Microarray analysis of IFN-gamma response genes in astrocytes

Mechanisms of Autoimmune Cell in DA Neuron Apoptosis of Parkinson's Disease: Recent Advancement

Parkinson's disease (PD) is a prevalent neurodegenerative disorder that manifests as motor and nonmotor symptoms due to the selective loss of midbrain DArgic (DA) neurons. More and more studies have shown that pathological reactions initiated by autoimmune cells play an essential role in the progression of PD. Autoimmune cells exist in the brain parenchyma, cerebrospinal fluid, and meninges; they are considered inducers of neuroinflammation and regulate the immune in the human brain in PD. For example, T cells can recognize α-synuclein presented by antigen-presenting cells to promote neuroinflammation. In addition, B cells will accelerate the apoptosis of DA neurons in the case of PD-related gene mutations. Activation of microglia and damage of DA neurons even form the self-degeneration cycle to deteriorate PD. Numerous autoimmune cells have been considered regulators of apoptosis, α-synuclein misfolding and aggregation, mitochondrial dysfunction, autophagy, and neuroinflammation of DA neurons in PD. The evidence is mounting that autoimmune cells promote DA neuron apoptosis. In this review, we discuss the current knowledge regarding the regulation and function of B cell, T cell, and microglia as well as NK cell in PD pathogenesis, focusing on DA neuron apoptosis to understand the disease better and propose potential target identification for the treatment in the early stages of PD. However, there are still some limitations in our work, for example, the specific mechanism of PD progression caused by autoimmune cells in mitochondrial dysfunction, ferroptosis, and autophagy has not been clarified in detail, which needs to be summarized in further work.

Calycosin alleviates H2 O2 -induced astrocyte injury by restricting oxidative stress through the Akt/Nrf2/HO-1 signaling pathway

Oxidative stress-induced brain cell damage is a crucial factor in the pathogenesis of reactive oxygen species (ROS)-associated neurological diseases. Further, studies show that astrocytes are an important immunocompetent cell in the brain and play a potentially significant role in various neurological diseases. Therefore, elimination of ROS overproduction might be a potential strategy for preventing and treating neurological diseases. Accumulating evidence indicates that calycosin, a main active ingredient in the Chinese herbal medicine Huangqi (Radix Astragali Mongolici), is a potential therapeutic candidate with anti-inflammation and/or anticancer effects. Here, we investigated the protective effect of calycosin in brain astrocytes by mimicking in vitro oxidative stress using H₂ O₂ . The results revealed that H₂ O₂ significantly induced ROS and inflammatory factor (tumor necrosis factor [TNF]-α and interleukin [IL]-1β) production, whereas post-treatment with calycosin dramatically and concentration-dependently suppressed H₂ O₂ -induced damage by enhancing cell viability, repressing ROS and inflammatory factor production, and increasing superoxide dismutase (SOD) expression. Additionally, we found that calycosin facilitated nuclear factor erythroid 2-related factor 2 (Nrf2) expression and promoted its nuclear translocation, thereby inducing the expression of antioxidant molecules (heme oxygenase [HO]-1 and SOD) following H₂ O₂ treatment. Moreover, calycosin did not attenuated H₂ O₂ -induced astrocyte damage and ROS production in the presence of the ML385 (a Nrf2-specific inhibitor) and following Nrf2 silencing. Furthermore, calycosin failed to increase Akt phosphorylation and mitigate H₂ O₂ -induced astrocyte damage in the presence of the LY294002 (a selective phosphatidylinositol 3-kinase inhibitor), indicating that calycosin-mediated regulation of oxidative-stress homeostasis involved Akt/Nrf2/HO-1 signaling. These findings demonstrated that calycosin protects against oxidative injury in brain astrocytes by regulating oxidative stress through the AKT/Nrf2/HO-1 signaling pathway.

DNA methylation-based surrogates of plasma proteins are associated with Parkinson's disease risk

BACKGROUND

The epigenome may reflect Parkinson's disease (PD) risk, which serves as a point of convergence of genetic and environmental risk factors. Here, we investigate whether blood DNA methylation (DNAm) markers are associated with PD risk.

METHODS

We selected 12 plasma proteins known as predictors of cardiovascular conditions and mortality to evaluate their effects on PD risk in a case-control study. In lieu of protein level measures, however, we assessed the influence of their DNAm surrogates. Primary analysis was restricted to 569 PD patients and 238 controls with DNAm data available. Using univariate logistic regression, we evaluated associations between the DNAm markers and PD.

RESULTS

Of the 12 DNAm surrogates, the most robustly associated were DNAm EFEMP-1 and DNAm CD56, which were associated with PD with and without controlling for blood cell composition. DNAm EFEMP-1 was associated with a decreased risk of PD (OR = 0.83 per SD, 95% CI = 0.70, 0.98) whereas DNAm CD56 was associated with an increased risk of PD (OR = 1.41, 95% CI = 1.11, 1.79).

CONCLUSIONS

Several DNAm markers, selected as part of a panel to track cardiovascular outcomes and mortality, were associated with PD risk. DNAm markers may inform of factors that are affected differentially in early PD patients compared with controls.

Studies in lung cancer cytokine proteomics: a review

INTRODUCTION

Proteins are molecules that have role in the progression of the diseases. Proteomics is a tool that can play an effective role in identifying diagnostic and therapeutic biomarkers for lung cancer. Cytokines are proteins that play a decisive role in activating body's immune system in lung cancer. They can increase the growth of the tumor (oncogenic cytokines) or limit tumor growth (anti-tumor cytokines) by regulating related signaling pathways such as proliferation, growth, metastasis, and apoptosis.

AREAS COVERED

In the present study, a total of 223 papers including 196 research papers and 27 review papers, extracted from PubMed and Scopus and published from 1997 to present, are reviewed. The most important involved-cytokines in lung cancer including TNF-α, IFN- γ, TGF-β, VEGF and interleukins such as IL-6, IL-17, IL-8, IL-10, IL-22, IL-1β and IL-18 are introduced. Also, the pathological and biological role of such cytokines in cancer signaling pathways is explained.

EXPERT OPINION

In lung cancer, the cytokine expression changes under the physiological conditions of the immune system, and inflammatory cytokines are associated with the progression of lung cancer. Therefore, the cytokine expression profile can be used in the diagnosis, prognosis, prediction of therapeutic responses, and survival of patients with lung cancer.

The Effects of Immune System Modulation on Prion Disease Susceptibility and Pathogenesis

Prion diseases are a unique group of infectious chronic neurodegenerative disorders to which there are no cures. Although prion infections do not stimulate adaptive immune responses in infected individuals, the actions of certain immune cell populations can have a significant impact on disease pathogenesis. After infection, the targeting of peripherally-acquired prions to specific immune cells in the secondary lymphoid organs (SLO), such as the lymph nodes and spleen, is essential for the efficient transmission of disease to the brain. Once the prions reach the brain, interactions with other immune cell populations can provide either host protection or accelerate the neurodegeneration. In this review, we provide a detailed account of how factors such as inflammation, ageing and pathogen co-infection can affect prion disease pathogenesis and susceptibility. For example, we discuss how changes to the abundance, function and activation status of specific immune cell populations can affect the transmission of prion diseases by peripheral routes. We also describe how the effects of systemic inflammation on certain glial cell subsets in the brains of infected individuals can accelerate the neurodegeneration. A detailed understanding of the factors that affect prion disease transmission and pathogenesis is essential for the development of novel intervention strategies.

The role of natural killer cells in Parkinson's disease

Numerous lines of evidence indicate an association between sustained inflammation and Parkinson's disease, but whether increased inflammation is a cause or consequence of Parkinson's disease remains highly contested. Extensive efforts have been made to characterize microglial function in Parkinson's disease, but the role of peripheral immune cells is less understood. Natural killer cells are innate effector lymphocytes that primarily target and kill malignant cells. Recent scientific discoveries have unveiled numerous novel functions of natural killer cells, such as resolving inflammation, forming immunological memory, and modulating antigen-presenting cell function. Furthermore, natural killer cells are capable of homing to the central nervous system in neurological disorders that exhibit exacerbated inflammation and inhibit hyperactivated microglia. Recently, a study demonstrated that natural killer cells scavenge alpha-synuclein aggregates, the primary component of Lewy bodies, and systemic depletion of natural killer cells results in exacerbated neuropathology in a mouse model of alpha-synucleinopathy, making them a highly relevant cell type in Parkinson's disease. However, the exact role of natural killer cells in Parkinson's disease remains elusive. In this review, we introduce the systemic inflammatory process seen in Parkinson's disease, with a particular focus on the direct and indirect modulatory capacity of natural killer cells in the context of Parkinson's disease.

Exocytosis of large-diameter lysosomes mediates interferon γ-induced relocation of MHC class II molecules toward the surface of astrocytes

Astrocytes are the key homeostatic cells in the central nervous system; initiation of reactive astrogliosis contributes to neuroinflammation. Pro-inflammatory cytokine interferon γ (IFNγ) induces the expression of the major histocompatibility complex class II (MHCII) molecules, involved in antigen presentation in reactive astrocytes. The pathway for MHCII delivery to the astrocyte plasma membrane, where MHCII present antigens, is unknown. Rat astrocytes in culture and in organotypic slices were exposed to IFNγ to induce reactive astrogliosis. Astrocytes were probed with optophysiologic tools to investigate subcellular localization of immunolabeled MHCII, and with electrophysiology to characterize interactions of single vesicles with the plasmalemma. In culture and in organotypic slices, IFNγ augmented the astrocytic expression of MHCII, which prominently co-localized with lysosomal marker LAMP1-EGFP, modestly co-localized with Rab7, and did not co-localize with endosomal markers Rab4A, EEA1, and TPC1. MHCII lysosomal localization was corroborated by treatment with the lysosomolytic agent glycyl-L-phenylalanine-β-naphthylamide, which reduced the number of MHCII-positive vesicles. The surface presence of MHCII was revealed by immunolabeling of live non-permeabilized cells. In IFNγ-treated astrocytes, an increased fraction of large-diameter exocytotic vesicles (lysosome-like vesicles) with prolonged fusion pore dwell time and larger pore conductance was recorded, whereas the rate of endocytosis was decreased. Stimulation with ATP, which triggers cytosolic calcium signaling, increased the frequency of exocytotic events, whereas the frequency of full endocytosis was further reduced. In IFNγ-treated astrocytes, MHCII-linked antigen surface presentation is mediated by increased lysosomal exocytosis, whereas surface retention of antigens is prolonged by concomitant inhibition of endocytosis.

Accelerated onset of CNS prion disease in mice co-infected with a gastrointestinal helminth pathogen during the preclinical phase

Prion infections in the central nervous system (CNS) can cause extensive neurodegeneration. Systemic inflammation can affect the progression of some neurodegenerative disorders. Therefore, we used the gastrointestinal helminth pathogen Trichuris muris to test the hypothesis that a chronic systemic inflammatory response to a gastrointestinal infection would similarly affect CNS prion disease pathogenesis. Mice were injected with prions directly into the CNS and subsequently orally co-infected with T. muris before the onset of clinical signs. We show that co-infection with a low dose of T. muris that leads to the development of a chronic T helper cell type 1-polarized systemic immune response accelerated the onset of clinical prion disease. In contrast, co-infection with a high dose of T. muris that induces a T helper cell type 2-polarized immune response did not affect prion disease pathogenesis. The reduced survival times in mice co-infected with a low dose of T. muris on d 105 after CNS prion infection coincided with enhanced astrocyte activation in the brain during the preclinical phase. These data aid our understanding of how systemic inflammation may augment the progression of neurodegeneration in the CNS.

Interferon-Gamma at the Crossroads of Tumor Immune Surveillance or Evasion

Interferon-gamma (IFN-γ) is a pleiotropic molecule with associated antiproliferative, pro-apoptotic and antitumor mechanisms. This effector cytokine, often considered as a major effector of immunity, has been used in the treatment of several diseases, despite its adverse effects. Although broad evidence implicating IFN-γ in tumor immune surveillance, IFN-γ-based therapies undergoing clinical trials have been of limited success. In fact, recent reports suggested that it may also play a protumorigenic role, namely, through IFN-γ signaling insensitivity, downregulation of major histocompatibility complexes, and upregulation of indoleamine 2,3-dioxygenase and of checkpoint inhibitors, as programmed cell-death ligand 1. However, the IFN-γ-mediated responses are still positively associated with patient's survival in several cancers. Consequently, major research efforts are required to understand the immune contexture in which IFN-γ induces its intricate and highly regulated effects in the tumor microenvironment. This review discusses the current knowledge on the pro- and antitumorigenic effects of IFN-γ as part of the complex immune response to cancer, highlighting the relevance to identify IFN-γ responsive patients for the improvement of therapies that exploit associated signaling pathways.

RNA Nanotherapeutics for the Amelioration of Astroglial Reactivity

In response to injuries to the CNS, astrocytes enter a reactive state known as astrogliosis, which is believed to be deleterious in some contexts. Activated astrocytes overexpress intermediate filaments including glial fibrillary acidic protein (GFAP) and vimentin (Vim), resulting in entangled cells that inhibit neurite growth and functional recovery. Reactive astrocytes also secrete inflammatory molecules such as Lipocalin 2 (Lcn2), which perpetuate reactivity and adversely affect other cells of the CNS. Herein, we report proof-of-concept use of the packaging RNA (pRNA)-derived three-way junction (3WJ) motif as a platform for the delivery of siRNAs to downregulate such reactivity-associated genes. In vitro, siRNA-3WJs induced a significant knockdown of Gfap, Vim, and Lcn2 in a model of astroglial activation, with a concomitant reduction in protein expression. Knockdown of Lcn2 also led to reduced protein secretion from reactive astroglial cells, significantly impeding the perpetuation of inflammation in otherwise quiescent astrocytes. Intralesional injection of anti-Lcn2-3WJs in mice with contusion spinal cord injury led to knockdown of Lcn2 at mRNA and protein levels in vivo. Our results provide evidence for siRNA-3WJs as a promising platform for ameliorating astroglial reactivity, with significant potential for further functionalization and adaptation for therapeutic applications in the CNS.

mRNA expression profile of mouse oligodendrocytes in inflammatory conditions

In this study, we performed transcriptome profiling of oligodendrocyte culture of mice treated with the remyelinating therapeutic agent benztropine in the presence and absence of interferon gamma (IFNγ). The results of this work are important for understanding the expression profile of oligodendrocytes under conditions of systemic inflammation in the central nervous system in multiple sclerosis as well as the mechanisms of cellular response to benztropine in light of its possible use for the treatment of multiple sclerosis.

Cyclic AMP signaling restricts activation and promotes maturation and antioxidant defenses in astrocytes

Background

cAMP signaling produces dramatic changes in astrocyte morphology and physiology. However, its involvement in phenotype acquisition and the transcriptionally mediated mechanisms of action are largely unknown.

Results

Here we analyzed the global transcriptome of cultured astroglial cells incubated with activators of cAMP pathways. A bulk of astroglial transcripts, 6221 annotated genes, were differentially regulated by cAMP signaling. cAMP analogs strongly upregulated genes involved in typical functions of mature astrocytes, such as homeostatic control, metabolic and structural support to neurons, antioxidant defense and communication, whereas they downregulated a considerable number of proliferating and immaturity-related transcripts. Moreover, numerous genes typically activated in reactive cells, such as scar components and immunological mediators, were repressed by cAMP. GSEA analysis contrasting gene expression profiles with transcriptome signatures of acutely isolated astrocytes and in situ evaluation of protein levels in these cells showed that cAMP signaling conferred mature and in vivo–like transcriptional features to cultured astrocytes.

Conclusions

These results indicate that cAMP signaling is a key pathway promoting astrocyte maturation and restricting their developmental and activation features. Therefore, a positive modulation of cAMP signaling may promote the normal state of differentiated astrocytes and favor the protection and function of neuronal networks.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2623-4) contains supplementary material, which is available to authorized users.

Correlating behaviour and gene expression endpoints in the dopaminergic system after modafinil administration in mouse

The mechanisms of action of modafinil continue to be poorly characterised and its potential for abuse in preclinical models remains controverted. The aim of this study was to further elucidate the mechanism of action of modafinil, through a potential behavioural and molecular association in the mouse. A conditioned place preference (CPP) paradigm was implemented to investigate the rewarding properties of modafinil. Whole genome expression and qRT-PCR analysis were performed on the ventral tegmental area (VTA), nucleus accumbens (NAC) and prefrontal cortex (PFC) of modafinil-treated and control animals. Modafinil administration (65 mg/kg) induced an increase in locomotor activity, an increase in the change of preference for the drug paired side after a conditioning period as well as changes to gene expression profiles in the VTA (120 genes), NAC (23 genes) and PFC (19 genes). A molecular signature consisting of twelve up-regulated genes was identified as common to the three brain regions. Multiple linear correlation analysis showed a strong correlation (R(2)>0.70) between the behavioural and molecular endpoints in the three brain regions. We show that modafinil had a concomitant effect on CPP, locomotor activity, and up-regulation of interferon-γ (IFN-γ) regulated genes (Gbp2, Gbp3, Gbp10, Cd274, Igtp), while correlating the latter set of genes with behaviour changes evaluated through the CPP. A potential association can be proposed based on the dysregulation of p47 family genes and Gbp family of IFN-γ induced GTPases. In conclusion, these findings suggest a link between the behavioural and molecular events in the context of modafinil administration.

Identifying the role of microRNAs in spinal cord injury

Spinal cord injury (SCI) is medically and socioeconomically debilitating, and effective treatments are lacking. The elucidation of the pathophysiological mechanisms underlying SCI is essential for developing effective treatments for SCI. MicroRNAs (miRNAs) are small non-coding RNA molecules (18-24 nucleotides long) that regulate gene expression by interacting with specific target sequences. Recent studies suggest that miRNAs can act as post-transcriptional regulators to inhibit mRNA translation. Bioinformatic analyses indicate that the altered expression of miRNAs has an effect on critical processes of SCI physiopathology, including astrogliosis, oxidative stress, inflammation, apoptosis, and neuroplasticity. Therefore, the study of miRNAs may provide new insights into the molecular mechanisms of SCI. Current studies have also provided potential therapeutic clinical applications that involve targeting mRNAs to treat SCI. This review summarizes the biogenesis and function of miRNAs and the roles of miRNAs in SCI. We also discuss the potential therapeutic applications of miRNA-based interventions for SCI.

Efficient subtractive cloning of genes activated by lipopolysaccharide and interferon γ in primary-cultured cortical cells of newborn mice

Innate immune responses play a central role in neuroprotection and neurotoxicity during inflammatory processes that are triggered by pathogen-associated molecular pattern-exhibiting agents such as bacterial lipopolysaccharide (LPS) and that are modulated by inflammatory cytokines such as interferon γ (IFNγ). Recent findings describing the unexpected complexity of mammalian genomes and transcriptomes have stimulated further identification of novel transcripts involved in specific physiological and pathological processes, such as the neural innate immune response that alters the expression of many genes. We developed a system for efficient subtractive cloning that employs both sense and antisense cRNA drivers, and coupled it with in-house cDNA microarray analysis. This system enabled effective direct cloning of differentially expressed transcripts, from a small amount (0.5 µg) of total RNA. We applied this system to isolation of genes activated by LPS and IFNγ in primary-cultured cortical cells that were derived from newborn mice, to investigate the mechanisms involved in neuroprotection and neurotoxicity in maternal/perinatal infections that cause various brain injuries including periventricular leukomalacia. A number of genes involved in the immune and inflammatory response were identified, showing that neonatal neuronal/glial cells are highly responsive to LPS and IFNγ. Subsequent RNA blot analysis revealed that the identified genes were activated by LPS and IFNγ in a cooperative or distinctive manner, thereby supporting the notion that these bacterial and cellular inflammatory mediators can affect the brain through direct but complicated pathways. We also identified several novel clones of apparently non-coding RNAs that potentially harbor various regulatory functions. Characterization of the presently identified genes will give insights into mechanisms and interventions not only for perinatal infection-induced brain damage, but also for many other innate immunity-related brain disorders.

Spinal actions of lipoxin A4 and 17(R)-resolvin D1 attenuate inflammation-induced mechanical hypersensitivity and spinal TNF release

Lipoxins and resolvins have anti-inflammatory and pro-resolving actions and accumulating evidence indicates that these lipid mediators also attenuate pain-like behavior in a number of experimental models of inflammation and tissue injury-induced pain. The present study was undertaken to assess if spinal administration of lipoxin A4 (LXA4) or 17 (R)-resolvin D1 (17(R)-RvD1) attenuates mechanical hypersensitivity in the carrageenan model of peripheral inflammation in the rat. Given the emerging role of spinal cytokines in the generation and maintenance of inflammatory pain we measured cytokine levels in the cerebrospinal fluid (CSF) after LXA4 or 17(R)-RvD1 administration, and the ability of these lipid metabolites to prevent stimuli-induced release of cytokines from cultured primary spinal astrocytes. We found that intrathecal bolus injection of LXA4 and17(R)-RvD1 attenuated inflammation-induced mechanical hypersensitivity without reducing the local inflammation. Furthermore, both LXA4 and 17(R)-RvD1 reduced carrageenan-induced tumor necrosis factor (TNF) release in the CSF, while only 17(R)-RvD1attenuated LPS and IFN-γ-induced TNF release in astrocyte cell culture. In conclusion, this study demonstrates that lipoxins and resolvins potently suppress inflammation-induced mechanical hypersensitivity, possibly by attenuating cytokine release from spinal astrocytes. The inhibitory effect of lipoxins and resolvins on spinal nociceptive processing puts them in an intriguing position in the search for novel pain therapeutics.

Matrix metalloproteinase-2 and -9 lead to fibronectin degradation in astroglia infected with Toxoplasma gondii

Toxoplasma gondii is a zoonotic parasite and its infection in human can induce toxoplasmic encephalitis in immune disorders. In this study, astroglia were infected with the TS-4 strain of T. gondii tachyzoite in vitro to investigate the changes of matrix metalloproteinase (MMP)-2, MMP-9 and their substrate fibronectin. MMP-2 and MMP-9 were significantly increased at 1 h, 6 h and 12 h post-infection (PI) in the cell homogenates, and increased at 6 h, 12 h, 24 h and 48 h PI in the cell-cultured supernatants. Fibronectin degradation also occurred at the same time points. In addition, immunocytochemistry showed that MMP-2 and MMP-9 localized in the cytoplasm, and confocal scanning laser microscopy revealed co-labeled patterns of MMP-2 and MMP-9 with fibronectin. MMP-2 and MMP-9 interacted with fibronectin, respectively. These results suggest that MMP-2 and MMP-9 induction from astroglia may contribute to extracellular matrix (ECM) degradation occurring in toxoplasmosis. Thus, we hypothesize that MMP-2 and MMP-9 cleave fibronectin and may contribute to the astroglia reaction and leukocyte migration to the sites of T. gondii replication during toxoplasmic encephalitis.

Immunity-related GTPase M (IRGM) proteins influence the localization of guanylate-binding protein 2 (GBP2) by modulating macroautophagy

The immunity-related GTPases (IRGs) are a family of proteins induced by interferon-γ that play a crucial role in innate resistance to intracellular pathogens. The M subfamily of IRG proteins (IRGM) plays a profound role in this context, in part because of the ability of its members to regulate the localization and expression of other IRG proteins. We present here evidence that IRGM proteins affect the localization of the guanylate-binding proteins (GBPs), a second family of interferon-induced GTP-binding proteins that also function in innate immunity. Absence of Irgm1 or Irgm3 led to accumulation of Gbp2 in intracellular compartments that were positive for both the macroautophagy (hereafter referred to as autophagy) marker LC3 and the autophagic adapter molecule p62/Sqstm1. Gbp2 was similarly relocalized in cells in which autophagy was impaired because of the absence of Atg5. Both in Atg5- and IRGM-deficient cells, the IRG protein Irga6 relocalized to the same compartments as Gbp2, raising the possibility of a common regulatory mechanism. However, other data indicated that Irga6, but not Gbp2, was ubiquitinated in IRGM-deficient cells. Similarly, coimmunoprecipitation studies indicated that although Irgm3 did interact directly with Irgb6, it did not interact with Gbp2. Collectively, these data suggest that IRGM proteins indirectly modulate the localization of GBPs through a distinct mechanism from that through which they regulate IRG protein localization. Further, these results suggest that a core function of IRGM proteins is to regulate autophagic flux, which influences the localization of GBPs and possibly other factors that instruct cell-autonomous immune resistance.

Species-specific microRNA roles elucidated following astrocyte activation

MicroRNAs (miRNAs) are short non-coding RNAs that play a central role in regulation of gene expression by binding to target genes. Many miRNAs were associated with the function of the central nervous system (CNS) in health and disease. Astrocytes are the CNS most abundant glia cells, providing support by maintaining homeostasis and by regulating neuronal signaling, survival and synaptic plasticity. Astrocytes play a key role in repair of brain insults, as part of local immune reactivity triggered by inflammatory or pathological conditions. Thus, astrocyte activation, or astrogliosis, is an important outcome of the innate immune response, which can be elicited by endotoxins such as lipopolysaccharide (LPS) and cytokines such as interferon-gamma (IFN-γ). The involvement of miRNAs in inflammation and stress led us to hypothesize that astrogliosis is mediated by miRNA function. In this study, we compared the miRNA regulatory layer expressed in primary cultured astrocyte derived from rodents (mice) and primates (marmosets) brains upon exposure to LPS and IFN-γ. We identified subsets of differentially expressed miRNAs some of which are shared with other immunological related systems while others, surprisingly, are mouse and rat specific. Of interest, these specific miRNAs regulate genes involved in the tumor necrosis factor-alpha (TNF-α) signaling pathway, indicating a miRNA-based species-specific regulation. Our data suggests that miRNA function is more significant in the mechanisms governing astrocyte activation in rodents compared to primates.

Upregulation of interferon-gamma-induced genes during prion infection

Global gene expression analysis allows for the identification of transcripts that are differentially regulated during a disease state. Many groups, including our own, have identified hundreds of genes differentially regulated in response to prion infection. Eleven transcripts, upregulated in the brains of prion-infected animals, which were classified in the literature as stimulated by the cytokine interferon-gamma (IFN-γ), were identified. This is intriguing, as IFN-γ has recently been detected in the brains of prion-infected animals. Quantitation of several genes, categorized as IFN-γ inducible, by quantitative real-time polymerase chain reaction (qRT-PCR) confirms that these transcripts are upregulated. Future approaches for delineating the role of IFN-γ-induced transcripts and their function in prion infection are described.

Astrocyte-restricted ablation of interleukin-17-induced Act1-mediated signaling ameliorates autoimmune encephalomyelitis

Interleukin-17 (IL-17) secreted by T helper 17 (Th17) cells is essential in the development of experimental autoimmune encephalomyelitis (EAE). However, it remains unclear how IL-17-mediated signaling in different cellular compartments participates in the central nervous system (CNS) inflammatory process. We examined CNS inflammation in mice with specific deletion of Act1, a critical component required for IL-17 signaling, in endothelial cells, macrophages and microglia, and neuroectoderm (neurons, astrocytes, and oligodendrocytes). In Act1-deficient mice, Th17 cells showed normal infiltration into the CNS but failed to recruit lymphocytes, neutrophils, and macrophages. Act1 deficiency in endothelial cells or in macrophages and microglia did not substantially impact the development of EAE. However, targeted Act1 deficiency in neuroectoderm-derived CNS-resident cells resulted in markedly reduced severity in EAE. Specifically, Act1-deficient astrocytes showed impaired IL-17-mediated inflammatory gene induction. Thus, astroctyes are critical in IL-17-Act1-mediated leukocyte recruitment during autoimmune-induced inflammation of the CNS.

Gene modulation and immunoregulatory roles of interferon gamma

Interferon-gamma (IFNgamma) is a central regulator of the immune response and signals via the Janus Activated Kinase (JAK)-Signal Transducer and Activator of Transcription (STAT) pathway. Phosphorylated STAT1 homodimers translocate to the nucleus, bind to Gamma Activating Sequence (GAS) and recruit additional factors to modulate gene expression. A bioinformatics analysis revealed that greater number of putative promoters of immune related genes and also those not directly involved in immunity contain GAS compared to response elements (RE) for Interferon Regulatory Factor (IRF)1, Nuclear factor kappa B (NFkappaB) and Activator Protein (AP)1. GAS is present in putative promoters of well known IFNgamma-induced genes, IRF1, GBP1, CXCL10, and other genes identified were TLR3, VCAM1, CASP4, etc. Analysis of three microarray studies revealed that the expression of a subset of only GAS containing immune genes were modulated by IFNgamma. As a significant correlation exists between GAS containing immune genes and IFNgamma-regulated gene expression, this strategy may identify novel IFNgamma-responsive immune genes. This analysis is integrated with the literature on the roles of IFNgamma in mediating a plethora of functions: anti-microbial responses, antigen processing, inflammation, growth suppression, cell death, tumor immunity and autoimmunity. Overall, this review summarizes our present knowledge on IFNgamma mediated signaling and functions.

Regulation of exocytotic protein expression and Ca2+-dependent peptide secretion in astrocytes

Vesicular transmitter release from astrocytes influences neuronal development, function and plasticity. However, secretory pathways and the involved molecular mechanisms in astroglial cells are poorly known. In this study, we show that a variety of SNARE and Munc18 isoforms are expressed by cultured astrocytes, with syntaxin-4, Munc18c, SNAP-23 and VAMP-3 being the most abundant variants. Exocytotic protein expression was differentially regulated by activating and differentiating agents. Specifically, proteins controlling Ca(2+)-dependent secretion in neuroendocrine cells were up-regulated after long-term 8Br-cAMP administration in astrocytes, but not by proinflammatory cytokines. Moreover, 8Br-cAMP treatment greatly increased the cellular content of the peptidic vesicle marker secretogranin-2. Release assays performed on cAMP-treated astrocytes showed that basal and stimulated secretogranin-2 secretion are dependent on [Ca(2+)](i). As shown release of the chimeric hormone ANP.emd from transfected cells, cAMP-induced differentiation in astrocytes enhances Ca(2+)-regulated peptide secretion. We conclude that astroglial cells display distinctive molecular components for exocytosis. Moreover, the regulation of both exocytotic protein expression and Ca(2+)-dependent peptide secretion in astrocytes by differentiating and activating agents suggest that glial secretory pathways are adjusted in different physiological states.

Upregulation of immunity-related GTPase (IRG) proteins by TNF-alpha in murine astrocytes

We examined the effect of tumor necrosis factor-alpha (TNF-alpha) on murine primary astrocytes. Proteomic analysis demonstrated that four new spots in the TNF-alpha-treated cells relative to untreated cells. Two of them were identified as Irgb6 and Irgd, members of immunity-related GTPase (IRG) proteins which are the key mediators of interferon-gamma (IFN-gamma)-induced resistance of pathogens in numerous cells. Gene expression analysis using RT-PCR showed that TNF-alpha dose-dependently increased the expression of both proteins. Immunocytochemical analysis showed that TNF-alpha increased the abundance of both proteins. A subcellular localization study demonstrated that TNF-alpha induced the partial colocalization of both proteins with the endoplasmic reticulum (ER) and Golgi apparatus, whereas IFN-gamma did not induce the colocalization of Irgd protein with the ER and Golgi. Combined stimulation with TNF-alpha and IFN-gamma had a synergistic effect on the expression of Irgb6 and an added effect on the expression of Irgd.

S100B's double life: intracellular regulator and extracellular signal

The Ca2+-binding protein of the EF-hand type, S100B, exerts both intracellular and extracellular functions. Recent studies have provided more detailed information concerning the mechanism(s) of action of S100B as an intracellular regulator and an extracellular signal. Indeed, intracellular S100B acts as a stimulator of cell proliferation and migration and an inhibitor of apoptosis and differentiation, which might have important implications during brain, cartilage and skeletal muscle development and repair, activation of astrocytes in the course of brain damage and neurodegenerative processes, and of cardiomyocyte remodeling after infarction, as well as in melanomagenesis and gliomagenesis. As an extracellular factor, S100B engages RAGE (receptor for advanced glycation end products) in a variety of cell types with different outcomes (i.e. beneficial or detrimental, pro-proliferative or pro-differentiative) depending on the concentration attained by the protein, the cell type and the microenvironment. Yet, RAGE might not be the sole S100B receptor, and S100B's ability to engage RAGE might be regulated by its interaction with other extracellular factors. Future studies using S100B transgenic and S100B null mice might shed more light on the functional role(s) of the protein.

The microglial networks of the brain and their role in neuronal network plasticity after lesion

Microglia are the resident inflammatory cells of the central nervous system (CNS) extending a network of processes in the CNS parenchyma. Following axon lesion to neurons, most extensively studied in motoneurons, there is a typical retrograde response at the cell body level, including the removal or 'stripping' of synapses from the perikaryon and dendrites of affected cells. Microglia have been attributed a main and active role in this process, although also an involvement of activated astrocytes has been suggested. The signaling pathways for this 'synaptic stripping' have so far been unknown, but recently some classical immune recognition molecules, the MHC class I molecules, have been shown to have a strong influence on the strength and pattern of the synapse elimination response. Since there is an expression of MHC class I in both neurons and glia, in particular microglia, as well as MHC class I related receptors in axons and microglia, there are good reasons to believe that classical immune recognition signaling between neurons and glia underlies part of the 'stripping' response. A role for microglia in an interplay with synapses based on this type of signaling is further exemplified by the fact that, in the absence of some MHC class I related receptors normally found on microglia during development, profound effects on synaptic function and biochemistry have been demonstrated. Such effects may be linked to the development of various disorders of the CNS, such as degenerative disease.

Directional responses following recombinant cytokine stimulation of rainbow trout (Oncorhynchus mykiss) RTS-11 macrophage cells as revealed by transcriptome profiling

Background

The early stages of the immune response are regulated by key cytokines including both interleukin 1β (IL-1β) and interferon-γ (IFN-γ) which stimulate panels of responsive genes via conserved signal transduction pathways. To further our understanding of the transcriptional response to these cytokines in lower vertebrates we have utilized microarray analysis to characterize the transcriptional response to recombinant rainbow trout IL-1β and IFN-γ in the trout macrophage cell line RTS-11.

Results

RNA was extracted from stimulated or control cells following 6 h incubation and used to hybridize to a salmonid cDNA microarray containing 16,006 different genes. Analysis of the arrays revealed mRNA transcripts that were differentially expressed as a result of exposure to the recombinant proteins, with some responses common for both cytokines. In general the recombinant IL-1β elicited a response where genes involved in the acute phase response were up-regulated, whilst the recombinant IFN-γ induced strong up-regulation of genes involved in the MHC class I antigen presentation pathway. Key genes were chosen that were differentially regulated and analysed by real time PCR at additional time points, up to 48 h following stimulation. This allowed a deeper insight into the kinetics of the response to the cytokines in this cell line.

Conclusion

We demonstrated that in fish both rIL-1β and rIFN-γ stimulated discrete panels of mRNA transcripts which indicted the cells were being directed towards different cellular functions, with IL-β inducing genes involved in the inflammatory response, whereas IFN-γ induced genes associated with antigen presentation.

IRG proteins: key mediators of interferon-regulated host resistance to intracellular pathogens

Immunity-related GTPases (IRG) (also known as p47 GTPases) are a family of proteins found in vertebrates, which play critical roles in mediating innate resistance to intracellular pathogens. The proteins are expressed at high levels following infection with bacteria, protozoa or viruses, as a consequence of interferon-stimulated transcription. Their absence in gene-targeted mice leads to profoundly decreased resistance to many bacteria and protozoa that varies markedly with the particular IRG protein that has been targeted. The proteins are thought to function by localizing to pathogen-containing vacuoles in host cells, such as macrophages, and then regulating the processing of the vacuole and ultimately driving elimination of the pathogen. This review details current knowledge of IRG proteins and their key roles in host resistance.

Downregulation of an astrocyte-derived inflammatory protein, S100B, reduces vascular inflammatory responses in brains persistently infected with Borna disease virus

Borna disease virus (BDV) is a neurotropic virus that causes a persistent infection in the central nervous system (CNS) of many vertebrate species. Although a severe reactive gliosis is observed in experimentally BDV-infected rat brains, little is known about the glial reactions contributing to the viral persistence and immune modulation in the CNS. In this regard, we examined the expression of an astrocyte-derived factor, S100B, in the brains of Lewis rats persistently infected with BDV. S100B is a Ca(2+)-binding protein produced mainly by astrocytes. A prominent role of this protein appears to be the promotion of vascular inflammatory responses through interaction with the receptor for advanced glycation end products (RAGE). Here we show that the expression of S100B is significantly reduced in BDV-infected brains despite severe astrocytosis with increased glial fibrillary acidic protein immunoreactivity. Interestingly, no upregulation of the expression of S100B, or RAGE, was observed in the persistently infected brains even when incited with several inflammatory stimuli, including lipopolysaccharide. In addition, expression of the vascular cell adhesion molecule 1 (VCAM-1), as well as the infiltration of encephalitogenic T cells, was significantly reduced in persistently infected brains in which an experimental autoimmune encephalomyelitis was induced by immunization with myelin-basic protein. Furthermore, we demonstrated that the continuous activation of S100B in the brain may be necessary for the progression of vascular immune responses in neonatally infected rat brains. Our results suggested that BDV infection may impair astrocyte functions via a downregulation of S100B expression, leading to the maintenance of a persistent infection.