Induction of chemokines in human astrocytes by picornavirus infection requires activation of both AP-1 and NF-kappa B

Emerging concerns of blood-brain barrier dysfunction caused by neurotropic enteroviral infections

Enteroviruses (EVs), comprise a genus in the Picornaviridae family, which have been shown to be neurotropic and can cause various neurological disorders or long-term neurological condition, placing a huge burden on society and families. The blood-brain barrier (BBB) is a protective barrier that prevents dangerous substances from entering the central nervous system (CNS). Recently, numerous EVs have been demonstrated to have the ability to disrupt BBB, and further lead to severe neurological damage. However, the precise mechanisms of BBB disruption associated with these EVs remain largely unknown. In this Review, we focus on the molecular mechanisms of BBB dysfunction caused by EVs, emphasizing the invasiveness of enterovirus A71 (EVA71), which will provide a research direction for further treatment and prevention of CNS disorders.

IFNAR signaling of neuroectodermal cells is essential for the survival of C57BL/6 mice infected with Theiler's murine encephalomyelitis virus

BACKGROUND

Theiler's murine encephalomyelitis virus (TMEV) is a single-stranded RNA virus that causes encephalitis followed by chronic demyelination in SJL mice and spontaneous seizures in C57BL/6 mice. Since earlier studies indicated a critical role of type I interferon (IFN-I) signaling in the control of viral replication in the central nervous system (CNS), mouse strain-specific differences in pathways induced by the IFN-I receptor (IFNAR) might determine the outcome of TMEV infection.

METHODS

Data of RNA-seq analysis and immunohistochemistry were used to compare the gene and protein expression of IFN-I signaling pathway members between mock- and TMEV-infected SJL and C57BL/6 mice at 4, 7 and 14 days post-infection (dpi). To address the impact of IFNAR signaling in selected brain-resident cell types, conditional knockout mice with an IFNAR deficiency in cells of the neuroectodermal lineage (NesCre±IFNARfl/fl), neurons (Syn1Cre±IFNARfl/fl), astrocytes (GFAPCre±IFNARfl/fl), and microglia (Sall1CreER±IFNARfl/fl) on a C57BL/6 background were tested. PCR and an immunoassay were used to quantify TMEV RNA and cytokine and chemokine expression in their brain at 4 dpi.

RESULTS

RNA-seq analysis revealed upregulation of most ISGs in SJL and C57BL/6 mice, but Ifi202b mRNA transcripts were only increased in SJL and Trim12a only in C57BL/6 mice. Immunohistochemistry showed minor differences in ISG expression (ISG15, OAS, PKR) between both mouse strains. While all immunocompetent Cre-negative control mice and the majority of mice with IFNAR deficiency in neurons or microglia survived until 14 dpi, lack of IFNAR expression in all cells (IFNAR-/-), neuroectodermal cells, or astrocytes induced lethal disease in most of the analyzed mice, which was associated with unrestricted viral replication. NesCre±IFNARfl/fl mice showed more Ifnb1, Tnfa, Il6, Il10, Il12b and Ifng mRNA transcripts than Cre-/-IFNARfl/fl mice. IFNAR-/- mice also demonstrated increased IFN-α, IFN-β, IL1-β, IL-6, and CXCL-1 protein levels, which highly correlated with viral load.

CONCLUSIONS

Ifi202b and Trim12a expression levels likely contribute to mouse strain-specific susceptibility to TMEV-induced CNS lesions. Restriction of viral replication is strongly dependent on IFNAR signaling of neuroectodermal cells, which also controls the expression of key pro- and anti-inflammatory cytokines during viral brain infection.

Immune Functions of Astrocytes in Viral Neuroinfections

Neuroinfections of the central nervous system (CNS) can be triggered by various pathogens. Viruses are the most widespread and have the potential to induce long-term neurologic symptoms with potentially lethal outcomes. In addition to directly affecting their host cells and inducing immediate changes in a plethora of cellular processes, viral infections of the CNS also trigger an intense immune response. Regulation of the innate immune response in the CNS depends not only on microglia, which are fundamental immune cells of the CNS, but also on astrocytes. These cells align blood vessels and ventricle cavities, and consequently, they are one of the first cell types to become infected after the virus breaches the CNS. Moreover, astrocytes are increasingly recognized as a potential viral reservoir in the CNS; therefore, the immune response initiated by the presence of intracellular virus particles may have a profound effect on cellular and tissue physiology and morphology. These changes should be addressed in terms of persisting infections because they may contribute to recurring neurologic sequelae. To date, infections of astrocytes with different viruses originating from genetically distinct families, including Flaviviridae, Coronaviridae, Retroviridae, Togaviridae, Paramyxoviridae, Picomaviridae, Rhabdoviridae, and Herpesviridae, have been confirmed. Astrocytes express a plethora of receptors that detect viral particles and trigger signaling cascades, leading to an innate immune response. In this review, we summarize the current knowledge on virus receptors that initiate the release of inflammatory cytokines from astrocytes and depict the involvement of astrocytes in immune functions of the CNS.

Overexpression of circARF3 mitigates TNF-α-induced inflammatory damage by up-regulating miR-125b

Encephalitis is the highest disability illness. We studied the function and mechanisms of circular RNA circARF3 (circARF3) in neurocyte cell inflammatory damage. CCK-8 assay and flow cytometry were, respectively, employed for examining the influences of tumor necrosis factor α (TNF-α), circARF3 and microRNA (miR)-125b on cell viability and apoptosis. The expression of circARF3 and miR-125b were changed by employing cell transfection and the results were determined by using qRT-PCR. Besides, the expression of Bcl-2, Bax, Cleaved-caspase-3, interleukin (IL)-1β, IL-6, IL-8 and cell pathways-related proteins were examined by using Western blot. The productions of IL-6, IL-8 and IL-1β were also tested by ELISA. The level of reactive oxygen species (ROS) was examined by ROS assay. We found that TNF-α caused inflammatory damage showing as suppressed cell viability, enhanced cell apoptosis, and increased cytokines production and ROS generation. Besides, TNF-α inducement also markedly reduced circARF3 expression. circARF3 overexpression mitigated TNF-α-induced cell inflammatory damage. Moreover, miR-125b was targeted and positively regulated by circARF3. Furthermore, miR-125b inhibition could reverse the influences of circARF3 overexpression. Besides, circARF3 restrained the JNK and NF-κB pathways by up-regulation of miR-125b. In conclusion, overexpression of circARF3 mitigated cell inflammatory damage via inactivation of JNK and NF-κB pathways and thereby up-regulation of miR-125b.

Molecular Pathogenicity of Enteroviruses Causing Neurological Disease

Enteroviruses are single-stranded positive-sense RNA viruses that primarily cause self-limiting gastrointestinal or respiratory illness. In some cases, these viruses can invade the central nervous system, causing life-threatening neurological diseases including encephalitis, meningitis and acute flaccid paralysis (AFP). As we near the global eradication of poliovirus, formerly the major cause of AFP, the number of AFP cases have not diminished implying a non-poliovirus etiology. As the number of enteroviruses linked with neurological disease is expanding, of which many had previously little clinical significance, these viruses are becoming increasingly important to public health. Our current understanding of these non-polio enteroviruses is limited, especially with regards to their neurovirulence. Elucidating the molecular pathogenesis of these viruses is paramount for the development of effective therapeutic strategies. This review summarizes the clinical diseases associated with neurotropic enteroviruses and discusses recent advances in the understanding of viral invasion of the central nervous system, cell tropism and molecular pathogenesis as it correlates with host responses.

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.

CCAAT/enhancer binding protein δ regulates glial proinflammatory gene expression

The transcription factor CCAAT/enhancer binding protein δ (C/EBPδ) is expressed in activated astrocytes and microglia and can regulate the expression of potentially detrimental proinflammatory genes. The objective of this study was to determine the role of C/EBPδ in glial activation. To this end, glial activation was analyzed in primary glial cultures and in the central nervous system from wild type and C/EBPδ(-/-) mice. In vitro studies showed that the expression of proinflammatory genes nitric oxide (NO)synthase-2, cyclooxygenase-2, and interleukin (IL)-6 in glial cultures, and the neurotoxicity elicited by microglia in neuron-microglia cocultures, were decreased in the absence of C/EBPδ when cultures were treated with lipopolysaccharide (LPS) and interferon γ, but not with LPS alone. In C/EBPδ(-/-) mice, systemic LPS-induced brain expression of NO synthase-2, tumor necrosis factor-α, IL-1β, and IL-6 was attenuated. Finally, increased C/EBPδ nuclear expression was observed in microglial cells from amyotrophic lateral sclerosis patients and G93A-SOD1 mice spinal cord. These results demonstrate that C/EBPδ plays a key role in the regulation of proinflammatory gene expression in glial activation and suggest that C/EBPδ inhibition has potential for the treatment of neurodegenerative disorders, in particular, amyotrophic lateral sclerosis.

NLRC4 inflammasome-mediated production of IL-1β modulates mucosal immunity in the lung against gram-negative bacterial infection

Bacterial flagellin is critical to mediate NLRC4 inflammasome-dependent caspase-1 activation. However, Shigella flexneri, a nonflagellated bacterium, and a flagellin (fliC) knockout strain of Pseudomonas aeruginosa are known to activate NLRC4 in bone marrow-derived macrophages. Furthermore, the flagellin-deficient fliC strain of P. aeruginosa was used in a mouse model of peritonitis to show the requirement of NLRC4. In a model of pulmonary P. aeruginosa infection, flagellin was shown to be essential for the induction of NLRC4-dependent caspase-1 activation. Moreover, in all P. aeruginosa studies, IL-1β production was attenuated in NLRC4(-/-) mice; however, the role of IL-1β in NLRC4-mediated innate immunity in the lungs against a nonflagellated bacterium was not explored. In this article, we report that NLRC4 is important for host survival and bacterial clearance, as well as neutrophil-mediated inflammation in the lungs following Klebsiella pneumoniae infection. NLRC4 is essential for K. pneumoniae-induced production of IL-1β, IL-17A, and neutrophil chemoattractants (keratinocyte cell-derived chemokines, MIP-2, and LPS-induced CXC chemokines) in the lungs. NLRC4 signaling in hematopoietic cells contributes to K. pneumoniae-induced lung inflammation. Furthermore, exogenous IL-1β, but not IL-18 or IL-17A, partially rescued survival, neutrophil accumulation, and cytokine/chemokine expression in the lungs of NLRC4(-/-) mice following infectious challenge. Furthermore, IL-1R1(-/-) mice displayed a decrease in neutrophilic inflammation in the lungs postinfection. Taken together, these findings provide novel insights into the role of NLRC4 in host defense against K. pneumoniae infection.

Induction of interleukin-8 by Naegleria fowleri lysates requires activation of extracellular signal-regulated kinase in human astroglial cells

Naegleria fowleri is a pathogenic free-living amoeba which causes primary amoebic meningoencephalitis in humans and experimental animals. To investigate the mechanisms of such inflammatory diseases, potential chemokine gene activation in human astroglial cells was investigated following treatment with N. fowleri lysates. We demonstrated that N. fowleri are potent inducers for the expression of interleukin-8 (IL-8) genes in human astroglial cells which was preceded by activation of extracellular signal-regulated kinase (ERK). In addition, N. fowleri lysates induces the DNA binding activity of activator protein-1 (AP-1), an important transcription factor for IL-8 induction. The specific mitogen-activated protein kinase kinase/ERK inhibitor, U0126, blocks N. fowleri-mediated AP-1 activation and subsequent IL-8 induction. N. fowleri-induced IL-8 expression requires activation of ERK in human astroglial cells. These findings indicate that treatment of N. fowleri on human astroglial cells leads to the activation of AP-1 and subsequent expression of IL-8 which are dependent on ERK activation. These results may help understand the N. fowleri-mediated upregulation of chemokine and cytokine expression in the astroglial cells.

TNF-α expression in Schwann cells is induced by LPS and NF-κB-dependent pathways

Lipopolysaccharide (LPS) is recognized by Toll-like receptor 4 and activates mitogen-activated protein kinase, which leads to the induction of proinflammatory cytokine gene expression. In vivo, Schwann cells (SCs) at the site of injury may also produce tumor necrosis factor-α (TNF-α). However, the precise mechanism that regulates TNF-α synthesis is still not clear. The nuclear transcription factor-κB (NF-κB) is an important transcription factor which is involved in the regulation of host immune responses. In the present study, we found that LPS possessed a comparable specific activity for activation of NF-κB-dependent gene expression in SCs. We also observed IκB-α/IκB-β degradation and the nuclear translocation of P65 due to LPS treatments. LPS-elicited TNF-α production in SCs was also drastically suppressed by SN50 (NF-κB inhibitor).

Melanoma differentiation-associated gene 5 is critical for protection against Theiler's virus-induced demyelinating disease

Infection of dendritic and glial cells with Theiler's murine encephalomyelitis virus (TMEV) induces various cytokines via Toll-like receptor- and melanoma differentiation-associated gene 5 (MDA5)-dependent pathways. However, the involvement and role of MDA5 in cytokine gene activation and the pathogenesis of TMEV-induced demyelinating disease are largely unknown. In this study, we demonstrate that MDA5 plays a critical role in the production of TMEV-induced alpha interferon (IFN-α) during early viral infection and in protection against the development of virus-induced demyelinating disease. Our results indicate that MDA5-deficient 129SvJ mice display significantly higher viral loads and apparent demyelinating lesions in the central nerve system (CNS) accompanied by clinical symptoms compared with wild-type 129SvJ mice. During acute viral infection, MDA5-deficient mice produced elevated levels of chemokines, consistent with increased cellular infiltration, but reduced levels of IFN-α, known to control T cell responses and cellular infiltration. Additional studies with isolated CNS glial cells from these mice suggest that cells from MDA5-deficient mice are severely compromised in the production of IFN-α upon viral infection, which results in increased cellular infiltration and viral loads in the CNS. Despite inadequate stimulation, the overall T cell responses to the viral determinants were significantly elevated in MDA5-deficient mice, reflecting the increased cellular infiltration. Therefore, the lack of MDA5-mediated IFN-α production may facilitate a massive viral load and elevated cellular infiltration in the CNS during early viral infection, leading to the pathogenesis of demyelinating disease.

Pro-inflammatory gene expression and neurotoxic effects of activated microglia are attenuated by absence of CCAAT/enhancer binding protein β

Background

Microglia and astrocytes respond to homeostatic disturbances with profound changes of gene expression. This response, known as glial activation or neuroinflammation, can be detrimental to the surrounding tissue. The transcription factor CCAAT/enhancer binding protein β (C/EBPβ) is an important regulator of gene expression in inflammation but little is known about its involvement in glial activation. To explore the functional role of C/EBPβ in glial activation we have analyzed pro-inflammatory gene expression and neurotoxicity in murine wild type and C/EBPβ-null glial cultures.

Methods

Due to fertility and mortality problems associated with the C/EBPβ-null genotype we developed a protocol to prepare mixed glial cultures from cerebral cortex of a single mouse embryo with high yield. Wild-type and C/EBPβ-null glial cultures were compared in terms of total cell density by Hoechst-33258 staining; microglial content by CD11b immunocytochemistry; astroglial content by GFAP western blot; gene expression by quantitative real-time PCR, western blot, immunocytochemistry and Griess reaction; and microglial neurotoxicity by estimating MAP2 content in neuronal/microglial cocultures. C/EBPβ DNA binding activity was evaluated by electrophoretic mobility shift assay and quantitative chromatin immunoprecipitation.

Results

C/EBPβ mRNA and protein levels, as well as DNA binding, were increased in glial cultures by treatment with lipopolysaccharide (LPS) or LPS + interferon γ (IFNγ). Quantitative chromatin immunoprecipitation showed binding of C/EBPβ to pro-inflammatory gene promoters in glial activation in a stimulus- and gene-dependent manner. In agreement with these results, LPS and LPS+IFNγ induced different transcriptional patterns between pro-inflammatory cytokines and NO synthase-2 genes. Furthermore, the expressions of IL-1β and NO synthase-2, and consequent NO production, were reduced in the absence of C/EBPβ. In addition, neurotoxicity elicited by LPS+IFNγ-treated microglia co-cultured with neurons was completely abolished by the absence of C/EBPβ in microglia.

Conclusions

These findings show involvement of C/EBPβ in the regulation of pro-inflammatory gene expression in glial activation, and demonstrate for the first time a key role for C/EBPβ in the induction of neurotoxic effects by activated microglia.

Fas ligation and tumor necrosis factor α activation of murine astrocytes promote heat shock factor-1 activation and heat shock protein expression leading to chemokine induction and cell survival

Death-inducing ligands tumor necrosis factor alpha (TNFα) and Fas ligand (FasL) do not kill cultured astrocytes; instead they induce a variety of chemokines including macrophage-inflammatory protein-1α/CC chemokine ligand 3 (CCL3), monocyte chemoattractant protein-1 (CC CCL-2), macrophage-inflammatory protein-2/CXC chemokine ligand 2 (CXCL2, a murine homologue of interleukin 8), and interferon-induced protein of 10 kDa (CXCL10). Induction is enhanced by protein synthesis inhibition suggesting the existence of endogenous inhibitors. ERK, NF-κB, heat shock factor-1 (HSF-1) and heat shock proteins were examined for their possible roles in signal transduction. Inhibition of ERK activation by PD98059 partially inhibited expression of all but FasL-induced CXCL10. Although inhibition of NF-κB DNA binding inhibited chemokine induction, PD98059 did not inhibit TNFα-induced NF-κB DNA binding suggesting that ERK serves an NF-κB-independent pathway. Heat shock itself induced astrocytic chemokine expression; both TNFα and FasL induced HSF-1 DNA binding and Hsp72 production; and Hsp72-induced chemokine expression. Inhibition of either HSF-1 binding with quercetin or heat shock protein synthesis with KNK437 compromised chemokine induction without compromising cell survival. These data suggest that the induction of heat shock proteins via HSF-1 contribute to the TNFα- and FasL-induced expression of chemokines in astrocytes.

CXCL1 regulates pulmonary host defense to Klebsiella Infection via CXCL2, CXCL5, NF-kappaB, and MAPKs

Pulmonary bacterial infections are a leading cause of death. Since the introduction of antibiotics, multidrug-resistant Klebsiella pneumoniae became an escalating threat. Therefore, development of methods to augment antibacterial defense is warranted. Neutrophil recruitment is critical to clear bacteria, and neutrophil migration in the lung requires the production of ELR(+) CXC chemokines. Although lung-specific CXCL1/keratinocyte cell-derived chemokine (KC) transgene expression causes neutrophil-mediated clearance of K. pneumoniae, the mechanisms underlying KC-mediated host defense against K. pneumoniae have not been explored. In this study, we delineated the host defense functions of KC during pulmonary K. pneumoniae infection using KC(-/-) mice. Our findings demonstrate that KC is important for expression of CXCL2/MIP-2 and CXCL5/LPS-induced CXC chemokine, and activation of NF-κB and MAPKs in the lung. Furthermore, KC derived from both hematopoietic and resident cells contributes to host defense against K. pneumoniae. Neutrophil depletion in mice before K. pneumoniae infection reveals no differences in the production of MIP-2 and LPS-induced CXC chemokine or activation of NF-κB and MAPKs in the lung. Using murine bone marrow-derived and alveolar macrophages, we confirmed KC-mediated upregulation of MIP-2 and activation of NF-κB and MAPKs on K. pneumoniae infection. Moreover, neutralizing KC in bone marrow-derived macrophages before K. pneumoniae challenge decreases bacteria-induced production of KC and MIP-2, and activation of NF-κB and MAPKs. These findings reveal the importance of KC produced by hematopoietic and resident cells in regulating pulmonary host defense against a bacterial pathogen via the activation of transcription factors and MAPKs, as well as the expression of cell adhesion molecules and other neutrophil chemoattractants.

EV71 induces COX-2 expression via c-Src/PDGFR/PI3K/Akt/p42/p44 MAPK/AP-1 and NF-kappaB in rat brain astrocytes

Enterovirus 71 (EV71) induces the expression of cyclooxgenase (COX)-2 served as a major neurotoxic factor in CNS injury. However, the mechanisms underlying EV71-initiated intracellular signaling pathways leading to COX-2 expression remain unknown. Therefore, we investigated the mechanisms underlying EV71-induced COX-2 expression and prostaglandin E(2) (PGE(2)) production in rat brain astrocytes (RBA)-1, determined by Western blotting, RT-PCR, and promoter assay. Here, we reported that EV71-induced COX-2 expression and PGE(2) production were attenuated by pretreatment with the inhibitors of c-Src (PP1), PDGFR (AG1296), PI3K (Wortmannin), MEK1/2 (PD98059), NF-kappaB (helenalin), and AP-1 (Tanshinone) and transfection with shRNA or siRNA of c-Src, PDGFR, p85, c-Jun, c-Fos, ERK1, or ERK2. We further observed that EV71-induced activation of Akt and p42/p44 MAPK were mediated via c-Src and PDGFR. Pretreatment with PP1 attenuated EV71-stimulated phosphorylation of Src, PDGFR, Akt, and p42/p44 MAPK. Inhibition of PI3K by Wortmannin attenuated EV71-induced Akt and p42/p44 MAPK phosphorylation, but had no effect on PDGFR phosphorylation, suggesting that PDGFR is an upstream and p42/p44 MAPK is a downstream component of PI3K/Akt in these responses. EV71-stimulated NF-kappaB translocation from the cytoplasm to the nucleus, IkappaBalpha degradation and NF-kappaB promoter activity were attenuated by pretreatment with helenalin, but not AG1296, Wortmannin, and PD98059. EV71-induced c-Jun mRNA expression was attenuated by pretreatment with PD98059, AG1296, or Wortmannin. These results demonstrate that in RBA-1 cells, EV71-induced COX-2 expression associated with PGE(2) production is mediated through activation of c-Src/PDGFR/PI3K/Akt/p42/p44 MAPK to initiate the expression of AP-1.

Theiler's virus infection induces TLR3-dependent upregulation of TLR2 critical for proinflammatory cytokine production

Theiler's murine encephalomyelitis virus (TMEV) infection directly induces many proinflammatory genes, including type I interferon (IFN) and a variety of cytokine genes. These virus-induced cytokines are a critical factor in developing TMEV-induced demyelinating disease. We have previously reported that the major activation signal for the cytokine genes is mediated via TLR3. In this study, we describe that TLR2 is upregulated via TLR3 signal and cooperatively participates in the expression of IL-6, IL-1beta, CCL2, and CCL5 genes following TMEV infection. The expression of these genes was significantly impaired in both TLR2-deficient and TLR3-deficient primary astrocytes. However, the induction of type I IFNs was not affected by TLR2 deficiency in the primary cells. TMEV infection led to TLR2-mediated NF-kappaB activation, but not IRF3 or IRF7 activation, critical for type I IFN production. More importantly, TLR3 was required for TMEV-induced early TLR2 upregulation in primary astrocytes leading to the production of TLR2-dependent cytokines such as IL-6. Interestingly, soluble factor(s) produced via TLR2/3-dependent signals appears to be partially associated with the downstream cytokine production. These results indicate that TMEV utilizes TLR3-induced TLR2 to induce inflammatory cytokines, which are critical to the development of immune-mediated demyelinating disease.

Coxsackievirus B3 induction of NFAT: requirement for myocarditis susceptibility

Ultraviolet (u.v.) inactivated coxsackievirus B3 (CVB3) induces rapid calcium flux in naïve BALB/c CD4+ T cells. CD4+ cells lacking decay accelerating factor (DAF-/-) show little calcium flux indicating that virus cross-linking of this virus receptor protein is necessary for calcium signaling in CVB3 infection. Interaction of CVB3 with CD4+ cells also activates NFAT DNA binding. To show that NFAT activation is crucial to CVB3 induced disease, wild-type mice and transgenic mice expressing dominant-negative NFAT (dnNFAT) mutant in T cells were infected and evaluated for myocarditis and pancreatitis 7 days later. Inhibition of NFAT in T cells prevented myocarditis but had no effect on pancreatitis. Virus titers in pancreas were equivalent in wild-type and dnNFAT animals but cardiac virus titers were increased in dnNFAT mice. Interferon-gamma (IFN gamma) expression was reduced in both CD4+ and V gamma 4+ T cells from dnNFAT mice compared to controls. FasL expression by V gamma 4+ cells was also suppressed. Inhibition of FasL expression by V gamma 4+ cells is consistent with myocarditis protection in dnNFAT mice.

Replication of Theiler's virus requires NF-kappa B-activation: higher viral replication and spreading in astrocytes from susceptible mice

To investigate viral replication and cell-cell spreading in astrocytes, recombinant Theiler's murine encephalomyelitis virus (TMEV) expressing green fluorescent protein (GFP) during the replication was generated. GFP and TMEV proteins were processed correctly in infected cells and production of viral proteins could be tracked by fluorescent microscopy. Viral replication of both wild-type TMEV and GFP-TMEV was dependent on the activation of NF-kappaB and partially MAP kinase, based on chemical inhibition studies. Viral replication was significantly reduced in primary astrocytes from NF-kappaB1 (p105)-deficient mice compared with that from wild-type control mice, whereas cytokine production was enhanced. These results suggest an association of canonical NF-kappaB subunits in viral replication, but not cytokine production. Viral replication was also suppressed in both IKKalpha and IKKbeta-deficient mouse embryonic fibroblasts (MEFs), compared with that in wild-type MEF. However, the inhibition was significantly greater in IKKbeta-deficient MEF, suggesting that IKKbeta plays a stronger role in supporting viral replication. Interestingly, viral replication and spreading in primary astrocytes from susceptible SJL/J mice were several-fold higher than those in astrocytes from resistant C57BL/6 mice, suggesting that higher viral replication levels in astrocytes may also contribute to the viral persistence in the central nervous system (CNS) of susceptible SJL/J mice. A relatively higher level of activated NF-kappaB was found in the nuclei of virus-infected SJL astrocytes compared with C57BL/6 astrocytes suggest that the NF-kappaB activation level affects on viral replication.

TRAIL induces MMP-9 expression via ERK activation in human astrocytoma cells

Matrix metalloproteinase-9 (MMP-9) is an important angiogenic and prognostic factor in malignant tumors. Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is known as the death ligand, which induces preferential apoptosis of transformed tumor cells. In this study, we investigated the biological functions of TRAIL, other than its role in induction of apoptosis. We demonstrated that TRAIL induces MMP-9 expression in human astrocytoma cells, which is preceded by activation of extracellular signal-regulated protein kinase (ERK). In addition, TRAIL induces the DNA-binding activity of NF-kappaB, an important transcription factor for MMP-9 induction. The specific MEK inhibitor, U0126, significantly blocks TRAIL-mediated NF-kappaB activation and subsequent MMP-9 induction. These findings indicate that TRAIL treatment in human astrocytoma cells leads to the activation of NF-kappaB and subsequent expression of MMP-9, which are dependent on ERK activation. Collectively, these results suggest that TRAIL has alternative biological functions in addition to its role in inducing apoptosis in human malignant astrocytoma cells.

Astrocytes in multiple sclerosis: a product of their environment

It has long been thought that astrocytes, like other glial cells, simply provide a support mechanism for neuronal function in the healthy and inflamed central nervous system (CNS). However, recent evidence suggests that astrocytes play an active and dual role in CNS inflammatory diseases such as multiple sclerosis (MS). Astrocytes not only have the ability to enhance immune responses and inhibit myelin repair, but they can also be protective and limit CNS inflammation while supporting oligodendrocyte and axonal regeneration. The particular impact of these cells on the pathogenesis and repair of an inflammatory demyelinating process is dependent upon a number of factors, including the stage of the disease, the type and microenvironment of the lesion, and the interactions with other cell types and factors that influence their activation. In this review, we summarize recent data supporting the idea that astrocytes play a complex role in the regulation of CNS autoimmunity.

Hydrogen peroxide enhances TRAIL-induced cell death through up-regulation of DR5 in human astrocytic cells

The central nervous system (CNS) is particularly vulnerable to reactive oxygen species (ROS), which have been implicated in the pathogenesis of various neurological disorders. The TNF superfamily of cytokines, especially tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), induces caspase-dependent cell death and is also implicated in various neurodegenerative diseases. In this study, we investigated the relationship between ROS and TRAIL-induced cell death. Exposure to hydrogen peroxide (H(2)O(2)) (100 microM) sensitized human astrocytic cells to TRAIL-induced cell death (up to 7-fold induction). To delineate the molecular mechanisms responsible for H(2)O(2)-induced sensitization, we examined expression of various genes (Caspase-8, Fas, FasL, DR4, DR5, DcR1, DcR2, TRAIL, TNFRp55) related to TRAIL-induced cell death. Treatment with H(2)O(2) significantly increased DR5 mRNA and protein expression in a time- and dose-dependent manner. H(2)O(2)-mediated cell death was blocked upon treatment with DR5:Fc protein, a TRAIL-specific antagonistic protein. These findings collectively suggest that oxidative stress sensitizes human astroglial cells to TRAIL-induced cell death through up-regulation of DR5 expression.

Substance P enhances NF-kappaB transactivation and chemokine response in murine macrophages via ERK1/2 and p38 MAPK signaling pathways

The neuropeptide substance P (SP), as a major mediator of neuroimmunomodulatory activity, modulates diverse functions of immune cells, including macrophages. In the current study, we focused on the yet uncertain role of SP in enhancing the inducible/inflammatory chemokine response of macrophages and the signaling mechanism involved. We studied the effect on the murine monocyte/macrophage cell line RAW 264.7 as well as isolated primary macrophages. Our data show that SP, at nanomolar concentrations, elicited selective chemokine production from murine macrophages. Among the chemokines examined, macrophage inflammatory protein-2 and monocyte chemoattractant protein-1 are two major chemokines that were synthesized by macrophages in response to SP. Furthermore, SP treatment strongly induced the classic pathway of IkappaB-dependent NF-kappaB activation and enhanced DNA binding as well as transactivation activity of the transcription factor. SP-evoked transcriptional induction of chemokines was specific, since it was blocked by treatment with selective neurokinin-1 receptor antagonists. Moreover, SP stimulation of macrophages activated the ERK1/2 and p38 MAPK but not JNKs. Blockade of these two MAPK pathways with specific inhibitors abolished SP-elicited nuclear translocation of phosphorylated NF-kappaB p65 and NF-kappaB-driven chemokine production, suggesting that the two MAPKs lie in the signaling pathways leading to the chemokine response. Collectively, our data demonstrate that SP enhances selective inflammatory chemokine production by murine macrophages via ERK/p38 MAPK-mediated NF-kappaB activation.

HIV-1 matrix protein p17 binds to monocytes and selectively stimulates MCP-1 secretion: role of transcriptional factor AP-1

HIV‐1 matrix protein p17 activates a variety of cell responses which play a critical role in viral replication and infection. Its activity depends on the expression of p17 receptors (p17R) on the surface of target cells. Whether p17 also plays a role in stimulating human monocytes, a major HIV‐1 reservoir, is not known. Here we show that human monocytes constitutively express p17Rs and that p17 selectively triggers these cells to produce MCP‐1. The effect of p17 on MCP‐1 expression was observed at the transcriptional level and was primarily dependent on the activation of the transcription factor AP‐1. p17 increased the binding activity of AP‐1 complexes in a time‐ and dose‐dependent manner. Deletion of the AP‐1 binding sites in the MCP‐1 promoter resulted in the lack of p17‐induced MCP‐1 transcription. In particular, the P3 binding site located between −69 and −63 position seems to be essential to MCP‐1 mRNA induction in p17‐treated monocytes. An ever increasing amount of evidences shows a tight link between biologically dysregulated monocytes, AP‐1 activation, MCP‐1 release and HIV‐1 pathogenesis. Overall our results suggest that p17 may play a critical role in the monocyte‐mediated inflammatory processes, which are suspected to be major precipitating events in AIDS‐defining diseases.

Induction of activator protein-1 and nuclear factor-kappaB as a prerequisite for disease development in susceptible SJL/J mice after theiler murine encephalomyelitis

Theiler murine encephalomyelitis (TME) represents an important mouse model of multiple sclerosis. Activator protein and nuclear factor-kappaB proteins are interacting transcription factors controlling the expression of cytokines involved in the demyelination process. However, specific expression patterns of these transcription factors in susceptible and resistant mouse strains and their relationship to demyelination remains to be determined. The expression of activator protein-1 (c-fos and c-jun) and nuclear factor-kappaB (p50 and p65) genes, TME virus, tumor necrosis factor-alpha, and interferon-gamma was investigated in the spinal cord of TME virus (BeAn strain)-infected SJL/J and C57BL/6 mice until 196 days postinfection (dpi) using reverse transcription-quantitative polymerase chain reaction. Additionally, c-fos, c-jun, and p50 expression was examined by applying immunohistochemistry. In susceptible SJL/J mice, in contrast to resistant C57BL/6 mice, all investigated mRNA transcripts were upregulated in the early (0-7 days dpi) and late phases (28-196 days dpi) of TME. In addition, white matter lesions of SL/J mice were characterized by c-jun-positive astrocytes and p50-positive mononuclear immune cells. Upregulation of activator protein-1 and nuclear factor-kappaB in resident glial cells in the early phase followed by strong downstream tumor necrosis factor-alpha production might account for disease development in susceptible SJL/J mice. In the late phase, the formation of JUN/JUN homodimers in intralesional astrocytes might contribute to the sustained release of proinflammatory cytokines, thereby promoting disease progression.

EV71 induces VCAM-1 expression via PDGF receptor, PI3-K/Akt, p38 MAPK, JNK and NF-κB in vascular smooth muscle cells

Enterovirus 71 (EV71) is a widespread virus that causes severe and fatal diseases in patients, including circulation failure. The mechanisms underlying EV71-initiated intracellular signaling pathways to influence host cell functions remain unknown. In this study, we identified a requirement for PDGFR, PI3-K/Akt, p38 MAPK, JNK, and NF-kappaB in the regulation of VCAM-1 expression by rat vascular smooth muscle cells (VSMCs) in response to viral infection. EV71 induced VCAM-1 expression in a time- and viral concentration-dependent manner. Infection of VSMCs with EV71 stimulated VCAM-1 expression and phosphorylation of PDGFR, Akt, and p38 MAPK which were attenuated by AG1296, wortmannin, and SB202190, respectively. The phosphorylation of JNK stimulated by EV71 was not detected under present conditions. In contrast, JNK inhibitor SP600125 inhibited EV71-induced VCAM-1 expression. Furthermore, VCAM-1 expression induced by EV71 was significantly attenuated by a selective NF-kappaB inhibitor (helenalin). Consistently, EV71-stimulated translocation of NF-kappaB into the nucleus and degradation of IkappaB-alpha as well as VCAM-1 mRNA expression was blocked by helenalin, AG1296, SB202190, SP600125, wortmannin, and LY294002. Moreover, the involvement of p38 MAPK, PI3-K/Akt, and NF-kappaB in EV71-induced VCAM-1 expression was reveled by that transfection with dominant negative plasmids of p38 MAPK, p85, Akt, NIK, IKK-alpha, and IKK-beta attenuated these responses. These findings suggest that in VSMCs, EV71-induced VCAM-1 expression was mediated through activation of PDGFR, PI3-K/Akt, p38 MAPK, JNK, and NF-kappaB pathways.

Expression of IL-27 p28 by Theiler's virus-infected macrophages depends on TLR3 and TLR7 activation of JNK-MAP-kinases

Theiler's murine encephalomyelitis virus (TMEV) causes a demyelinating disease (DD) due to infection of macrophages, stimulation of macrophage Toll-like receptor (TLR)3 and TLR7 pathways, activation of Mitogen-activated protein kinases (MAPK)s, and production of macrophages cytokines. Because expression of IL-27, a macrophage cytokine composed of p28 and EBI3 subunits, has been implicated in DD, we examined IL-27 subunit mRNA expression during TMEV infection of RAW264.7 cells, a macrophage cell line. TMEV infection of RAW264.7 cells did not affect cell viability, resulted in viral RNA replication, as well as p28 and EBI3 expression. Expression of p28 in TMEV-infected RAW264.7 cells depended on TLR3 and TLR7, as well as JNK but not p38 or ERK MAPKs. Since TMEV causes DD in SJL/J but not B10.S mice we determined the difference in expression of IL-27 subunit mRNA in SJL/J compared to B10.S macrophages. SJL/J macrophages expressed significantly more p28 mRNA after TMEV infection and after stimulation with TLR3 and TLR7 agonists compared with B10.S macrophages. Therefore, macrophages expression of IL-27 p28 mRNA in response to TMEV is due to activation of TLR3, TLR7, and JNK MAPKs pathways.

Castration of male C57L/J mice increases susceptibility and estrogen treatment restores resistance to Theiler's virus-induced demyelinating disease

Intracerebral inoculation of Theiler's murine encephalomyelitis virus (TMEV) results in immune-mediated demyelination in selective mouse strains. We have previously demonstrated that the males of C57L mice are significantly more susceptible to TMEV-induced demyelinating disease. To assess further the hormonal influence for this gender-associated differential susceptibility, estrogen-treated, castrated C57L mice were infected with TMEV and compared with sham-operated and/or placebo-treated mice. Interestingly, castration further elevated the susceptibility to virally induced demyelinating disease compared with sham-castrated control mice, and prolonged treatment of castrated mice with estrogen restored the resistance to the level of control mice. These results strongly suggest that sex hormone levels contribute to the gender-biased susceptibility to TMEV-induced demyelinating disease. Mice treated with estrogen showed a significantly decreased level of virus-specific Th1 responses both in the periphery and in the CNS. In addition, in vitro estrogen treatment was able to inhibit viral replication directly in macrophages, consistent with the lower level of viral RNA in microglia/macrophages in the CNS from castrated estrogen-treated mice compared with controls. Also, estrogen treatment inhibited VCAM-1 expression induced by tumor necrosis factor-alpha in cerebral vascular endothelial (CVE) cells via inhibition of nuclear factor-kappaB (NFkappaB), which is produced in various glial cells upon TMEV infection. Overall, estrogen treatment appears to exert its effects on viral replication, induction of immune responses, as well as infiltration of activated immune cells into the CNS via inhibition of NFkappaB function.

Coxsackievirus B3 induces T regulatory cells, which inhibit cardiomyopathy in tumor necrosis factor-alpha transgenic mice

Innate immunity promotes both the generation of autoimmunity and immunoregulation of adaptive immunity. Transgenic mice expressing the tumor necrosis factor-alpha (TNF-alpha) gene under the cardiac myosin promoter (TNF1.6 mice) develop dilated cardiomyopathy. Transgenic mice show extensive cardiac inflammation, suggesting that immunopathogenic mechanisms may promote cardiomyopathy. Two coxsackievirus B3 (CVB3) variants infect and replicate in the heart. H3 variant is highly myocarditic, but H310A1 variant activates CD4(+) T regulatory cells, which protect against viral myocarditis. T-cell depletion of TNF1.6 mice using monoclonal anti-CD3 or anti-CD4 antibody significantly reduced heart size and plasma troponin I concentrations compared with control TNF1.6 mice. Cardiomyopathy in TNF1.6 mice correlates to a CD4(+)Th1 response and autoimmune IgG2a antibodies. TNF1.6 mice infected with H310A1 virus reduced heart size and cardiac inflammation corresponding to the activation of CD4(+)CD25(+)FoxP3(+) (T regulatory cells). Immunosuppression is dependent on IL-10 but not TGFbeta. Adoptive transfer of the CD4(+)CD25(+) cells from H310A1-infected mice into uninfected TNF1.6 recipients abrogated cardiomyopathy. Exogenous administration of recombinant TNF-alpha to H310A1-infected mice for 4 days abrogated immunosuppression. Cardiac enlargement in TNF1.6 mice is partly attributable to T-cell activation and humoral autoimmunity caused by cytokine expression. T regulatory cells induced by H310A1 virus abrogate autoimmunity caused by TNF-alpha overexpression. H3 virus infection induces high levels of systemic TNF-alpha, whereas H310A1 virus does not. The low TNF-alpha response during H310A1 infections is likely responsible for the T regulatory cell response in these animals.

Induction of chemokine and cytokine genes in astrocytes following infection with Theiler's murine encephalomyelitis virus is mediated by the Toll-like receptor 3

Theiler's murine encephalomyelitis virus (TMEV) infection in the central nervous system (CNS) induces a demyelinating disease similar to human multiple sclerosis. TMEV infection results in activation of various chemokine and cytokine genes that are important in the initiation of an inflammatory response. We have previously shown that the production of these chemokines and cytokines in astrocytes is induced via the NF-kappaB pathway following TMEV and Coxsackie virus infection. In this study, we investigated whether the NF-kappaB-dependent inflammatory responses after TMEV infection is triggered through TLR3 and/or TLR7. The activation of NF-kappaB or IRF/ISRE, as well as the production of both MCP-1/CCL2 and IL-8/CXCL8, was observed in only TLR3-transfected HEK 293 cells, but not in TLR7-tranfected cells. The potential involvement of TLR3 in mouse embryonic fibroblasts and primary astrocytes was further investigated following transfection with wildtype or dominant negative form of TLRs and MyD88, as well as astrocytes from TLR3- and MyD88-deficient mice. Similarly, the activation of transcription factors and chemokine genes is induced in these mouse cells through primarily TLR3 signaling pathway, but not TLR7 or other MyD88-mediated pathways following TMEV infection. However, the TLR3-mediated cellular activation does not appear to affect the level of viral replication in astrocytes. These results strongly suggest that TLR3-signaling by TMEV alone is sufficient to induce the initial inflammatory cytokine responses that could be very important for the outcome of virus-induced encephalitis and/or demyelinating diseases, such as multiple sclerosis.

Transforming growth factor-beta1 differentially mediates fibronectin and inflammatory cytokine expression in kidney tubular cells

Transforming growth factor-beta(1) (TGF-beta(1)) is not only an important fibrogenic but also immunomodulatory cytokine in the human kidney. We have recently demonstrated that TGF-beta(1) induces interleukin-8 (IL-8), macrophage chemoattractant protein-1 (MCP-1), and fibronectin production in renal proximal tubular (HK-2) cells. However, the unique dependence of IL-8, MCP-1, and fibronectin on TGF-beta(1) expression is unknown. The TGF-beta(1) gene was effectively silenced in HK-2 cells using small-interference (si) RNA. Basal secretion of IL-8 and MCP-1 decreased (both P < 0.05) but, paradoxically, fibronectin increased (P < 0.05) in TGF-beta(1)-silenced cells compared with cells transfected with nonspecific siRNA. Significant increases were observed in mRNA for the TGF-beta(2) (P < 0.05), TGF-beta(3) (P < 0.05) isoforms and pSmad2 (P < 0.05), which were reflected in protein expression. Concurrent exposure to pan-specific TGF-beta antibody reversed the observed increase in fibronectin expression, suggesting that TGF-beta(2) and TGF-beta(3) isoforms mediate the increased fibronectin expression in TGF-beta(1)-silenced cells. An increase in the DNA binding activity of activator protein-1 (AP-1; P < 0.05) was also observed in TGF-beta(1)-silenced cells. In contrast, nuclear factor-kappaB (NF-kappaB) DNA binding activity was significantly decreased (P < 0.0005). These studies demonstrate that TGF-beta(1) is a key regulator of IL-8 and MCP-1, whereas fibronectin expression is regulated by a complex interaction between the TGF-beta isoforms in the HK-2 proximal tubular cell line. Decreased expression of TGF-beta(1) reduces chemokine production in association with reduced NF-kappaB DNA binding activity, suggesting that immunomodulatory pathways in the kidney are specifically dependent on TGF-beta(1). Conversely, decreased expression of TGF-beta(1) results in increased TGF-beta(2), TGF-beta(3), AP-1, and pSmad2 that potentially mediates the observed increase in fibronectin.

Involvement of cytokines in human immunodeficiency virus-1 protein Tat and methamphetamine interactions in the striatum

Human immunodeficiency virus-1 (HIV-1) infection of the brain causes elevation in pro-inflammatory cytokines and inflammatory changes in the striatum. HIV-1-infected individuals who also abuse drugs including the psychostimulant methamphetamine (MA) develop more severe encephalitis and neuronal damage compared to HIV-1-infected patients who do not abuse drugs. In previous studies, we demonstrated that the HIV-1 protein Tat and MA interacted to cause enhanced loss of dopamine in the rat striatum via the destruction of dopaminergic terminals. Since both Tat and MA activate glia and induce cytokine production, we investigated the role of cytokines in the synergistic neurotoxicity induced by Tat and MA using cytokine arrays. Significant increases in monocyte chemotactic protein (MCP-1), interleukin-1 alpha (IL-1alpha) and tissue inhibitor of metalloproteinase-1 (TIMP-1) levels were noted 4 h following Tat + MA treatment compared to saline, Tat or MA. MCP-1 and TIMP-1 levels remained elevated 16 h after Tat + MA compared to saline or MA but were not different from the Tat-treated group at this time point. Weak, but significant elevations in cytokine-induced neutrophil chemoattractant-3 (CINC-3), ciliary neurotrophic factor (CNTF) and macrophage inflammatory protein-3 alpha (MIP-3alpha) were also noted with Tat + MA. The interaction of Tat and MA was prevented in mice genetically deficient in MCP-1 with a consequent attenuation of Tat + MA neurotoxicity. Our findings suggest that HIV-1 infection with concurrent drug abuse might profoundly increase chemokine levels in the striatum resulting in enhanced damage to the dopaminergic system.

Lipopolysaccharides-activated human astroglioma cells induce apoptotic death of T-lymphocytes via c-Jun N-terminal kinases-dependent up-regulation of TRAIL

In the present study, we report that activated human astroglioma cells can injure T-lymphocytes by producing tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL). Treatment with lipopolysaccharides (LPS), a well-known immune stimulator, increased the expression levels of TRAIL mRNA and protein in human astroglioma cells. The increase of TRAIL mRNA expression by LPS was preceded by phosphorylation of the c-Jun N-terminal kinase (JNK) and consequently abrogated in the presence of the specific JNK inhibitor SP600125. The up-regulation of TRAIL expression was well co-related with AP-1 activation. Activated human astroglioma cells markedly induced the apoptotic death of T-lymphocytes. Pre-treatment with the TRAIL antagonistic protein TRAIL-R2:Fc prevented the death of T-lymphocytes caused by activated human astroglioma cells. The present results suggest that astroglioma cells may down-regulate T-lymphocytes via up-regulation of TRAIL.

The Synthetic Cannabinoid R(+)WIN 55,212-2 Inhibits the Interleukin-1 Signaling Pathway in Human Astrocytes in a Cannabinoid Receptor-independent Manner

R(+)WIN 55,212-2 is a synthetic cannabinoid that controls disease progression in models of multiple sclerosis. This is associated with its ability to reduce migration of leukocytes into the central nervous system. Because leukocyte migration is dependent on induction of adhesion molecules and chemokines by pro-inflammatory cytokines, we examined the effects of R(+)WIN 55,212-2 on their expression. Using 1321N1 astrocytoma and A-172 glioblastoma as cell models we show that R(+)WIN 55,212-2, but not its inactive chiral form S(-)WIN 55,212-2, strongly inhibits the interleukin-1 (IL-1) induction of the adhesion molecules intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) and the chemokine IL-8. This inhibition is not mediated via the CB1 or CB2 cannabinoid receptors, because their selective antagonists and pertussis toxin failed to affect the inhibitory effects of R(+)WIN 55,212-2. Furthermore reverse transcription-PCR analysis did not detect the expression of either receptor in 1321N1 cells. R(+)WIN 55,212-2 was shown to inhibit adhesion molecule and chemokine expression at the level of transcription, because it strongly inhibited the IL-1 induction of ICAM-1, VCAM-1, and IL-8 mRNAs and blocked the IL-1 activation of their promoters. The NFkappaB pathway was then assessed as a lead target for R(+)WIN 55,212-2. NFkappaB was measured by expression of a transfected NFkappaB-regulated reporter gene. Using this assay, R(+)WIN 55,212-2 strongly inhibited IL-1 activation of NFkappaB. Furthermore R(+)WIN 55,212-2 inhibited the ability of overexpressed Myd88, Tak-1, and IKK-2 to induce the reporter gene suggesting that R(+)WIN 55,212-2 acts at or downstream of IKK-2 in the IL-1 pathway. However R(+)WIN 55,212-2 failed to inhibit IL-1-induced degradation of IkappaBalpha, excluding IKK-2 as a direct target. In addition electrophoretic mobility shift and chromatin immunoprecipitation assays showed that R(+)WIN 55,212-2 does not regulate the IL-1-induced nuclear translocation of NFkappaB or the ability of the latter to bind to promoters regulating expression of ICAM-1 and IL-8. These data suggest that R(+)WIN 55,212-2 blocks IL-1 signaling by inhibiting the transactivation potential of NFkappaB.

Induction of proinflammatory mediators requires activation of the TRAF, NIK, IKK and NF-kappaB signal transduction pathway in astrocytes infected with Escherichia coli

Escherichia coli is associated with inflammation in the brain. To investigate whether astrocytes are involved in E. coil-induced inflammation, we assessed the levels of expression of proinflammatory mediators produced by E. coli-infected astrocytes. E. coli infection in primary human astrocytes and cell lines increased expression of the CXC chemokine IL-8/GRO-alpha, the CC chemokine MCP-1, TNF-alpha, and iNOS. E. coli infection activated p65/p50 heterodimeric NF-kappaB and concurrently decreased the signals of IkappaBalpha. Blocking the NF-kappaB signals by IkappaBalpha-superrepressor-containing retrovirus or antisense p50 oligonucleotide transfection resulted in down-regulation of expression of the proinflammatory mediators. Furthermore, superrepressors of IkappaBalpha, IkappaB kinase (IKK) or NF-kappaB inducing kinase (NIK) inhibited the up-regulated expression of the downstream target genes of NF-kappaB such as IL-8 and MCP-1, and superrepressors of TNF receptor-associated factor (TRAF)2 and TRAF5 also inhibited expression of the E. coli-induced target genes of NF-kappaB. These results indicate that proinflammatory mediators such as the CXC chemokine IL-8/GRO-alpha, the CC chemokine MCP-1, TNF-alpha, and iNOS can be expressed in E. coli-infected astrocytes via an NF-kappaB pathway, suggesting that these mediators may contribute to inflammation in the brain, including infiltration of inflammatory cells.

Innate immune response induced by Theiler's murine encephalomyelitis virus infection

Although the causative agents of human multiple sclerosis (MS) are not known, it is suspected that a viral infection may be associated with the initiation of the disease. Several viral disease models in mice have been studied to understand the pathogenesis of demeylination. In particular, Theiler's murine encephalomyelitis virus-induced demyelinating disease (TMEV-IDD) has been extensively studied as a relevant model. Various cytokines and chemokines are produced upon viral infection by different cell types, including antigen-presenting cells (APCs) such as macrophages; dendritic cells (DCs); and glial cells, such as astrocytes, microglia, and oligoden-drocytes. The upregulation of the corresponding molecules are also found in MS and are likely to play an important role in the protection and/or pathogenesis of chronic inflammatory demyelinating disease. In this review, the type of cells and molecules, gene-activation mechanisms as well as their potential roles in protection and pathogenesis will be discussed.

Inflammatory gene expression in Coxsackievirus B-4-infected human islets of Langerhans

The event that triggers the autoimmune destruction of insulin-producing beta-cells in type 1 diabetes mellitus (T1DM) is still unknown. Enterovirus, especially Coxsackievirus, infections have long been associated with this disease. Cytokines and chemokines induced by an enterovirus infection may act to trigger the autoimmune reactions that produce T1DM. Gene expression was examined in isolated human islets infected with a Coxsackievirus-B4 (CBV-4) strain causing lytic infection (V89-4557) and in islets infected with a CBV-4 strain establishing persistent infection (VD2921). Microarray analysis indicated that infection with the CBV-4 strains resulted in specific induction of a number of inflammatory genes, including IL-1beta, IL-6, IL-8, MCP-1, and RANTES. Importantly, the inflammatory genes induced by the CBV-4 infections differed in the two strains, with more cytokines being induced by the non-lytic CBV-4 strain than by the lytic strain. These cytokines and chemokines have the potential to rapidly induce inflammatory reactions when expressed in vivo and could contribute to the autoimmune reactions associated with the development of T1DM.

Neutrophil-specific chemokines are produced by astrocytic cells but not by neuronal cells

BACKGROUND

Neutrophils have a central role in the inflammatory conditions of the central nervous system (CNS). ELR chemokines direct neutrophil migration, but the source of chemokines in the CNS is unclear. We quantified chemokine production using cell-line models of astrocytic and neuronal cells, specifically NT2.N cells, a human line with characteristics of immature neurons, and NT2.A cells, a line with characteristics of astrocytes.

OBJECTIVE

In NT2.N and NT2.A cells, and their parent cell line NT2, we sought to: (1) quantify ELR chemokines, (2) determine receptor (CXCR-1 and CXCR-2) expression, and (3) measure the function of the chemokines generated from these cells.

DESIGN/METHODS

NT2 cells were differentiated into NT2.N cells and NT2.A cells with all trans retinoic acid and mitosis inhibitors. Chemokine concentrations in culture supernatants were determined by ELISA. Immunofluorescence was used to detect CXCR-1 and CXCR-2. RT-PCR was used to determine chemokine and chemokine receptor mRNA. Chemotaxis assays were used to assess function.

RESULTS

ELR chemokines were not detected in supernatants of NT2 or NT2.N cells, although mRNA for GRO-gamma/CXCL3 was found in both. In contrast, in NT2.A cells, mRNA and protein were present for GCP-2/CXCL6, GRO-alpha/CXCL1, GRO-gamma/CXCL3, and IL-8/CXCL8. CXCR-1 and CXCR-2 were expressed on NT2, NT2.N, and NT2.A cells detected by immunofluorescent staining and RT-PCR. Supernatants of NT2.A cells resulted in neutrophil chemotactic function of 30.5 +/- 3.9%, greater than NT2 cells (12.3 +/- 1.6%, mean +/- SEM, P < 0.01).

CONCLUSIONS

We speculate that astrocytes are a source of ELR chemokines in the human CNS and that neurons and astrocytes can respond to those chemokines.

Ethanol increases nuclear factor-kappa B activity in human astroglial cells

Alcohol abuse adversely affects essentially all the organs of the body, either directly or indirectly. Ethanol may contribute to brain damage via inflammation. Ethanol may also alter CNS immunocompetence and further the progression of certain CNS infections. Nuclear factor (NF)-kappa B helps regulate inflammatory gene expression in glia. It is possible that ethanol effects on CNS pathology are partly a consequence of ethanol modulation of NF-kappa B-associated pathways in glia. We have assessed the effects of 0.5-6 h ethanol exposure on cytokine (5 ng/ml interleukin-1 beta + 100 ng/ml interferon gamma + 30 ng/ml tumor necrosis factor-alpha)-induced NF-kappa B activation in human A172 astroglial cells. Immunoblot analysis indicated that NF-kappa B p65 nuclear translocation occurred within 0.5 h after cytokine stimulation. Stimulation in the presence of ethanol resulted in increased nuclear p65 levels at 3 h, with 200 mM causing a greater increase than 50 mM ethanol. Gel shift assay data suggested that cytokine-induced NF-kappa B binding activity was greatest in cells exposed to 50 mM ethanol, followed by 200 and 0 mM ethanol exposed cells, respectively. Thus, in cytokine-stimulated cells, 200 mM ethanol resulted in greater nuclear p65 levels, yet, 50 mM ethanol exposure resulted in more pronounced DNA binding by NF-kappa B. These findings demonstrate that acute ethanol enhances p65 activity in human astroglia and further support the hypothesis that ethanol-mediated brain pathology involves modulation of NF-kappa B pathways. A better understanding of the mechanistic events involved in ethanol-induced CNS pathology should provide for therapeutic strategies to combat detrimental effects of alcohol on the CNS.