The isolation and characterisation of nerve growth factor from the prostate gland of the guinea-pig

In vitro effect of nerve growth factor on the main traits of rabbit sperm

BACKGROUND

The nerve growth factor (NGF), a member of the neurotrophins family, plays an important role not only in the nervous but also in other non-nervous systems such as the reproductive system. The aim of the paper is to study the in vitro effect of NGF on rabbit sperm functions.

METHODS

Ten adult rabbit bucks were collected five times, and pooled semen samples have been analysed. NGF was quantified in seminal plasma, and the distribution of NGF receptors (TrKA and p75NTR) in sperm was established. Moreover, the dose-effect of NGF on motility rate and track speed was evaluated. Successively, the effect of the neutralisation of NGF receptors was assessed to verify the specific role of each receptor. Untreated sperm were used as control.

RESULTS

Our study identified several interesting results: i) We detected NGF in seminal plasma and TrKA and p75NTR in sperm surface. In particular, TrKA is localised in the head and p75NTR in the midpiece and tail of rabbit sperm. ii) Once the optimal dose of NGF (100 ng/mL) was established, its addition affected both kinetics and other physiological traits (capacitation, apoptosis and necrosis) of rabbit sperm. (iii) The neutralisation of TrKA and p75NTR receptors affected sperm traits differently. In particular, sperm speed, apoptosis and capacitation seemed mainly modulated via p75NTR receptor, whereas motile, live cells, necrosis and acrosome reaction were modulated via TrKA.

CONCLUSION

For the first time, we showed the presence of p75NTR in rabbit sperm. NGF affects kinetic and other physiological traits of rabbit sperm. Most of these changes are modulated by the receptors involved (TrKA or p75NTR). Considering that some seminal disorders in human have been correlated with a lower NGF concentration and no studies have been done on the possible involvement of NGF receptors, these findings also provide new insights on human fertility.

Extracellular pH and neuronal depolarization serve as dynamic switches to rapidly mobilize trkA to the membrane of adult sensory neurons

Activation of the nerve growth factor (NGF) receptor trkA and tissue acidosis are critically linked to inflammation-associated nociceptor sensitization. This study explored how increased acidity is linked to sensory neuron sensitization to NGF. Adult Wistar rat primary sensory neurons grown at physiological pH 7.4, then either kept at pH 7.4 or challenged for 30 min in pH 6.5 medium, provided a model of acidosis. Nonpermeabilizing trkA immunofluorescence revealed a significant increase in trkA mobilization to the plasma membrane from intracellular stores in response to proton challenge. This was confirmed using a surface protein biotinylation assay and Brefeldin A disruption of the rough endoplasmic reticulum-Golgi-trans-Golgi network. Mobilization of trkA to the membrane at pH 6.5 was abolished in neurons treated with the acid-sensitive ion channel blocker, amiloride. While elevated levels of NGF-independent trkA phosphorylation occurred at pH 6.5 alone, the level of activation was significantly increased in response to NGF challenge. Exposure of sensory neurons to pH 6.5 medium also resulted in strong calcium (Ca(2+)) transients that were reversible upon reintroduction to physiological pH. The pH 6.5-induced mobilization of trkA to the membrane was Ca(2+) dependent, as BAPTA-AM Ca(2+) chelation abrogated the response. Interestingly, KCl-induced depolarization was sufficient to induce mobilization of trkA to the cell surface at pH 7.4, but did not augment the response to pH 6.5. In conclusion, increased mobilization of trkA to neuronal membranes in response to either acidosis or neuronal depolarization provides two novel mechanisms by which sensory neurons can rapidly sensitize to NGF and has important implications for inflammatory pain states.

Transport and elimination of recombinant human NGF during long-term delivery to the brain

The gene for human nerve growth factor (NGF) has been cloned into a mammalian cell line and large quantities of recombinant human NGF (rhNGF) can now be produced for clinical use, but little is known about the fate of rhNGF following delivery to the brain. In this study, we implanted polymer matrices containing 125I-labeled rhNGF into the brains of adult rats and measured spatial distributions of the released protein for 8 weeks after implantation. NGF content in the tissue was determined by counting gamma radiation in thick (1 mm) sections and by autoradiography of thin (20 microns) sections. For the first several days, the rate of NGF release from the polymer matrix was high (approximately 100 ng/day); maximal NGF concentrations, measured at the polymer-tissue interface, were correspondingly high (> 20 micrograms/ml) though day 4. At later times, the release rate decreased (2-10 ng/day) and lower maximal concentrations were observed (1-10 micrograms/ml). NGF levels were always highest in the tissue sections closest to the polymer; during the 8 weeks of the experiment, NGF levels measured in thick sections decreased 100-fold, from 30 ng/section at day 2 to 0.3 ng/section at day 54. The first 10-fold decrease occurred during the first 10 days of the study; a further 6 weeks was required to achieve the second 10-fold decrease. Throughout the experiment, the majority of NGF remained within a restricted zone around the polymer at all times; the mass of NGF decreased to 10% of the maximal level within 2-3 mm of the polymer matrix. At early times (< 1 week), radiolabel corresponding to > 20 pg of NGF was also detected in regions of the brain further removed from the polymer. Comparison of local rhNGF concentration profiles with a simple mathematical model indicated that rhNGF diffuses through the brain interstitial space and is eliminated with a half-life of approximately 45 min, although elimination appears to be substantially slower in white matter regions. This limited ability of NGF to penetrate and be retained within the brain tissue indicates that NGF will need to be delivered almost directly to the target tissue for efficacy.

Bitis arietans nerve growth factor is a disulphide-linked homodimer

1. Nerve growth factor from Bitis arietans venom was isolated in high yield and purified to homogeneity using a rapid two-step procedure involving gel exclusion chromatography and reversed-phase HPLC. 2. On polyacrylamide gel electrophoresis in SDS, the NGF migrates as a 25 kDa homodimer and is thus atypical of other Viperid NGFs. 3. Evidence suggests that, unlike mammalian beta NGFs, the subunits of the Bitis arietans homodimer are covalently linked by a disulphide bond(s). 4. Partial sequence analysis shows that only 6 out of the first 21 amino acids are identical with those of cobra NGF including cys-14 and val-21 which are known to be important for NGF activity.

Biochemical characterization of recombinant human nerve growth factor

Recombinant human nerve growth factor (rhNGF) was expressed and secreted by Chinese hamster ovary cells and purified to homogeneity using ion-exchange and reversed-phase (RP) chromatography. The isolated product was shown to be consistent with a 120-amino-acid residue polypeptide chain by amino acid composition, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), RP-HPLC, and mass spectrometry and with an N-terminal sequence consistent with that expected from the cDNA for human nerve growth factor. By size-exclusion chromatography, rhNGF behaves like a noncovalent dimer. Limited enzymatic digests of the 120-residue monomer produced additional species of 118 (trypsin, removal of the C-terminal Arg119-Ala120 sequence) and 117 (trypsin plus carboxypeptidase B, removal of the C-terminal Arg118-Arg119-Ala120 sequence) residues. Each of these species was isolated by high-performance ion-exchange chromatography and characterized by amino acid and N-terminal sequence analyses, SDS-PAGE, RP-HPLC, and mass spectrometry. All three species were present in the digests as both homodimeric and heterodimeric combinations and found to be equipotent in both the chick dorsal root ganglion cell survival and rat pheochromocytoma neurite extension assays.

Activity and biospecificity of proteolyzed forms and dimeric combinations of recombinant human and murine nerve growth factor

Purified recombinant human nerve growth factor (rhNGF) and submaxillary gland-derived murine NGF (muNGF) were characterized by amino acid composition, polyacrylamide gel electrophoresis (PAGE), reversed-phase HPLC (RP-HPLC), and high-performance ion-exchange chromatography (HPIEC). Limited tryptic digest of the N and C termini of the 120-residue form of rhNGF produced a species of 109 residues (10-118). The previously observed natural murine analogue of this variant, muNGF lacking the first eight N-terminal amino acids, was also isolated as a homodimer. Both species were purified using HPIEC and characterized by amino acid analysis, N-terminal sequence, PAGE, and RP-HPLC analysis. Each of the four homodimeric species was evaluated in some or all of the following biological assays for NGF: chick dorsal root and sympathetic ganglion assays and rat pheochromocytoma-12 cell line neurite extension assay. The 118-residue homodimeric versions of both rhNGF and muNGF displayed equivalent bioactivity, whereas the N terminal-modified molecules presented activity reduced by 50- to 100-fold. Utilizing HPIEC, we have examined the ability of the monomeric forms of any two of the homogeneous dimeric species of rhNGF to recombine. We have shown that not only can all of the previously described species form dimers by recombination, but an interspecies dimer can be created between muNGF and rhNGF.

The NGF complex from the African rat Mastomys natalensis

The 7S NGF complex from the male mouse submaxillary gland consists of the alpha, gamma, and beta subunits in the ratio alpha 2 gamma 2 beta. The beta (NGF) subunit contains all the known biolocial activity of 7S NGF. The alpha and gamma subunits are both members of glandular kallikrein gene family, yet only gamma subunit has protease activity. The gamma subunit plays a role in the processing of preproNGF to its mature form, while the role of the alpha subunit is not yet understood. Despite the fact that 7S NGF has been extensively characterized, no other NGF complex has been characterized, nor have the alpha or gamma subunits been observed in tissues which express NGF. We have therefore purified and characterized the NGF complex from the submaxillary glands of the rat Mastomys natalensis in order to more fully understand the roles of the alpha and gamma subunits. The NGF complex from M. natalensis contains subunits similar to those found in mouse 7S NGF. Although similar, there are significant differences between mouse and M. natalensis NGF complexes, especially in the degree of post-translational modification of the gamma and NGF subunits, the expression of esterase activity and the ease with which the complexes dissociate. Evidence is presented that suggests that the NGF complex from M. natalensis may consist of subunits in the ratio alpha 2 gamma beta. The amino acid sequence of the M. natalensis NGF suggests some, but not all, ways in which these differences arise.

Expression of the beta-nerve growth factor gene in male sex organs of the mouse, rat, and guinea pig

Steady-state nerve growth factor (NGF) mRNA levels were estimated in male sex organs of the mouse, rat, and guinea pig by RNA blot hybridization analysis. The abundance of NGF mRNAs was in the order vas deferens greater than epididymis greater than or equal to seminal vesicles much greater than testis. NGF mRNA levels in these organs were compared with those estimated for other rat peripheral tissues and were found to correlate with the density of their sympathetic innervation, with the exception of guinea pig prostate. Castration had no significant effect on NGF mRNA levels in the guinea pig prostate, suggesting that NGF synthesis in this tissue is not under direct androgen control. NGF-like and proNGF-like immunoreactivities were localized by immunohistochemical techniques in the secretory cells of the glandular epithelium of the guinea pig prostate and in germ cells in the seminiferous tubules of the mouse testis.

Structure and biosynthesis of nerve growth factor

Most of our knowledge about NGF comes from extensive study of the mouse submaxillary gland protein. NGF from this source is isolated as a high molecular weight complex consisting of beta-NGF and two subunits, alpha and gamma, belonging to the kallikrein family of serine proteases. There are few other tissues where NGF is found in sufficient quantities for protein purification and study, although new molecular biological techniques have accelerated the study of NGFs from a variety of species and tissues. Mouse submaxillary gland NGF is synthesized as a large precursor that is cleaved at both N- and C-terminals to produce mature NGF. This biologically active molecule can be further cleaved by submaxillary gland proteases. The roles of the alpha and gamma subunits in the processing of the beta-NGF precursor, the modulation of the biological activity of beta-NGF, and the protection of mature beta-NGF from degradation have been well studied in the mouse. However, the apparent lack of alpha and gamma subunits in most other tissues and species and the existence of a large family of murine kallikreins, many of which are expressed in the submaxillary gland, challenge the relevance of murine high molecular weight NGF as a proper model for NGF biosynthesis and regulation. It is important therefore to identify and characterize other NGF complexes and to study their subunit interactions, biosynthesis, processing, and regulation. This review points out a number of other species and tissues in which the study of NGF has just begun. At this time, there exist many more questions than answers regarding the presence and the functions of NGF processing and regulatory proteins. By studying NGF in other species and tissues and comparing the processing and regulation of NGF from several sources, we will discover the unifying concepts governing the expression of NGF biological activity.

The role of endocrine therapy in prostatic cancer

When judged by randomized clinical trial, current endocrine therapies offer symptomatic relief to prostatic cancer patients for an average period of 1-2 years following initiation of therapy. Medical castration with LHRH analogues is a safe and effective way of achieving 'castrate' levels of circulating androgens without the undesirable aspects of surgery. While there is some evidence for the value of combined therapies using these agents in combination with anti-androgens for 'total androgen blockade' in some patients, overall this approach has not been shown to offer advantages over castration, either surgical or medical, alone in controlled trials. Secondary endocrine therapy does not offer convincing objective response rates, suggesting that disease progression is independent of androgens.

Nerve growth factor induces functional nicotinic acetylcholine receptors on rat sensory neurons in culture

Neonatal sensory neurons from rat nodose ganglia express nicotinic acetylcholine receptors when grown in tissue culture without other cell types. The present study investigates the role of nerve growth factor in inducing these receptors. Nerve growth factor has little effect on the growth and survival of nodose neurons in culture, although most neurons were found by quantitative radioautography to have high-affinity nerve growth factor receptors. Nerve growth factor strongly influenced the expression of nicotinic receptors on these neurons: the proportion of acetylcholine-sensitive neurons was approximately 60% in cultures with nerve growth factor compared with 15% in cultures grown without nerve growth factor. The proportion of acetylcholine-sensitive neurons increased over the first week, plateaued by day 12 and remained high for at least three weeks. In contrast, without NGF, the proportion of acetylcholine-sensitive neurons was low throughout the three-week period. The results indicate that nerve growth factor is an important factor in promoting nicotinic receptors on these neurons in culture.

Isolation and sequence of a cDNA clone of beta-nerve growth factor from the guinea pig prostate gland

The guinea pig prostate gland contains high levels of nerve growth factor similarly to the mouse submandibular gland. Nerve growth factor from the guinea pig prostate gland cross-reacts weakly with antisera directed against mouse nerve growth factor, is associated with different proteins, and may be processed by a different mechanism. We have isolated a full-length cDNA clone for nerve growth factor from a library prepared from RNA of the guinea pig prostate gland. The guinea pig cDNA contains 1,075 nucleotides and is very similar to the shorter of two predominant nerve growth factor transcripts present in the mouse submandibular gland. The cDNA sequence predicts a precursor protein of 241 amino acids that is 86% identical to the mouse amino acid sequence. Only 10 amino acid changes are present in the C-terminal region corresponding to the mature 118 amino acid beta-nerve growth factor of the mouse. Dibasic amino acid processing sites that are present at the N- and C-termini of the mature protein sequence and two other dibasic amino acid sites, representing potential processing sites within the propeptide, are all conserved, suggesting a similar mechanism of processing.

A role for nerve growth factor in collateral reinnervation from sensory nerves in the guinea pig

We have investigated whether chronic nerve growth factor (NGF) depletion affects the development of a transmedian collateral reinnervation. The extent of transmedian innervation of the skin supplied by the left inferior alveolar nerve (IAN) was determined either immediately, 2 days or 7-9 weeks after sectioning and preventing regeneration of the contralateral IAN and in another group of animals left to recover for 7-9 weeks but also autoimmunised against NGF. Transmedian innervation was measured by recording the area from which a jaw-opening reflex could be evoked and by recording activity in the left IAN during mechanical and electrical stimulation of the skin. Nerve recording during electrical stimulation revealed extensive transmedian collateral reinnervation 7-9 weeks after denervation but this was prevented by NGF autoimmunisation. No change in transmedian innervation could be detected in any of the groups by nerve recording during mechanical stimulation and reflex responses revealed changes in the anaesthetic area which could not be attributed to collateral reinnervation. These results suggest that NGF plays an important role in collateral reinnervation from high-threshold sensory nerves.

Molecular cloning of a cDNA encoding the nerve growth factor precursor from Mastomys natalensis

Mastomys natalensis is an African rat that has high levels of nerve growth factor (NGF) in its submaxillary glands. Like in the mouse, Mastomys NGF is found as a high-molecular-weight complex. However, the Mastomys complex differs from the mouse complex, in that the gamma-subunit is either missing or is less tightly bound in the Mastomys NGF complex. In the mouse, the gamma-subunit has been implicated in the processing of the beta-NGF precursor. The possible lack of gamma-subunits in the Mastomys NGF high-molecular-weight complex suggested that the Mastomys beta-NGF precursor might differ from the mouse beta-NGF precursor in some of its processing sites. In particular, Mastomys beta-NGF might lack the C-terminal dipeptide cleavage site implicated in beta-gamma subunit interactions in mouse NGF. In order to test this hypothesis, we isolated and sequenced a cDNA clone for Mastomys beta-NGF. We report here the cloning and sequencing of a cDNA coding for beta-NGF from Mastomys natalensis. The cDNA library was prepared from Mastomys submaxillary gland mRNA and the beta-NGF clone was isolated using a mouse cDNA as a probe. The nucleotide sequence of Mastomys beta-NGF is 95% homologous to that of mouse beta-NGF. In particular, the Mastomys beta-NGF precursor contains the same three C-terminal residues as the mouse, suggesting that the Mastomys beta-NGF precursor could interact with a gamma-like subunit.(ABSTRACT TRUNCATED AT 250 WORDS)

Properties of receptors for nerve growth factor in the mature rat nervous system

The binding properties of receptors for nerve growth factor (NGF) in the adult rat nervous system have been analyzed in membrane fractions from discrete regions and in radioautographs of tissue sections. Steady-state experiments with both preparations revealed specific binding of radioiodinated NGF that was heterogeneous in distribution and affinity. Of the regions in the central nervous system that were sampled, the dorsal spinal cord and basal forebrain were richest in NGF receptor. By 4 independent methods of analysis a high-affinity binding site was detected in the basal forebrain with half-maximal saturation estimated at 20-60 pM NGF. Binding at lower affinity was also seen but difficult to analyze quantitatively. Cross-linking studies followed by electrophoresis showed the NGF receptor in the rat basal forebrain to have an apparent molecular weight of 90 kDa. The binding and molecular properties of NGF receptors on adult mammalian neurons resemble those described on other NGF-responsive cells.

Nerve growth factor-like immunoreactivities in rodent salivary glands and testis

A series of polyclonal affinity-purified antibodies against mouse submandibular-gland nerve growth factor (NGF) are described. Using the submandibular gland of the male mouse and indirect immunofluorescence, the specificity and sensitivity of affinity-purified immunoglobulins and various other fractions from the immunized animals have been tested. It will be shown that affinity-purification schemes, including pre-purification of protein A-fractionated immunoglobulins to remove antibodies that bind to unrelated hydrophilic and hydrophobic proteins, significantly enhance the signal-to-noise ratio and specificity of the antibodies. The antibodies effectively detect NGF-like immunoreactivity in both fresh and fixed glandular tissue. Optimal fixation procedures are described. Fluorescence intensities are linearly correlated to log antibody concentration. By use of the best antibody fractions and optimal fixation protocols, the distribution of NGF-like immunoreactivity is described in eight different salivary glands (rat and mouse, male and female, submandibular and sublingual glands). In addition to the well-known large numbers of immunoreactive cells in the submandibular gland of the male mouse, immunoreactive cells were found in the sublingual gland of male mice and in the submandibular and sublingual glands of female mice. One antibody revealed a weak specific fluorescence also in the submandibular gland of the male mouse. In a survey of genital organs of male mice, one antibody revealed fluorescence in the germ cell line. We conclude that several polyclonal affinity-purified antibodies have been characterized that show a strong NGF-dependent binding to the secretory granules of tubular cells in the submandibular gland of male mice. These antibodies should make it possible to locate endogenous and perturbed NGF levels immunocytochemically, e.g., in the peripheral and central nervous system, where NGF concentrations may be several orders of magnitude lower than in the salivary glands.

The induction of a regenerative propensity in sensory neurons following peripheral axonal injury

Injury of the peripheral axons of primary sensory neurons has been previously shown to increase the probability that the corresponding central axons would grow from the injured spinal cord into a peripheral nerve graft. This phenomenon has been used to investigate the nature of extrinsic cues from injured nerves that enhanced regenerative propensity within sensory neurons. In 13 groups of rats, a segment of the right sciatic nerve was grafted to the dorsal columns of the spinal cord and the left sciatic nerve was subjected to mechanical injury, injection of colchicine or infusion of nerve growth factor. Subsequently, neurons in lumbar dorsal root ganglia with axons growing from the spinal cord into a graft were identified by retrograde perikaryal labelling and compared for the two sides. The aim was to mimic or modify the inductive effect of nerve transaction by alternative or additional manipulation of the nerve. Growth of central axons was less enhanced by peripheral axonal interruption if the length of the proximal stump was increased or if a distal stump was present to permit rapid regeneration. However, the regenerative response following nerve transection was altered little by crushing the proximal stump or injecting it with colchicine or nerve growth factor. It is suggested that sensory neurons are stimulated to regenerate by peripheral axonal injuries that reduce some normal retrograde regulatory influence of Schwann cells.

Isolation and characterization of nerve growth factor from Vipera berus berus (common viper) venom

Nerve growth factor from Vipera berus berus venom was purified by gel filtration on Sephadex G-100 (superfine), ion-exchange-chromatography on DEAE-Sephadex A-50 and chromatofocusing on PBE 118. The Vipera berus berus venom NGF consists of multiple molecular forms with pls in the interval 9.1-9.7. All isoforms have identical mol. wts approximately 35,000 +/- 3000 (in gel filtration) and 17,000 +/- 2000, 15,000 +/- 2000 (by SDS electrophoresis with beta-mercaptethanol). V. berus berus venom NGF reacted with monoclonal antibodies against Viper lebetina NGF and caused differentiation of pheochromocytoma PC12 cells.

A human prostatic growth factor (hPGF): partial purification and characterization

A growth factor capable of stimulating DNA synthesis of BALB/3T3 cells was purified about 1,000-fold from the cytosol of human benign hypertrophic prostates by heparin-Sepharose chromatography; the growth factor bound to the column in the presence of 0.5 M NaCl was eluted with 1.5-1.7 M NaCl. Its molecular weight and isoelectric point were estimated to be 11,000-13,000 and 10.5, respectively. It was sensitive to heat- and acid-treatments but resistant to disulfide-reducing agent. The final preparation was able to stimulate DNA synthesis at 10 ng/ml. The degree of stimulation was dependent on serum concentration in the assay system; the degree of maximum stimulation increased about 5 times as serum concentration increased from 0.2 to 2%.

On the immunology of nerve growth factor

We report some experiments on the immunological properties of nerve growth factor from the venom of Heloderma horridum and from bull seminal vesicles. On the basis of these results, taken together with results already in the literature, we propose an operational definition of the term nerve growth factor.

Isolation and characterization of nerve growth factor from Vipera lebetina (snake) venom

Nerve growth factor from Vipera lebetina venom was purified by gel filtration and ion exchange chromatography steps. The NGF preparation obtained is a glycoprotein with weak arginine esterase activity. It hydrolyzes benzoylarginine ethyl ester (BAEE). Vipera lebetina NGF consists of multiple forms of protein with pI in the interval 9-10.5. All isoforms have identical molecular weights of 32,500.

Immunohistochemical localization of nerve growth factor and epidermal growth factor in guinea pig prostate gland

Prostate glands of adult guinea pigs were stained for nerve growth factor (NGF) and epidermal growth factor (EGF) by immunohistochemical methods. Both NGF and EGF were localized diffusely in the cytoplasm of the glandular epithelial cells, and also in their secretory products. These findings suggest that NGF and EGF are synthesized, stored, and secreted by the glandular epithelial cells of the prostate.

Comparative biochemistry of the guinea-pig: a partial checklist

A great deal is known about guinea-pig biochemistry, but the information is scattered and difficult to assemble. The guinea-pig also possesses a number of unusual biochemical features which add to its interest. For these reasons we have compiled a list of biochemical characteristics of the guinea-pig, organized in a series of tables, with brief discussions of some of the entries.