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Biomedical subjects

R M Ransohoff

Publications and source records attributed to R M Ransohoff.

At least 37 records · Page 2Linked to original sources
PubMed2001

TNF-alpha down-regulates CXCR4 expression in primary murine astrocytes.

CXC chemokine receptor 4 (CXCR4) is a co-receptor for human immunodeficiency virus (HIV) infection and is believed to be involved in the pathogenesis of AIDS-associated neurologic disorders and brain tumors. The physiological roles of CXCR4 in developmental patterning of the nervous and hematopoietic system; gastrointestinal angiogenesis; and cardiac organogenesis were established by studies in gene-targeted mice. Studies on CXCR4 expression and regulation in neuroepithelial cells are fundamental for understanding its physiopathologic roles in the central nervous system (CNS). We show here that CXCR4 expression by primary mouse astrocytes is suppressed by exposure to tumor necrosis factor-alpha (TNF-alpha). TNF-alpha caused a pronounced down-regulation of CXCR4 mRNA in a dose- and time-dependent manner. TNF-alpha-mediated decrease of CXCR4 mRNA accumulation resulted in decreased CXCR4 protein expression. As a result, the ability of stromal cell-derived factor-1alpha (SDF-1alpha) to induce activation of MAP kinases, Erk1/2 was impaired. The half life of CXCR4 mRNA in the presence and absence of TNF-alpha stimulation was comparable, suggesting that TNF-alpha down-regulated CXCR4 mRNA at the transcriptional level. These results suggest that TNF-alpha could modulate HIV and brain tumor pathogenesis and immune-mediated inflammation in the central nervous system (CNS) by regulation of CXCR4 expression.

AIDS Dementia Complex↗
PubMed2001

Investigating chemokines and chemokine receptors in patients with multiple sclerosis: opportunities and challenges.

Multiple sclerosis is an autoimmune demyelinating disease of the human central nervous system with an unknown etiology. Crucial to its pathogenesis is the accumulation and activation of mononuclear cells in the central nervous system. Chemokines and their receptors are proposed to play a major role in the inflammatory recruitment of leukocytes. Besides analyses of relationships between chemokine or chemokine receptor gene polymorphisms and multiple sclerosis susceptibility and severity, analyses of chemokines and their receptors in patients with multiple sclerosis remain descriptive. In clinical material, chemokines and chemokine receptors can be examined in body fluids (blood and cerebrospinal fluid) and in brain tissues obtained via biopsy or autopsy. Research results will be summarized in this review, and a general model of leukocyte migration into the central nervous system under normal and inflammatory conditions will be proposed. Furthermore, opportunities and challenges for future investigations will be identified.

Brain Chemistry↗
PubMed2001

CCR1+/CCR5+ mononuclear phagocytes accumulate in the central nervous system of patients with multiple sclerosis.

Mononuclear phagocytes (monocytes, macrophages, and microglia) are considered central to multiple sclerosis (MS) pathogenesis. Molecular cues that mediate mononuclear phagocyte accumulation and activation in the central nervous system (CNS) of MS patients may include chemokines RANTES/CCL5 and macrophage inflammatory protein-1alpha/CCL3. We analyzed expression of CCR1 and CCR5, the monocyte receptors for these chemokines, on circulating and cerebrospinal fluid CD14+ cells, and in MS brain lesions. Approximately 70% of cerebrospinal fluid monocytes were CCR1+/CCR5+, regardless of the presence of CNS pathology, compared to less than 20% of circulating monocytes. In active MS lesions CCR1+/CCR5+ monocytes were found in perivascular cell cuffs and at the demyelinating edges of evolving lesions. Mononuclear phagocytes in early demyelinating stages comprised CCR1+/CCR5+ hematogenous monocytes and CCR1-/CCR5- resident microglial cells. In later stages, phagocytic macrophages were uniformly CCR1-/CCR5+. Cultured in vitro, adherent monocytes/macrophages up-regulated CCR5 and down-regulated CCR1 expression, compared to freshly-isolated monocytes. Taken together, these findings suggest that monocytes competent to enter the CNS compartment derive from a minority CCR1+/CCR5+ population in the circulating pool. In the presence of ligand, these cells will be retained in the CNS. During further activation in lesions, infiltrating monocytes down-regulate CCR1 but not CCR5, whereas microglia up-regulate CCR5.

Adult↗
PubMed2001

Chemokines CXCL10 and CCL2: differential involvement in intrathecal inflammation in multiple sclerosis.

Studies of chemokines in cerebrospinal fluid (CSF) of patients with active multiple sclerosis (MS) have indicated that specific chemokines may have important roles in disease pathogenesis. We previously reported that CSF concentrations of CXCL10 (previously known as IP-10) were elevated in MS patients in relapse, whilst levels of CCL2 (MCP-1) were reduced. Here, we report a serial analysis of CSF CXCL10 and CCL2 concentrations in 22 patients with attacks of MS or acute optic neuritis (ON) treated with methylprednisolone, and 26 patients treated with placebo in two randomized controlled trials. Chemokine concentrations were measured by enzyme linked immunosorbent assay (ELISA) in CSF obtained at baseline and after 3 weeks, and were compared with other measures of intrathecal inflammation. At baseline CSF concentrations of CCL2 were significantly lower in the patient group than in controls. The levels of CXCL10 were higher in the patient group than in controls but two outliers in the control group also had high CSF concentrations of CXCL10. The CSF concentrations of CXCL10 did not change over time or after treatment. The CSF concentration of CXCL10 was positively correlated with the CSF leukocyte count, the CSF concentration of neopterin, matrix metalloproteinase (MMP)-9, and intrathecal IgG and IgM synthesis. The concentration of CCL2 increased between baseline for 3 weeks in both groups, more distinctly so in patients treated with methylprednisolone. CCL2 correlated negatively with MMP-9 and IgG synthesis levels. CXCL10 may be involved in the maintenance of intrathecal inflammation whereas CCL2 correlates negatively with measures of inflammation, suggesting differential involvement of CXCL10 and CCL2 in CNS inflammation.

Anti-Inflammatory Agents↗
PubMed2001

Regulation of monocyte chemoattractant protein (MCP)-1 transcription by interferon-gamma (IFN-gamma) in human astrocytoma cells: postinduction refractory state of the gene, governed by its upstream elements.

Monocyte chemoattractant protein (MCP)-1 is expressed by astrocytes in diverse inflammatory states and is a key regulator of monocyte recruitment to the central nervous system (CNS). In the current study, we addressed mechanisms by which transcription of the human MCP-1 gene (hMCP-1) was terminated, after induction by interferon (IFN)-gamma. Our results demonstrated that IFN-gamma-induced transcription of hMCP-1 was followed by a refractory state, during which hMCP-1 was resistant to restimulation by either IFN-gamma or heterologous activators such as TNF-alpha. This refractory state affected the hMCP-1 gene selectively, as other IFN-gamma-inducible genes remained responsive to restimulation. The IFN-gamma-induced hMCP-1 refractory state was governed at the transcriptional level and was sensitive to protein synthesis inhibitors, suggesting a requirement for newly expressed components. A minimal 213 base pair hMCP-1 regulatory element directed both IFN-gamma-mediated transcription and the subsequent refractory state. We previously demonstrated that IFN-gamma treatment resulted in coordinate protein occupancy in vivo of two hMCP-1 promoter elements, a gamma-activated site (GAS) and a GC-rich element. During the refractory state, IFN-gamma treatment failed to induce protection of either the hMCP-1 GAS element or the GC box. These results furnish insight into the expression of hMCP-1 during CNS inflammation and provide the first delineation of an IFN-gamma-induced transcriptional refractory state.

Astrocytoma↗
PubMed2001

Constitutive expression of growth-related oncogene and its receptor in oligodendrogliomas.

OBJECTIVE: Gliomas may result from transformation of glial precursor cells. In the developing rat central nervous system (CNS), a paracrine pathway involving the cytokines growth-related oncogene (GRO1) and platelet-derived growth factor (PDGF) A chain closely regulates oligodendrocyte precursor cell number. The purpose of the present study was to analyze whether abnormal expression and activity of the GRO1-PDGF pathway is present in human gliomas. METHODS: Tumor specimens were studied to compare the messenger ribonucleic acid with the protein expression of components of the GRO1-PDGF pathway. Neutralizing antibodies were used in vitro to analyze whether the pathway contributed to tumor cell proliferation. RESULTS: Immunohistochemistry demonstrated that all components of the GRO1-PDGF pathway (GRO1 protein, its receptor CXCR2, PDGF A chain, and its receptor PDGFalphaR) were expressed by tumor cells in 6 (86%) of 7 of oligodendrogliomas as well as by 0 of 4 diffuse astrocytomas (World Health Organization Grades II and III) and 2 (18%) of 11 glioblastomas. Analysis by reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assay showed CXCR2 messenger ribonucleic acid and GRO1 protein expression were present in oligodendrogliomas. Functional analyses with neutralizing antibodies limited bromodeoxyuridine incorporation in vitro by oligodendroglioma tumor cells, demonstrating a requirement for the GRO1-PDGF pathway in the proliferation of these cells. CONCLUSION: The GRO1-PDGF pathway was primarily expressed and functional in oligodendrogliomas. The tightly controlled paracrine pathway that regulates oligodendrocyte precursor proliferation in the developing rodent CNS was constitutively active in most oligodendrogliomas in the present study. The presence of this aberrantly functioning oncogenic pathway in a subset of primary CNS tumors opens new avenues to glioma treatment that are based directly on the biology of the proliferative glial cell type, a novel strategy for primary CNS tumor therapy.

Brain↗
PubMed2001

TNF-alpha mediates SDF-1 alpha-induced NF-kappa B activation and cytotoxic effects in primary astrocytes.

Stromal-derived cell factor-1 alpha (SDF-1 alpha; CXCL12) and its receptor, CXCR4, are constitutively expressed on neuroepithelial cells and are believed to be involved in both development and pathological processes, such as AIDS-associated neurologic disorders. Here, we demonstrate that SDF-1 alpha activates NF-kappa B, stimulates production of chemokines and cytokines, and induces cell death in primary astrocytes, effects that depend on ongoing secretion of TNF-alpha. SDF-1 alpha upregulated TNF-alpha mRNA and protein secretion, as well as TNF receptor 2 expression. TNF-alpha treatment mimicked SDF-1 alpha induction of NF-kappa B, IL-1 alpha/beta, and RANTES, as well as cell death; neutralizing antibodies against TNF-alpha opposed these responses. We also found that SDF-1 alpha activated Erk1 and Erk2 (Erk1/2) MAPK in a biphasic fashion. Early Erk1/2 activation was stimulated directly by SDF-1 alpha and late activation was mediated by TNF-alpha. PD98059 suppression of early Erk1/2 activation correlated with reduction of SDF-1 alpha-induced TNF-alpha expression. Late Erk1/2 activation was involved in TNF-alpha-stimulated NF-kappa B activation and cytokine induction. SDF-1 alpha was induced in reactive CXCR4-positive astrocytes near axotomized spinal cord motor neurons, consistent with autocrine SDF-1/CXCR4 signaling in these cells. We propose that these novel effects of SDF-1 alpha are relevant to the pathogenic and developmental roles of SDF-1 alpha in the CNS.

Animals↗
PubMed2001

Targeting the chemokine system for multiple sclerosis treatment.

Multiple sclerosis (MS) is the most common demyelinating disorder of the human central nervous system (CNS). The typical pathological hallmark of active MS is the presence of inflammatory foci disseminated in the CNS. It is believed that the composition of inflammatory infiltrates is determined in part by the spectrum of chemokines produced in a focus of inflammation. Numerous studies suggest chemokine involvement in MS pathogenesis. Interfering with chemokine-chemokine-receptor interactions may potentially lead to prevention and/or amelioration of CNS inflammatory processes. Initial studies to obtain 'proof-of-principle' used neutralizing antibodies in small animal models of MS. The subsequent generation of chemokine receptor inhibitors were modified chemokine peptides. At present, the development of small molecule antagonists to chemokine receptors is the dominant approach. Current evidence suggests that chemokines and their receptors are promising targets for effective treatment of MS and other CNS inflammatory and autoimmune diseases.

Animals↗
PubMed2000

Sequential expression of chemokines in experimental autoimmune neuritis.

Recruitment of inflammatory cells is of critical importance in the pathogenesis of immune-mediated demyelinating diseases in the peripheral nervous system (PNS). Evidence is increasing that chemokines might play a key role in this process, since they promote leukocyte entry into the nervous system during immune-mediated inflammation. In the present study we report the expression pattern of the chemokines interferon-gamma-inducible protein (IP)-10, monocyte chemoattractant protein (MCP)-1, macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, and regulated upon activation normal T cell expressed and secreted (RANTES) in sciatic nerves from animals with myelin-induced experimental autoimmune neuritis, using a semiquantitative reverse transcriptase-PCR dot-blot hybridization assay. The mRNAs for MIP-1alpha and MIP-1beta were found to be upregulated with peak values at day 13 post-immunization (p.i.), preceding maximum disease severity. In contrast, mRNAs for MCP-1, RANTES, and IP-10 exhibited peak levels coincident with peak of the disease at day 15 p.i. Increased mRNA expression was associated with enhanced protein levels, as demonstrated by immunoblotting for each chemokine investigated. Immunohistochemistry for IP-10 protein revealed immunoreactivity associated with perineurial endothelial cells. RANTES protein was localized immunohistologically to invading T lymphocytes. Our findings suggest that chemokines, which act towards T cells and mononuclear phagocytes, are sequentially upregulated during the clinical course of EAN and thus may contribute to the pathogenesis of inflammatory demyelinating diseases of the PNS.

Animals↗
PubMed2000

Matrix metalloprotease-9 release from monocytes increases as a function of differentiation: implications for neuroinflammation and neurodegeneration.

Naïve monocytes extravasate in response to monocyte chemoattractant-1 (MCP-1) and subsequently, following differentiation within tissue, carry out effector functions. Consistent with this concept, expression of the MCP-1 receptor CCR2 decreases with monocyte differentiation, as production of cytokines increases (Fantuzzi et al., 1999). Because matrix metalloproteases (MMPs) may also play an important role in the ability of monocytes to migrate into tissues and/or to promote pathogen clearance/tissue injury, we have examined production of matrix metalloprotease-9 as a function of both monocyte differentiation in vitro and expression of CCR2. Increased time in culture, which is linked to monocyte differentiation, resulted in enhanced production of MMP-9, assessed by gelatin substrate zymography. Further, CCR2-negative monocytes produced greater quantities of MMP-9 than did naïve CCR2-positive cells. Our results indicate that MMP-9 release increases during monocyte differentiation, consistent with a prominent role in effector functions. Because extracellular matrix proteins are important to cell structure and survival (Wee Yong et al., 1998), increased expression of MMP-9 could contribute to tissue damage following monocyte differentiation.

Cell Differentiation↗
PubMed2000

Role of the intracellular domain of the human type I interferon receptor 2 chain (IFNAR2c) in interferon signaling. Expression of IFNAR2c truncation mutants in U5A cells.

A human cell line (U5A) lacking the type I interferon (IFN) receptor chain 2 (IFNAR2c) was used to determine the role of the IFNAR2c cytoplasmic domain in regulating IFN-dependent STAT activation, interferon-stimulated gene factor 3 (ISGF3) and c-sis-inducible factor (SIF) complex formation, gene expression, and antiproliferative effects. A panel of U5A cells expressing truncation mutants of IFNAR2c on their cell surface were generated for study. Janus kinase (JAK) activation was detected in all mutant cell lines; however, STAT1 and STAT2 activation was observed only in U5A cells expressing full-length IFNAR2c and IFNAR2c truncated at residue 462 (R2.462). IFNAR2c mutants truncated at residues 417 (R2. 417) and 346 (R2.346) or IFNAR2c mutant lacking tyrosine residues in its cytoplasmic domain (R2.Y-F) render the receptor inactive. A similar pattern was observed for IFN-inducible STAT activation, STAT complex formation, and STAT-DNA binding. Consistent with these data, IFN-inducible gene expression was ablated in U5A, R2.Y-F, R2.417, and R2.346 cell lines. The implications are that tyrosine phosphorylation and the 462-417 region of IFNAR2c are independently obligatory for receptor activation. In addition, the distal 53 amino acids of the intracellular domain of IFNAR2c are not required for IFN-receptor mediated STAT activation, ISFG3 or SIF complex formation, induction of gene expression, and inhibition of thymidine incorporation. These data demonstrate for the first time that both tyrosine phosphorylation and a specific domain of IFNAR2c are required in human cells for IFN-dependent coupling of JAK activation to STAT phosphorylation, gene induction, and antiproliferative effects. In addition, human and murine cells appear to require different regions of the cytoplasmic domain of IFNAR2c for regulation of IFN responses.

Animals↗
PubMed2000

Peroxisome proliferator-activated receptor-gamma activators inhibit IFN-gamma-induced expression of the T cell-active CXC chemokines IP-10, Mig, and I-TAC in human endothelial cells.

Peroxisome proliferator-activated receptor-gamma (PPARgamma), a member of the nuclear hormone receptor superfamily originally shown to play an important role in adipocyte differentiation and glucose homeostasis, is now known to regulate inflammatory responses. Given the importance of endothelial cell (EC)-derived chemokines in regulating leukocyte function and trafficking, we studied the effects of PPARgamma ligands on the expression of chemokines induced in ECs by the Th1 cytokine IFN-gamma. Treatment of ECs with PPARgamma activators significantly inhibited IFN-gamma-induced mRNA and protein expression of the CXC chemokines IFN-inducible protein of 10 kDa (IP-10), monokine induced by IFN-gamma (Mig), and IFN-inducible T-cell alpha-chemoattractant (I-TAC), whereas expression of the CC chemokine monocyte chemoattractant protein-1 was not altered. PPARgamma activators decreased IFN-inducible protein of 10 kDa promoter activity and inhibited protein binding to the two NF-kappaB sites but not to the IFN-stimulated response element ISRE site. Furthermore, PPARgamma ligands inhibited the release of chemotactic activity for CXC chemokine receptor 3 (CXCR3)-transfected lymphocytes from IFN-gamma-stimulated ECs. These data suggest that anti-diabetic PPARgamma activators might attenuate the recruitment of activated T cells at sites of Th1-mediated inflammation.

Chemokine CXCL10↗
PubMed2000

Elevated levels of the chemokine GRO-1 correlate with elevated oligodendrocyte progenitor proliferation in the jimpy mutant.

The dysmyelinating mutant jimpy (jp) arises from a point mutation in the mouse gene encoding proteolipid protein and is characterized by severe dysmyelination attributable to oligodendrocyte death. This mutant was used to investigate the regulation of oligodendrocyte progenitor proliferation in the postnatal spinal cord. At postnatal day 18, jp spinal cord contained a three- to eightfold greater number of proliferating oligodendrocyte progenitor cells than did wild-type (wt) spinal cord. Increased proliferation in jp spinal cord was accompanied by a twofold increase in the number of progenitor cells. Semiquantitative reverse transcriptase-PCR revealed no change in the level of mRNA encoding the platelet-derived growth factor A, transforming growth factor-beta, or insulin-like growth factor-I, all of which have been implicated as regulators of proliferation and differentiation of oligodendrocyte progenitor cells. There was, however, a 17-fold increase in the level of mRNA encoding the chemokine GRO-1 and a 5- to 6-fold increase in GRO-1 protein in the jp spinal cord. Double immunofluorescence labeling revealed elevated levels of GRO-1 in reactive astrocytes in jp spinal cord white matter. In vitro studies indicated that extracts from jp spinal cord stimulated oligodendrocyte progenitor proliferation. Furthermore, removal of GRO-1 from jp extracts by immunoprecipitation reduced the proliferation of progenitor cells to a level similar to that achieved by wt extracts. These findings suggest a novel mechanism by which proliferation of oligodendrocyte progenitor cells is regulated in the postnatal spinal cord in response to insult.

Animals↗
PubMed2000

Endothelial cell expression of monocyte chemotactic protein-1, tissue factor, and thrombomodulin on hydrophilic plasma polymers.

Endothelial cells (EC) from human aortas, microvessels, and pulmonary arteries were examined for their expression and activity of monocyte chemotactic protein-1 (MCP-1), tissue factor, and thrombomodulin in response to tumor necrosis factor-alpha (TNFalpha) on the hydrophilic plasma polymers gamma-butyrolactone (GBL) and N-vinyl-2-pyrrolidone (NVP), along with a fibronectin (FN) control. RNAs isolated from EC grown on these substrates were subjected to reverse transcription-polymerase chain reaction (RT-PCR) and dot-blot analysis. EC expression of MCP-1 and tissue factor was very low in the absence of TNFalpha but high for constitutively expressed thrombomodulin. TNFalpha induced EC expression and activity of MCP-1 and tissue factor and suppressed that of thrombomodulin on all substrates. Greater differences were seen with regard to cell origin, but little difference was seen among substrates. Basal secretion of MCP-1 was very low in aortic and pulmonary artery EC and even less in microvascular EC. TNFalpha increased MCP-1 secretion significantly in aortic and pulmonary artery EC but to a lesser extent in microvascular EC. In contrast, tissue factor expression was greater in pulmonary artery EC compared to microvascular and aortic EC. Basal expression of thrombomodulin was largely comparable for all three cell types grown on different surfaces, but TNFalpha suppressed thrombomodulin to different extents depending on the origin of the EC. The activity of tissue factor and thrombomodulin and the secretion of MCP-1 by EC were largely correlated with the expression of these genes. We conclude that EC origin may be an important determinant of cellular function on hydrophilic plasma polymer substrates. However, the differences in cellular function due to variations in substrate surface hydrophilicity could have been masked by the extracellular matrix remodeling that presumably occurred during EC growth to confluence.

4-Butyrolactone↗
PubMed2000

Chemokines and chemokine receptors in inflammation of the nervous system: manifold roles and exquisite regulation.

This article focuses on the production of chemokines by resident glial cells of the nervous system. We describe studies in two distinct categories of inflammation within the nervous system: immune-mediated inflammation as seen in experimental autoimmune encephalomyelitis (EAE) or multiple sclerosis (MS) and post-traumatic inflammation. We provide evidence that chemokines play a role in amplifying the inflammatory reaction in EAE (and, probably, MS). In the context of neural trauma, chemokines appear to be primary stimuli for leukocyte recruitment. Strikingly, expression of monocyte chemoattractant protein (MCP)-1 and interferon-gamma-inducible protein-10 (IP-10) are largely restricted to astrocytes or other glial cells in these diverse pathological states. The remainder of the review focuses on studies that address the molecular mechanisms which underlie transcriptional regulation of three astrocyte-derived chemokines: MCP-1, IP-10 and beta-R1/interferon-gamma-inducible T-cell chemoattractant (I-TAC). Based on these studies, we propose that the complex promoters of these genes are marvelously organized for flexible and efficient response to challenge. In the case of MCP-1, several different stimuli can elicit gene transcription, acting through a conserved mechanism that includes binding of inducible transcription factors and recruitment of the constitutive factor Sp1. For IP-10 and beta-R1/I-TAC, it appears that efficient gene transcription occurs only in highly inflammatory circumstances that produce aggregates of simultaneous stimuli. These characteristics, in turn, mirror the expression patterns of the endogenous genes: MCP-1 is expressed under a variety of circumstances, while IP-10 appears primarily during immune-mediated processes that feature exposure of resident neuroglia to high levels of inflammatory cytokines.

Autoimmune Diseases of the Nervous System↗