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Biomedical subjects

W D Matthew

Publications and source records attributed to W D Matthew.

At least 19 recordsLinked to original sources
PubMed2001

Apolipoprotein E modulates glial activation and the endogenous central nervous system inflammatory response.

Apolipoprotein E (apoE) is a 299 amino acid protein that is associated with risk of developing Alzheimer's Disease (AD) and outcome after acute brain injury. To investigate the possibility that apoE modulates glial activation we studied the effect of endogenous apoE on inflammatory gene regulation in vitro and in vivo. Our results indicate that apoE downregulates CNS production of TNFalpha, Il-1beta, and Il-6 mRNA following stimulation with lipopolysaccharide (LPS). This effect of endogenous apoE on inflammatory gene regulation appears to be specific, and may account for the biological role that apoE plays in acute and chronic human neurological disease.

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PubMed2001

Impairment of the blood-nerve and blood-brain barriers in apolipoprotein e knockout mice.

Apolipoprotein E (apoE) is well characterized as a plasma lipoprotein involved in lipid and cholesterol metabolism. Recent studies implicating apoE in Alzheimer's disease and successful recovery from neurological injury have stimulated much interest in the functions of apoE within the brain. To explore the functions of apoE within the nervous system, we examined apoE knockout (KO) mice. Previously, we showed that apoE KO mice have a delayed response to noxious thermal stimuli associated with a loss and abnormal morphology of unmyelinated fibers in the sciatic nerve. From these data, we hypothesized that apoE KO mice could have an impaired blood-nerve barrier (BNB). In this report, we demonstrate functionally impaired blood-nerve and blood-brain barriers (BBB) in apoE KO mice using immunofluorescent detection of serum protein leakage into nervous tissue as a diagnostic for decreased BNB and BBB integrity. Extensive extravasation of serum immunoglobulin G (IgG) is detected in the sciatic nerve, spinal cord, and cerebellum of apoE KO but not WT mice. In a subpopulation of apoE KO mice, IgG also extravasates into discrete cortical and subcortical locations, including hippocampus. Loss of BBB integrity was additionally confirmed by the ability of exogenously supplied Evans blue dye to penetrate the BBB and to colocalize with IgG immunoreactivity in CNS tissue. These observations support a role for apoE in maintaining the integrity of the BNB/BBB and suggest a novel relationship between apoE and neural injury.

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PubMed1998

Endogenous apolipoprotein E suppresses LPS-stimulated microglial nitric oxide production.

The human apolipoprotein (apo) E4 isoform is associated with an increased risk for Alzheimer's disease (AD) and poor prognosis after acute CNS injury. Addition of human apoE inhibits murine microglial activation in culture, suggesting that microglia might be an important physiological target of apoE. In the present study, we examined the role of endogenous murine apoE in modulating microglial nitric oxide (NO) production following lipopolysaccharide (LPS) stimulation. Brain cultures from apoE-deficient mouse pups showed enhanced NO production relative to cultures from wild-type mice and from transgenic mice expressing the human apoE3 isoform, demonstrating that endogenous apoE produced by glial cultures is capable of inhibiting microglial function. ApoE produced within the brain may suppress microglial reactivity and thus alter the CNS response to acute and chronic injury.

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PubMed1998

Peripheral sensory nerve defects in apolipoprotein E knockout mice.

Apolipoprotein E (apoE), a plasma lipoprotein involved in lipid metabolism, is also proposed to have important functions within the central and peripheral nervous systems. To investigate the function of apoE in the peripheral nervous system, we examined the structure of sciatic nerves in apoE-deficient (apoE KO) mice. In the normal peripheral nervous system, apoE is produced by nonmyelinating Schwann cells, suggesting a role for apoE in the support of unmyelinated thermal and nociceptive sensory afferents. Using electron microscopy, we have found that apoE KO mice have abnormal and reduced numbers of unmyelinated axons within the sciatic nerve. ApoE KO unmyelinated axons are irregularly shaped and separated by very little Schwann cell cytoplasm. ApoE KO myelinated fibers and myelin are ultrastructurally normal. Consistent with these morphological findings, apoE KO mice display reduced sensitivity to noxious thermal stimuli. These data provide in vivo support for the hypothesis that apoE promotes neuronal health and survival.

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PubMed1997

Apolipoprotein E binds to and potentiates the biological activity of ciliary neurotrophic factor.

Expression of apolipoprotein E (apoE) and ciliary neurotrophic factor (CNTF), a pleiotropic neuron survival factor, increases in the CNS in response to injury. Although CNTF is believed to act as a survival factor after injury in the CNS, the functions of apoE in the CNS remain mainly unknown. Similarities between apoE and CNTF, including coinciding patterns of postinjury expression, extracellular localization, homologous tertiary structure, and ability to form homodimers led us to examine the possibility that apoE and CNTF directly associate and thereby facilitate the neurotrophic activity of CNTF. We identified two binding interactions between apoE and CNTF: (1) reversible binding of both the apoE3 and apoE4 isoforms to CNTF under nondenaturing conditions, and (2) a higher avidity, SDS-stable binding of apoE3 with CNTF. Purified lipid-free apoE, as well as apoE in cerebrospinal fluid, binds CNTF. We demonstrate here that the survival-promoting activity of CNTF on cultured hippocampal neurons is potentiated by apoE. In the absence of apoE, survival of hippocampal neurons with 1 ng/ml CNTF was 20% above control survival values. In contrast, in the presence of apoE, survival of hippocampal neurons with 1 ng/ml CNTF was 40% above control survival values. These data, which indicate a novel function for apoE in the nervous system, support the hypothesis that apoE secreted locally at sites of injury can facilitate neural repair by promoting the activity of certain growth factors, in particular CNTF.

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PubMed1997

Neurite outgrowth is enhanced by anti-idiotypic monoclonal antibodies to the ganglioside GM1.

Exogenously added gangliosides enhance sprouting, neurite outgrowth, and other neuronal activities; this effect may be initiated when a ganglioside binds to a membrane protein or when a ganglioside intercalates into the plasma membrane. To test whether binding to membrane proteins is sufficient for ganglioside-mediated activity, anti-idiotypic antibodies were generated that mimic the functional binding sites of the ganglioside GM1 as described by M. J. Riggott and W. D. Matthew (1996, Glycobiology, 6, 581-589). These anti-idiotypic antibodies are proteinaceous probes that model the biochemical and biological effects of gangliosides. Those anti-idiotypic ganglioside (AIG) monoclonal antibodies (mAb's) were selected based on their ability to bind a known GM1 binding protein, the beta-subunit of cholera toxin. These studies described neuronal cell surface proteins that were identified by immunocytochemistry and Western blotting using these AIG mAb's. Here we show that AIG mAb's mimic the functional properties of GM1 in that they facilitate neurite outgrowth from central and peripheral nervous system neurons in in vitro bioassays. In addition, AIG mAb binding modulates second messenger activity, suggesting that membrane protein binding alone is sufficient to invoke intracellular activation. The similarity in the pattern of protein tyrosine phosphorylation evoked by GM1 and the anti-idiotypic ganglioside antibodies suggests that the AIG mAb's modulate neurite outgrowth in a manner similar to that of GM1. Because antibodies cannot intercalate into the plasma membrane, these results suggest that the ganglioside GM1 can mediate neuronal cellular activity by binding to cell surface proteins.

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PubMed1997

Apolipoprotein E suppresses glial cell secretion of TNF alpha.

Apolipoprotein E (apoE) is a 299 amino acid protein with multiple biological functions. Initially described in the context of cholesterol metabolism, apoE also has immunomodulatory properties and recent evidence has implicated a role for apoE in neurological disease. One possibility is that apoE, which is the predominant apolipoprotein produced intra-axially, may modify the CNS response to acute and chronic injury. We prepared mixed neuronal-glial cultures from apoE deficient mouse pups and measured secretion of TNF alpha after stimulation with lipopolysaccharide (LPS) in the presence and absence of human recombinant apoE3 and E4. We demonstrate that preincubation with apoE blocks glial secretion of TNF alpha in a dose-dependent manner. This effect is independent of any direct effect of apoE on cell viability and is greatest when apoE is preincubated with the cell culture for 24 h.

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PubMed1996

Glial growth factor 2, a soluble neuregulin, directly increases Schwann cell motility and indirectly promotes neurite outgrowth.

Schwann cells proliferate, migrate, and act as sources of neurotrophic support during development and regeneration of peripheral nerves. Recent studies have demonstrated that neuregulins, a family of growth factors secreted by developing motor and peripheral neurons, influence Schwann cell development. In this study, we use three distinct assays to show that glial growth factor 2 (GGF2), a secreted neuregulin, exerts multiple effects on mature Schwann cells in vitro. At doses submaximal for proliferation, GGF2 increases the motility of Schwann cells cultured on peripheral nerve cryosections. Furthermore, in a novel bioassay, focal application of GGF2 causes directed migration in conventional monolayer cultures of directed migration of Schwann cells. At higher doses, GGF2 causes proliferation, as described previously. In a new explant culture system designed to emulate entubulation repair of transected peripheral nerves, GGF2 concentrations greater than necessary to saturate the mitotic response induce the secretion by Schwann cells of activities that promote sympathetic neuron survival and outgrowth. These findings support a model in which neuregulins secreted by peripheral neurons are key components of reciprocal neuron-glia interactions that are important for peripheral nerve development and regeneration.

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PubMed1996

Generating monoclonal antibodies to neuronal antigens.

Methods for generating monoclonal antibodies directed to the functional sites of neuronal antigens are reviewed. These methods include optimal antigen preparation and presentation as well as selective targeting and manipulation of the antigenic response. We describe our use of the immunosuppressant drug, cyclophosphamide, to produce a selective immune response to rare, poorly immunogenic, or actively suppressed antigens. These techniques allow us to generate antibodies to the functional sites of neuronal antigens, such as cell surface molecules. Such antibodies are directed to complex carbohydrates, proteins, protein complexes and glycolipids that form the active site of neuronal antigens. We can use these antibodies in the molecular dissection of functional active sites that are inaccessible to genetic manipulation. These techniques favor the generation of antibodies that can be used to understand and manipulate neuronal cellular activity.

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PubMed1996

Anti-idiotypic monoclonal antibodies to GM1 identify ganglioside binding proteins.

Ganglioside stimulated neurite outgrowth may be due to ganglioside binding to membrane proteins or to intercalation into the membrane. To test that ganglioside binding proteins could be found on neuronal surfaces, anti-idiotypic ganglioside monoclonal antibodies (AIG mAbs) were generated to mimic the biological properties of the GM1 ganglioside. The AIG mAbs were identified by their ability to bind to a known GM1 binding protein, the beta-subunit of cholera toxin. For the two AIG mAbs studied, AIG5 and AIG20, binding to beta-CT was blocked most strongly by GM1. This data also suggests that AIG5 and AIG20 mimic different but overlapping epitopes of the ganglioside GM1. Western blotting and immunoprecipitation of mammalian tissues reveals four potential ganglioside binding proteins of molecular weight 93, 66, 57, and 45 kDa. Immunocytochemistry demonstrates neuronal surface label with the AIG mAbs, which suggests that gangliosides, enriched on the neuronal surface membrane, are co-localized with putative ganglioside binding proteins. In bioassays, the AIG mAbs promote neuronal sprouting. This shows that these antibodies can be used to study the biological effects of ganglioside binding to neuronal surface proteins, and the role of gangliosides in the activation of neurite outgrowth.

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PubMed1995

Interaction of apolipoprotein E with laminin increases neuronal adhesion and alters neurite morphology.

The extracellular matrix protein laminin profoundly affects neuronal adhesion, spreading, differentiation, and growth by binding integrin-type cell surface receptors. Laminin binds other basement membrane components, including heparan sulfate proteoglycans. Apolipoprotein E (apoE) also binds basement membrane and heparan sulfate proteoglycans and colocalizes with s-laminin in the neuromuscular junction. We sought to determine whether apoE interacts with laminin and whether, as a result, apoE alters the regulation of neuronal adhesion and differentiation by laminin. We demonstrate high-avidity interaction between apoE and laminin in vitro. Compared to laminin alone, a laminin-apoE substrate produces increased numbers of live, attached hippocampal neurons in culture. In addition, neurons grown on laminin-apoE substrates have larger growth cones, increased neuritic branching, and flattened cell bodies compared to neurons grown on laminin alone. ApoE may be important in the development and maintenance of neurons in the central nervous system by regulating interactions between the neuron and the extracellular matrix.

Apolipoproteins E↗
PubMed1995

Neurotrophins affect the pattern of DRG neurite growth in a bioassay that presents a choice of CNS and PNS substrates.

Neurons can be categorized in terms of where their axons project: within the central nervous system, within the peripheral nervous system, or through both central and peripheral environments. Examples of these categories are cerebellar neurons, sympathetic neurons, and dorsal root ganglion (DRG) neurons, respectively. When explants containing one type of neuron were placed between cryosections of neonatal or adult sciatic nerve and neonatal spinal cord, the neurites exhibited a strong preference for the substrates that they would normally encounter in vivo: cerebellar neurites generally extended only on spinal cord, sympathetic neurites on sciatic nerve, and DRG neurites on both. Neurite growth from DRG neurons has been shown to be stimulated by neurotrophins. To determine whether neurotrophins might also affect the substrate preferences of neurites, DRG were placed between cryosections of neonatal spinal cord and adult sciatic nerve and cultured for 36 to 48 hours in the presence of various neurotrophins. While DRG cultured in NGF-containing media exhibited neurite growth over both spinal cord and sciatic nerve substrates, in the absence of neurotrophins DRG neurites were found almost exclusively on the CNS cryosection. To determine whether these neurotrophin-dependent neurite patterns resulted from the selective survival of subpopulations of DRG neurons with distinct neurite growth characteristics, a type of rescue experiment was performed: DRG cultured in neurotrophin-free medium were fed with NGF-containing medium after 36 hours in vitro and neurite growth examined 24 hours later; most DRG exhibited extensive neurite growth on both peripheral and central nervous system substrates.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1995

CD9 plays a role in Schwann cell migration in vitro.

To identify molecules that regulate Schwann cell migration, we have generated a panel of monoclonal antibodies against Schwann cell surface antigens that modulate Schwann cell migration in in vitro bioassays. One of these antibodies, SMRA1, recognizes a 26 kDa Schwann cell surface membrane protein identified here as CD9. SMRA1 enhances Schwann cell migration on two biologically relevant substrates: living axons of cultured dorsal root ganglion neurons, and cryostat sections of sciatic nerve. This CD9-induced regulation of Schwann cell motility is correlated with a rise in cytosolic calcium and enhanced tyrosine phosphorylation of several Schwann cell proteins. These results, together with the findings of Hadjiargyrou and Patterson (1994), implicate CD9 as an important regulator of Schwann cell behavior in peripheral nerve.

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PubMed1994

Nerve growth factor and its low-affinity receptor promote Schwann cell migration.

Migrating Schwann cells in developing or regenerating peripheral nerves are known to express dramatically increased levels of nerve growth factor (NGF) and the low-affinity NGF receptor (LNGFR). Schwann cells do not express detectable pp140trk, the NGF-activated receptor tyrosine kinase which is essential for neuronal responses to NGF. The temporal correlation observed in Schwann cells between migration and the enhanced expression of NGF and LNGFR suggests that NGF and LNGFR may promote Schwann cell migration. To test this possibility, we examined the effects of NGF on Schwann cell migration on cryostat sections of biologically relevant NGF-poor and NGF-rich substrates--normal or denervated peripheral (sciatic) nerve, untreated or pretreated with NGF. Results show that Schwann cells migrate more rapidly on denervated than on normal sciatic nerve. Antibodies to NGF or to LNGFR strongly, but incompletely, inhibit enhanced migration on denervated nerves. Pretreatment of denervated nerve sections with NGF increases further the rate of Schwann cell migration. The same antibodies to NGF or to LNGFR abolish this response. These results suggest that one function of the elevated levels of NGF known to be present in embryonic and regenerating peripheral nerves is to promote the migration of Schwann cells. In contrast to neurons, where pp140trk appears to be the functionally critical NGF receptor, NGF responses in Schwann cells depend on LNGFR.

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PubMed1994

Merosin promotes neurite growth and Schwann cell migration in vitro and nerve regeneration in vivo: evidence using an antibody to merosin, ARM-1.

Monoclonal antibodies that block the cellular function(s) of specific antigens can provide valuable probes for in vitro and in vivo bioassays. With the goal of understanding the molecular basis of neuron-Schwann cell interactions during development and regeneration, we have sought antibodies that interfere with the function of merosin, the predominant laminin isoform present in the Schwann cell basement membrane. To identify the biological functions of merosin in the peripheral nervous system, we studied Schwann cell migration and neurite outgrowth in vitro and nerve regeneration in vivo, in the presence and the absence of a monoclonal antibody that we believe binds to merosin, ARM-1 (Anti Rodent Merosin-1). The ARM-1 antibody blocked both neurite outgrowth and Schwann cell migration in vitro. This antibody also reduced neuritic branching in vitro. In vivo, the ARM-1 antibody blocked the regeneration of sympathetic nerve fibers in the rat iris. The blockade of neurite outgrowth and Schwann cell migration by ARM-1 antibody suggests that merosin is involved in facilitating the two most critical cellular events during the normal development and regeneration of peripheral nerves, i.e., axon growth and Schwann cell migration. Furthermore, the regulation of both Schwann cell migration and axon growth by the ARM-1 antigen implies that these two cellular events obey a common set of molecular signals during the development and regeneration of peripheral nerves.

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PubMed1991

An in vitro bioassay for neurite growth using cryostat sections of nervous tissue as a substratum.

An in vitro bioassay is described that can be used for studying neurite growth, cell adhesion, and cell migration, as well as other cellular behaviors. The bioassay, which uses tissue sections as substrata for either dissociated cell preparations or explants, offers several distinct advantages over other commonly used bioassays. In particular, this bioassay approximates in vivo cellular environments, and the preparation of large numbers of tissue sections as substrata is relatively straight forward and simple. The method can be employed for studying cell behavior on different ages or types of tissue, as a bioassay for screening antibodies for their ability to perturb a particular cellular behavior, and for assessing the biological activities of growth factors absorbed to specific tissue environments. We present a detailed description of the method, including the variety of options to be considered at each step in the procedure, with an emphasis on using the assay to study neurite growth.

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