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Biomedical subjects

Jack P Antel

Publications and source records attributed to Jack P Antel.

At least 19 recordsLinked to original sources
PubMed2007

Simvastatin regulates oligodendroglial process dynamics and survival.

Simvastatin, a lipophilic statin that crosses the blood-brain barrier, is being evaluated as a potential therapy for multiple sclerosis (MS) due to its anti-inflammatory properties. We assessed the effects of simvastatin on cultures of rat newborn and human fetal oligodendrocyte progenitor cells (OPCs) and human adult mature oligodendrocytes (OLGs) with respect to cellular events pertaining to myelin maintenance and repair. Short-term simvastatin treatment of OPCs (1 day) induced robust process extension, enhanced differentiation to a mature phenotype, and decreased spontaneous migration. These effects were reversed by isoprenoid products and mimicked with an inhibitor of Rho kinase (ROCK), the downstream effector of the isoprenylated protein RhoA GTPase. Prolonged treatment (2 days) caused process retraction that was rescued by cholesterol, and increased cell death (4 days) partially rescued by either cholesterol or isoprenoid co-treatment. In comparison, simvastatin treatment of human mature OLGs required a longer initial time course (2 days) to induce significant process outgrowth, mimicked by inhibiting ROCK. Prolonged treatment of mature OLGs was associated with process retraction (6 days) and increased cell death (8 days). Human-derived OPCs and mature OLGs demonstrated an increased sensitivity to simvastatin relative to the rodent cells, responding to nanomolar versus micromolar concentrations. Our findings indicate the importance of considering the short- and long-term effects of systemic immunomodulatory therapies on neural cells affected by the MS disease process. (c) 2006 Wiley-Liss, Inc.

Animals↗
PubMed2006

Isolation of a natural inhibitor of human malignant glial cell invasion: inter alpha-trypsin inhibitor heavy chain 2.

Malignant central nervous system (CNS) tumors, such as glioblastoma multiforme, invade the brain and disrupt normal tissue architecture, making complete surgical removal virtually impossible. Here, we have developed and optimized a purification strategy to isolate and identify natural inhibitors of glioma cell invasion in a three-dimensional collagen type I matrix. Inter alpha-trypsin inhibitor heavy chain 2 (ITI H2) was identified from the most inhibitory fractions and its presence was confirmed both as a single protein and in a bikunin-bound form. Stable overexpression in U251 glioma cells validated ITI H2's strong inhibition of human glioma cell invasion together with significant inhibition of cell proliferation and promotion of cell-cell adhesion. Analysis of primary human brain tumors showed significantly higher levels of ITI H2 in normal brain and low-grade tumors compared with high-grade gliomas, indicating an inverse correlation with malignancy. The phosphatidylinositol 3-kinase/Akt signaling cascade seemed to be one of the pathways involved in the effect of ITI H2 on U251 cells. These findings suggest that reduction of ITI H2 expression correlates with brain tumor progression and that targeting factors responsible for its loss or restoring the ITI supply exogenously may serve as potential therapeutic strategies for a variety of CNS tumors.

Alpha-Globulins↗
PubMed2006

A new clinically relevant approach to expand myelin specific T cells.

Human self-reactive T cells are potentially involved in many autoimmune diseases. Although ex vivo detection of self-reactive T cells is possible, exhaustive functional characterization of these cells is impeded by their low frequency. In vitro expansion of antigen (Ag) specific T cells is typically achieved by using autologous (fresh or frozen) irradiated peripheral blood mononuclear cells (PBMCs), EBV-immortalized B cells or dendritic cells in the presence of Ag. These approaches require a large blood volume. We explored a method successfully applied for tumor specific T cells using in vitro expanded autologous B cells. PBMCs were stimulated with irradiated CD40L-expressing fibroblasts and IL-4, resulting in an enriched population of B cell that expressed high levels of MHC and co-stimulatory molecules, essential hallmarks of antigen presenting cells (APCs). Expanded B cells were loaded with Ag, irradiated and then used as APCs to stimulate T cells. The specificity of T cell lines was assessed by comparing their proliferation and IFN-gamma secretion when cultured with antigen-loaded B cells vs. unloaded B cells. T cell lines exhibiting antigen-specific proliferation and/or IFN-gamma secretion were expanded. Using this method, MBP and MOG specific CD4(+) and CD8(+) T cell lines were obtained from multiple donors in comparable numbers to those obtained using the traditional approach (i.e. fresh PBMCs as APCs) and were kept in culture for many weeks. We have shown that myelin specific CD4(+) and CD8(+) T cells can be expanded from a relatively small volume of blood (50-100 ml) from multiple donors using expanded B cells as APCs.

Amino Acid Sequence↗
PubMed2006

Potential for interferon beta-induced serum antibodies in multiple sclerosis to inhibit endogenous interferon-regulated chemokine/cytokine responses within the central nervous system.

BACKGROUND: A proportion of patients with multiple sclerosis (MS) receiving systemic interferon beta therapy will develop serum neutralizing antibodies (NAbs) that can reduce the activity of the drug. Interferon-beta (IFN-beta) is produced by glial cells within the central nervous system. Although systemic interferon beta does not access the central nervous system, titers of serum NAbs may be sufficient that some will access the central nervous system. OBJECTIVE: To address whether serum samples that contain high titers of NAbs could inhibit glial cell production of chemokines and cytokines that are regulated by endogenous IFN-beta. DESIGN: We used an in vitro assay involving toll-like receptor 3 ligand (polyinosinic-polycytidylic acid) signaling to assess the effect of serum samples containing high titers of NAbs (1800-20 000 U) on production of the chemokine CXCL10 and the cytokine interleukin 6 by human astrocytes. RESULTS: Serum samples positive for NAbs significantly inhibited polyinosinic-polycytidylic acid-induced CXCL10 and IL-6 production by astrocytes. CONCLUSION: High-titer NAbs to interferon beta may block endogenous IFN-beta function and alter the chemokine/cytokine microenvironment within the central nervous system, thereby modulating the profile and course of the local inflammatory response.

Adult↗
PubMed2006

Natalizumab effects on immune cell responses in multiple sclerosis.

OBJECTIVE: Our objective was to study in vivo biological effects of natalizumab on immune cell phenotype and function in multiple sclerosis (MS) patients. METHODS: Blood was obtained before and after serial monthly natalizumab infusions to track functional expression of VLA-4 and migratory capacity of immune cells. The impact of infusion on activation thresholds of immune cells was evaluated. RESULTS: Preinfusion VLA-4 expression differed across immune cell subsets. Natalizumab significantly, albeit partially, diminished VLA-4 expression on circulating immune cells. Cell subsets were differentially affected. Treatment significantly decreased migratory capacity of immune cells, correlating well with changes in VLA-4 expression. Effects of a single dose were not saturating and did not persist through the monthly dose interval. Infusion effect varied across patients but was remarkably stable in individual patients, over multiple infusions. Treatment significantly modulated proliferative responses of immune cells. INTERPRETATION: To our knowledge, we provide first proof of concept that natalizumab diminishes migratory capacity of immune cells. Our prospective study further shows that effects of therapy likely (1) differ for distinct immune cell subsets, (2) are not sustained over current dose interval, (3) have unique profiles in individual patients, and (4) include modulation of activation threshold of immune cells. Monitoring these parameters could be relevant to ongoing safety and efficacy considerations.

Antibodies, Monoclonal↗
PubMed2006

Leukemia inhibitory factor is produced by myelin-reactive T cells from multiple sclerosis patients and protects against tumor necrosis factor-alpha-induced oligodendrocyte apoptosis.

In multiple sclerosis (MS), damage to oligodendrocytes is believed to be caused by an aberrant immune response initiated by autoreactive T cells. Increasing evidence indicates that these T cells are not exclusively detrimental but might also exert protective effects. We report for the first time that myelin-reactive T-cell clones from eight MS patients (6/19) and five healthy controls (4/11) produce leukemia inhibitory factor (LIF), a member of the neuropoietic family of neurotrophins. In addition, T-cell clones specific for tetanus toxoid, CD4(+) and CD8(+) T cells, and monocytes, but not B cells, secreted LIF. LIF-producing T lymphocytes and macrophages were also identified immunohistochemically in both active and chronic-active MS lesions. We further demonstrated dose-dependent protective effects of LIF on tumor necrosis factor-alpha-induced apoptosis of oligodendrocytes. In conclusion, our data demonstrate that peripheral and CNS-infiltrating T cells from MS patients produce LIF, a protective factor for oligodendrocytes. This study emphasizes that secretion of LIF may contribute to the neuroprotective effects of autoreactive T cells.

Animals↗
PubMed2006

Continued administration of ciliary neurotrophic factor protects mice from inflammatory pathology in experimental autoimmune encephalomyelitis.

Multiple sclerosis is an inflammatory disease of the central nervous system that leads to loss of myelin and oligodendrocytes and damage to axons. We show that daily administration (days 8 to 24) of murine ciliary neurotrophic factor (CNTF), a neurotrophic factor that has been described as a survival and differentiation factor for neurons and oligodendrocytes, significantly ameliorates the clinical course of a mouse model of multiple sclerosis. In the acute phase of experimental autoimmune encephalomyelitis induced by myelin oligodendrocyte glycoprotein peptide 35-55, treatment with CNTF did not change the peripheral immune response but did reduce the number of perivascular infiltrates and T cells and the level of diffuse microglial activation in spinal cord. Blood brain barrier permeability was significantly reduced in CNTF-treated animals. Beneficial effects of CNTF did not persist after it was withdrawn. After cessation of CNTF treatment, inflammation and symptoms returned to control levels. However, slight but significantly higher numbers of oligodendrocytes, NG2-positive cells, axons, and neurons were observed in mice that had been treated with high concentrations of CNTF. Our results show that CNTF inhibits inflammation in the spinal cord, resulting in amelioration of the clinical course of experimental autoimmune encephalomyelitis during time of treatment.

Animals↗
PubMed2005

TLR signaling tailors innate immune responses in human microglia and astrocytes.

The specific signals mediating the activation of microglia and astrocytes as a prelude to, or consequence of, CNS inflammation continue to be defined. We investigated TLRs as novel receptors mediating innate immune responses in human glial cells. We find that microglia express mRNA for TLRs 1-9, whereas astrocytes express robust TLR3, low-level TLR 1, 4, 5, and 9, and rare-to-undetectable TLR 2, 6, 7, 8, and 10 mRNA (quantitative real-time PCR). We focused on TLRs 3 and 4, which can signal through both the MyD88-dependent and -independent pathways, and on the MyD88-restricted TLR2. By flow cytometry, we established that microglia strongly express cell surface TLR2; TLR3 is expressed at higher levels intracellularly. Astrocytes express both cell surface and intracellular TLR3. All three TLRs trigger microglial activation upon ligation. TLR3 signaling induces the strongest proinflammatory polarizing response, characterized by secretion of high levels of IL-12, TNF-alpha, IL-6, CXCL-10, and IL-10, and the expression of IFN-beta. CXCL-10 and IL-10 secretion following TLR4 ligation are comparable to that of TLR3; however, other responses were lower or absent. TLR2-mediated responses are dominated by IL-6 and IL-10 secretion. Astrocytes respond to TLR3 ligation, producing IL-6, CXCL-10, and IFN-beta, implicating these cells as contributors to proinflammatory responses. Initial TLR-mediated glial activation also regulates consequent TLR expression; while TLR2 and TLR3 are subject to positive feedback, TLR4 is down-regulated in microglia. Astrocytes up-regulate all three TLRs following TLR3 ligation. Our data indicate that activation of innate immune responses in the CNS is not homogeneous but rather tailored according to cell type and environmental signal.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Microglia and multiple sclerosis.

Microglia participate in all phases of the multiple sclerosis (MS) disease process. As members of the innate immune system, these cells have evolved to respond to stranger/danger signals; such a response within the central nervous system (CNS) environment has the potential to induce an acute inflammatory response. Engagement of Toll-like receptors (TLRs), a major family of pattern-recognition receptors (PRRs), provides an important mechanism whereby microglia can interact with both exogenous and endogenous ligands within the CNS. Such interactions modulate the capacity of microglia to present antigens to cells of the adaptive immune system and thus contribute to the initiation and propagation of the more sophisticated antigen-directed responses. This inflammatory response introduces the potential for bidirectional feedback between CNS resident and infiltrating systemic cells. Such interactions acquire particular relevance in the era of therapeutics for MS because the infiltrating cells can be subjected to systemic immunomodulatory therapies known to change their functional properties. Phagocytosis by microglia/macrophages is a hallmark of the MS lesion; however, the extent of tissue damage and the type of cell death will dictate subsequent innate responses. Microglia/macrophages are armed with a battery of effector molecules, such as reactive nitrogen species, that may contribute to CNS tissue injury, specifically to the injury of oligodendrocytes that is associated with MS. A therapeutic challenge is to modulate the dynamic properties of microglia/macrophages so as to limit potentially damaging innate responses, to protect the CNS from injury, and to promote local recovery.

Animals↗
PubMed2005

Interferon beta promotes nerve growth factor secretion early in the course of multiple sclerosis.

BACKGROUND: Interferon beta therapy has been shown to reduce the rate of clinical relapse and the frequency of magnetic resonance imaging-defined T2- weighted lesions in patients with multiple sclerosis (MS). When given early, interferon beta also reduces the rate of development of brain atrophy and improves axonal integrity. Nerve growth factor (NGF) can retard the severity and course of experimental allergic encephalomyelitis. OBJECTIVE: To determine whether interferon beta effects on patients with MS could be related to modulation of neurotrophin production within the central nervous system. DESIGN: We studied neurotrophin production by human glial and brain endothelial cells in response to coculture with MS patient-derived lymphocytes, and correlated levels of NGF secretion with clinical and magnetic resonance imaging-defined markers of disease. RESULTS: We demonstrate that production of NGF by human brain microvascular endothelial cells is triggered by interaction with T lymphocytes derived from MS patients. No such response was observed using human adult microglia or human fetal astrocytes. Nerve growth factor production by endothelial cells was potentiated by pretreating lymphocytes with interferon beta in vitro, and by using lymphocytes derived from MS patients treated with interferon beta in vivo. By using this assay, we show that levels of NGF induced by lymphocytes from MS patients inversely correlate with magnetic resonance imaging measures of brain atrophy and axonal injury. CONCLUSION: These findings suggest that interferon beta-mediated production of NGF at the level of the blood-brain barrier, whether acting as an immunomodulator or directly on neural cells, is another potential mechanism contributing to the magnetic resonance imaging-defined effect of interferon beta on brain atrophy when given early in the course of MS.

Adult↗
PubMed2005

Kinin B1 receptor expression on multiple sclerosis mononuclear cells: correlation with magnetic resonance imaging T2-weighted lesion volume and clinical disability.

BACKGROUND: We have previously shown that the inducible kinin B(1) receptor is expressed on T lymphocytes during relapses and progression in multiple sclerosis. OBJECTIVE: To evaluate the correlation between the expression of B1 receptor on peripheral blood mononuclear cells derived from patients who have multiple sclerosis with serial, clinical magnetic resonance imaging and immunological study-derived measures. DESIGN: Using frozen samples obtained from a high-frequency magnetic resonance imaging-immunological study, we analyzed B1 receptor messenger RNA (mRNA) expression in peripheral blood-derived mononuclear cells serially collected from 6 patients with multiple sclerosis and 8 healthy control subjects by semiquantitative radioactive duplex reverse transcriptase-polymerase chain reaction amplification. Time-course kinin B1-actin mRNA ratios were subsequently compared with corresponding clinical magnetic resonance imaging and immune parameters. RESULTS: The time-course kinin B1-actin mRNA ratio correlated positively with the Expanded Disability Status Scale index (P<.001), occurrence of clinical relapse (P = .02), volume of lesion on T2-weighted images (P<.003) and interleukin 2 receptor and major histocompatibility complex class II expression on CD4+ lymphocytes, but not with gadolinium-enhancing lesions. The time-course kinin B1-actin mRNA ratios were 5 to 25 times lower in samples derived from healthy controls. CONCLUSION: The correlation of kinin B1 receptor mRNA levels with dynamic clinical and magnetic resonance imaging measures suggests that expression of this receptor can serve as an index of disease activity in multiple sclerosis.

Adult↗
PubMed2005

Th1 and Th2 lymphocyte migration across the human BBB is specifically regulated by interferon beta and copolymer-1.

Lymphocyte migration into the central nervous system is a central event in lesion formation in MS. Both interferon beta (IFNbeta) and copolymer-1 (Cop-1) reduce the overall lymphocyte entry into the brain through the blood-brain barrier (BBB) as judged by MRI based studies. In this study, we used a modified Boyden chamber assay in which human brain microvascular endothelial cell (HBEC) monolayers are grown on a fibronectin coated transwell membrane to evaluate in vitro migration of allo-antigen Th1 and Th2 lymphocytes across brain endothelium. We confirmed previous observations showing that migration rates of Th2 lymphocytes across HBECs were higher than migration rates of Th1 cells. When HBECs were pre-treated with IFNbeta (100 U/ml) 30 min prior to migration, the migration rate of Th1 was significantly decreased (45% reduction) while the migration of Th2 remained unchanged. Addition of Cop-1 (30 microg/ml) to HBEC monolayers 30 min prior to migration significantly increased the migration rate of Th2 cells and did not affect the migration of Th1 cells. We did not observe any changes in (1) the expression of adhesion molecules on the surface of HBECs and (2) the pattern of chemokine production by HBECs after IFNbeta or Cop-1 treatment. The changes in cellular migration rates were not paralleled with changes in diffusion of large molecular weight tracers across brain ECs. Our data support the notion that immuno-modulators used for the treatment of MS selectively and differentially regulate the migration of T helper lymphocyte subsets and that Cop-1 promotes trans-endothelial migration of Th2 cells across the BBB.

Adult↗
PubMed2004

Resistance of human adult oligodendrocytes to AMPA/kainate receptor-mediated glutamate injury.

Multiple sclerosis is an inflammatory disease of the CNS leading to the destruction of oligodendrocytes (OLs), myelin sheaths and axons. The mediators of tissue injury remain unknown. Glutamate, which can be released by activated immune cells or produced within the CNS, has been implicated as a potential mediator of tissue injury in multiple sclerosis. alpha-Amino-3-hydroxy-5-methyl-4-isoxazole proprionic acid (AMPA) and kainate are highly toxic when added to rodent OL cultures. Using OLs derived from human adult surgical specimens, we investigated AMPA/kainate receptor expression and the effects of receptor stimulation on the viability of human OLs. We find that human adult OLs in vitro express low levels of ionotropic glutamate receptors and are resistant to excitotoxicity mediated by high and sustained doses of AMPA or kainate, even when receptor desensitization is blocked. In contrast, rat OLs show strong AMPA receptor expression and are susceptible to excitotoxicity, as previously demonstrated. Furthermore, we show in human brain sections that OLs do not express AMPA receptors in situ and that glial expression of AMPA receptors is limited to astrocytes. The apparent lack of glutamate receptor expression on human OLs and their resistance to AMPA/kainate toxicity should be considered when postulating mechanisms of tissue injury in multiple sclerosis.

Adult↗
PubMed2004

Type 2 monocyte and microglia differentiation mediated by glatiramer acetate therapy in patients with multiple sclerosis.

Glatiramer acetate (GA) therapy of patients with multiple sclerosis (MS) represents a unique setting in which in vivo Th2 deviation of T cells is consistently observed and associated with clinical benefit in a human autoimmune disease. We postulated that APCs are important targets of GA therapy and demonstrate that treatment of MS patients with GA reciprocally regulates the IL-10/IL-12 cytokine network of monocytes in vivo. We further show that Th1- or Th2-polarized GA-reactive T cells isolated from untreated or treated MS patients mediate type 1 and 2 APC differentiation of human monocytes, based on their ability to efficiently induce subsequent Th1 and Th2 deviation of naive T cells, respectively. These observations are extended to human microglia, providing the first demonstration of type 2 differentiation of CNS-derived APCs. Finally, we confirm that the fundamental capacity of polarized T cells to reciprocally modulate APC function is not restricted to GA-reactive T cells, thereby defining a novel and dynamic positive feedback loop between human T cell and APC responses. In the context of MS, we propose that GA therapy results in the generation of type 2 APCs, contributing to Th2 deviation both in the periphery and in the CNS of MS patients. In addition to extending insights into the therapeutic mode of action of GA, our findings revisit the concept of bystander suppression and underscore the potential of APCs as attractive targets for therapeutic immune modulation.

Adult↗
PubMed2004

Inflammatory potential and migratory capacities across human brain endothelial cells of distinct glatiramer acetate-reactive T cells generated in treated multiple sclerosis patients.

We asked whether GA-reactive T cells with distinct cytokine profiles (Th2 versus Th1/Th0), induced during GA therapy of multiple sclerosis (MS) patients, have different migratory capacities across human brain endothelial cells (HBECs), and distinct effects on inflammatory responses at the level of the blood-brain barrier (BBB). We confirmed that GA therapy induces a range of GA-reactive T cells defined by distinct profiles of cytokine expression. Supernatants from Th0/Th1 GA-reactive cells significantly upregulated pro-inflammatory chemokine and adhesion molecule expression in HBECs. Post-treatment Th2-polarized GA-reactive cells were significantly less pro-inflammatory but did not suppress the effects induced by Th1 cells. All lines migrated across a HBEC/fibronectin-based model of the BBB with similar efficiencies. We conclude that the spectrum of GA-reactive T cells induced in treated MS patients may differentially impact inflammatory responses at the BBB level. Future studies will determine whether this could contribute to variable clinical response to GA therapy.

Adult↗