CNTF and LIF act on neuronal cells via shared signaling pathways that involve the IL-6 signal transducing receptor component gp130.

Ciliary neurotrophic factor (CNTF) has a variety of actions within the nervous system. While some of the actions of leukemia inhibitory factor (LIF) on neurons resemble those of CNTF, LIF also has broad actions outside of the nervous system that in many cases mimic those of interleukin-6 (IL-6). Comparison of the tyrosine phosphorylations and gene activations induced by CNTF and LIF in neuron cell lines reveals that they are indistinguishable and also very similar to signaling events that characterize LIF and IL-6 responses in hematopoietic cells. We provide a basis for the overlapping actions of these three factors by demonstrating that the shared CNTF and LIF signaling pathways involve the IL-6 signal transducing receptor component gp130. Thus, the receptor system for CNTF is surprisingly unlike those used by the nerve growth factor family of neurotrophic factors, but is instead related to those used by a subclass of hematopoietic cytokines.     

Mast cells in neuroimmune function: Neurotoxicological and neuropharmacological perspectives

Mast cells are located in close proximity to neurons in the peripheral and central nervous systems, suggesting a functional role in normal and aberrant neurodegenerative states. They also possess many of the features of neurons, in terms of monoaminergic systems, responsiveness to neurotrophins and neuropeptides and the ability to synthesise and release bioactive neurotrophic factors. Mast cells are able to secrete an array of potent mediators which may orchestrate neuroinflammation and affect the integrity of the blood-brain barrier. The cross-talk between mast cells, lymphocytes, neurons and glia constitutes a neuroimmune axis which is implicated in a range of neurodegenerative diseases with an inflammatory and/or autoimmune component, such as multiple sclerosis and Alzheimer's disease. Mast cells appear to make an important contribution to developing, mature and degenerating nervous systems and this should now be recognised when assessing the neurotoxic potential of xenobiotics.Abbreviations AChE acetylcholinesterase - ALS amyotrophic lateral sclerosis - APP amyloid precursor protein - BBB blood-brain barrier - BDNF brain-derived neurotrophic factor - CGRF calcitonin gene-related peptide - CNS central nervous system - CNTF ciliary neurotrophic factor - CSF cerebrospinal fluid - C48/80 compound 48/80 - CTMC connective tissue mast cells - EAA excitatory amino acids - EAE experimental allergic encephalomyelitis - ECMA ethylcholine mustard aziridinium ion - FACS fluorescent activated cell sorter - 5HT 5-hydroxytryptamine (serotonin) - HMT histamine-N-methyltransferase - HPMC human placental mast cells - HRNGF human recombinant nerve growth factor - IgE immunoglobulin E - MMC methyl mercuric chloride - MAOI monoamine oxidase inhibitors - MDMA methylenedioxymetamphetamine - MS multiple sclerosis - NGF nerve growth factor - NT3 neurotrophin 3 - PNS peripheral nervous system - RBMC rat brain mast cells - ROS reactive oxygen species - RPMC rat peritoneal mast cells - SLE systemic lupus erythematosus - SP substance P - TCA trichloroacetic acid - THA tetrahydroacridine - TCA tricyclic antidepressants Special issue dedicated to Dr. Robert Balázs.     

Regulation of bone marrow stromal cell differentiation by cytokines whose receptors share the gp130 Protein

The bone marrow stroma consists of a heterogeneous population of cells which participate in osteogenic, adipogenic, and hematopoietic events. The murine stromal cell line, BMS2, exhibits the adipocytic and osteoblastic phenotypes in vitro. BMS2 differentiation was examined in response to cytokines which share the gp130 signal transducing protein within their receptor complex. Four of the cytokines (interleukin 6, interleukin 11, leukemia inhibitory factor, and oncostatin M) inhibited hydrocortisone-induced adipocyte differentiation in a dose dependent manner based on lipid accumulation and lipoprotein lipase enzyme activity. Inhibition occurred only when the cytokines were present during the initial 24 h of the induction period; after 48 h, their effects were diminished. Likewise, these cytokines increased alkaline phosphatase enzyme activity twofold in preadipocyte BMS2 cells. Both leukemia inhibitory factor and oncostatin M induced early active gene expression in resting preadipocyte BMS2 cells and decreased the steady state mRNA level of a unique osteoblastic gene marker, osteocalcin. A fifth cytokine whose receptor complex shares the gp130 protein, ciliary neurotrophic factor, did not significantly regulate stromal cell differentiation when added by itself. However, with the addition of a missing component of its receptor complex, ciliary neurotrophic factor receptor α protein, this cytokine also inhibited BMS2 adipogenesis. Together, these data indicate that the cytokines whose receptors share the gp130 protein can modulate stromal cell commitment to the adipocyte and osteoblast differentiation pathways.     

An evolutionary perspective on the role of mesencephalic astrocyte-derived neurotrophic factor (MANF): At the crossroads of poriferan innate immune and apoptotic pathways

The mesencephalic astrocyte-derived neurotrophic factor (MANF) belongs to a recently discovered family of neurotrophic factors. MANF can be secreted but is generally resident within the endoplasmic reticulum (ER) in neuronal and non-neuronal cells, where it is involved in the ER stress response with pro-survival effects. Here we report the discovery of the MANF homolog SDMANF in the sponge Suberites domuncula. The basal positioning of sponges (phylum Porifera) in the animal tree of life offers a unique vantage point on the early evolution of the metazoan-specific genetic toolkit and molecular pathways. Since sponges lack a conventional nervous system, SDMANF presents an enticing opportunity to investigate the evolutionary ancient role of these neurotrophic factors. SDMANF shares considerable sequence similarity with its metazoan homologs. It also comprises a putative protein binding domain with sequence similarities to the Bcl-2 family of apoptotic regulators. In Suberites, SDMANF is expressed in the vicinity of bacteriocytes, where it co-localizes with the toll-like receptor SDTLR. In transfected human cells, SDMANF was detected in both the organelle protein fraction and the cell culture medium. The intracellular SDMANF protein level was up-regulated in response to both a Golgi/ER transport inhibitor and bacterial lipopolysaccharides (LPS). Upon LPS challenge, transfected cells revealed a decreased caspase-3 activity and increased cell viability with no inducible Bax expression compared to the wild type. These results suggest a deep evolutionary original cytoprotective role of MANF, at the crossroads of innate immune and apoptotic pathways, of which a neurotrophic function might have arisen later in metazoan evolution.     

Inhibition of protein synthesis prevents cell death in sensory and parasympathetic neurons deprived of neurotrophic factor in vitro

Shortly after neurons begin to innervate their targets in the developing vertebrate nervous system they become dependent on the supply of a neurotrophic factor, such as nerve growth factor (NGF) for survival. Recently, Martin et al. (1988) have shown that inhibiting protein synthesis prevents the death of NGF-deprived sympathetic neurons, suggesting that NGF promotes neuronal survival by suppressing an active cell death program. To determine if other neurotrophic factors may regulate neuronal survival by a similar mechanism we examined the effects of inhibiting protein and RNA synthesis in other populations of embryonic neurons that require different neurotrophic factors, namely: 1) trigeminal mesencephalic neurons, a population of proprioceptive neurons that are supported by brain-derived neurotrophic factor; 2) dorsomedial trigeminal ganglion neurons, a population of cutaneous sensory neurons that are supported by NGF; 3) and ciliary ganglion neurons, a population of parasympathetic neurons that are supported by ciliary neuronotrophic factor. Blocking either protein or RNA synthesis rescued all three populations of neurons from cell death induced by neurotrophic factor deprivation in vitro. Thus, at least three different neurotrophic factors appear to promote survival by a similar mechanism that may involve the suppression of an endogenous cell death program.     

Umbilical cord blood stem cells can expand hematopoietic and neuroglial progenitors in vitro

The ability of hematopoietic tissue-derived adult stem cells to transdifferentiate into neural progenitor cells offers an interesting alternative to central nervous system (CNS)- or embryonic-derived stem cells as a viable source for cellular therapies applied to brain regeneration. Umbilical cord blood (CB) due to its primitive nature and it unproblematic collection appears as a promising candidate for multipotent stem cell harvest. We developed a negative immunomagnetic selection method that depletes CB from hematopoietic lineage marker-expressing cells, hence isolating a discrete lineage negative (LinNeg) stem cell population (0.1% of CB mononucleated cell [MCN] population). In liquid culture supplemented with thrombopoietin, flt-3 ligand, and c-kit ligand (TPOFLK), CB LinNeg stem cells could expand primitive nonadherent hematopoietic progenitors (up to 47-fold) and simultaneously produce slow-dividing adherent cells with neuroglial progenitor cell morphology over 8 weeks. Laser scanning confocal microscopy analysis identified these adherent cells to express glial fibrillary acidic protein (GFAP). Gene expression analysis showed upregulation of primitive neuroglial progenitor cell markers including, GFAP, nestin, musashi-1, and necdin. ELISA quantification of liquid culture supernatant revealed the in vitro release of transforming growth factor beta-1 (TGFbeta1), glial cell line-derived neurotrophic factor (GDNF) suggesting their contribution to CB LinNeg stem cell transdifferentiation into neuroglial progenitors. Our study supports that a single CB specimen can be pre-expanded in TPOFLK to produce both primitive hematopoietic and neuropoietic progenitors, hence widening CB clinical potential for cellular therapies.     

Cutting edge: clonally restricted production of the neurotrophins brain-derived neurotrophic factor and neurotrophin-3 mRNA by human immune cells and Th1/Th2-polarized expression of their receptors.

Neurotrophins, such as neurotrophin-3 (NT-3) and brain-derived neurotrophic factor (BDNF), are potent regulators of neuronal functions. Here we show that human immune cells also produce NT-3 mRNA, secrete BDNF, and express their specific receptors trkB and trkC. The truncated trkB receptor, usually expressed in sensory neurons of the central nervous system, was also constitutively expressed in unstimulated Th cells. Full-length trkB was detectable in stimulated PBMC, B cell lines, and Th1, but not in Th2 and Th0 cell clones. Clonally restricted expression was also observed for trkC, until now not detected on blood cells. The Th1 cytokine IL-2 stimulated production of trkB mRNA but not of trkC, whereas the Th2 cytokine IL-4 enhanced NT-3 but not BDNF mRNA expression. Microbial Ags, which influence the Th1/Th2 balance, could therefore modulate the neurotrophic system and thereby affect neuronal synaptic activity of the central nervous system.     

Immunoreactivity to glial cell line-derived neurotrophic factor and its receptors in the trout pancreas: a further endocrine-exocrine relationship?

Glial cell line-derived neurotrophic factor (GDNF) is a growth factor promoting the survival of several neuronal populations in the central, peripheral and autonomous nervous system. Outside the nervous system, GDNF functions as a morphogen in kidney development and regulates spermatogonial differentiation. GDNF exerts its roles by binding to glial cell line-derived neurotrophic factor receptor (GFR) a1, which forms a heterotetramic complex with rearranged during transfection (RET) proto-oncogene product, a tyrosine kinase receptor. In this study we report the presence of GDNF-, RET- and GFRa1-like immunoreactivity in the pancreas of juvenile trout. GDNF immunoreactivity was observed in the islet cells, while GFRa1- and RET- immunoreactivity was observed in the exocrine portion. These findings suggest a paracrine role of GDNF towards exocrine cells showing GDNF receptors GFRa1 and RET. The relationship could reflect physiological interactions, as previously indicated in mammalian pancreas, and/or a trophic role by endocrine cells on exocrine parenchyma, which shows a conspicuous increase during animal growth.     

Lithium increases expression of p21WAF/Cip1 and survivin in human glioblastoma cells

Lithium is the most widely prescribed mood stabilizer, but the precise molecular mechanisms underlying its therapeutic function are not yet fully elucidated. Recent preclinical and clinical evidence indicates its neuroprotective and neurotrophic effects. As a tight coupling of function and metabolism in the central nervous system between glial cells and neurons has recently been detected, lithium's effect on glial cells may participate also in the total beneficial effects of this drug. The aim of the present study was to analyze molecular mechanisms induced in human glioblastoma A1235 cells by the treatment with lithium, especially its influence on the expression of apoptosis-related genes. Lower levels of lithium (0.5 mmol/L and 2 mmol/L) did not cause any cytotoxicity or changes in the cell cycle phase distribution following 72 h incubation. However, a higher dose (20 mmol/L) was cytostatic for glioblastoma cells, and caused accumulation of cells in G₂/M phase of the cell cycle. The treatment with lithium did not alter the levels of Bcl-2 or procaspase-3 and did not cleave PARP, but increased the levels of p21^WAF/Cip1 and survivin. Thus, increased expression of p21^WAF/Cip1 (a protein with antiapoptotic function), and survivin (a protein that supports the growth of cells by suppression of apoptosis and promotion of cell proliferation) may be the early events in the long-term cell response to lithium that are involved in the beneficial effects of this drug.     

NGF and the local control of nerve terminal growth

It is generally believed that the mechanism of action of neurotrophic factors involves uptake of neurotrophic factor by nerve terminals and retrograde transport through the axon and back to the cell body where the factor exerts its neurotrophic effect. This view originated with the observation almost 20 years ago that nerve growth factor (NGF) is retrogradely transported by sympathetic axons, arriving intact at the neuronal cell bodies in sympathetic ganglia. However, experiments using compartmented cultures of rat sympathetic neurons have shown that neurite growth is a local response of neurites to NGF locally applied to them which does not directly involve mechanisms in the cell body. Recently, several NGF-related neurotrophins have been identified, and several unrelated molecules have been shown to act as neurotrophic or differentiation factors for a variety of types of neurons in the peripheral and central nervous systems. It has become clear that knowledge of the mechanisms of action of these factors will be crucial to understanding neurodegenerative diseases and the development of treatments as well as the means to repair or minimize neuronal damage after spinal injury. The concepts derived from work with NGF suggest that the site of exposure of a neuron to a neurotrophic factor is important in determining its response. 1994 John Wiley & Sons, Inc.     

Oral administration of royal jelly facilitates mRNA expression of glial cell line-derived neurotrophic factor and neurofilament H in the hippocampus of the adult mouse brain

Royal jelly (RJ) is known to have a variety of biological activities toward various types of cells and tissues of animal models, but nothing is known about its effect on brain functions. Hence, we examined the effect of oral administration of RJ on the mRNA expression of various neurotrophic factors, their receptors, and neural cell markers in the mouse brain. Our results revealed that RJ selectively facilitates the mRNA expression of glial cell line-derived neurotrophic factor (GDNF), a potent neurotrophic factor acting in the brain, and neurofilament H, a specific marker predominantly found in neuronal axons, in the adult mouse hippocampus. These observations suggest that RJ shows neurotrophic effects on the mature brain via stimulation of GDNF production, and that enhanced expression of neurofilament H mRNA is involved in events subsequently caused by GDNF. RJ may play neurotrophic and/or neuroprotective roles in the adult brain through GDNF.     

Neurite outgrowth in PC12 cells stimulated by acetyl-l-carnitine arginine amide

Senescence of the central nervous system is characterized by a progressive loss of neurons that can result in physiological and behavioral impairments. Reduction in the levels of central neurotrophic factors or of neurotrophin receptors may be one of the causes of the onset of these degenerative events. Thus, a proper therapeutic approach would be to increase support to degenerating neurons with trophic factors or to stimulate endogenous neurotrophic activity. Here we report that acetyl-l-carnitine arginine amide (ST-857) is able to stimulate neurite outgrowth in rat pheochromocytoma PC12 cells in a manner similar to that elicited by nerve growth factor (NGF). Neurite induction by ST-857 requires de novo mRNA synthesis and is independent of the action of several common trophic factors. The integrity of the molecular structure of ST-857 is essential for its activity, as the single moieties of the molecule have no effect on PC12 cells, whether they are tested separately or together. Also, minor chemical modifications of ST-857, such as the presence of the arginine moiety at a position other than the amino one, completely abolish its neuritogenic effect. Lastly, the presence of ST-857 in the culture medium competes with the high affinity NGF binding in a dose dependent fashion. These results, although preliminary, are suggestive of a possible role for ST-857 in the development of therapeutic strategies to counteract degenerative diseases of the CNS.     

Apoptosis in the Nervous System

Apoptosis (from the Greek apoptosis, i.e., falling of leaves) is the phenomenon of programmed cell death, which plays an important role in the normal embryonic development and maintenance of the homeostasis of the differentiated tissues of adult organisms. Completion of the apoptosis process is accompanied by specific morphological and biochemical changes in the involved cells. Various disturbances in the control of apoptosis underlie various neurodegenerative diseases, the formation of malignant tumors, autoimmune disturbances, and developmental abnormalities. A deficit of neurotrophic factors leads to apoptosis of neurons. The survival of specific cell populations of neurons is controlled by neurotrophic factors and their combinations. Oncogene bcl-2, a repressor of cell death, belongs to the better-studied factors controlling apoptosis. The terminal stages of cell death, including the death of neurons, depend on the activation of caspases, specifically caspase-1 (interleukin-1-converting enzyme). Ca²⁺and reactive forms of oxygen play an important role in the initiation of apoptosis by changing the mitochondrial permeability. Neuregulin, a factor of neuronal origin, is the main controlling factor in apoptosis of Schwann cells, and this process determines the size of their definitive population. Fibroblast growth factor b diminishes the apoptosis of Schwann cells in regenerating nerve fibers.     

Masseteric Nerve Injury Increases Expression of Brain-Derived Neurotrophic Factor in Microglia Within the Rat Mesencephalic Trigeminal Tract Nucleus

The distribution of brain-derived neurotrophic factor was examined in the rat mesencephalic trigeminal tract nucleus after transection and crush of the masseteric nerve. In the intact mesencephalic trigeminal tract nucleus, brain-derived neurotrophic factor was detected in small cells with fine processes. These cells and processes were occasionally located adjacent to tyrosine kinase B receptor-immunoreactive sensory neurons. The transection and crush of the masseteric nerve increased expression of brain-derived neurotrophic factor in the nucleus. The number and size of brain-derived neurotrophic factor-immunoreactive cells and processes were dramatically elevated by the nerve injury. As a result, the density of brain-derived neurotrophic factor-immunoreactive profiles in the mesencephalic trigeminal tract nucleus at 7 days after the injury was significantly higher compared with the intact nucleus. Double immunofluorescence method also revealed that brain-derived neurotrophic factor-immunoreactive cells were mostly immunoreactive for OX-42 but not glial fibrillary acidic protein. In addition, the retrograde tracing method demonstrated that brain-derived neurotrophic factor-immunoreactive cells and processes surrounded retrogradely labeled neurons which showed tyrosine kinase B receptor-immunoreactivity. These findings indicate that the nerve injury increases expression of brain-derived neurotrophic factor in microglia within the mesencephalic trigeminal tract nucleus. The glial neurotrophic factor may be associated with axonal regeneration of the injured primary proprioceptor in the trigeminal nervous system.     

bFGF与BDNF对损伤后成年小鼠离体培养嗅觉上皮细胞发育的影响

在成熟神经系统中,嗅觉上皮（ＯＥ）很特殊,它能不断产生新的神经元。本文用细胞培养、组织化学和免疫细胞化学技术对成年小鼠的ＯＥ进行了研究。实验显示：双极细胞ＮＦ、ＮＳＥ、ＭＡＰ２、ＯＭＰ和ｔａｕ蛋白免疫染色为阳性,但ｋｅｒａｔｉｎ免疫染色为阴性,说明双极细胞是神经元。用不同浓度血清的培养基。离体培养成年小鼠的ＯＥ,观察碱性成纤维细胞生长因子（ｂＦＧＦ）和脑源神经营养因子（ＢＤＮＦ）对ＯＥ细胞数量和突