Mast cells synthesize, store, and release nerve growth factor

The vanilloid receptor as a putative target of diverse chemicals in multiple chemical sensitivity

The vanilloid receptor (TRPV1 or VR1), widely distributed in the central and peripheral nervous system, is activated by a broad range of chemicals similar to those implicated in Multiple Chemical Sensitivity (MCS) Syndrome. The vanilloid receptor is reportedly hyperresponsive in MCS and can increase nitric oxide levels and stimulate N-methyl-D-aspartate (NMDA) receptor activity, both of which are important features in the previously proposed central role of nitric oxide and NMDA receptors in MCS. Vanilloid receptor activity is markedly altered by multiple mechanisms, possibly providing an explanation for the increased activity in MCS and symptom masking by previous chemical exposure. Activation of this receptor by certain mycotoxins may account for some cases of sick building syndrome, a frequent precursor of MCS. Twelve types of evidence implicate the vanilloid receptor as the major target of chemicals, including volatile organic solvents (but not pesticides) in MCS.

Regulation of NGF and BDNF by dexamethasone and theophylline in human peripheral eosinophils in allergics and non-allergics

BACKGROUND

Recent studies have shown that the neurotrophins NGF and BDNF are produced by eosinophils. The influence of neurotrophins in allergic diseases including asthma has been described. The regulation by pharmacological substance remains unclear.

OBJECTIVES

The aim of this study was to assess whether approved pharmacological substances in the treatment of asthma such as corticosteroids or theophylline regulate neurotrophins on a cellular level.

METHODS

Eosinophils were purified by negative immunoselection from allergics and non-allergic donors. Eosinophils were incubated with dexamethasone and theophylline and supernatants were collected for measurement of neurotrophic factors. The content of neurotrophins in eosinophil lysates was determined by ELISA. Regulation of stored NGF and BDNF was demonstrated by Western-blotting and flow cytometry while influence on transcription level was demonstrated by RT-PCR.

RESULTS

Eosinophils produce and release the neurotrophins NGF and BDNF at different levels in allergics and non-allergics. Dexamethason lead to a significant downregulation of NGF in eosinophils of allergics. The levels of BDNF were not significantly reduced. Theophylline did not influence the levels of NGF nor BDNF significantly.

CONCLUSIONS

The production of the neurotrophin NGF was downregulated by an established substance such as dexamethasone. This might further contribute to the pharmacological potential of corticosteroids in allergic asthma.

Monocytes of allergics and non-allergics produce, store and release the neurotrophins NGF, BDNF and NT-3

INTRODUCTION

Recent studies have shown that neurotrophins (NTs) are involved in inflammatory processes. Elevated plasma levels of NTs were found allergic diseases with the highest levels in allergic asthma. However, the exact cellular sources involved in the regulation and release of neurotrophins in allergic inflammation are still not well defined.

OBJECTIVE

The aim of this study was to assess whether monocytes of allergic and non-allergic subjects produce, store and release the neurotrophins NGF, BDNF and NT-3.

METHODS

Monocytes of allergic and non-allergic donors were purified by immunomagnetic selection. APAAP-staining for the presence of NTs and their receptors was performed. RT-PCR and Western blot evaluated the production and storage of NTs. Monocytes were incubated and supernatants were collected for measurement of neurotrophic factors after stimulation with lipopolysaccharide (LPS) as inflammatory stimulus. The neurotrophin content in lysates and cell culture supernatants was determined by ELISA.

RESULTS

Human monocytes express the neurotrophins NGF, BDNF and NT-3 but also their specific receptors TrkA, TrkB and TrkC. RT-PCR amplification of isolated mRNA demonstrated expression of the examined neurotrophins. Proteins were detectable by Western blot. NTs were found in the monocyte lysates and supernatants at different levels in allergic and non-allergic donors. Cell stimulation with LPS leads to release of NGF and NT3.

CONCLUSIONS

Monocytes, produce, store and release NGF, BDNF and NT-3. They are a possible source of elevated neurotrophin levels found in allergy and asthma.

Nikolaou K, Vrachnis N. Neurotrophin-3 and FLT3 tyrosine kinase receptor in perinatal life

Our aim is to determine—in 30 healthy full-term infants and their mothers—circulating levels of neurotrophin-3 (NT-3) (important for antenatal and postnatal brain development and implicated in the immune response) and FLT3 tyrosine kinase receptor (FLT3) (controlling hematopoiesis and found in the nervous tissue), in the fetal and neonatal life. NT-3 levels, in contrast to FLT3 ones, increased significantly on the fourth postnatal day in relation to the low levels found in the mother, fetus, and day 1 neonate (P = .03, respectively). Maternal and umbilical NT3 levels positively correlated with respective FLT3 levels (P = .003 and P = .03). Circulating NT-3 levels increased in early neonatal life, possibly due to exposure to various stimuli soon after birth. FLT3 levels do not seem to behave accordingly, although these two substances probably synergize.

[Confocal laser scanning microscopy to study molecular mechanism of mast cell activation]

In the immune system, mast cells are a key cell type in the pathogenesis of immunoglobulin E (IgE)-dependent hypersensitivity reactions. Engagement of the high-affinity IgE receptors by multivalent antigens initiates the downstream activation of signal-transducing enzymes and evokes degranulation and cytokine production via an increase in the intracellular Ca2+ concentration. In addition, mast cells also play a prominent role in non-IgE-mediated hypersensitivity reactions. Mast cells are closely apposed to nerves in vivo and are likely to be regulated functionally by nerves. However, the molecular mechanisms for mast cell activation in an IgE-dependent and -independent manner have not been fully clarified. Confocal laser scanning microscopy has played an essential role in cell biology by allowing visualization of specific intracellular signaling molecules with high spatiotemporal resolution in living cells. We have studied intracellular movements of Ca2+ using a specific fluorescent probe and several types of signaling molecules using derivatives of green fluorescent protein in a living single mast cell using a microscopic strategy. We here describe our imaging analysis of the calcium signals to the nucleus, the movement of secretory granules in the degranulation process, and the nucleocytoplasmic shuttling of mitogen-activated protein kinase in mast cells. Further, we demonstrate that direct communication between mast cells and nerves occurs. These findings provide useful information from a new perspective to understand the molecular mechanisms of allergic reaction and inflammation.

The release of nerve growth factor from the nasal mucosa following toluene diisocyanate

Toluene diisocyanate (TDI) produces rhinitis, nasal irritation, and increased synthesis and release of substance P (SP) from airway sensory nerves. Nerve growth factor (NGF) secretion in the nasal cavity is believed to mediate the irritant-induced upregulation of SP, but the cellular source of NGF in the nasal mucosa remains unclear. Studies to localize a source of NGF within the nasal mucosa are complicated by inflammatory-cell influx into the nasal mucosa following TDI, which obscures immunocytochemical identification of endogenous NGF sources. The purpose of this study was to determine the cellular source of NGF within the nasal mucosa following irritant exposure using a combined in vivo and ex vivo approach to reduce or eliminate contribution from inflammatory cells. Both nasal cavities of adult, male Sprague-Dawley rats were instilled with 5 microl of 10% TDI or control vehicle. After 15 min, nasal lavages were performed and the nasal mucosa was removed and placed into culture for 3 or 24 h. NGF was measured in the lavage supernatant and the culture media. Fifteen minutes after TDI exposure, NGF was significantly increased in the nasal lavage fluid. NGF levels in the culture medium of nasal mucosa from rats exposed to TDI ex vivo were significantly increased compared to controls following a 3-h culture. NGF levels in media after 24 h in culture was higher than at the 3-h point, but there was no difference between control and TDI groups. Since the nasal mucosa was removed prior to inflammatory cell influx, these findings suggest that cells in the nasal mucosa release NGF following exposure to TDI.

Endogenous NGF regulates CGRP expression in human monocytes, and affects HLA-DR and CD86 expression and IL-10 production

Our recent results on autocrine nerve growth factor (NGF) synthesis in B lymphocytes, which directly regulates the expression and release of calcitonin gene-related peptide (CGRP), a neuropeptide known to down-regulate immune response, led us to propose an anti-inflammatory action of NGF. In the present work, we investigated whether the endogenous synthesis of NGF can regulate the expression of CGRP in other antigen-presenting cells, such as monocytes, and whether this may have a functional effect. Our data indicate that human monocytes synthesize basal levels of NGF and CGRP and that, following lipopolysaccharide (LPS) stimulation, NGF and CGRP expression are both up-regulated. When endogenous NGF is neutralized, the up-regulation of CGRP expression induced by LPS is inhibited. The expression of membrane molecules involved in T-cell activation such as human leukocyte antigen-DR (HLA-DR) and CD86 is affected by endogenous NGF, and similar effects were obtained using a CGRP(1) receptor antagonist. In addition, NGF deprivation in LPS-treated monocytes significantly decreases interleukin 10 (IL-10) synthesis. Our findings indicate that endogenous NGF synthesis has a functional role and may represent a physiologic mechanism to down-regulate major histocompatibility complex (MHC) class II and CD86 expression and alter the development of immune responses.

Significance of Conversation between Mast Cells and Nerves

More and more studies are demonstrating interactions between the nervous system and the immune system. However, the functional relevance of this interaction still remains to be elucidated. Such associations have been found in the intestine between nerves and mast cells as well as between eosinophils and plasma cells. Similar morphologic associations have been demonstrated in the liver, mesentery, urinary bladder, and skin. Unmyelinated axons especially were found to associate with mast cells as well as Langerhans' cells in primate as well as murine skin. Although there are several pathways by which immune cells interact with the nervous system, the focus in this review will be on the interaction between mast cells and nerves.

Nerve growth factor and its receptors in asthma and inflammation

Nerve growth factor (NGF) is a high molecular weight peptide that belongs to the neurotrophin family. It is synthesized by various structural and inflammatory cells and activates two types of receptors, the TrkA (tropomyosin-receptor kinase A) receptor and the p75(NTR) receptor, in the death receptor family. NGF was first studied for its essential role in neuronal growth and survival. Recent reports indicate that it may also help mediate inflammation, especially in the airways. Several studies in animals have reported that NGF may induce bronchial hyperresponsiveness, an important feature of asthma, by increasing sensory innervation. It may also induce migration and activation of inflammatory cells, which infiltrate the bronchial mucosa, and of structural cells, including epithelial, smooth muscle cells and pulmonary fibroblasts. Increased NGF expression and release is observed in asthma patients after bronchial provocation with allergen. Taken together, the data from the literature suggest that NGF may play a role in inflammation, bronchial hyperresponsiveness and airway remodelling in asthma and may help us to understand the neuro-immune cross-talk involved in chronic inflammatory airway diseases.

The Spermatogenic Ig Superfamily/Synaptic Cell Adhesion Molecule Mast-Cell Adhesion Molecule Promotes Interaction with Nerves

Nerve-mast cell interaction is involved in both homeostatic and pathologic regulations. The molecules that sustain this association have not been identified. Because synaptic cell adhesion molecule (SynCAM), alternatively named spermatogenic Ig superfamily (SgIGSF), is expressed on both nerves and mast cells and because it binds homophilically, this molecule may be a candidate. To examine this possibility, mast cells with or without SgIGSF/SynCAM were cocultured with superior cervical ganglion neurons that express SgIGSF/SynCAM, and the number of mast cells attached to neurites was counted. The attachment of mast cells with SgIGSF/SynCAM, i.e., bone marrow-derived mast cells (BMMC) from wild-type mice, was inhibited dose-dependently by blocking Ab to SgIGSF/SynCAM. Mast cells without SgIGSF/SynCAM, i.e., BMMC from microphthalmia transcription factor-deficient mice and BMMC-derived cell line IC-2 cells, were defective in attachment to neurite, and transfection with SgIGSF/SynCAM normalized this. When the nerves were specifically activated by scorpion venom, one-quarter of the attached IC-2 cells mobilized Ca(2+) after a few dozen seconds, and ectopic SgIGSF/SynCAM doubled this proportion. At points of contact between neurites and wild-type BMMC, SgIGSF/SynCAM was locally concentrated in both neurites and BMMC. SgIGSF/SynCAM on mast cells appeared to predominantly mediate attachment and promote communication with nerves.

Brain mast cells and therapeutic potential of vasoactive intestinal peptide in a Parkinson's disease model in rats: brain microdialysis, behavior, and microscopy

In the present study, the effect of systemically administered vasoactive intestinal peptide (VIP) (25 ng/kg i.p.) was investigated on drug-induced rotational behavior, extra-cellular dopamine levels and histology of corpus striatum in a 6-hydroxydopamine (6-OHDA)-induced rat model of Parkinson's disease. After 15 days of 6-OHDA lesion, apomorphine-induced (0.05 mg/kg s.c.) rotational behavior of the animals significantly increased and extra-cellular dopamine levels of corpus striatum were significantly reduced. VIP reversed the rotational deficits but did not alter the decrease in striatal dopamine levels. On the other hand, histological data indicate that VIP significantly reduced neuronal death and demyelination. Electron microscopic appearance of mast cells showed ultra-structural variety between VIP-treated and 6-OHDA lesioned groups. VIP activates mast cells without any evidence of typical exocytosis, and possibly mast cells could participate in neuroprotection. Our results suggest that systemically administered VIP can attenuate the motor response changes, neuronal cell death, and myelin sheet loss characteristically associated with 12 microg 6-OHDA administration into the rat striatum. Brain mast cells seem to participate in neuronal protection. Possibly, protective cues could be produced by brain mast cells.

Neurotrophic Factor Expression after Focal Brain Ischemia Preceded by Different Preconditioning Strategies

BACKGROUND

Both prolonged brain ischemia and preconditioning (PC) induce expression of neurotrophic factors. However, the influence of PC on their expression after a long-term ischemia remains vague. Previously, we have found various effects of PC on mRNA levels of different cytokines after focal brain ischemia. Thus, we investigated mRNA expression of nerve growth factor, brain-derived neurotrophic factor (BDNF) and ciliary neurotrophic factor after 90-min middle cerebral artery occlusion (MCAo) preceded by ischemic or chemical PC.

METHODS

MCAo was induced in rats using the suture method. PC had been carried out 3 days earlier. There were 4 experimental groups: MCAo alone; ischemic PC and MCAo; chemical PC and MCAo, and sham-operated rats. Expression of mRNAs in the ipsi- and contralateral cortex was studied by semiquantitative RT-PCR at 12 and 24 h after MCAo.

RESULTS

Despite clearly neuroprotective effects of both PC strategies, mRNA levels of neurotrophic factors were similar in tolerant and nontolerant rats. Only BDNF mRNA expression, 12 h after reperfusion, was lower when ischemic PC was applied prior to long-term ischemia.

CONCLUSIONS

These results suggest that PC generally does not change the expression of neurotrophic factor expression after a long-term focal brain ischemia compared to the nontolerant state.

Anti-allergic activity of a Kampo (Japanese herbal) medicine "Sho-seiryu-to (Xiao-Qing-Long-Tang)" on airway inflammation in a mouse model

Effects of a Kampo (Japanese herbal) medicine "Sho-seiryu-to (SST, Xiao-Qing-Long-Tang in Chinese)", which has been used for the treatment of allergic bronchial asthma clinically, were examined on ovalbumin (OVA)-sensitized allergic airway inflammation model (i.e., bronchial asthma) in a mouse. When SST was orally administered at 0.5 g/kg/day from day 1 to 6 days after OVA inhalation, SST reduced the OVA-specific IgE antibody titer in bronchoalveolar lavage (BAL) fluids at 7 days after the OVA inhalation. CD4(+) T cells obtained from the mouse lung produced more interleukin (IL)-4 and IL-5 but less interferon (IFN)-gamma than T cells from nonsensitized control animals. However, oral administration of SST reduced the production of IL-4 and IL-5 and the production of IFN-gamma returned to the control level. In addition, the IL-4 level was increased in the BAL fluid of the OVA-sensitized animals compared to the nonsensitized control, while the IFN-gamma levels decreased. SST reduced the IL-4 levels in the BAL fluids and returned the IFN-gamma level to control levels. Nerve growth factor (NGF) was increased in the BAL fluids of the OVA-sensitized mice over that of nonsensitized mice, but oral administration of SST augmented the NGF levels to approximately 2 times higher than in the sensitized mice. Although lung cells obtained from sensitized mice produced higher levels of NGF than nonsensitized mice, oral administration of SST augmented the production of NGF by the lung cells even higher ( approximately 2 times more than cells from sensitized mice). Administration of anti-NGF antibody to the airway blocked the effects of SST. These results suggest that SST modulates Th1/Th2 balance in the lungs and augmentation of NGF in the lungs may be related to the effects of SST. Pinellic acid (9S, 12S, 13S-trihydroxy-10E-octadecenoic acid), one component of the herbs of SST [Int. Immunopharmacol. 2 (2002) 1183], was purified from the tuber of Pinellia ternata Breitenbach. Oral administration of pinellic acid (50 microg/kg/day) also reduced the OVA-specific IgE antibody titer in BAL fluids from the sensitized mouse. This result suggests that pinellic acid is one of active ingredient(s) in SST.

Beta adrenergic inhibition of capsaicin-induced, NK1 receptor-mediated nerve growth factor biosynthesis in rat skin

Excitation of primary afferent neurons stimulates the expression of cytokines and nerve growth factor (NGF) in innervated tissues. Since NGF is a neurotrophic and immunomodulatory factor contributing to inflammatory hyperalgesia and tissue response to injury, this study was conducted in order to investigate the mechanisms by which afferent neuron stimulation by topical application of capsaicin increases NGF in the rat skin. Thereby it was sought to identify possible targets for pharmacological modulation of NGF biosynthesis. Topical capsaicin (>1 mg/ml ethanol) caused a concentration- and time-dependent increase in the concentration of NGF in rat skin. The capsaicin-induced increase of NGF was not significantly affected by indomethacin administered at a dose (2 mg/kg) that abolishes prostaglandin E2 biosynthesis. The NGF increase was suppressed by treatment of rats with the selective tachykinin NK1 receptor antagonist SR140333 (0.1 mg/kg), and by the beta adrenergic agonist terbutaline (0.3 mg/kg). The effect of terbutaline was reversed by the beta adrenergic antagonist propranolol (1 mg/kg). Terbutaline also inhibited the increase in NGF caused by intraplantar injection of the NK1 receptor agonist substance P (SP), but did not significantly affect that caused by carrageenan. The results show that topical administration of capsaicin causes a primarily NK1 receptor-dependent increase in the NGF content of rat skin, which is susceptible to inhibition by beta adrenergic agonists. These observations not only suggest regulation of skin NGF biosynthesis by afferent neuronal and adrenergic mechanisms, but also indicate possible targets for pharmacological modulation of skin NGF biosynthesis.

Unilateral spinal nerve ligation leads to an asymmetrical distribution of mast cells in the thalamus of female but not male mice

Mast cells are restricted to the leptomeninges and thalamus of healthy mice. These populations are increased by stress and highly sensitive to reproductive hormones. To examine the influence of nociception, a form of stress, on thalamic mast cells, we ligated the left fifth lumbar spinal nerve of male and female mice to induce hyperalgesia. Two, 7 and 14 days later, mice were killed and thalami examined histologically using toluidine blue stain. The total number of thalamic mast cells was not influenced by ligation of the spinal nerve compared to sham-operation in either female or male mice. However, in females, the percent of thalamic mast cells located on the side of the thalamus contralateral to the ligation was greater on days 2 and 7, coincident with mechanical hyperalgesia. At these times, areas in which mast cells were most dense contralateral to nerve-injury included the posterior (Po) and lateral geniculate (LG) nuclei compared to their symmetrical distribution in sham-operated mice. These data suggest that local nociceptive signals to each side of the thalamus rather than stress hormones influence the location of mast cells during the development of allodynia and hyperalgesia. In addition, both hyperalgesia and mast cell distribution induced by nerve-ligation differ in females compared to males, reflecting a novel neuroimmune response to pain within the CNS.

Transcriptional down-regulation of neurotrophin-3 in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) leads to progressive development of airflow limitation and is characterised by cough, mucus hypersecretion and inflammatory changes. These characteristic features of the disease may be modulated by neural mediators such as neurotrophins (NT). Here we examined the expression and transcriptional regulation of neurotrophins in bronchial biopsies of COPD patients and compared the data to control biopsies. Histology revealed characteristic changes in the COPD tissues, including remodelling of the epithelial lining. RT-PCR demonstrated the mRNA expression of neurotrophins in all biopsies. Immunohistochemistry confirmed the expression of different proteins. To assess changes in the transcriptional expression level, quantitative real-time PCR was carried out and revealed differential mRNA expression of neurotrophins, with marked down-regulation of NT-3 mRNA expression and constant levels of nerve growth factor (NGF), brain-derived nerve factor (BDNF), and NT-4/5 mRNA expression. The present data on neurotrophin-specific transcriptional down-regulation of NT-3 in human COPD indicate a pathophysiological role for neurotrophins in COPD.

Ablation of TrkA function in the immune system causes B cell abnormalities

The nerve growth factor (NGF) receptor TrkA is widely expressed in non-neural tissues suggesting pleiotropic functions outside the nervous system. Based on pharmacological and immuno-depletion experiments, it has been hypothesized that NGF plays an important role in the normal development and function of the immune system. However, attempts to unravel these functions by conventional gene targeting in mice have been hampered by the early postnatal lethality caused by null mutations. We have developed a novel 'reverse conditional' gene targeting strategy by which TrkA function is restored specifically in the nervous system. Mice lacking TrkA in non-neuronal tissues are viable and appear grossly normal. All major immune system cell populations are present in normal numbers and distributions. However, mutant mice have elevated serum levels of certain immunoglobulin classes and accumulate B1 cells with aging. These data, confirmed in a classical reconstitution model using embryonic fetal liver from TrkA-null mice, demonstrate that endogenous NGF modulates B cell development through TrkA in vivo. Furthermore, they demonstrate that many of the dramatic effects previously reported by pharmacological or immuno-depletion approaches do not reflect physiological developmental roles of TrkA in the immune system.

Plasticity of the different neuropeptide-containing nerve fibres in the tongue of the diabetic rat

Common oral complications of diabetes mellitus are xerostomia, impairment of taste, atrophic lesions of the tongue, leukoplakia, lichen oris planus, and tumours, which might be the consequence of chronic inflammation and changes in innervation. In this work, we examined the density of different neuropeptide-containing nerve fibres immunohisto- and immunocytochemically in the root of the control and diabetic rat's tongue. Quantitative analysis showed that the number of immunoreactive (IR) nerve fibres was decreased after 1 week of the streptozotocin treatment, which was prevented by immediate insulin treatment. However, after 4 weeks duration of diabetes, the number of all investigated IR nerve fibres increased significantly (p<0.05), which was further enhanced by the delayed insulin treatment. The numbers of substance P (SP) and vasoactive intestinal polypeptide IR perikarya were also increased by insulin treatment. The electron-microscopic investigations showed that some of the nerve terminals from diabetic animals were found in degeneration. After 4 weeks duration of diabetes, the number of inflammatory cells as well as the mast cell/nerve fibre contacts was also increased. The immunocells also showed IR for SP and neuropeptide Y in the diabetic rats. The insulin treatment decreased both the number and the immunoreactivity of these cells. The increased synthesis and/or regeneration of neuropeptide-containing nerves might indicate the plasticity of nerve fibres in diabetes mellitus, which might happen as a consequence of the changes in the level of neurotrophic factors released by increased number of inflammatory cells or as an effect of insulin.

Activation of extracellular signal-regulated protein kinase in the dorsal root ganglion following inflammation near the nerve cell body

Inflammation of the primary afferent proximal to the dorsal root ganglion (DRG) and the DRG itself is known to produce radicular pain. Here, we examined pain-related behaviors and the activation of extracellular signal-regulated protein kinase (ERK) in the DRG after inflammation near the DRG somata. Inflammation of the L4/5 nerve roots and DRG induced by complete Freund's adjuvant (CFA) produced mechanical allodynia on the ipsilateral hindpaw and induced an increase in the phosphorylation of ERK, mainly in tyrosine kinase (trk) A-expressing small- and medium-size neurons. This CFA-induced increase in ERK phosphorylation was mediated through trk receptors, because intrathecal treatment with the tyrosine kinase inhibitor, K252a, reduced the activation of ERK. On the other hand, an increase in brain-derived neurotrophic factor (BDNF) mRNA/protein in the DRG concomitant with the ERK activation was also observed. Furthermore, we found that nerve growth factor (NGF) injection directly into the L4/5 nerve roots and DRG produced mechanical allodynia, and an increase in the phosphorylation of ERK and BDNF expression in the DRG, but the mitogen-activated protein kinase (MAPK) kinase1/2 inhibitor, U0126, inhibited the effects induced by NGF. Therefore, we suggest that after inflammation near the cell body, NGF synthesized within the nerve root and DRG induces BDNF expression through trkA receptors and intracellular ERK-MAPK. The activation of MAPK in the primary afferents may be involved in the pathophysiological mechanisms of inflammation-induced radiculopathy and MAPK pathways in the primary afferents may be potential targets for pharmacological intervention for neuropathic pain produced by inflammation near the DRG somata.

Cannabinoid CB2 receptor activation inhibits mechanically evoked responses of wide dynamic range dorsal horn neurons in naïve rats and in rat models of inflammatory and neuropathic pain

Peripheral cannabinoid 2 receptors (CB2 receptors) modulate immune responses and attenuate nociceptive behaviour in models of acute and persistent pain. The aim of the present study was to investigate whether peripheral CB2 receptors modulate spinal processing of innocuous and noxious responses and to determine whether there are altered roles of CB2 receptors in models of persistent pain. Effects of local administration of the CB2 receptor agonist JWH-133 (5 and 15 microg/50 microL) on mechanically evoked responses of spinal wide dynamic range (WDR) neurons in noninflamed rats, rats with carrageenan-induced hindpaw inflammation, sham operated rats and spinal nerve-ligated (SNL) rats were determined in anaesthetized rats in vivo. Mechanical stimulation (von Frey filaments, 6-80 g) of the peripheral receptive field evoked firing of WDR neurons. Mechanically evoked responses of WDR neurons were similar in noninflamed, carrageenan-inflamed, sham-operated and SNL rats. Intraplantar injection of JWH-133 (15 microg), but not vehicle, significantly (P < 0.05) inhibited innocuous and noxious mechanically evoked responses of WDR neurons in all four groups of rats. In many cases the selective CB2 receptor antagonist, SR144528 (10 microg/50 microL), attenuated the inhibitory effects of JWH-133 (15 microg) on mechanically evoked WDR neuronal responses. The CB1 receptor antagonist, SR141716A, did not attenuate the inhibitory effects of JWH-133 on these responses. Intraplantar preadministration of JWH-133 also inhibited (P < 0.05) carrageenan-induced expansion of peripheral receptive fields of WDR dorsal horn neurons. This study demonstrates that activation of peripheral CB2 receptors attenuates both innocuous- and noxious-evoked responses of WDR neurons in models of acute, inflammatory and neuropathic pain.

Involvement of substance P, CGRP and histamine in the hyperalgesia and cytokine upregulation induced by intraplantar injection of capsaicin in rats

Intraplantar (i.pl.) injection of small doses of capsaicin has been shown to produce hyperalgesia and upregulation of the levels of proinflammatory cytokines. The present work aimed at investigating the possible mediation of these effects by sensory neuropeptides and mast cells. Various groups of rats received i.pl. injection of capsaicin alone or preceded by the injection of antagonists to substance P (SP), calcitonin gene-related protein (CGRP) and histamine (H1, H2) or the mast cell blocker ketotifen. All pretreatments prevented, in a dose-related manner, the capsaicin-induced hyperalgesia. The SP, H2 antagonists and ketotifen prevented the upregulation of all cytokines and nerve growth factor (NGF) levels, while the CGRP and H1 antagonists showed only attenuation of the NGF level.

The many functions of nerve growth factor: multiple actions on nociceptors

Nerve growth factor (NGF) initially interested neurobiologists because of its effects in the developing nervous system. It is now clear that NGF functions throughout the life of the animal with a wide repertoire of actions. In the sensory nervous system it primarily influences the structure and function of nociceptors. Here, we provide a brief review of these actions and raise the overriding biological questions of why these multiple actions occur and how they are carried out.

Nerve growth factor and its functional receptor TrkA are up-regulated in murine decidual tissue of stress-triggered and substance P-mediated abortion

PROBLEM

Stress, elicited by environmental and social conditions, is known to affect the homeostasis of the nervous, endocrine and immune systems. In pregnancy, perceived stress results in a predomination of inflammatory abortion-associated Th1 cytokines over immunosuppressive, pregnancy-protective-associated Th2 cytokines, putatively via neuropeptide substance P (SP). Nerve growth factor (NGF), an important trophic factor for sympathetic neurons, has been implicated in the responsiveness of immune-competent cells through its functional receptor, tropomyosin receptor kinase (TrkA). Thus, the aim of the present study was to identify a cross-talk between distinct neurotrophic and immune mediators in pregnancy maintenance.

METHOD OF STUDY

Using immune fluorescence, we evaluated decidual and placental expression of NGF and TrkA on gestation day (gd) 13.5 in the abortion-prone mouse model CBA/J x DBA/2J in (1) CBA/J female control mice; (2) CBA/J mice exposed to stress on gd 5.5; and (3) CBA/J mice injected with SP on gd 5.5 to mimick stress perception.

RESULTS

Stress and SP injection significantly increased the abortion rate and up-regulated decidual NGF and TrkA expression compared with the control. Stress, but not SP injection down-regulated placental NGF, whereas no changes in placental TrkA were observed.

CONCLUSION

Our data suggest a functional role for NGF in stress-triggered, SP-mediated abortion.

[Nerve growth factor (NGF) in inflammation and asthma]

INTRODUCTION

The nerve growth factor (NGF) is known as a factor involved in neuronal growth and survival. From recent studies it may also be considered as a mediator of inflammation, in particular in the airways.

STATE OF ART

Several animal studies have shown that NGF may increase the sensory innervation, and participate in the bronchial hyperresponsiveness and inflammation observed in the airways of asthmatic patients. Different cell types are capable of secreting NGF: inflammatory cells that infiltrate the bronchial mucosa, and structural cells such as epithelial cells, smooth muscle cells and pulmonary fibroblasts. Furthermore, increased NGF levels have been detected in the bronchoalveolar lavage fluid from asthmatic patients.

PERSPECTIVES AND CONCLUSION

Altogether, these results suggest that NGF may play a role in inflammation, bronchial hyperresponsiveness and airway remodelling in asthma, and may lead to a better understanding of the mechanisms occurring in chronic inflammatory diseases, in particular asthma.

Nerve growth factor mediates alterations of colonic sensitivity and mucosal barrier induced by neonatal stress in rats

BACKGROUND & AIMS

Maternal deprivation (MD) increases nerve growth factor (NGF) expression and colonic mast cell density and alters visceral sensitivity. This study aimed to establish whether NGF overexpression induced by neonatal stress is involved in altered visceral sensitivity and gut mucosal integrity in adult rats.

METHODS

Male Wistar rat pups were either submitted to MD and treated with anti-NGF antibodies or left with their dam and treated daily with NGF. All rats were tested 10 weeks later for visceral sensitivity and 12 weeks later for gut permeability, myeloperoxidase activity, and mast cell numbers. Colonic NGF and NGF receptor expression were determined at 14 days and 12 weeks of age. To determine the involvement of colonic NGF overexpression and mast cell hyperplasia in visceral hyperalgesia induced by MD, neonatally deprived adult rats received anti-NGF antibodies or doxantrazole.

RESULTS

MD increased visceral sensitivity to rectal distention, gut permeability, colonic myeloperoxidase activity, and mast cell density, and anti-NGF antibodies abolished these effects. Neonatal daily treatment with NGF mimicked the alterations induced by MD on both rectal sensitivity and mucosal barrier. In deprived compared with nondeprived rats, colonic NGF immunostaining and NGF messenger RNA were increased at 14 days and 12 weeks. Overexpression of NGF receptor messenger RNA, present at 14 days, was not observed later. Moreover, adult deprived rats treated with doxantrazole or anti-NGF antibodies exhibited normal gut permeability and visceral sensitivity to rectal distention.

CONCLUSIONS

These data indicate that NGF triggers and maintains long-term alterations of visceral sensitivity and gut mucosal integrity induced by MD.

Neurotrophin-3 regulates mast cell functions in neonatal mouse skin

Nerve growth factor (NGF) has long been recognized as an important mast cell (MC) growth factor. To explore whether other neurotrophins (NTs) of the NGF family, which are widely expressed in mouse skin, affect the numbers and/or functions of MCs we examined the effects of NT-3 on neonatal skin MCs. We demonstrate that TrkC, the high affinity NT-3 receptor, is expressed by virtually all neonatal skin MCs in C57BL/6 mice, which indicates that MCs can respond to NT-3. Skin of neonatal and early postnatal NT-3-overexpressing mice (promoter: K14) displayed significantly and up to twofold increased numbers of MCs during the first 20 days after birth, as compared to wild-type mice. To check whether this increase in MC numbers in NT-3 transgenic mice reflects a higher rate of proliferation, we performed immunohistochemistry, which revealed that only 1-2% of all skin MCs both in NT-3-overexpressing and in wild-type controls showed Ki-67-positive nuclei, suggesting that the observed differences in the number of MCs do not reflect a higher rate of MC proliferation. Additionally, we show that the effect of NT-3 on the number of MCs is most likely to be stem cell factor (SCF)-independent, because NT-3 significantly downregulates secretion of SCF-protein in cultured dermal fibroblasts, as assessed by enzyme-linked immunosorbent assay. Numbers of skin MCs in neonatal TrkC-deficient mice were found to be modestly reduced, as compared to wild-type mice, indicating that NT-3 can modulate the number of MCs directly via TrkC, although TrkC does not seem to be essential for the number of basal MCs. To further analyze the effects of NT-3 on MCs, we stimulated skin organ culture of early postnatal C57BL/6 mouse skin with 5-50 ng/ml NT-3, which induced a significant increase in MC degranulation, as visualized by Giemsa staining. However, stimulation of isolated neonatal dermal skin MCs with NT-3 in vitro failed to result in MC activation, as measured by serotonin release. Our data suggest a role for NT-3 in the maturation of MCs, such as a TrkC-mediated stimulation of the differentiation of pre-existing, less mature MCs and/or by enhancing the migration of circulating MC precursors into the skin.

The effect of promethazine on postoperative pain: a comparison of preoperative, postoperative, and placebo administration in patients following total abdominal hysterectomy

BACKGROUND

Histamine receptors are involved in the development of inflammatory pain and hyperalgesia, and the use of antihistamines is advocated as an alternative for pain therapy and treatment of postoperative nausea and vomiting. We investigated the influence of timing of promethazine administration on postoperative pain outcomes.

METHODS

Ninety female patients undergoing total abdominal hysterectomy were randomly divided into three groups. All individuals received infusions of promethazine and normal saline before anaesthesia induction, and postoperatively the Pre group received promethazine 0.1 mg kg(-1) before anaesthesia and saline postoperatively, and the Post group received saline before anaesthesia and promethazine 0.1 mg kg(-1) postoperatively, while the Control group received two equivalent volumes of saline. Patients were treated using patient-controlled intravenous analgesia (PCA). The primary endpoint was pain intensity and morphine consumption. The secondary endpoint was postoperative nausea and vomiting.

RESULTS

Postoperative morphine usage was significantly lower in the Pre group (24.1 +/- 3.9 mg) relative to the Post (30.0 +/- 4.6 mg) and Control groups (32.1 +/- 4.8 mg) during the first 24 h postoperatively (P<0.05). The number and incidence of patients suffering from postoperative nausea in the first 24 h was six (21%), seven (23%), and 15 (47%) in the Pre, Post, and Control groups, respectively (P<0.05). The number and incidence of patients vomiting in the first 24 h was three (10%), two (7%), and 10 (32%) in the Pre, Post, and Control groups, respectively (P<0.05). The number of patients asking for rescue antiemetic in the first 24 h was one (3%), two (7%), and seven (22%) in the Pre, Post, and Control groups, respectively (P<0.05).

CONCLUSIONS

Our results suggest that preoperative administration of promethazine 0.1 mg kg(-1) reduces postoperative morphine consumption compared with postoperative and placebo administration, and that use of promethazine reduces PONV and the number of patients asking for rescue antiemetic in the first 24 h after surgery when compared with placebo.

The Effect of Short-Term Epidural Local Anesthetic Blockade on Urinary Levels of Substance P in Interstitial Cystitis

We investigated the effect of epidural local anesthetic blockade on urinary substance P levels in five patients suffering from painful flare-ups of interstitial cystitis. Urine was collected in 24-h intervals commencing at the onset of an epidural bolus of 0.25% bupivacaine followed by maintenance epidural infusions of 0.05% bupivacaine. Substance P was measured by radioimmunoassay. After initiation of the epidural infusion, urinary substance P levels increased and then declined in all patients. All patients reported a decrease in pain intensity. We hypothesize that acute release, followed by depletion, of substance P from bladder sensory nerve endings accounts for the transient increase of peptide levels in urine and may contribute to the decrease in pain intensity during a 3-day epidural infusion.

IMPLICATIONS

Substance P levels in urine initially increased and then declined in a series of 5 patients who achieved pain control by epidural local anesthetic infusion during a flare-up of interstitial cystitis.

Expression of nerve growth factor in the airways and its possible role in asthma

Nerve growth factor (NGF), in addition to its essential role in neuronal growth and survival, may also act as an inflammatory mediator. As several animal studies have shown, NGF appears to play a part in the development of airway hyperresponsiveness and in the increased sympathetic and sensory innervation of the lung. It also has a profound effect on airway inflammation and asthma-related symptoms. Sources of NGF in the airways are numerous: inflammatory cells infiltrated into the bronchial mucosa, and structural cells including lung fibroblasts, airway epithelial and smooth muscle cells. These cells, by releasing more NGF in inflammatory conditions, may contribute to the increased NGF levels observed in bronchoalveolar lavage fluid and serum from patients with asthma. Taken together, these results suggest that NGF is an important mediator in both inflammation and asthma.

Interactions between the cells of the immune and nervous system: neurotrophins as neuroprotection mediators in CNS injury

Inflammatory processes in the central nervous system (CNS) are considered neurotoxic, although recent studies suggest that they also can be beneficial and confer neuroprotection (neuroprotective autoimmunity). Cells from the immune system have been detected in CNS injury and found to produce and secrete a variety of neurotrophins such as NGF, BDNF, NT-3 and NT-4/5, and to express (similarly to neuronal cells), members of the tyrosine kinase (Trk) receptor family such as TrkA, TrkB and TrkC. Indeed, autocrine and paracrine interactions are observed at the site of CNS injury, resulting in a variety of homologic-heterologic modulations of immune and neuronal cell function. The end result of the inflammatory process, neurotoxicity and/or neuroprotection, is a function of the fine balance between the two cellular systems, i.e., of the complex signaling relationships between anti-inflammatory neuroprotective factors (neurotrophins and other chemical mediators) and proinflammatory neurotoxic factors (TNF, free radicals, certain cytokines, etc.). Autoimmune neuroprotection is a novel therapeutic approach aimed at shifting the balance between the immune and neuronal cells towards survival pathways in a variety of CNS injuries. This review focuses on data supporting this concept and its future therapeutical implications for optic nerve injury and multiple sclerosis.

Neurofibromin-deficient Schwann cells secrete a potent migratory stimulus for Nf1+/- mast cells

The NF1 tumor suppressor gene encodes a GTPase-activating protein called neurofibromin that negatively regulates Ras signaling. Mutations in NF1 cause neurofibromatosis type 1 (NF1). The development of neurofibromas, which are complex tumors composed of multiple cell types, is a hallmark of NF1. Somatic inactivation of murine Nf1 in Schwann cells is necessary, but not sufficient, to initiate neurofibroma formation. Neurofibromas occur with high penetrance in mice in which Nf1 is ablated in Schwann cells in the context of a heterozygous mutant (Nf1+/-) microenvironment. Mast cells infiltrate neurofibromas, where they secrete proteins that can remodel the ECM and initiate angiogenesis. Thus, identification of mechanisms responsible for mast cell migration to tumor microenvironments is important for understanding tumorigenesis and for designing potential therapies. Here, we show that homozygous Nf1 mutant (Nf1-/-) Schwann cells secrete Kit ligand (KitL), which stimulates mast cell migration, and that Nf1+/- mast cells are hypermotile in response to KitL. Furthermore, we link hyperactivation of the Ras-class IA-PI3K-Rac2 pathway to increased Nf1+/- mast cell migration. Thus, these studies identify a novel interaction between Nf1-/- Schwann cells and Nf1+/- mast cells that is likely to be important in neurofibroma formation.

Role of nerve growth factor in the trinitrobenzene sulfonic acid-induced colonic hypersensitivity

The majority of patients with digestive disorders display visceral pain. In these troubles, visceral pain threshold is decreased, demonstrating visceral hypersensitivity. There is growing evidence that nerve growth factor (NGF) may function as a mediator of persistent pain states. This hypothesis was tested in a model of colonic hypersensitivity measured by isobaric distension in conscious rats. This study was designed to evaluate (1) the effect of exogenous NGF on colonic pain threshold, (2) the involvement of NGF in trinitrobenzene sulfonic acid (TNBS)-induced colonic hypersensitivity, by testing an anti-NGF antibody, and (3) finally the involvement of sensory nerves on NGF and TNBS effects using rats treated neonatally with capsaicin. Intra-peritoneal injection of NGF (0.1-100 ng/rat) decreased in a dose-related manner colonic pain threshold in naive rats. This effect was reversed by anti-NGF antibody (1/2000; 2 ml/kg). TNBS-induced colonic hypersensitivity was also reversed by anti-NGF antibody (1/2000; 2 ml/kg): 37.7 +/- 1.7 and 17.6 +/- 0.7 mmHg (p<0.01) for anti-NGF antibody- and vehicle-treated group, respectively. Neonatal capsaicin pre-treatment inhibited NGF- and TNBS-induced decrease in colonic pain threshold: 49.4 +/- 5.3 versus 22.3 +/- 1.6 mmHg (p<0.01) for capsaicin versus vehicle in NGF-treated rats and 39.6 +/- 3.3 versus 18.0 +/- 1.0 mm Hg (p<0.001) for capsaicin versus vehicle in TNBS-treated rats. These data suggest that the action of NGF on sensory neurons contributes to the development of visceral hypersensitivity and that anti-NGF strategy may be of some therapeutic benefits in digestive sensory disorders.

Nerve growth factor and wound healing

The wound healing process following tissue injury consists of a highly regulated sequence of events. Besides many biological activities on both neuronal and nonneuronal cells, nerve growth factor (NGF) has been proposed as an important component of wound healing and tissue repair process in vivo and in vitro. For example, NGF accelerates the rate of wound healing both in normal mice and healing-impaired diabetic mice, and has a potent pharmacological effect in the treatment for ulcer of the skin and cornea in humans. This review summarizes the evidence for the role of NGF in wound healing and tissue repair, and introduces its clinical utility as a therapeutic agent for various diseases.

Expression of Nerve Growth Factor (NGF), and Its Receptors trkA and p75 in Ovaries of the Cyclic Golden Hamster (Mesocricetus auratus) and the Regulation of Their Production by Luteinizing Hormone

In the present study, changes in localization of nerve growth factor (NGF) and its receptors, trkA and p75 in the ovary were investigated during the estrous cycle of the golden hamster. The effect of LH surge on changes in localization of NGF, trkA and p75 in the ovary was also investigated. NGF and its receptors trkA and p75 were localized in oocytes, granulosa cells and theca cells of various stages of follicles throughout the estrous cycle. NGF and its two receptors were also present in numerous interstitial cells and luteal cells. The number of interstitial cells staining positively for NGF and its two receptors was greater in ovaries of day 1 (day 1=day of ovulation) than the other days during the estrous cycle. Treatment with the antiserum against luteinizing hormone releasing hormone (LHRH-AS) at 1100 h on day 4 completely blocked ovulation. There were few positive reactions for NGF and its two receptors in interstitial cells 24 hr after LHRH-AS injection. The effect of LHRH-AS treatment was blocked by a single injection of 10 IU human chorionic gonadotropin. The distinct widespread distribution of NGF and its two receptors in the ovary of golden hamsters suggest that NGF may be an important growth factor for regulation of ovarian function. Furthermore, the LH surge may be an important factor for inducing production of NGF and its two receptors in interstitial cells of the cyclic golden hamster.

Perinatal changes of brain-derived neurotrophic factor in pre- and fullterm neonates

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is abundant in brain and peripheral nerves, affects normal development, growth and survival and is implicated in immune response.

AIM

To determine in single preterm (P) and fullterm (F) neonates, circulating intra- and extrauterine levels of BDNF, supposingly reflecting their neuronal and immune maturity.

STUDY DESIGN

Prospective study.

SUBJECTS

Thirty healthy, appropriate for gestational age (AGA) F (mean gestational age 39.2+/-1.4 weeks), 15 healthy AGA P (29.4+/-1.3 weeks), and their mothers.

OUTCOME MEASURES

BDNF was measured by enzyme immunoassay methods in the serum of: mothers at the first stage of labor (MS), the umbilical cord (UC) and the neonates on days 1 (N1) and 4 (N4) postpartum.

RESULTS

Levels of BDNF in (a). FMS did not differ from PMS, but both were significantly higher than respective (F or P) UC, N1 and N4 (p ranging from <0.01 to <0.001), (b). FUC, FN1 and FN4 were significantly higher than PUC (p<0.001), PN1 (p<0.03) and PN4 (p<0.02), respectively, (c). PN1 increased significantly as compared to PUC (p<0.05).

CONCLUSIONS

Higher BDNF MS levels may reflect the mature nervous and immune systems of mothers. Higher BDNF levels in F than P may also be due to advanced maturity in the former. Increased BDNF levels in PN1 as compared to PUC may indicate stimulation of immune response with exposure to antigenic stimuli from the extrauterine environment. Nevertheless, this stimulation is insufficient in P, who by decreasing N4 levels are by far less protected than F.

Nerve growth factor and substance P regulation in nasal sensory neurons after toluene diisocyanate exposure

Toluene diisocyanate (TDI) exposure produces rhinitis and nasal irritation, and increases the synthesis and release of substance P (SP) from airway sensory nerves. The mechanism leading to enhanced SP production following irritant inhalation remains unclear, but may involve actions of nerve growth factor (NGF). NGF binds trkA receptors located on sensory nerve terminals. Activation of trkA receptors initiates kinase-signaling cascades, which ultimately may increase SP. However, the effects of inhaled irritants on NGF release are not known. In this study, NGF levels in nasal lavages were examined following instillation of 10% TDI into both nasal cavities. NGF was significantly increased 2, 6, 12, and 24 h after TDI exposure compared with controls. The increase in NGF preceded the neuronal and mucosal increases in SP. Pretreatment with K252a, a nonselective tyrosine-kinase inhibitor, prevented the increase in SP-immunoreactivity in TG neurons and epithelial nerve fibers and the inflammatory response to TDI exposure. Because NGF binds to trkA tyrosine-kinase receptors, the NGF released during TDI exposure may mediate SP upregulation in airway sensory neurons, innervating the nasal cavity.

Induced maturation of frog mast cells by nerve growth factor during ontogenesis

The effect of nerve growth factor (NGF) on ontogenesis of frog mast cells was investigated in vivo by histochemical, morphometric, and ultrastructural analysis. Three groups of tadpoles at various stages of development were used. In the first group, the larvae received i.p. injections of 1 ng NGF/g; the second group received 10 ng NGF/g, while the control group received only the vehicle. The first recognizable mast cells arose symmetrically in the tongue at stage 26 of Witschi's standard table. At stages 26 and 29, the mast cell number in the NGF-injected tadpoles was significantly higher than the control group. From stage 29 onward, the mast cell number rapidly increased in all groups. No significant differences in mast cell number were observed between the control group and the NGF-injected groups at stages 31 and 33. Electron microscopy revealed that at metamorphic climax (stage 33), the mast cells in the NGF-treated groups were more mature than those in the control group. Therefore, nerve growth factor at early stages of tadpole development is likely to induce differentiation of mast cell precursors, while at later stages it is likely to induce maturation of immature mast cells. The close anatomical association between mast cells and perineurium, observed during nerve development, is intriguing. Already in the early stages of nerve development, the mast cells form a network around Schwann cell-axon complexes, together with the perineurial cells. At climax, the mast cells are located between the perineurial layers, suggesting that they may play a role in the tissue-nerve barrier of the perineurium. Nerve growth factor also seems to induce perineurial cell maturation.

New insights on the involvement of Nerve Growth Factor in allergic inflammation and fibrosis

Nerve Growth Factor (NGF), that was originally discovered for its properties of stimulating growth and differentiation of neurons, is now also considered responsible for several activities in the immune system and beyond. Mast cells and eosinophils, key cells of allergic inflammation, are a source of NGF and are influenced by it. These observations have prompted studies on NGF in allergy and tissue repair. Recent evidences link NGF and these two processes. While NGF is clearly a new tool in the management of untreatable ulcers, its role in allergic inflammation, although appearing to be pro-inflammatory, is still not clearly defined.

Nerve growth factor (NGF) and lenses: effects of NGF in an in vitro rat model of cataract

BACKGROUND

The aims of this study are to investigate the presence and production of nerve growth factor (NGF) in the rat lens in basal conditions and to evaluate, in vitro, the role of NGF in a model of xylose-induced cataract.

METHODS

Rat lenses were dissected and the expression of NGF, NGF mRNA and high-affinity NGF-receptor (TrkA) was evaluated by immunohistochemistry, immunoenzymatic assay (ELISA) and in-situ hybridization (ISH) techniques. To investigate the role of NGF in cataract formation we used an in vitro model of sugar-induced cataract by culturing rat lenses for 48 h in Eagle's minimum essential medium (MEM) supplemented with xylose. To evaluate the potential protective effect of NGF on xylose-induced cataract formation, exogenous NGF at different concentrations or antibodies neutralizing endogenous NGF (NGF-Ab) or aspecific antibodies were added to xylose-cultured lenses, and the following cataract-related parameters were evaluated and compared to xylose-treated lenses. Cataract formation was evaluated using three different parameters: staging of the cataract by lens photography, quantification of lens transparency in terms of gray level medium (GLM) and evaluation of the hydration percentage (H%) of the lens. To investigate the role of endogenous NGF in cataract onset, NGF levels were evaluated and compared in lenses cultured in xylose supplemented medium versus lenses cultured in control culture medium.

RESULTS

The epithelium from fresh rat lenses expresses NGF-receptor, NGF protein and NGF-mRNA. NGF levels in fresh lens were 54.0 +/- 24.5 pg/g as quantified by ELISA. Xylose-cultured lenses develop cataract changes, including a decrease of GLM and an increase in hydration percentage, associated with a decrease in NGF levels when compared to lenses cultured in the control culture medium. The addition of NGF to xylose-cultured lenses reduces cataract formation, increasing GLM and decreasing the hydration percentage as compared to xylose-treated lenses. On the other hand, the addition of NGF-Ab induces an increase in cataract formation and lens hydration.

CONCLUSIONS

This study demonstrates that rat lens epithelium expresses and synthesizes NGF. Moreover, immunohistochemistry shows that lens epithelial cells also express the NGF receptor. Although the functional significance of TrkA on lens epithelium is at present not clear, the expression of NGF and its high-affinity receptor on the same cells together with our experimental results suggest that NGF is involved in supporting trophism and/or the function of the lens epithelium.

Nerve growth factor overexpression and autocrine loop in breast cancer cells

We show here that nerve growth factor (NGF), the canonical neurotrophic factor, is synthesized and released by breast cancer cells. High levels of NGF transcript and protein were detected in breast cancer cells by reverse transcription-PCR, Western blotting, ELISA assay and immunohistochemistry. Conversely, NGF production could not be detected in normal breast epithelial cells at either the transcriptional or protein level. Confocal analysis indicated the presence of NGF within classical secretion vesicles. Breast cancer cell-produced NGF was biologically active, as demonstrated by its ability to induce the neuronal differentiation of embryonic neural precursor cells. Importantly, the constitutive growth of breast cancer cells was strongly inhibited by either NGF-neutralizing antibodies or K-252a, a pharmacological inhibitor of NGF receptor TrkA, indicating the existence of an NGF autocrine loop. Together, our data demonstrate the physiological relevance of NGF in breast cancer and its potential interest as a marker and therapeutic target.

The neurotrophins nerve growth factor, brain-derived neurotrophic factor, neurotrophin-3, and neurotrophin-4 are survival and activation factors for eosinophils in patients with allergic bronchial asthma

Neurotrophins (nerve growth factor [NGF], brain-derived neurotrophic factor [BDNF], neurotrophin [NT]-3, and NT-4) have been observed in elevated concentrations in allergic diseases. Neurotrophin levels are up-regulated endobronchially after allergen challenge. This coincides with an influx of activated eosinophils into the bronchial lumen. These eosinophils have an increased viability and CD69 expression 18 h after segmental allergen provocation (SAP) which is not present in peripheral blood. To investigate whether these observations are related we studied the influence of neurotrophins on eosinophil function in allergic asthma. Incubation with NGF, BDNF, NT-3, or NT-4 caused a significant increase in the viability and CD69 expression of isolated eosinophils from bronchoalveolar lavage fluid (BALF) but not from peripheral blood, suggesting a unique sensitivity of endobronchial eosinophils to neurotrophins. To elucidate the underlying mechanisms expression of the neurotrophin receptors p75NTR, trkA, trkB, and trkC on eosinophils was analyzed by RT-PCR and immunocytology. After SAP expression of all neurotrophin receptors was markedly elevated on eosinophils from BALF. Our findings suggest that neurotrophin-mediated activation of bronchial eosinophils might play a role in the regulation of eosinophilic inflammation in allergic asthma.

Mechanisms of sensitization of the response of single dorsal root ganglion cells from adult rat to noxious heat

We investigated the regulation by nerve growth factor of the response of sensory neurons to noxious heat (>43 degrees C). In dissociated dorsal root ganglion neurons (<30 micro m) from adult rat we demonstrated, using perforated patch clamp recording, that the inward current elicited in response to noxious heating is enhanced by nerve growth factor and reduced by capsazepine. The tachyphylaxis observed in response to the second of two heat pulses was reversed in most cells when nerve growth factor was introduced into the medium during the 5 min between the two heat stimuli, similar to findings using capsaicin [X. Shu & L.M. Mendell (1999) Neurosci. Lett.274, 159-162]. The threshold temperature did not change systematically after nerve growth factor. Using antibodies to TRPV1 and trkA in a subset of cells from which we recorded, we found a virtually perfect correlation between expression of TRPV1 and sensitivity to noxious heat. In addition, trkA expression was perfectly correlated with the ability of nerve growth factor to reverse tachyphylaxis. Thus, this physiological test is a reliable measure of trkA expression in cells sensitive to noxious heat. In agreement with studies in heterologous cells expressing trkA and TRPV1, pharmacologically blocking phospholipase C abolished the effect of nerve growth factor on heat-evoked currents in cells verified to express trkA. We conclude that the response of dorsal root ganglion neurons to noxious heat is conditioned by nerve growth factor in the same way as their response to capsaicin and that these responses require the presence of trkA and TRPV1.

Neurotrophins and the immune system

The neurotrophins are a family of polypeptide growth factors that are essential for the development and maintenance of the vertebrate nervous system. In recent years, data have emerged indicating that neurotrophins could have a broader role than their name might suggest. In particular, the putative role of NGF and its receptor TrkA in immune system homeostasis has become a much studied topic, whereas information on the other neurotrophins is scarce in this regard. This paper reviews what is known about the expression and possible functions of neurotrophins and their receptors in different immune tissues and cells, as well as recent data obtained from studies of transgenic mice in our laboratory. Results from studies to date support the idea that neurotrophins may regulate some immune functions. They also play an important role in the development of the thymus and in the survival of thymocytes.

Localization and content of nerve growth factor in peripheral blood eosinophils of atopic dermatitis patients

BACKGROUND

Atopic dermatitis (AD) is a chronic and relapsing eczematous skin disorder characterized by eosinophilia. Nerve growth factor (NGF) modulates the allergic response through interactions with immune-inflammatory cells. Eosinophils have been reported to store NGF as a preformed mediator.

OBJECTIVE

To gain further insight into the significance of eosinophils in association with NGF in the pathogenesis of AD, the localization of NGF within eosinophils and the difference of the eosinophil-derived NGF content in the peripheral blood of normal volunteers vs. AD patients were investigated.

METHODS

We examined the localization of NGF within human eosinophils using the post-embedding immunoelectron microscopy and compared NGF content in freshly isolated eosinophil sonicates from the peripheral blood of 31 normal volunteers vs. 42 AD patients by immunoenzymatic assay. A possible correlation between the levels of NGF and major basic protein was also examined.

RESULTS

Immunoelectron microscopic studies revealed that NGF was localized in the central core of normal eosinophil granules, where major basic protein is also present as a preformed mediator, in homogeneous granules and in intergranular ductal or vesicular structures adjacent to specific granules of eosinophils. NGF content in eosinophils was significantly increased in AD patients. Furthermore, there was a significant correlation between levels of NGF and major basic protein in eosinophils of AD patients.

CONCLUSIONS

Increased levels of NGF contained in eosinophils of the peripheral blood from AD patients, when released with other mediators such as basic proteins, could promote inflammation and local tissue damage.

Lumbar 5 ventral root transection-induced upregulation of nerve growth factor in sensory neurons and their target tissues: a mechanism in neuropathic pain

We have previously demonstrated that profound and persistent neuropathic pain as displayed by mechanical and cold allodynia and thermal hyperalgesia can be produced by a lumbar 5 ventral root transection (L5 VRT) model in adult rats in which only the motor nerve fibers were injured without axotomy of sensory neurons. However, the underlying mechanisms remain to be determined. In this study, by examining its changes in expression and by inhibiting its functions using a neutralizing antibody, we have investigated whether nerve growth factor (NGF), a neurotrophic factor known to have a function in regulating nerve injury-induced pain, is involved in the development of neuropathic pain induced by L5 VRT. Motor nerve injury by L5 VRT resulted in a de novo expression of NGF mRNA in a subpopulation of small sensory neurons and pericellular satellite cells in ipsilateral L5 dorsal root ganglion. NGF protein expression was also increased by sensory neurons with various sizes and by keratinocytes in the target tissue ipsilateral skin. Systemic administration of NGF antiserum twice within 17 days markedly attenuated L5 VRT-induced mechanical allodynia but not the cold allodynia and thermal hyperalgesia. These findings suggest that NGF is an important pain mediator in the generation of mechanical sensitivity induced by L5 VRT.