Receptors for nerve growth factor on rat spleen mononuclear cells

Expression of nerve growth factor receptors by human peripheral blood mononuclear cells

In the rat, nerve growth factor (NGF) has been shown to affect immune reactivity by binding to cell surface receptors on a subpopulation of splenic mononuclear cells. This binding occurs in a specific and saturable fashion to what appear to be low-affinity (type II) NGF receptors (NGFR). Immunofluorescence studies here showed that NGFR are also present on a proportion of human peripheral blood mononuclear cells (PBMC). Equilibrium binding studies demonstrated that the binding of NGF to its receptors on PBMC occurs with a single equilibrium binding constant (mean) of 2.11 X 10(-9) M. The number of receptors per cell was determined to be approximately 6.94 X 10(3) receptors/cell. These results would suggest a role for NGF in the regulation of immune function in man, as well as in animals.

NGF primed spleen cells injected in brain of developing rats differentiate into mast cells

The aim of this work was to study the topographic distribution and the morphological behaviour of nerve growth factor (NGF) primed spleen cells injected into the lateral ventricles of developing rat brain. Serial coronal brain sections showed that these transplanted cells acquire phenotypical characteristics similar to those of mast cells (MCs) and that they enhance local neovascularization. These results, together with the observation that these cells are located in proximity to the hippocampus, a brain tissue which contains one of the highest levels of NGF, provide a model for studying the relationship between NGF and MC differentiation and secretion.

Developmental and regional expression of beta-nerve growth factor receptor mRNA in the chick and rat

Hybridization probes from the transmembrane region of the chick NGF receptor (NGF-R) that show high homology with the rat NGF-R were used to demonstrate an abundant 4.5 kb NGF-R mRNA in the chick embryo at E3.5. The level remained high until E12 but decreased to adult levels by E18. The highest levels at E8 were in spinal cord, bursa of Fabricius, gizzard, femoralis muscle, and skin. In situ hybridization to E7 embryos showed high expression of the NGF-R gene in spinal cord, particularly the lateral motor column, and in dorsal root, sympathetic, and nodose ganglia. NGF-R mRNA expression was observed throughout brain development and in all regions of the adult brain, with high levels in cerebellum and septum. Lymphoid tissues of chick and rat also expressed the receptor. The complex and widespread expression of NGF-R mRNA in areas not known to be NGF targets suggests broader functions for NGF.

Nerve growth factor promotes human hemopoietic colony growth and differentiation

Nerve growth factor (NGF) is a neurotropic polypeptide necessary for the survival and growth of some central neurons, as well as sensory afferent and sympathetic neurons. Much is now known of the structural and functional characteristics of NGF, whose gene has recently been cloned. Since it is synthesized in largest amounts by the male mouse submandibular gland, its role exclusively in nerve growth is questionable. NGF also causes histamine release from rat peritoneal mast cells in vitro, and we have shown elsewhere that it causes significant, dose-dependent, generalized mast cell proliferation in the rat in vivo when administered neonatally. Our experiments now indicate that NGF causes a significant stimulation of granulocyte colonies grown from human peripheral blood in standard hemopoietic methylcellulose assays. Further, NGF appears to act in a relatively selective fashion to induce the differentiation of eosinophils and basophils/mast cells. Depletion experiments show that the NGF effect may be T-cell dependent and that NGF augments the colony-stimulating effect of supernatants from the leukemic T-cell (Mo) line. The hemopoietic activity of NGF is blocked by polyclonal and monoclonal antibodies to NGF. We conclude that NGF may indirectly act as a local growth factor in tissues other than those of the nervous system by causing T cells to synthesize or secrete molecules with colony-stimulating activity. In view of the synthesis of NGF in tissue injury, the involvement of basophils/mast cells and eosinophils in allergic and other inflammatory processes, and the association of mast cells with fibrosis and tissue repair, we postulate that NGF plays an important biological role in a variety of repair processes.

Nerve growth factor binding in aged rat central nervous system: effect of acetyl-L-carnitine

The nerve growth factor protein (NGF) has been demonstrated to affect neuronal development and maintenance of the differentiated state in certain neurons of the peripheral and central nervous system (CNS) of mammals. In the CNS, NGF has sparing effects on cholinergic neurons of the rodent basal forebrain (BF) following lesions where it selectively induces choline acetyltransferase (ChAT). NGF also induces ChAT in the areas to which BF provides afferents. In aged rats, there is a reduction in the NGF-binding capacity of sympathetic ganglia. Here, we wish to report that there is a decrease in the NGF-binding capacity of the hippocampus and basal forebrain of aged (26-month-old) rats as compared to 4-month-old controls but no change in NGF binding in cerebellum. In all instances, equilibrium binding dissociation constants did not differ significantly. Treatment of rats with acetyl-L-carnitine, reported to improve cognitive performance of aged rats, ameliorates these age-related deficits.

Activation of phosphoinositide hydrolysis by nerve growth factor and lysophosphatidylserine in rat peritoneal mast cells

Histamine secretion in rat peritoneal mast cells stimulated by nerve growth factor requires a synergistic signal delivered by lysophosphatidylserine. To study the signal-transducing system activated by these compounds, phospholipid metabolism has been investigated in these cells. Phospholipid labeling with 32PO4 reveals a 5-9-fold stimulation of phosphatidic acid, phosphatidylinositol and phosphatidylcholine synthesis. Increased synthesis of phosphatidylinositol is also monitored using [3H]inositol incorporation. When [3H]inositol-labeled mast cells are incubated in the presence of Li+, nerve growth factor and lysophosphatidylserine enhance the accumulation of inositol monophosphate, inositol bisphosphate and inositol trisphosphate. Similar to the induced histamine release, accumulation of inositol phosphates (a) does not occur when the two agonists are added separately; (b) is inhibited when lysophosphatidyl-L-serine is replaced by lysophosphatidyl-D-serine; and (c) is enhanced in the presence of extracellular Ca2+. The data suggest that the interactive stimulus of nerve growth factor and lysophosphatidylserine is transmitted through the polyphosphoinositide-phospholipase C system.

The immunomodulatory effect of nerve growth factor

A prolonged application of nerve growth factor (NGF) to neonatal prepuberal rats induced selective hypertrophy and hyperfunction of ganglionic sympathetic neurons. This was accompanied by higher density and fluorescence intensity of varicose adrenergic fibers and terminals in the immunocompetent organs, total increase of catecholamines in them, catecholamine diffusion into the intercellular space, and their accumulation by macrophages and mast cells. The plaque-forming and lymphocyte blast transformation responses were activated, signs of increased lymphocyte migration to peripheral lymphoid tissues appeared, and histamine concentration in the thymus and spleen increased. All of the foregoing indicate the immunomodulatory effect of NGF and the dependence of immune responsiveness of the organism on the functional state of the adrenergic moiety. The net effect of the increase is attributed to non-specific protein sensitization, changes in the sympathetic (and, probably, somatic) nervous system, and direct action on immunocompetent cells.

Expression of human nerve growth factor receptor on cells derived from all three germ layers

Nerve growth factor (NGF) is a protein which promotes the survival and differentiation of neuronal cells in vitro and plays an important role in neuronal development. In this study, we have examined the expression of the receptor for NGF (NGFR) in human neuronal and nonneuronal cells, both in tissue culture and in vivo. In addition to cell lines derived from neuroblastoma, astrocytoma, and melanoma, all of which share a common neuroectodermal origin, NGFR was detected in a number of cultured cells of mesenchymal, epithelial, and hematopoietic derivation. Immunohistochemical analysis showed that NGFR is expressed in several nonneural human tissues, and the cell types in which NGFR was found include derivatives from all three germ layers. Thus, our findings demonstrate that NGFR is much more widely expressed in human cells and tissues than was previously thought.

Nerve growth factor supports growth of rat skeletal myotubes in culture

Effects of nerve growth factor (NGF) were examined on the growth of rat skeletal myotubes in culture and the expression of Na-K pump activity in this preparation. We found NGF to cause an immediate increase in electrogenic Na-K pump activity as determined by electrogenic component of membrane potential (Em) and ouabain-sensitive 86Rb uptake. When given chronically, NGF was able to replace serum as an essential supplement for development of cultured myotubes. Thus, when maintained in a serum-free, basal nutrient medium (DMEM), myotubes progressively deteriorated as indicated by morphological appearance, Em and the number of [3H]ouabain binding sites compared with myotubes grown in normal, serum-supplemented growth medium (GM). In contrast, the presence of NGF in DMEM completely prevented the deterioration of these properties, their values actually exceeding those in GM. These findings demonstrate a trophic effect of NGF on bioelectric properties of neonatal mammalian muscle cells.

Binding constants of soluble NGF-receptors in rat oligodendrocytes and astrocytes in culture

The neuronotrophic factor NGF binds to peripheral neurons of the dorsal root ganglion and the sympathetic nervous system. NGF binds to a cell surface receptor, NGFR, on these cells and displays Kd's of 10(-9) and 10(-11)M. NGF receptors have also been reported for basal forebrain magnocellular neurons. In addition, NGF specifically binds to NGFR on Schwann cells although the biological significance of this binding is not known. Here we report that NGF binds in a saturable and specific fashion to receptors on cultured isolated populations of rat astrocytes but not to oligodendrocytes. The binding to astrocytes in culture displayed a Kd of 2.7 +/- 1.0 nM with 36,000 receptors per cell.

Nerve growth factor receptors in human neuroblastoma cells

Receptors for the nerve growth factor protein (NGFR) present in the human neuroblastoma cell line LAN-1 were characterized. LAN-1 cells display high-affinity (type I, with KD value of 5.9 X 10(-11) M) and low-affinity (type II, with KD value of 9.2 X 10(-9) M) binding to NGF. NGFR were fractionated by preparative isoelectric focusing in a granulated gel (PEGG). High-affinity binding was found in the 5.9-6.2 pH region of the PEGG, and low-affinity binding in the 4.6-4.8 and 8.8-9.3 pH ranges. After further analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) we observed both 92.5- and 200-kDa molecular species associated with NGF binding activity. The 200-kDa protein was found in fractions displaying high-affinity NGF binding and the 92.5-kDa protein in fractions displaying low-affinity NGF binding. Equilibrium binding analysis of NGF in PEGG fractions confirmed the presence of two specific saturable binding sites with KD values similar to those observed for whole dissociated cells. When NGFR II activity from the acidic region of the PEGG chromatogram was incubated with NGFR II from the basic region of the PEGG chromatogram, there was no change in NGF binding or in the number of apparent NGF receptors. However, incubation of these same fractions with a fraction having only NGFR I showed an apparent increase in high-affinity NGF binding and a decrease in low-affinity NGF binding. Immunoprecipitation of this "mixed" fraction and analysis on SDS-PAGE under reduced and nonreduced conditions showed 200-kDa and 92.5-kDa proteins under nonreduced conditions and a 92.5-kDa protein under reduced conditions. Our findings are consistent with the hypothesis that there are two distinct NGF receptors in NGF-responsive cells. The interconvertibility of low- and high-affinity receptors and the possible existence of a modulator type protein or of "silent" type receptors are also in agreement with our findings.

The influence of nerve growth factor on the in vitro proliferative response of rat spleen lymphocytes

Splenic lymphocytes and accessory cells express receptors for nerve growth factor (NGF), a well-characterized neurotropic peptide that influences the development and survival of neuronal elements in the central and peripheral nervous systems. In the present study, we report that when rat splenic mononuclear cells (MC) are incubated in the presence of NGF, a dose-dependent increase in DNA synthesis occurs during 96-120 hours of culture as measured by 3H thymidine (3H-Thd) uptake. The minimal molar concentration of NGF at which the increased proliferative response of the cells (3.7 nM) is seen corresponded to the equilibrium disassociation binding constant of the MC (Kd = 2.5 nM), suggesting that the response was a consequence of receptor-ligand interaction. In addition, NGF was able to potentiate the lymphoproliferative response to several T-cell and B-cell mitogens. Significantly increased 3H-Thd uptake by NGF-stimulated cells was noted for concanavalin A (Con A), phytohemagglutinin (PHA), and lipopolysaccharide (LPS), particularly at suboptimal dosages of mitogen. Thus it appears that the NGF receptors on rat splenic MC are physiologically relevant and that NGF can modulate proliferation of T- and B- cells.

Effect of injury on nerve growth factor uptake by sensory ganglia

The level of the nerve growth factor protein, NGF, in vivo has a profound influence on axonal sprouting by sensory neurons of vertebrate dorsal root ganglia. There is evidence also that NGF may play similar roles in cholinergic central structures in brain. In both instances, retrograde transport of NGF has been demonstrated. Here we examined uptake of NGF by DRG neurons in response to contusion injury of the spinal cord. Under these conditions there was uptake and transport of NGF into large DRG neurons via central processes but no uptake by non-DRG central neurons. Thus, any effects of NGF on spinal neurons or their processes would be secondary to the direct effects of NGF on DRG neurons.