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R M Ransohoff

Publications and source records attributed to R M Ransohoff.

At least 73 records · Page 4Linked to original sources
PubMed1998

p48/STAT-1alpha-containing complexes play a predominant role in induction of IFN-gamma-inducible protein, 10 kDa (IP-10) by IFN-gamma alone or in synergy with TNF-alpha.

Human IFN-gamma-inducible protein, 10 kDa (hIP-10) and murine IP-10 (mIP-10) genes are induced by IFN-gamma alone, and synergistically induced by TNF-alpha and IFN-gamma. Upstream regions of the human and murine genes contain conserved regulatory motifs, including an IFN-stimulated response element (ISRE), which governs response of the mIP-10 gene to IFN-gamma. Trans-acting factors mediating the IFN-gamma response via ISRE remain incompletely defined. We examined ISRE-binding factors in the regulation of the hIP-10 gene. The requirement of p48 for hIP-10 induction by IFN-gamma, with or without TNF-alpha, was demonstrated using p48-deficient U2A cells. An hIP-10 promoter-reporter mutant (mISRE3) that was relatively deficient for binding a related factor, IFN regulatory factor-1 (IRF-1) but competent for binding p48, was induced as well as the wild-type hIP-10 promoter, supporting the interpretation that p48 played a necessary and sufficient role in hIP-10 transcription. Genomic in vivo footprinting revealed IFN-gamma/TNF-alpha-inducible binding at the ISRE consistent with the presence of p48 and associated factors, but not with IRF-1. Induction of hIP-10 by TNF-alpha/IFN-gamma also required NFkappaB binding sites, which were protected in vivo and bound p65 homodimeric NFkappaB in vitro. These results documented the essential role of p48 (complexed with STAT-1alpha) for induction and sustained transcription of the IP-10 gene, strongly suggesting that IRF-1 is not required for IP-10 induction by these inflammatory cytokines.

Base Sequence↗
PubMed1998

Regulation of human IP-10 gene expression in astrocytoma cells by inflammatory cytokines.

Because of its prominent expression in central nervous system inflammatory pathology by astrocytes, we examined the mechanism of human IP-10 (hIP-10) gene induction by interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) in astrocytoma cells. When present together, IFN-gamma and TNF-alpha induced robust accumulation of hIP-10 mRNA, but hIP-10 mRNA was minimally induced when astrocytoma cells were treated with individual cytokines. This pattern of expression resembled that previously described for murine IP-10 (mIP-10) gene induction in fibroblasts and in rat astroglia. Nuclear run-on experiments showed that the synergistic effect of the cytokines resulted from an increased rate of IP-10 transcriptional initiation. Functional analysis of the hIP-10 promoter after deletion and substitution mutagenesis indicated that an interferon-stimulated response element (ISRE) governed both simple response to IFN-gamma and synergy with TNF-alpha. Synergistic induction of hIP-10 also required an ISRE-proximal nuclear factor kappa-B (NFkappaB) binding site. TNF-alpha-induced NFkappaB binding activity at this site was composed of RelA (p65) homodimers. Our results document that cis-elements through which cytokines mediate synergistic induction of IP-10 in mouse and human are strictly conserved despite divergence elsewhere within the proximal 5'-flanking region.

Animals↗
PubMed1998

Chemokine regulation of experimental autoimmune encephalomyelitis: temporal and spatial expression patterns govern disease pathogenesis.

Experimental autoimmune encephalomyelitis (EAE) is a CD4+ Th1-mediated demyelinating disease of the central nervous system that serves as a model for multiple sclerosis (MS). There are several considerations that suggest a role for chemokines in the disease process. First, chemokines are highly expressed in the central nervous system with a tight temporal relationship to disease activity. Second, in vivo neutralization studies showed a distinct role for specific chemokines in the evolution of the process. Third, the selective and differential expression of chemokines in differing models of EAE bears a close relationship to the patterns of inflammatory pathology. Fourth, the spatial distribution of chemokine expression could plausibly contribute to lesion architecture. Finally, preliminary observations in MS material suggest that chemokine expression observed in EAE may provide useful information regarding the pathogenesis of inflammation in MS. We propose that temporal and spatial expression of chemokines are crucial factors, complementing adhesion molecule up-regulation, that regulate EAE disease activity.

Acute Disease↗
PubMed1998

Selective chemokine mRNA accumulation in the rat spinal cord after contusion injury.

Following traumatic injury to the spinal cord, hematogenous inflammatory cells including neutrophils, monocytes, and lymphocytes infiltrate the lesion in a distinct temporal sequence. To examine potential mechanisms for their recruitment, we measured chemokine mRNAs in the contused rat spinal cord, using specific and sensitive reverse transcriptase polymerase chain reaction (RT-PCR) dot-blot hybridization assays. The neutrophil chemoattractant GRO-alpha was 30-fold higher than control values at 6 hr postinjury and decayed rapidly thereafter. LIX, a highly related alpha-chemokine, also was elevated early postinjury. Monocyte chemoattractant peptide (MCP)-1 and MCP-5 mRNAs, potent chemoattractants for monocytes, were significantly elevated at the lesion epicenter at 12 and 24 hr postinjury and declined thereafter. Interferon-gamma-inducible protein, 10 kDa (IP-10), chemoattractant towards activated T-lymphocytes, was significantly elevated at 6 and 12 hr postinjury. The dendritic cell chemoattractant MIP-3alpha also was increased, perhaps contributing to the development of T-cell autoreactivity to neural components after spinal cord injury (SCI) in rats. Other beta-chemokines, including MIP-1alpha and RANTES (regulated on expression normal T-cell expressed and secreted), were minimally affected by SCI. Expression of chemokines, therefore, directly precedes the influx of target neutrophils, monocytes, and T-cells into the spinal cord postinjury, as noted previously. Thus, selective chemokine expression may be integral to inflammatory processes within the injured spinal cord as a mechanism of recruitment for circulating leukocytes.

Animals↗
PubMed1998

IFN-gamma induction of the human monocyte chemoattractant protein (hMCP)-1 gene in astrocytoma cells: functional interaction between an IFN-gamma-activated site and a GC-rich element.

We characterized regulation of the human monocyte chemoattractant protein-1 (hMCP-1) gene by IFN-gamma in astrocytoma cells, because astroglial cells express chemokines in several central nervous system inflammatory states. It was found that IFN-gamma-induced hMCP-1 transcription was rapid, transient, and mediated by a 213-bp promoter-proximal regulatory region of the gene. Our studies on both in vitro and in vivo states of the hMCP-1 regulatory region established requirement of an IFN-gamma-activated site (GAS) and the presence of IFN-gamma-inducible GAS-binding activity involving at least STAT-1alpha for IFN-gamma-induced hMCP-1 expression. Unexpectedly, in vivo genomic footprinting of the proximal regulatory region of the IFN-gamma-induced gene revealed protection of a GC-rich sequence (GC box) with the same temporal pattern as that seen at the GAS; in vitro, this GC-rich element is associated with nuclear factor Sp1. These observations suggested a cooperative interaction between the GAS and the GC box element. Interestingly, site-specific mutations that abolished GC-box or GAS-element function produced clearly disparate results. Disruption of the GC box did not affect fold induction by IFN-gamma but reduced promoter-reporter expression by half. Conversely, GAS mutation abrogated induction but did not affect the magnitude of expression. These results establish the importance of the GAS element for induction of hMCP-1 and further our understanding of IFN-gamma-mediated transcriptional induction by providing the first evidence in vivo for inducible signaling to the GC box by this cytokine.

Astrocytoma↗
PubMed1998

Axonal transection in the lesions of multiple sclerosis.

BACKGROUND: Multiple sclerosis is an inflammatory demyelinating disease of the central nervous system and is the most common cause of neurologic disability in young adults. Despite antiinflammatory or immunosuppressive therapy, most patients have progressive neurologic deterioration that may reflect axonal loss. We conducted pathological studies of brain tissues to define the changes in axons in patients with multiple sclerosis. METHODS: Brain tissue was obtained at autopsy from 11 patients with multiple sclerosis and 4 subjects without brain disease. Fourteen active multiple-sclerosis lesions, 33 chronic active lesions, and samples of normal-appearing white matter were examined for demyelination, inflammation, and axonal pathologic changes by immunohistochemistry and confocal microscopy. Axonal transection, identified by the presence of terminal axonal ovoids, was detected in all 47 lesions and quantified in 18 lesions. RESULTS: Transected axons were a consistent feature of the lesions of multiple sclerosis, and their frequency was related to the degree of inflammation within the lesion. The number of transected axons per cubic millimeter of tissue averaged 11,236 in active lesions, 3138 at the hypocellular edges of chronic active lesions, 875 in the hypocellular centers of chronic active lesions, and less than 1 in normal-appearing white matter from the control brains. CONCLUSIONS: Transected axons are common in the lesions of multiple sclerosis, and axonal transection may be the pathologic correlate of the irreversible neurologic impairment in this disease.

Adolescent↗
PubMed1998

Expression of monocyte chemoattractant protein (MCP-1) and nitric oxide synthase-2 following cerebral trauma.

Traumatic injury to the brain initiates multiple interrelated processes that involve parenchymal, vascular, and infiltrating inflammatory cells. Nitric oxide (NO) and chemokines have been implicated as regulators of the central nervous system injury response. Following a cryogenic lesion of the cerebral cortex in mice, mRNA for NO synthase (NOS)-2 was detected by reverse transcriptase polymerase chain reaction ipsilaterally 12 h after injury and persisted for 2 weeks. While mRNA was also detected contralaterally, the time course of expression was shorter (1 week). By immunohistochemistry, NOS-2 protein was initially detected ipsilaterally 12 h after injury in infiltrating inflammatory cells. Astroglial cells expressed NOS-2 from 24 to 72 h after injury. The expression of monocyte chemoattractant protein (MCP-1) mRNA peaked at 6 h on the lesion side, remained for 24 h and then declined by 48 h. On the unlesioned side, MCP-1 mRNA was expressed to a much lesser extent and had declined by 24 h. The up-regulation of MCP-1 was relatively specific as a closely related mRNA encoding IP-10 was not significantly increased. These findings implicate a role for NOS-2 and MCP-1 as potential regulators of cellular events following cryogenic cerebral trauma.

Animals↗
PubMed1998

Do chemokines mediate leukocyte recruitment in post-traumatic CNS inflammation?

Hematogenous leukocytes infiltrate the CNS after inflammatory stimuli, including infection, mechanical trauma and excitotoxic neuronal necrosis. However,the role of leukocytic inflammation in promoting or hindering tissue repair is poorly understood. Identification of signals that lead to leukocyte recruitment and activation is essential for the designing of interventions that modulate inflammation, thus improving neurological outcome. Chemokines are small pleiotropic chemoattractant cytokines whose target specificity suggests an important role in determining the cellular composition of inflammatory infiltrates. Chemokine expression profiles in the CNS during autoimmune and post-traumatic inflammation correlate well with the composition of leukocyte infiltrates, and expression studies in systems such as transgenic mice, suggest that chemokines have potent functional attributes in CNS physiology. We propose that selective chemokine expression by CNS cells is crucial for post-traumatic leukocyte accumulation.

Animals↗
PubMed1998

Etiology and pathogenesis of multiple sclerosis.

The cause of multiple sclerosis (MS) remains unknown despite decades of intense research. The major research disciplines that have been brought to bear on this question include genetics, epidemiology, neuropathology, immunology, and virology. Recent advances in the understanding of the inflammatory characteristics of the MS lesion may herald the development of specific and effective treatments. The goal of this research is to improve our management of a disease that remains the major cause of neurologic disability among young adults in North America and Europe.

Autoimmune Diseases↗
PubMed1998

In vivo effects of interferon beta-1a on immunosuppressive cytokines in multiple sclerosis.

Recombinant interferon beta (IFNbeta) benefits patients with relapsing remitting multiple sclerosis (MS), but the mechanisms of action are unknown. We studied in vivo immunologic effects of IFNbeta treatment and their relationship to clinical efficacy. Cytokines were measured in blood and CSF from MS patients participating in a placebo-controlled phase III clinical trial and an open-label phase IV [corrected] tolerability study of IFNbeta-1a. Additionally, immunologic studies were conducted in animals with proteolipid protein (PLP)-induced chronic relapsing experimental autoimmune encephalomyelitis. Single intramuscular (IM) injections of IFNbeta-1a (6 MIU, 30 microg) were associated with significant in vivo upregulation of interleukin-10 (IL-10) and IL-4 but not IFNgamma mRNA in peripheral blood mononuclear cells. Forty-eight hours after each IFNbeta-1a injection, serum IL-10 levels increased and remained elevated for 1 week. IFNbeta-1a recipients in the placebo-controlled phase III clinical trial showed significantly increased concentrations of CSF IL-10 after 2 years of treatment. This response correlated with a favorable therapeutic response. Exposure of PLP-reactive murine T-cell lines to IFNbeta resulted in increased antigen-driven expression of IL-4 and IL-10 and reduced encephalitogenicity. IFNbeta-1a injections induce systemic and intrathecal immunosuppressive cytokines. Myelin-specific T cells treated with IFNbeta-1a demonstrate increased immunosuppressive cytokine expression and reduced encephalitogenicity. The relationship between increased CSF IL-10 and response to therapy suggests that induction of IL-10 is a mechanism underlying IFNbeta-1a effects in MS patients.

Animals↗
PubMed1997

TGF-beta suppresses IFN-gamma induction of class II MHC gene expression by inhibiting class II transactivator messenger RNA expression.

Recently, a non-DNA binding protein, class II transactivator (CIITA), has been shown to be required for constitutive and IFN-gamma-inducible class II MHC transcription. The cytokine TGF-beta inhibits IFN-gamma-induced class II MHC expression at the transcriptional level. In this study, we provide evidence that TGF-beta blocks IFN-gamma-induced CIITA mRNA accumulation. TGF-beta down-regulates class II MHC and CIITA mRNA accumulation in human astroglioma and fibrosarcoma cell lines, but TGF-beta does not destabilize the CIITA message, suggesting an effect at the transcriptional level. In cells that stably overexpressed CIITA, leading to a constitutive class II MHC-positive phenotype, the inhibitory effect of TGF-beta on class II MHC was abrogated, but the cells remained responsive for expression of TGF-beta-inducible genes. Cell lines that possessed defects in TGF-beta signaling also became refractory to inhibition of IFN-gamma-induced CIITA and class II MHC expression. Our data indicate that TGF-beta suppresses IFN-gamma-induced class II MHC expression by inhibiting accumulation of CIITA mRNA.

Astrocytoma↗
PubMed1997

Chemokines in neurological disease models: correlation between chemokine expression patterns and inflammatory pathology.

We have recently determined chemokine expression profiles in a variety of models of neural trauma and immune-inflammation. The results indicate the following: (1) Chemokine expression in posttraumatic inflammation is generally restricted to the monocyte chemoattractant MCP-1, and occurs before hematogenous cell entry into neural tissues. Therefore MCP-1 is an excellent candidate for a mediator of leukocyte recruitment in these settings. (2) Chemokine expression in immune-inflammation is diverse and includes both alpha- and beta-chemokines. Chemokine production can be attributed to parenchymal and infiltrating cell populations. Early signs of inflammation precede chemokine expression, which is believed to exert the crucial function of amplifying the immune-mediated inflammatory reaction. These observations provide a basis for evaluating model neurological disorders in transgenic mice that express chemokines ectopically or in mice that are deficient in chemokine ligands or receptors as a consequence of gene targeting. Ultimately, a clear definition of roles of chemokines and their receptors in neurological diseases will suggest rational intervention.

Animals↗
PubMed1997

Synchronous synthesis of alpha- and beta-chemokines by cells of diverse lineage in the central nervous system of mice with relapses of chronic experimental autoimmune encephalomyelitis.

Chemokines are secreted peptides that exhibit selective chemoattractant properties for target leukocytes. Two subfamilies, alpha- and beta-chemokines, have been described, based on structural, genetic, and functional considerations. In acute experimental autoimmune encephalomyelitis (EAE), chemokines are up-regulated systemically and in central nervous system (CNS) tissues at disease onset. Functional significance of this expression was supported by other studies; intervention with an antichemokine antibody abrogated passive transfer of EAE, and chemokines expressed in brains of transgenic mice recruited appropriate leukocyte populations into the CNS compartment. Chemokine expression in the more relevant circumstance of chronic EAE has not been addressed. We monitored the time course and cellular sources of chemokines (monocyte chemoattractant protein-1, macrophage inflammatory protein-1 alpha, interferon-gamma-inducible protein of 10 kd, KC, and regulated on activation, normal T-cell expressed and secreted cytokine) in CNS and peripheral tissues during spontaneous relapses of chronic EAE. We found coordinate chemokine up-regulation in brain and spinal cord during clinical relapse, with expression confined to CNS tissues. Monocyte chemoattractant protein-1, interferon-gamma-inducible protein of 10 kd, and KC were synthesized by astrocytic cells, whereas macrophage inflammatory protein-1 alpha and regulated on activation, normal T-cell expressed and secreted cytokine were elaborated by infiltrating leukocytes. The results demonstrate stringent regulation of multiple chemokines in vivo during a complex organ-specific autoimmune disease. We propose that chemokine expression links T-cell antigen recognition and activation to subsequent CNS inflammatory pathology in chronic relapsing EAE.

Animals↗