Increase In Nerve Growth Factor Content Research Articles

Quantitative analysis of nerve growth factor in the amniotic fluid during chick embryonic development

Nerve growth factor (NGF) and most neurotrophic factors support the proliferation and survival of particular types of neurons. Besidesthe pivotal role of NGF in the development of neuronal cells, it also has important functions on non-neuronal cells. The amnion surrounds the embryo, providing an aqueous environment for the embryo. A wide range of proteins has been identified in human amniotic fluid (AF). In this study, total protein concentration (TPC) and NGF level in AF samples from chick embryos were measured using a Bio-Rad protein assay, enzyme linked immunosorbent assay (ELISA) and Western blot. TPC increased from days E10 to day E18. There was a rapid increase in AF TPC on day E15 when compared to day E16. No significant changes in NGF levels have been seen from day E10 to day E14. There was a rapid increase in NGF content on days E15 and E16, and thereafter the levels decreased from day E16 to day E18. Since, NGF is important in brain development and changes in AF NGF levels have been seen in some CNS malformations, changes in the TPC and NGF levels in AF during chick embryonic development may be correlated with cerebral cortical development. It is also concluded that NGF is a constant component of the AF during chick embryogenesis.

Dynamic changes in nerve growth factor and substance P in the murine hair cycle induced by depilation

Increasing evidence suggests that various neurotrophins and neuropeptides play an important role in the progression of hair follicle cycling. Among them, nerve growth factor (NGF) and substance P (SP) have attracted special interest recently. However, the interaction between these factors during hair cycling has not yet been systematically studied. We therefore investigated the mutual relationships between NGF and SP and the mechanism by which the anagen stage of the hair cycle is initiated. Fluctuations in numbers of SP-positive nerve fibers and variations in amounts of SP, NGF, and another neurotrophic factor, glial cell-derived neurotrophic factor, in skin in the C57BL/6 mouse depilation-induced hair cycle model, together with the spatiotemporal expression patterns of each of these factors, were followed simultaneously by enzyme-linked immunosorbent assay and immunohistochemistry. The main finding was that a surge in NGF expression and a rapid increase in NGF content in skin is an initial event within 1 day after depilation, followed by elevation of SP content and numbers of SP-containing fibers 2 days after the increase in NGF. Our findings suggest that a rapid and abundant increase in NGF plays a key role in the induction and progression of anagen hair cycling through keratinocyte growth promotion. NGF may also induce plastic changes such as sprouting and hyperplasia in dermal nerve fibers and enhance their SP production. Elevated levels of SP in skin may additionally contribute to the progression of consecutive anagen hair cycles.

Increase in NGF content and nerve fiber sprouting in human allergic contact eczema.

There is increasing evidence for an intimate interaction of the skin and the nervous system. As known from animal studies, nerve growth factor (NGF) is essential for the innervation density and functional properties of sensory neurons of the skin during embryogenesis and in adulthood, and possibly during cutaneous inflammation. This study examined NGF content and sprouting of nerves during the elicitation phase of contact allergy in human skin. Skin biopsies from patients (n=14) undergoing patch-testing were taken from positive test sites and control back skin 96 h after antigen application. NGF content was measured by enzyme-linked immunofluorescence assay. Immunohistochemistry was performed for protein gene product 9.5 (PGP9.5), a marker that stains all neuronal elements, and growth-associated protein 43 (GAP43), a marker for axonal growth cones. The NGF content was significantly increased in lesional skin in comparison with normal skin (4.2+/-0.6 pg to 2.9+/-0.5 pg NGF per mg wet weight). The length of epidermal PGP9.5-immunoreactive (ir) fibers in lesional skin significantly increased from 3.4+/-0.9 mm in normal skin to 5.3+/-1.0 mm in contact eczema, whereas dermal fibers were unaltered (11.1+/-2.7 mm vs 9.5+/-2.1 mm, respectively). GAP43-ir nerve endings were significantly increased in both epidermis (1.6+/-0.3 mm to 2.6+/-0.4 mm) and dermis (0.5+/-0.1 mm to 1.8+/-0.2 mm) in contact eczema. Thus, we have provided evidence for an NGF-mediated nerve-fiber sprouting in human contact eczema. This may have a functional impact on skin-associated immune cells, in particular mast cells and Langerhans cells.

Receptor‐mediated regulation of neuropeptide gene expression in astrocytes

One of the functions of glial receptors is to regulate synthesis and release of a variety of neuropeptides and growth factor peptides, which in turn act on neurons or other glia. Because of the potential importance of these interactions in injured brain, we have examined the role of two different receptors in the regulation of astrocyte neuropeptide synthesis. Stimulation of beta-adrenergic receptors on type 1 astrocytes resulted in increased mRNA and protein for the proenkephalin (PE) and somatostatin genes. This receptor also increased expression of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF). The potential role of opiate receptors was examined in several ways. Treatment of newborn rats for 7 days with the opiate antagonist naltrexone, prior to preparation of astrocytes, had no effect on PE mRNA or met-enkephalin content but resulted in a significant increase in NGF content. However, treatment of astrocytes in culture with met-enkephalin, morphine, or naltrexone had no effect on any of these parameters. No opiate binding could be detected, using either etorphine or bremazocine, to membranes of astrocytes prepared from cortex, cerebellum, striatum, or hippocampus of 1-day, 7-day, or 14-day postnatal rats. Thus we conclude that type 1 astrocytes do not express opiate receptors and that the in vivo effects of naltrexone are mediated indirectly via some other cell type/receptor.

Lactoferrin promotes nerve growth factor synthesis/secretion in mouse fibroblast L-M cells.

Fibroblast cells are known to have an ability to synthesize and secrete nerve growth factor (NGF). To investigate the mechanism of action of the iron-binding protein, lactoferrin (Lf), on cultured animal cells, the effect of bovine Lf (bLf) on NGF synthesis/secretion in mouse fibroblast cells was examined. Both apo- and holo-bLf induced an increase in NGF content in the cell-conditioned medium(CM) of mouse L-M cells, a line derived from L929 fibroblast cells, with similar effectiveness. The increase in NGF content in the CM of L-M cells cultured with bLf was not dependent on the induction of increase in cell numbers, but was due to induction of de novo synthesis of NGF in individual cells by bLf. Human Lf(hLf) also increased NGF content. However, apo- and holo-bovine transferrin (bTf) failed to stimulate the NGF synthesis. The time-dependent induction of NGF in L-M cells by bLf was different from that induced by basic fibroblast growth factor (bFGF) and bLf showed an additive effect with bFGF. These results suggest that the induction of NGF synthesis depends on a mechanism different from iron transport or bFGF.

Stimulation by bovine lactoferrin of nerve growth factor synthesis/secretion in mouse L-M cells.

Cultured mouse fibroblasts synthesize and secrete nerve growth factor (NGF). To learn the mechanism of action of an iron-binding protein, lactoferrin (Lf), on cultured animal cells, we have examined the effects of bovine Lf (bLf) on NGF synthesis/secretion in mouse L-M cells, a line derived from L929 fibroblast cells. Both apo- and holo-bLf induced an increase in NGF content in the cell-conditioned medium (CM) with similar effectiveness. Neither apo- nor holo- bovine transferrin (bTf) was effective, indicating that the observed induction of NGF production cannot be attributed to stimulation of iron transport. A basic peptide fragment of bLf (residues 17-41) isolated from a pepsin hydrolyzate of bLf was found to be effective for stimulation of NGF synthesis/secretion in L-M cells. This observation demonstrates that the basic nature of Lf is important for its interaction with fibroblast cells.

Interleukin-1 β and tumor necrosis factor-α synergistically stimulate nerve growth factor (NGF) release from cultured rat astrocytes

Nerve growth factor (NGF) may mediate responses to brain injury. To examine regulation of NGF gene expression with respect to neural trauma we examined the effects of interleukin-1 β (IL-1β) and tumor necrosis factor-α (TNF-α) on NGF production in cultures of rat astroglial cells. Purified neocortical astrocytes in serum-free medium were treated with IL-1β, TNF-α or both. Whereas IL-1β and TNF-α alone elicited only small effects, simultaneous addition elicited within 48 h a large (3- to 6-fold) increase in NGF content in culture supernatants. Our data are consistent with a role for cytokines in NGF synthesis and release in the injured central nervous system (CNS).

Nerve growth factor increases in adult rat brain after hypoxic injury

Brain injury increases the synthesis of many growth and trophic factors. We have measured nerve growth factor (NGF) content in brain of adult rats with bilateral carotid artery occlusion exposed to 7% O 2. Five days after hypoxia the NGF content was increased in neostriatum, hippocampus and cerebral neocortex, areas exhibiting focal neuronal degeneration and inflammation. The increase was not related to changes in choline acetyltransferase activity that was only reduced in heavily damaged cortex. The findings may indicate that the increase in NGF content was due to enhanced NGF synthesis by inflammatory cells including stimulated glia.

Catecholamines induce an increase in nerve growth factor content in the medium of mouse L-M cells.

L-M cells, a mouse fibroblast cell line, synthesized and secreted a nerve growth factor (NGF). The neurite outgrowth stimulatory activity, immunoreactivity, molecular weight, and isoelectric point of L-M cell NGF were identical to those of beta-NGF of the mouse submaxillary gland. Treatment of the cells with either norepinephrine or epinephrine in the range of 0.05-0.2 mM for 24 h resulted in a 3-20-fold increase in NGF content in the medium of the L-M cells. The NGF of epinephrine-treated cell was identical to that of control cell. The stimulation of the increase in NGF content was observed after a 4-h lag time. The rate of incorporation of [3H]leucine into trichloroacetic acid-insoluble materials was essentially unchanged during the treatment. These results suggested that norepinephrine and epinephrine stimulated the de novo synthesis and secretion of NGF protein. Evidence is also presented to indicate that the effects of the drugs are due to the catechol part of the molecule and not mediated by adrenergic receptors.