In the central nervous system (CNS), the cellular processes of astrocytes make intimate contact with essentially all areas of the brain. They have also been shown to be functionally coupled to neurons, oligodendrocytes, and other astrocytes via both contact-dependent and non-contact-dependent pathways. These observations have led to the suggestion that a major function of astrocytes in the CNS is to maintain the homeostatic environment, thus promoting the proper functioning of the neuronal network. Inflammation in the CNS disrupts this process either transiently or permanently and, as such, is thought to be tightly regulated by both astrocytes and microglia. The remarkable role that single cytokines, such as TNF and IL-1, may play in this process has now been well accepted, but the extent of the reprogramming of the transcriptional machinery initiated by these factors remains to be fully appreciated. With the advent of microarray technology, a more comprehensive analysis of this process is now available. In this report we review data obtained with this technology to provide an overview of the extent of changes induced in astrocytes by the cytokine IL-1.
Abstract-The interaction between a smart target and a smart MIMO radar is investigated from a game theory perspective. Since the target and the radar form an adversarial system, their interaction is modeled as a two-person zero-sum game. The mutual information criterion is used in formulating the utility functions. The unilateral, hierarchical, and symmetric games are studied, and the equilibria solutions are derived.
SUMMARY:Foreign material emboli following cerebral, cardiac, and peripheral catheterizations have been reported since the mid-1990s. Catheter coatings have been frequently implicated. The most recent surge of interest in this phenomenon within the neurointerventional community is associated with procedures using flow-diversion devices for the treatment of cerebral aneurysms. Following coil-supported Pipeline embolization in 4 cases and stent-supported coiling in 1, 5 patients developed multiple subcentimeter enhancing lesions, usually with surrounding edema and variable magnetic susceptibility in the vascular territories of the treated aneurysms. Conventional angiography findings were unrevealing. Laboratory work-up showed mild CSF protein elevation with no leukocytosis. Brain biopsy in 2 cases revealed granulomatous angiitis encasing foreign material, identical in stain appearance to a polyvinylpyrrolidone catheter coating. Corticosteroid administration typically produced clinical improvement. A heterogeneous radiographic and clinical course was noted, with rise and fall in the number of enhancing lesions in 2 patients and persistence in others. The etiology may be related to widespread adoption of increasingly sophisticated catheterization techniques.
Cryptococcus neoformans monoclonal antibody immune complex (IC) induces beta-chemokines and phagocytosis in primary human microglia via activation of Fc receptor for immunoglobulin G (FcgammaR). In this report, we investigated microglial FcgammaR signal-transduction pathways by using adenoviral-mediated gene transfer and specific inhibitors of cell-signaling pathways. We found that Src inhibitor PP2 and Syk inhibitor piceatannol inhibited phagocytosis, macrophage-inflammatory protein-1alpha (MIP-1alpha) release, as well as phosphorylation of extracellular-regulated kinase (ERK) and Akt, consistent with Src/Syk involvement early in FcgammaR signaling. Constitutively active mitogen-activated protein kinase kinase (MEK) induced MIP-1alpha, and Ras dominant-negative (DN) inhibited IC-induced ERK phosphorylation and MIP-1alpha production. These results suggest that the Ras/MEK/ERK pathway is necessary and sufficient in IC-induced MIP-1alpha expression. Neither Ras DN nor the MEK inhibitor U0126 inhibited phagocytosis. In contrast, phosphatidylinositol-3 kinase (PI-3K) inhibitors Wortmannin and LY294002 inhibited phagocytosis without affecting ERK phosphorylation or MIP-1alpha production. Conversely, Ras DN or U0126 did not affect Akt phosphorylation. Together, these results demonstrate distinct roles played by the PI-3K and Ras/MEK/ERK pathways in phagocytosis and MIP-1alpha induction, respectively. Our results demonstrating activation of functionally distinct pathways following microglial FcgammaR engagement may have implications for human central nervous system diseases.
The cytokine IL-1β is a major activator of primary human fetal astrocytes in culture, leading to the production of a wide range of cytokines and chemokines important in the host defense against pathogens. IL-1β, like TLR4, signals via the MyD88/IL-1βR-associated kinase-1 pathway linked to activation of NF-κB and AP-1. Recent studies have shown that TLR4 also signals independently of MyD88, resulting in the activation of IFN regulatory factor 3 (IRF3), a transcription factor required for the production of primary antiviral response genes such as IFN-β. Using a functional genomics approach, we observed that IL-1β induced in astrocytes a group of genes considered to be IFN-stimulated genes (ISG), suggesting that IL-1β may also signal via IRF3 in these cells. We now show, using real-time PCR, that in astrocytes IL-1β induces the expression of IFN-β, IRF7, CXCL10/IFN-γ-inducible protein-10, and CCL5/RANTES. Chemokine expression was confirmed by ELISA. We also show that IL-1β induces phosphorylation and nuclear translocation of IRF3 and delayed phosphorylation of STAT1. The dependency of IFN-β, IRF7, and CXCL10/IFN-γ-inducible protein-10 gene expression on IRF3 was confirmed using a dominant negative IRF3-expressing adenovirus. The robust induction by IL-1β of additional ISG noted on the microarrays, such as STAT1, 2′5′-oligoadenylate synthetase 2, and ISG15, also supports an active signaling role for IL-1β via this pathway in human fetal astrocytes. These data are the first to show that IL-1β, in addition to TLRs, can stimulate IRF3, implicating this cytokine as an activator of genes involved in innate antiviral responses in astrocytes.
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