Characterization and partial purification of a novel neuronotrophic factor from bovine seminal vesicle

Effects of castration on the expression of the NGF and TrkA in the vas deferens and accessory male genital glands of the rat

Nerve Growth Factor (NGF) is a member of the neurotrophin family. Neurotrophins exert their effects by binding to corresponding receptors, which are formed by the tyrosine protein kinases TrkA, TrkB, and TrkC, and the low affinity p75NTR receptor. The role of neurotrophins in the biology of male genital organs is far from clear. In particular, little is known about the influence of sex hormones on the expression of neurotrophins and their receptors. In the present study, using immunohistochemistry and real time RT-PCR, we investigated the expression of NGF and TrkA in the vas deferens and accessory male genital glands in normal and castrated rats.In normal rats, both NGF- and TrkA-immunoreactivities (IR) were localized in the epithelial layer of the vas deferens. NGF-IR was also found in the stroma and epithelium of the vesicular gland and prostate. TrkA-IR was distributed in the epithelial cells of vesicular and prostate glands. The nerves were weakly immunoreactive in all the examined organs. After castration the immunoreactivities increased. Real-time RT-PCR experiments indicated that NGF and TrkA mRNA levels increased significantly after castration. These results suggest that NGF and TrkA are expressed in the internal male genital organs of the rat and that their expression is downregulated by androgen hormones. We hypothesize NGF and TrkA play a role in the processes that regulate the involution of these organs under conditions of androgen deprivation.

Expression of nerve growth factor (NGF), and its receptors TrkA and p75 in the reproductive organs of the adult male rats

Immunolocalization of nerve growth factor (NGF) and its receptors, TrkA and p75 in the reproductive organs of adult male rats was investigated. Sections of the testis, efferent duct, epididymis, deferent duct, seminal vesicle, coagulating gland and prostate of adult male rats were immunostained by the avidin-biotin-peroxidase complex methods (ABC). NGF was expressed in Leydig cells, primary spermatocytes and pachytene spermatocytes in the testis. TrkA only immunoreacted to elongate spermatids and p75 showed positive immunostaining in the Sertoli cells, Leydig cells, the pachytene spermatocytes and elongate spermatids. Immunoreactions for NGF and its two receptors were detected in epithelial cells of efferent duct, deferent duct and epididymis. In addition, immunoreactions for NGF and its two receptors were also observed in columnar secretory epithelium lines of the seminal vesicles, prostate and coagulating gland. These results suggest that NGF is an important growth factor in gonadal function of adult male rats.

Distribution of CNTF receptor alpha protein in the central nervous system of the chick embryo

Ciliary neurotrophic factor (CNTF) promotes the survival and differentiation of various neuronal and glial cell populations in the nervous system of vertebrates. In mammals, the ligand-binding alpha-subunit of the CNTF receptor (CNTFRalpha) is expressed in a variety of neuronal populations, including all CNTF-responsive cells. Previous studies suggested that functional differences in the CNTF/CNTF receptor system between chicks and mammals exist. The purpose of the present study was to examine the temporal and spatial expression pattern of the chick CNTFRalpha protein during CNS development. Receptor expression was detectable by immunoblotting in all CNS areas tested but showed area-specific developmental regulation. Interestingly, two variants of CNTFRalpha, 69 and 65 kD, were identified by immunoblotting with a shift from the higher to the lower molecular mass species occurring during development. Immunoreactivity for CNTFRalpha protein was preferentially observed in neuropil and white matter structures of the developing CNS while neuronal somata generally appeared unlabeled. For example, expression was observed in the olfactory system, in the telencephalon, in parts of the somatosensory system, in components of the tectofugal pathway, in the cerebellum, and in auditory brainstem nuclei. Fiber tracts that exhibit CNTFRalpha immunoreactivity were the lateral forebrain bundle, occipitomesencephalic tract, quintofrontal tract, and vestibular nerve. Our study identifies potential new targets of a chick CNTF-related molecule and reveals significant regional differences of CNTFRalpha protein expression between chick and mammals. These results suggest that the CNTF receptor performs distinct developmental functions in different animals.

Trophic factors from chromaffin granules promote survival of peripheral and central nervous system neurons

Chromaffin cells of the adrenal medulla were used to study the release of neurotrophic factors operationally defined by their capacity to promote the in vitro survival of embryonic neurons from the peripheral and central nervous system. Chromaffin cells are closely related to sympathetic neurons in terms of their transmitters and specific proteins and, like sympathetic neurons, receive preganglionic cholinergic, aminergic and peptidergic neuronal inputs. The issue of whether chromaffin cells store and secrete neurotrophic factors is therefore pertinent to the question whether trophic mechanisms may be involved in neuronal interactions and what modes of secretion are employed to liberate neurotrophic factors from neurons. Cell culture media conditioned by purified bovine chromaffin cells supported several neuron populations in vitro. Stimulation of the chromaffin cells with the cholinergic agonist carbachol (10(-4) M) increased in parallel the output of neurotrophic factor activity (assayed on chick ciliary ganglionic neurons) as well as two components specifically located in chromaffin granules, chromogranin A and catecholamines. The release of all three components was partially blocked by the Ca2+ channel blocker verapamil (10(-5) M), suggesting co-storage and -release of neurotrophic factors, chromogranin A and catecholamines in/from chromaffin granules. Neurotrophic factor activity for ciliary ganglionic neurons accumulating in the medium of unstimulated chromaffin cells decreased with time, and so did catecholamines. In contrast, amounts of neurotrophic factors and catecholamines released by challenging cells with carbachol did not significantly decline up to 62 h. The neurotrophic factor activity tested on chick ciliary, sensory and spinal cord neurons as well as on rat hippocampal neurons was heat- and trypsin-labile and could not be blocked by polyclonal antibodies against bovine nerve growth factor and the chromogranin A, B, and C. Defined fragments of chromogranin A and pancreastatin were devoid of neurotrophic activity. Our results suggest the presence of one or several neurotrophic factors in chromaffin granules, which can be released by exocytosis and may be potentially relevant for the maintenance of neurons innervating the adrenal medulla.

Is there a long-lasting effect of a short-term nerve growth factor application on axotomized rat septohippocampal neurons?

Loss of choline acetyltransferase (ChAT)-immunoreactive neurons in the medial septum (MS) following fimbria transection can be prevented by nerve growth factor (NGF) application. Here we have studied the long-term effects of a short-term NGF treatment starting immediately after lesion and lasting for the first 3 weeks. We demonstrate that this NGF treatment rescues many ChAT neurons after short survival time (3 weeks) but does not have a long-lasting (6 months) effect on both ChAT- and parvalbumin-immunopositive (GABAergic) MS neurons.

A heparin-binding protein in porcine seminal plasma stimulates neurite outgrowth on neuroblastoma cells in culture

A protein of neurite outgrowth activity has been identified in porcine seminal plasma after ammonium sulfate precipitation and affinity chromatography on heparin-Sepharose. Upon SDS-PAGE, the polypeptide is shown to have a M(r) of 16,000-18,000. Biologically by induction of neuritic processes on neuroblastoma cells, and immunologically by cross-reaction with specific antisera, this seminal plasma protein differs from acidic fibroblast growth factor (aFGF), basic fibroblast growth factor (bFGF) and nerve growth factor (NGF). The neurite outgrowth activity is relatively stable at pH 3-7 and under denaturing conditions of 8 M urea and beta-mercaptoethanol, but is inactivated by treatment of trypsin. This appears to be a novel protein, enhancing morphological differentiation of neuroblastoma cells in culture.

Basic fibroblast growth factor promotes transmitter storage and synthesis in cultured chromaffin cells

We have studied the effects of basic fibroblast growth factor (bFGF), which occurs in the adrenal medulla, on the survival, morphological phenotype, storage capacity for catecholamines and induction of the synthesizing enzymes tyrosine hydroxylase (TH) and phenylethanolamine-N-methyltransferase (PNMT) of cultured chromaffin cells from young postnatal rats. Basic FGF (40 ng/ml), like nerve growth factor (NGF; 40 ng/ml) prevented a drastic numerical decrease of chromaffin cells over a 4-day culture period, but, in contrast to NGF, did not induce neurite outgrowth, unless the cells were maintained for 7 days. Basic FGF was also more effective than NGF in maintaining the initial storage capacity for catecholamines, and even increased it under certain culture conditions (laminin instead of polyornithine, or 200 ng instead of 40 ng/ml). Basic FGF and NGF did not induce TH and PNMT activities beyond their initial levels, but partially prevented the reduction of TH activity seen after 4 days in culture. Based on the present data and the previously reported greater in vitro survival and transmitter stability of older chromaffin cells, which contain bFGF, and the relative instability of young postnatal chromaffin cells, which express no or very low levels of bFGF until 8 days postnatally, but respond to it, we hypothesize that bFGF is an important autocrine/paracrine maintenance factor for adult chromaffin cells.

Basic Fibroblast Growth Factor in the Adrenal Gland

The importance of trophic agents for the development and maintenance of neurons and their presence in mesenchyme-derived neuronal target organs such as muscle is well exemplified by the protein nerve growth factor (NGF) and its synthesis in target areas of sympathetic and sensory nerves. Stringent conceptualization of target organ-regulated neuronal maintenance would imply that neurons were able to provide trophic support to their presynaptic counterparts. We present data suggesting that basic fibroblast growth factor (bFGF), a mitogen and trophic factor for several neuron populations in vitro, may be such a protein involved in retrograde trophic neuron - neuron interaction. Basic FGF or a closely related protein is present in the adrenal medulla and its sympathetic neuron-like chromaffin cells. A polyclonal antibody specific for bFGF recognizes an 18 kD band in Western blots of bFGF-enriched bovine adrenal medulla extracts and immunostains isolated bovine chromaffin cells. This antibody also blocks the bFGF-like activity present in adrenal medullary extracts and chromaffin granule extracts that both promote in vitro survival of embryonic chick ciliary ganglionic neurons. Furthermore, like bFGF, the soluble proteins of bovine chromaffin granules are mitogenic for cultured bovine aorta endothelial cells. Electrothermal unilateral destruction of the adrenal medulla causes the disappearance of 25% of Nissl-stained neurons in the ipsilateral intermediolateral column (IML) of the spinal cord between levels Th7 and L1, which contains the preganglionic neurons projecting to the adrenal medulla. Substitution of the adrenal medulla by gel foams soaked with bFGF prevents neuron losses in the IML. The effects are specific in that NGF and cytochrome C are ineffective. Our results suggest that bFGF is located in chromaffin cells and maintains target-deprived autonomic spinal cord neurons, thus possibly acting as an interneuronal trophic messenger in vivo.

Basic fibroblast growth factor and nerve growth factor administered in gel foam rescue medial septal neurons after fimbria fornix transection

Basic fibroblast growth factor (bFGF) recently has been established as a survival- and transmitter-promoting neurotrophic agent for embryonic neurons in vitro. Its local application to lesioned adult optic and sciatic nerves has been shown to rescue axotomized retinal and sensory neurons that otherwise die. Following transection of the fimbria fornix pathway connecting the medial septum (MS) to the hippocampus, MS neurons undergo severe cell death, which can be prevented partially by infusion of nerve growth factor (NGF). In the same lesion paradigm, we find that 87% of these neurons visualized by cresyl-violet staining have disappeared by 4 weeks after unilateral fimbria fornix transection in adult rats. Implantation of gel foam soaked with 8 micrograms bFGF reduced neuron death to 68%. A similar rescue effect was seen with 0.3 microgram NGF. NGF administered at 20 micrograms reduced cell losses to 54%. Thus, bFGF rescued 22% and NGF at 20 micrograms 38% of the neurons that otherwise would have died. Choline acetyltransferase immunocytochemistry revealed dramatic losses of cholinergic neurons on the lesioned, compared with the unlesioned, side. Cholinergic neuron death was clearly reduced by the bFGF and NGF treatments. Basic FGF, in contrast to NGF, did not prevent a reduction in size of surviving neuronal cell bodies. Considered in the context of FGF being present in brain and hippocampal neurons, our results suggest a possible role for FGF as a neurotrophic factor for CNS neurons in vivo.

Survival and neuritic growth of sympathoadrenal (chromaffin) precursor cells in vitro

Chromaffin precursor cells from embryonic rat adrenal glands were isolated at 16.3 and 20.3 days of gestation and purified by centrifugation on density gradients. Approximately 50% of the cells of both age groups that had attached to the culture substratum by 12 hr survived during a 4-day culture period in the absence of exogenous trophic factors. Nerve growth factor (NGF) and a C6 glioma-cell-conditioned medium (C6-CM) had no or a very moderate promoting effect on survival. The glucocorticoid dexamethasone (DEX) supported the survival of 70-80% of the cells that otherwise would have died. Spontaneous neuritic growth of the sympathoadrenal precursor cells was significantly more pronounced with cells isolated at embryonic day (E) 16.3 than at E20.3. NGF had a significantly smaller promoting effect on neurite ougrowth at E16.3 than at E20.3. C6-CM induced neurite outgrowth from 25% (E16.3) and 35% (E20.3) of the surviving cells. DEX (10(-6) M) completely abolished spontaneous neuritic growth and partially suppressed C6-CM-mediated fiber outgrowth. These data underscore the importance of glucocorticoids for the maintenance and development of an endocrine morphologic phenotype of sympathoadrenal precursors. They suggest that the cells may be initially driven by growth factors other than NGF into a neuronal direction and that they lack NGF-responsiveness and -dependence during the early stages of their development.

Ciliary neuronotrophic factor stimulates choline acetyltransferase activity in cultured chicken retina neurons

It has been demonstrated that cultured cholinergic retinal neurons from 8-day-old chicken embryos respond to a polypeptide factor present in retinal cell-conditioned medium (RCM) and in retinal extracts. Compared with control cultures, the activity of acetyl-CoA:choline O-acetyltransferase (EC 2.3.1.6; ChAT) is enhanced more than twofold in neuronal retinal cultures grown for 7 days in the presence of RCM. The present study demonstrates that both ciliary neuronotrophic factor (CNTF), which is characterized by its trophic activity on parasympathetic ciliary neurons, and RCM exhibit identical stimulatory effects on ChAT activity in retinal monolayer cultures. Similarly, RCM supports the in vitro survival of ciliary neurons to the same extent as CNTF. The active species in RCM has a molecular weight (20,900 +/- 1,000) identical to that of CNTF, as determined by preparative sodium dodecyl sulfate gel electrophoresis. The results indicate that cholinergic retinal neurons represent a central neuronal target for CNTF or a closely related protein.

Immunocytochemical demonstration of fibroblast growth factor in cultured chick and rat neurons

The presence of fibroblast growth factor (FGF) was investigated by immunocytochemistry in cultured neuronal cells derived from the peripheral (PNS) and the central nervous system (CNS) of chick and rat embryos. Polyclonal antimouse FGF antibodies, which cross-react with basic and acidic FGF, were used in the peroxidase immunocytochemical staining method. FGF immunoreactivity was found in neurons. Staining intensity in chick and rat brain neuronal cells increased during the culture period, reached a maximum after 6-8 days, and subsequently declined. Embryonic chick ciliary and dorsal root ganglionic (DRG) neurons as well as DRG neurons from newborn rat displayed intense FGF immunoreactivity at 12 and 48 hr in culture. Nonneuronal cells were not stained. The data demonstrate for the first time that cultured neurons from the CNS and PNS contain FGF.

Pharmacological effects of nerve growth factor and fibroblast growth factor applied to the transectioned sciatic nerve on neuron death in adult rat dorsal root ganglia

Sciatic nerve transection performed on adult rats caused neuronal losses after 4 weeks in the L4-6 dorsal root ganglia (DRG) of 35% as compared to the unlesioned side. Nerve growth factor (NGF) administered at a single dose of 6000 Biological Units in silicone tubes fixed to the proximal nerve stump completely prevented these cell losses. Basic fibroblast growth factor (bFGF) also protected DRG neurons, but at the concentrations applied (6000 Trophic Units, tested on embryonic chick ciliary ganglion neurons), failed to maintain cell numbers identical to unoperated side. Our data indicate that NGF and bFGF protect adult sensory neurons from lesion-induced death. Preliminary results suggest that local accumulation of neurotrophic activities at the proximal nerve stump elicited by NGF and, possibly bFGF, might be involved in the beneficial effects of these proteins on the maintenance of axotomized sensory neurons.