Down-regulation of transforming growth factor-beta gene expression by antisense oligodeoxynucleotides increases recombinant interferon-gamma-induced nitric oxide synthesis in murine peritoneal macrophages

Increasing evidence indicates that the production of nitric oxide (NO) by inducible NO synthase (iNOS) is tightly regulated. Transforming growth factor-beta (TGF-beta) is a family of multifunctional peptides secreted during macrophage activation, but several lines of evidence suggest that TGF-beta is selectively suppressive for macrophage NO production. We therefore reasoned that a strategy employing oligodeoxynucleotides (ODN) complementary to TGF-beta mRNA (antisense ODN) might increase NO production in interferon-gamma (IFN-gamma) treated murine peritoneal macrophages. To evaluate this concept, we tested the effects of antisense ODN targeted to TGF-beta mRNA (25-mer ODN complementary to TGF-beta mRNA sequences) by introducing them into the medium of cultured macrophages. Phosphorothioation of ODN was employed to retard their degradation. Antisense ODN had no effect on NO production by itself, whereas IFN-gamma alone had a modest effect. When antisense ODN were used in combination with IFN-gamma, there was a marked cooperative induction of NO production. These effects of antisense ODN were associated with decreased TGF-beta expression in activated macrophages. However, sense ODN had no effect. Adding anti-TGF-beta antibodies to the IFN-gamma-treated macrophages mimicked the positive effect of antisense ODN on NO production. In addition, the effects of either antisense ODN or anti-TGF-beta antibodies were blocked by adding exogenous TGF-beta in cultured macrophages. These results indicate that the generation of TGF-beta by activated macrophages provides a self-regulating mechanism by which the temporal and perhaps spatial production of NO, a reactive and potentially toxic mediator, can be finely regulated.

Complement and cytokine gene expression in cultured microglial derived from postmortem human brains

Microglia were successfully cultured from human brain tissue from normal and neurologically diseased cases obtained 3.5-10 hours postmortem. Final cell preparations were more than 99% pure as judged by latex bead phagocytosis, expression of microglial phenotypic markers, and absence of astrocytic markers. The expression of complement genes C1qB, C3, and C4 as well as genes for interleukin-(IL-)1 alpha, IL-1 beta, IL-6, tumor necrosis factor (TNF)alpha, IL-1 receptor antagonist, and transforming growth factor beta, but not inducible nitric oxide synthase, by these cells was detected by polymerase chain reaction (PCR) analysis. The pattern of gene expression was evaluated following stimulation of the cells with lipopolysaccharide, phorbol myristate acetate, gamma interferon, and beta amyloid peptide. There was considerable variation in gene response to these activating agents. However, it was of interest that beta-amyloid peptide (1-40) increased the expression of IL-1 beta mRNA in these cells. The number of cases in this study was too small to permit evaluation of microglial response according to the disease state, but the results demonstrate the potential for such studies in the future.

Low-affinity nerve growth factor receptor immunoreactivity in the human urinary bladder

The localization of low-affinity nerve growth factor receptor (LNGFR) in the human urinary bladder was examined immunohistochemically using the mouse monoclonal antibody (ME20-4) against human LNGFR. LNGFR immunoreactivity was present in the human urinary bladder. The distribution of LNGFR-positive fibers was more abundant in the mucosa than in the muscle layer. Results also showed that some LNGFR-positive fiber bundles contained tyrosine hydroxylase immunoreactivity. Electron microscopic examination revealed that LNGFR immunoreactivity was located on the surface of Schwann cells, and frequently on the interface of axons and Schwann cells.

Differential effects of beta and gamma interferons on expression of major histocompatibility complex antigens and intercellular adhesion molecule-1 in cultured fetal human astrocytes

We investigated the modulatory effects of human interferon beta (IFN-beta) and gamma (IFN-gamma) on expression of class I and II major histocompatibility complex (MHC) antigens and intercellular adhesion molecule-1 (ICAM-1) in fetal human astrocytes in culture using flow cytometry and immunocytochemistry. Under the baseline condition, class I MHC antigen and ICAM-1 were expressed in a moderate number (23 to 76%) of astrocytes, whereas class II MHC antigen was expressed in only a small number (0.3 to 8%) of astrocytes. Following a 72-hour treatment with IFN-gamma (10 to 100 U/ml), expression of all three antigens increased greatly. Expression of class I MHC antigen was also elevated by exposure to IFN-beta (10 and 100 IU/ml). However, IFN-beta did not significantly induce expression of class II MHC antigen or ICAM-1. Furthermore, IFN-beta significantly reduced IFN-gamma-induced expression of class II MHC antigen but not of class I MHC antigen or of ICAM-1. The differential effects of IFN-beta and IFN-gamma on expression of class I and II MHC antigens and ICAM-1 in fetal human astrocytes suggest that interferons serve as modulators of astrocyte function at sites of inflammation in the human CNS.

Properties of inward and outward potassium currents in cultured mouse motoneurons

Inward rectifier potassium currents and calcium-dependent potassium currents have been studied in cultured embryonic mouse motoneurons. Sustained unitary inward rectifier potassium currents were recorded from cell-attached patches and the channel conductance was dependent on external K+ concentration with a value of 25 pS when external K+ was 140 mM. The channel open probability exhibited a sigmoidal dependence on potential with the largest values (near 0.7) at depolarizing patch potentials. Inactivating inward rectifier potassium currents were also recorded in some cell-attached patches following voltage steps to hyperpolarizing potentials with the rate of inactivation faster with larger hyperpolarizing steps. Whole-cell inward rectifier potassium currents increased from an initial level to a steady-state level with hyperpolarizing steps to -120 mV from a holding potential of -60 mV; with larger hyperpolarizing commands the peak currents decayed to the steady-state. The steady-state current-voltage relation exhibited a region of negative slope resistance. External Cs+ (0.5-1 mM) reduced the amplitudes of macroscopic currents and diminished the open times of unitary currents consistent with block of open rectifying channels with an estimated KD for channel block of 1 mM. A large conductance calcium-dependent potassium channel was isolated in inside-out patches with a conductance of 240 pS with symmetrical 140 mM K+ across the patches and a conductance of 110 pS when the external K+ was reduced to 5 mM. With symmetrical K+ the channel open probability exhibited a sigmoid dependence on potential with the largest values, in excess of 0.8, associated with patch depolarization. The dependence of open probability on potential was dependent on the concentrations of internal Ca2+ and external K+. Properties of inward rectifier and calcium-dependent K+ channels, such as the voltage dependence of open probability, are involved in the establishment of cellular excitability in motoneurons. Future studies will be useful to investigate whether channel properties of motoneurons are altered after cell treatment with neurotoxic agents including oxygen radicals or excitotoxic amino acids.

Ganglioside markers GD3, GD2, and A2B5 in fetal human neurons and glial cells in culture

Expression of ganglioside markers GD3, GD2, and A2B5 was investigated in primary cell cultures isolated from fetal human brains of 12-15 weeks' gestation by immunocytochemistry. None of neuron-specific enolase (NSE)+ neurons expressed GD3, while large numbers of NSE+ neurons expressed GD2 (72%) or A2B5 (48%). In GFAP+ astrocytes, GD3 was expressed in a small population (3%) with a high proliferative capacity. GD2 expression was observed in 20% of GFAP+ astrocytes, while A2B5 was identified in a very small number (2%) of GFAP+ astrocytes. GD2 was coexpressed in a small population (11%) of GD3+ astrocytes, while A2B5 was colocalized in more than 50% of GD3+ astrocytes. In galactocerebroside+ oligodendrocytes, GD3 expression was not observed but a small population (8-9%) expressed GD2 and A2B5. In Ricinus communis agglutinin (RCA)+ microglia, neither GD3, GD2, nor A2B5 were identified. Our results indicate that in fetal human brain cell cultures, GD3 is expressed in a small population of astrocytes, while both GD2 and A2B5 are expressed in a large population of neurons and smaller populations of astrocytes and oligodendrocytes. Our results suggest that both GD3 and A2B5, cell type-specific markers for oligodendrocyte-type 2 astrocyte progenitor cells in the rat central nervous system, could not be utilized as valid markers for glial precursor cells in fetal human brain cell cultures.

Proliferation and differentiation of fetal human oligodendrocytes in culture

Phenotypic expression and proliferative capacity of the cells of oligodendrocyte lineage were investigated in primary cultures isolated from fetal human brains of 12-15 weeks' gestation using double immunolabeling with Ranscht-monoclonal antibody (R-mAb) or O4 and antibromodeoxyuridine (BrdU) antibody. Cultured cells of oligodendrocyte lineage consisted of a major population of R-mAb+O4- cells and minor populations of R-mAb-O4+ and R-mAb+O4+ cells. Most of the R-mAb+O4- cells exhibited a uni-, bi-, or tripolar immature morphology, while the majority of the R-mAb+O4+ cells exhibited a multipolar mature morphology. R-mAb-O4+ cells contained a mixture of immature and mature cell types. When incubated in serum-free culture medium containing BrdU for 4 days, 42% of total oligodendrocytes expressed nuclear BrdU immunolabeling. R-mAb+ cells exhibited a higher degree of BrdU immunolabeling, indicating that they have greater capacities for proliferation than O4+ cells. The large majority of BrdU+ cells exhibited an immature morphology. Inclusion of insulin, insulin-like growth factor (IGF)-I, basic fibroblast growth factor (bFGF), or fetal bovine serum in culture medium did not stimulate proliferation of oligodendrocytes, while platelet-derived growth factor (PDGF) or PDGF plus bFGF increased the number of R-mAb+BrdU+ and O4+BrdU+ cells over control, even though the results were not statistically significant. In addition, insulin and IGF-I induced a 3-fold increase in the number of R-mAb+O4+ cells, indicating that they promoted differentiation of oligodendrocytes. The present study indicates that fetal human oligodendrocytes in culture exhibit a considerable degree of proliferative capacity without requirement of exogenous growth factors and that both insulin and IGF-I promote their differentiation.

HSP72 induction by heat stress in human neurons and glial cells in culture

Expression of 72-kDa heat shock protein (HSP72) induced by heat stress was investigated in cultured neurons and glial cells isolated from fetal human brains using immunoblotting and immunocytochemistry. Under the unstressed condition, a low level of HSP72 expression was observed in astrocytes, microglia, oligodendrocytes, and neurons. Under the heat-stressed condition, an increased expression of HSP72 was observed in all cell types with specific location in the nuclear and cytoplasmic regions. Following heat stress, HSP72 was expressed intensely in more than 50% of astrocytes and microglia during 8-24 h post-recovery, while it was detectable in only 9% of oligodendrocytes and 3% of neurons at 48 h post-recovery. These results indicate that heat stress induces a predominant expression of HSP72 in astrocytes and microglia, and more limited HSP72 expression in oligodendrocytes and neurons in fetal human neural cells in culture. The differential patterns of HSP72 induction in human neural cells by heat stress suggest that cellular mechanisms by which the heat shock response is regulated are different among various cell types in the human central nervous system.

Rapidly proliferating glial cells isolated from adult mouse brain have a differentiative capacity in response to cyclic AMP

A glial cell line designated as B2 was generated from primary cultures of oligodendrocytes/astrocytes isolated from an adult BALB/c mouse brain and maintained for over 1 year. Phenotypic characteristics of B2 cells were investigated by immunolabeling with cell type-specific markers for oligodendrocytes (O4 and galactocerebroside (GalC)), astrocytes (glial fibrillary acidic protein (GFAP)), and immature neuroectodermal cells (vimentin). When cultured in a serum-containing medium, B2 cells exhibited a bipolar or a tripolar process-bearing morphology and proliferated with a 24-28 h doubling time, without requirement of exogenous growth factors. Under this culture condition, vimentin was identified in all of the B2 cells, GFAP in 7%, and O4 and GalC in less than 1% of the cells. When cultured in a serum-free medium containing 1 mM dibutyryl cyclic AMP (dbcAMP), B2 cells extended longer processes and 45% of the cells expressed cell type-specific markers for oligodendrocytes or astrocytes. GFAP was identified in 29% of B2 cells, O4 in 16%, and GalC in 6% of the cells, although, neither O4+GFAP+ nor GalC+GFAP+ cells were observed. B2 cells proliferated in response to phorbol 12-myristate 13-acetate (PMA), basic fibroblast growth factor (bFGF), insulin, insulin-like growth factor (IGF-I) and platelet-derived growth factor (PDGF), but not to dbcAMP, forskolin (FK), or retinoic acid (RA). These results indicate that B2 cells are distinct from typical oligodendrocytes and astrocytes with respect to their great proliferative potential, and suggest that B2 cells, with a capacity to differentiate into oligodendrocytes and astrocytes in response to cyclic AMP, may represent a population of glial precursor cells in the adult mouse central nervous system (CNS).

The role of intracellular free calcium in motor neuron disease

The intracellular calcium (Ca2+) concentrations of motoneurons can be altered by the influx of Ca2+ into the cell by the opening of voltage-dependent Ca2+ channels and ligand-gated channels linked to Ca2+ influx, especially by the N-methyl-D-aspartate (NMDA) type of excitatory amino acid receptor. Intracellular Ca2+ concentration is also affected by the release of Ca2+ buffered in mitochondria and endoplasmic reticulum. Evidence that motoneurons may be selectively vulnerable to Ca(2+)-induced cell death include the following observations: (i) the presence of excitatory amino acid receptors on the cell membranes of motoneurons, some of which would permit Ca2+ influx (e.g. NMDA receptors); (ii) the availability of the presynaptic terminal for antibody-mediated effects leading to changes in cell permeability and Ca2+ influx; and (iii) the limited amounts of intracellular Ca(2+)-binding proteins such as calbindin D28K and parvalbumin in motoneurons. Elevation of intracellular free Ca2+ may also be a common event in a number of independent mechanisms leading to motoneuron death in motor neuron disease.

Intracellular calcium concentrations during metabolic inhibition in the motoneuron cell line NSC-19

Changes in the concentrations of intracellular free calcium ([Ca2+]i) and adenine nucleotides were determined in response to metabolic inhibitors in the motoneuron cell line NSC-19. The NADH dehydrogenase inhibitor amobarbital (Amytal) and the mitochondrial uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP) were used to alter energy metabolism. Exposure of cells to 5 mM Amytal did not significantly change ATP concentrations but produced transient elevations of [Ca2+]i of approximately 80 nM, which were reduced by 32% when cells were studied in Ca(2+)-free solutions. CCCP (10 microM) caused a transient reduction in ATP concentration of 33%. CCCP also produced sustained elevations of [Ca2+]i of about 280 nM, which were reduced by 47% when in Ca(2+)-free solutions. In spite of the sustained elevation of [Ca2+]i induced by CCCP, NSC-19 showed no reduction in cell viability after 48 h compared with controls. Ruthenium red, a blocker of Ca2+ uptake by mitochondria, had little effect on the CCCP-induced [Ca2+]i increment. KCl or glutamate did not produce significant changes in [Ca2+]i, indicating that these cells do not possess significant numbers of voltage-dependent Ca2+ channels or excitatory amino acid receptor-gated channels. [Ca2+]i values in these cells were modified by changes in extracellular Ca2+ concentrations. In Ca(2+)-containing solutions, inhibition of Na+/Ca2+ exchange by amiloride and bepridil led to increased [Ca2+]i, as did blockade of Ca2+ ATPase by vanadate, suggesting that membrane transporters are important in Ca2+ efflux in NSC-19. The present studies indicate that exposure of NSC-19 cells to Amytal and CCCP produces Ca2+ increments by release from internal stores, as well as by transmembrane influx. These results demonstrate that small increments in [Ca2+]i can be produced by metabolic inhibitors or other compounds and that such changes are not associated with immediate cell death. Changes in [Ca2+]i could potentially result in abnormal cell function secondary to altered action of Ca(2+)-dependent enzymes.

Differential expression of Lewis(x) and sialyl-Lewis(x) antigens in fetal human neural cells in culture

Lewis(x) is a cell-surface carbohydrate antigen defined by the trisaccharide structure, Gal beta 1-->4 (Fuc alpha 1-->3) GlcNAc. Expression of Lewis(x) and sialyl-Lewis(x) antigens in primary cell cultures isolated from fetal human brains of 12-15 weeks gestation was investigated by double immunolabelling with antibodies against monomeric Lewis(x) (4C9), oligomeric Lewis(x) (FH4), and sialylated oligomeric Lewis(x) (FH6) antigens and cell type-specific markers. The monomeric Lewis(x) antigen was expressed in more than 15% of astrocytes and 100% of oligodendrocytes, whereas it was not identified in neurons or in microglia. The oligomeric Lewis(x) antigen was undetectable in any cell types, while the sialylated oligomeric Lewis(x) antigen was expressed in more than 95% of microglia but not in any other cell types. The cell type-specific expression of Lewis(x) and sialyl-Lewis(x) antigens in fetal human glial cells suggests that these fucose-containing carbohydrate molecules play roles in intercellular recognition between distinct cell types during the development of the human central nervous system.

Oxygen radical-induced neurotoxicity in spinal cord neuron cultures

The neurotoxic effects of oxygen radicals on spinal cord neuron cultures derived from fetal mouse have been studied. Oxygen radicals, superoxide radical and hydrogen peroxide, were generated by adding xanthine oxidase and hypoxanthine in the culture medium. Exposure of neurons to this oxygen radical-generating system resulted in a significant cell death and decrease of choline acetyltransferase (ChAT) activity in a time-dependent manner in spinal cord neuron cultures. The decrease in cell viability and ChAT enzyme activity induced by the oxygen radicals was blocked by scavengers such as superoxide dismutase (SOD), catalase, and tetrakis (2-pyridylmethyl) ethylenediamine (TPEN), a metal chelator. Antagonists of the N-methyl-D-aspartate (NMDA) receptor, including MK801 (a noncompetitive NMDA antagonist), D-2-amino-5-phosphonovaleric acid (APV) (a competitive NMDA antagonist), and 7-chlorokynurenic acid (an antagonist at the glycine site associated with the NMDA receptor), similarly blocked oxygen radical-induced decrease in cell viability and ChAT activity in spinal cord neuron cultures. These results indicate that both oxygen radicals and excitotoxic amino acids were involved in the oxidant-initiated neurotoxicity of spinal cord neurons.

HSP72 induction by heat stress is not universal in mammalian neural cell lines

Heat-induced expression of 72-kDa heat shock protein (HSP72) was investigated in a panel of neuronal and non-neuronal cell lines by immunoblotting and immunocytochemistry using monoclonal antibodies directed to HSP72. By immunoblotting, HSP72 expression was observed in most cell lines of mouse (SN6.1b, CL8c4.7, NSC34.6, B2A, C2C12), rat (PC12, C-6, L3), and human (NB-1, GOTO, IMR-32, HeLa) origin under the heat-stressed condition. The mouse neuroblastoma cell line N18TG2, however, did not express HSP72 under the heat-stressed condition. By immunocytochemistry, HSP72 was undetectable in the heat-stressed N18TG2 cells, while it was identified in the heat-stressed SN6.1b cells, a clonal hybrid neuron between N18TG2 and mouse septal cholinergic neuron. By exposure to a priming sublethal heat shock, SN6.1b cells but not N18TG2 cells acquired a significant level of tolerance to a subsequent lethal heat shock. These results suggest that heat-induced expression of HSP72 may contribute to acquisition of the thermotolerant state in SN6.1b cells.

Co-expression of mRNA for neurotrophic factors in human neurons and glial cells in culture

Enriched populations of neurons and astrocytes of 93-99% purity were obtained from mixed cultures of four human fetal brains. Total cellular RNA was extracted from cell pellets and reverse transcribed into cDNA. Five microliters of cDNA were subjected to PCR amplification using primers specific for sequences of NGF, BDNF, NT-3 and CNTF. PCR products were separated through 5% acrylamide gel and identified by DNA sequencing. Results showed that neurons expressed detectable levels of mRNA for NGF in all four cultures; BDNF and NT-3 mRNA was seen only in two cultures; CNTF mRNA was not detected in all four cultures. Astrocytes expressed mRNA for NGF, BDNF, and NT-3 but not for CNTF in all cultures examined. Astrocytic expression of mRNA for NGF, BDNF and NT-3 was found during the active cell proliferation as well as at a phase of mitotic quiescence. This study provides evidence that dissociated cell cultures of human neurons produce NGF, BDNF and NT-3 in early stages of their development and that astrocytes are constitutively committed to synthesize neurotrophic factors, NGF, BDNF and NT-3. The active synthesis of selected neurotrophic factors by neurons and astrocytes is relevant in supporting migration, survival and differentiation of developing neurons in vivo.

Glutamate neurotoxicity in mesencephalic dopaminergic neurons in culture

The neurotoxic effect of glutamate in cultured mouse mesencephalic dopaminergic neurons was investigated. Neuron-rich cell cultures were prepared from 13-14-day-old fetal mouse ventral mesencephalic tissue. Cultures were exposed to glutamate for 10 min and evaluated for glutamate neurotoxicity (GNT) 18-24 hr later by tyrosine hydroxylase (TH) immunostaining, microtubule associated protein-2 (MAP2) immunostaining, and radiolabeled dopamine uptake assay. In glutamate-exposed cultures, the number of TH-positive neurons and the level of dopamine uptake were reduced to 40% (35-45%) and 50% (47-52%), respectively, of control cultures. The number of MAP2-positive neurons was also reduced to 47%, indicating that the GNT was not restricted or selective to dopaminergic neurons. It is concluded that GNT was mediated by the N-methyl-D-aspartic acid (NMDA) receptor from the following observations: 1) GNT was completely blocked by MK-801, an NMDA receptor antagonist; 2) NMDA itself was as toxic as glutamate; 3) 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), an antagonist of the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid/kainate (AMPA/KA) receptor, did not block GNT; 4) kainate did not show neurotoxicity at a low concentration; and 5) two modulators of the NMDA receptor, 7-chlorokynurenic acid and magnesium, were effective in blocking GNT. Protective effects of phorbol myristate acetate, a tumor promoter, and gangliosides (GM1 and GT1b) on GNT were also demonstrated. Possible interactions between GNT and several protein kinase cascades were also investigated. Forskolin, an activator of adenyl cyclase and protein kinase A, showed some protective effect on GNT. But okadaic acid, an inhibitor of phosphatases, and genistein, a tyrosine kinase inhibitor, did not show any protective effect. These results suggest that 1) glutamate is capable of causing neuronal death in the substantia nigra; 2) GNT on dopaminergic neurons is mainly mediated by the NMDA receptor under the conditions of our study; 3) protein kinase C translocation is a key mechanism of GNT; and 4) there is an interplay of a signal transduction system in the pathomechanism of GNT.

Midkine that promotes survival of fetal human neurons is produced by fetal human astrocytes in culture

Midkine (MK), a retinoic acid responsive gene product, is a novel heparin-binding growth factor with an apparent molecular weight of 14-kDa. In fetal human neuron cultures, addition of recombinant human MK (10-100 ng/ml) resulted in a 3-fold increase in the number of surviving neurons under the serum-free culture condition. Production of MK was identified in the conditioned medium of astrocyte-enriched cultures by immunoblotting but not in the medium of neuron-enriched cultures. The level of MK production was not affected by treatment with retinoic acid. These results indicate that in the developing human central nervous system, astrocytes secrete MK that exhibits potent trophic activity to neurons.

Effects of tumor necrosis factor on inward potassium current and cell morphology in cultured human oligodendrocytes

The effects of recombinant human tumor necrosis factor-alpha (rhTNF-alpha) on inward rectifier potassium [K(IR)] currents and on cell morphology have been studied in cultured human oligodendrocytes. Cell-attached patches were used to isolate and record unitary currents through an inward rectifier K+ channel with a conductance of 23 pS. In control oligodendrocytes the mean open times showed an exponential dependence on patch potential with an e-fold decrease over a patch hyperpolarization of 28 mV. Treatment of oligodendrocytes with rhTNF (at 250 ng/ml for 24-48 h) had significant actions to diminish the mean open times of K(IR) relative to control values. At cell resting potential the mean open times were reduced by 60% after rhTNF application; the amplitudes of unitary currents or the extrapolated zero-current potentials were not significantly changed by the cytokine. The rhTNF treatments were not cytotoxic to cultured human oligodendrocytes; however, in some experiments rhTNF caused evident retraction of cell processes.

Midkine, a novel neurotrophic factor, promotes survival of mesencephalic neurons in culture

Midkine (MK), a retinoic acid responsive gene product, is a novel neurotrophic factor with a molecular weight of 14,000. MK at the optimal concentration of 10 ng/ml promoted the survival of mouse mesencephalic neurons in culture as demonstrated by the increased number of microtubule-associated protein-2 (MAP2) immunostaining-positive and tyrosine hydroxylase immunostaining-positive neurons and an elevated uptake of radiolabeled dopamine. These results suggest that MK has ubiquitous neurotrophic activity towards mesencephalic neurons which contain a large number of dopaminergic neurons.

Retinoic acid responsive gene product, midkine, has neurotrophic functions for mouse spinal cord and dorsal root ganglion neurons in culture

Midkine (MK) is the product of a retinoic acid responsive gene and is a member of a new family of heparin-binding growth factors. Neurotrophic effects of MK were examined using cultured spinal cord and dorsal root ganglion (DRG) neurons derived from fetal mouse. MK, which was added to the culture medium at concentrations of 1-100 ng/ml, promoted survival of both types of neurons approximately 5-fold after 7 days in culture. For spinal cord neurons, the increased survival was reflected in an increase of choline acetyltransferase activity. MK also promoted neurite extension in spinal cord (2-fold) and DRG (1.7-fold) neurons. The survival-promoting activity of MK to these neurons was comparable to that of basic fibroblast growth factor (bFGF) and leukemia inhibitory factor (LIF). In spite of its significant effects on fetal neurons, MK was ineffective in sustaining survival of DRG neurons derived from postnatal mice. From these results, we conclude that MK is a neurotrophic factor to embryonic spinal cord and DRG neurons, and we propose that MK plays a significant role in embryogenesis of the nervous system.

CD44 expression in human astrocytes and oligodendrocytes in culture

CD44 is a glycoprotein present on the surface of some lymphocyte cell populations and other non-lymphoid cells, and is involved in many functions related to cell-cell and cell-matrix interactions. In this study, expression of CD44 antigen in primary neural cell cultures derived from fetal and adult human brains was investigated. In cultures processed for double immunofluorescence staining, approximately 80% of fetal astrocytes and more than 95% of adult astrocytes expressed the CD44 antigen on the cell bodies and processes; CD44 was also detected in 50-60% of adult oligodendrocytes. Neurons in fetal brain cell cultures did not express CD44 at all. Western blot analysis performed in astrocyte- and in neuron-enriched cultures confirmed the results from immunostaining and showed that the antibody against CD44 reacted with a polypeptide, of approximately 80 kD, that is present exclusively in the astrocyte-enriched cultures, but absent in neuron-enriched cultures. Our results indicate that CD44 glycoprotein is constitutively expressed in the human cells of glial cell lineage and its role is likely to be associated with normal neuroglia-mediated adhesion/recognition processes.

Midkine is a mediator of retinoic acid induced neuronal differentiation of embryonal carcinoma cells

Midkine (MK) is a novel growth factor and is the product of a retinoic acid responsive gene. When P19 murine embryonal carcinoma (EC) cells were exposed to MK, they differentiated into neurons, and the neuronal differentiation was accompanied by expression of choline acetyltransferase activity. Synthesis and release of MK in the EC cells treated with retinoic acid were shown by Western blot analysis, and rabbit anti-MK antibody attenuated the action of retinoic acid to induce the neuronal differentiation. These results indicate that MK is one of the mediators of retinoic acid action to induce the neuronal differentiation in EC cells.

Midkine, a novel neurotrophic factor, is present in senile plaques of Alzheimer disease

An affinity purified antibody specific for midkine (MK) stained senile plaques in the brain of Alzheimer disease (AD) patients. After formic acid treatment, plaque staining was dramatically enhanced, and almost all beta-amyloid protein (BAP) deposits were also immunoreactive for MK. MK-immunoreactivity was not observed in normal cellular components nor in other pathological lesions including tangles in AD brain. Control brain sections were not immunoreactive for MK. The presence of MK in AD brain but not in control brain was confirmed by Western blotting. MK appears to be involved in the pathological process leading to senile plaque formation.

Novel isoforms of mouse myelin basic protein predominantly expressed in embryonic stage

Myelin basic protein (MBP), a major protein of myelin, is thought to play an important role in myelination, which occurs postnatally in mouse. Here we report that the MBP gene is expressed from the 12th embryonic day in mouse brain and that most of the predominant embryonic isoforms are not those reported previously. These isoforms have a deletion of a sequence encoded by exon 5 from the well-known isoforms. These isoforms show a unique developmental profile, i.e., they peak in the embryonic stage and decrease thereafter. In jimpy, a dysmyelinating mutant, the level of these isoforms remains high even in the older ages. These results suggest that MBPs have heretofore unknown functions unrelated to myelination before myelinogenesis begins. The possible presence of 18 isoforms of MBP mRNA, which are classified into at least three groups with different developmental profiles, is also reported here.