 and SE365). Aprepitant, when added to microglia cultures infected with CSF-derived HIV-1 strains (JAGO or JRFL), significantly inhibited viral replication. Aprepitant also enhanced the anti-HIV-1 activity of enfuvirtide (an HIV-1 fusion inhibitor) in HIV-1-infected macrophages. Over a concentration range of 10-9 to 10-5 M, aprepitant had little cytotoxic effect (less than 10%) on macrophages during the in vitro cultures. Autologous human serum (≤20%) had little effect on the anti-HIV-1 activity of aprepitant in macrophages. These observations provide additional evidence to support the potential use of NK-1R antagonists as therapeutic and immunomodulatory agents for the treatment of HIV-1 infection. Keywords: aprepitant, macrophage, HIV-1, neurokinin 1 receptor Less
Over 50% of all human immunodeficiency virus type 1 (HIV-1) infections worldwide are caused by subtype C strains, yet most research to date focuses on subtype B, the subt... More
Over 50% of all human immunodeficiency virus type 1 (HIV-1) infections worldwide are caused by subtype C strains, yet most research to date focuses on subtype B, the subtype most commonly found in North America and Europe. The HIV-1 trans-acting regulatory protein (Tat) is essential for regulating productive replication of HIV-1. Tat is secreted by HIV-infected cells and alters several functions of uninfected bystander cells. One such function is that, by acting at the cell membrane, subtype B Tat stimulates the production of tumor necrosis factor (TNF) and chemokine (C-C motif) ligand 2 (CCL2) from human monocytes and can act as a chemoattractant. In this study, we show that the mutation of a cysteine to a serine at residue 31 of Tat commonly found in subtype C variants significantly inhibits the abilities of the protein to bind to chemokine (C-C motif) receptor 2 (CCR2), induce intracellular calcium flux, stimulate TNF and CCL2 production, and inhibit its chemoattractant properties. We also show that TNF is important in mediating some effects of extracellular Tat. This report therefore demonstrates the important functional differences between subtype C and subtype B Tat and highlights the need for further investigation into the different strains of HIV-1. Less
HIV type 1 (HIV-1)-associated dementia (HAD) is believed to occur due to aberrant activation of monocyte-derived macrophages and brain-resident microglial cells by viral ... More
HIV type 1 (HIV-1)-associated dementia (HAD) is believed to occur due to aberrant activation of monocyte-derived macrophages and brain-resident microglial cells by viral proteins as well as by the proinflammatory mediators released by infected cells. To investigate the inflammatory aspects of the disease, we examined the levels of soluble CD40L (sCD40L) in paired samples of plasma and cerebrospinal fluid obtained from 25 HIV-infected individuals. A significantly higher level of sCD40L was detected in both cerebrospinal fluid and plasma from HIV-infected patients with cognitive impairment, compared with their nonimpaired counterparts. The contribution of sCD40L to the pathogenesis of HAD was then examined by in vitro experiments. rCD40L synergized with HIV-1 Tat to increase TNF-alpha release from primary human monocytes and microglia, in an NF-kappaB-dependent manner. The mechanistic basis for this synergism was attributed to a Tat-mediated up-regulation of CD40 in monocytes and microglia. Finally, the CD40L-mediated increase in TNF-alpha production by monocytes was shown to be biologically important; immunodepletion experiments revealed that TNF-alpha was essential for the neurotoxic effects of conditioned medium recovered from Tat/CD40L-treated monocytes. Taken together, our results show that CD40 signaling in microglia and monocytes can synergize with the effects of Tat, further amplifying inflammatory processes within the CNS and influencing neuronal survival. Less
The spirochete Borrelia burgdorferi is the agent of Lyme disease, which causes central nervous system manifestations in up to 20% of patients. We investigated the respons... More
The spirochete Borrelia burgdorferi is the agent of Lyme disease, which causes central nervous system manifestations in up to 20% of patients. We investigated the response of human brain microglial cells, glial progenitors, neurons, astrocytes, as well as peripheral blood monocytes to stimulation with B. burgdorferi. We used oligoarrays to detect changes in the expression of genes important for shaping adaptive and innate immune responses. We found that stimulation with B. burgdorferi lysate increased the expression of Toll-like receptors (TLRs) 1 and 2 in all cell types except neurons. However, despite similarities in global gene profiles of monocytes and microglia, only microglial cells responded to the stimulation with a robust increase in HLA-DR, HLA-DQ, and also coexpressed CD11-c, a dendritic cell marker. In contrast, a large number of HLA-related molecules were repressed at both the RNA and the protein levels in stimulated monocytes, whereas secretion of IL-10 and TNF-alpha was strongly induced. These results show that signaling through TLR1/2 in response to B. burgdorferi can elicit opposite immunoregulatory effects in blood and in brain immune cells, which could play a role in the different susceptibility of these compartments to infection. Less
