Mast cells synthesize, store, and release nerve growth factor

An emerging role of mast cells in cerebral ischemia and hemorrhage

Mast cells (MCs) are perivascularly located resident cells of hematopoietic origin, recognized as effectors in inflammation and immunity. Their subendothelial location at the boundary between the intravascular and extravascular milieus, and their ability to rapidly respond to blood- and tissue-borne stimuli via release of potent vasodilatatory, proteolytic, fibrinolytic, and proinflammatory mediators, render MCs with a unique status to act in the first-line defense in various pathologies. We review experimental evidence suggesting a role for MCs in the pathophysiology of brain ischemia and hemorrhage. In new-born rats, MCs contributed to brain damage in hypoxic-ischemic insults. In experimental cerebral ischemia/reperfusion, MCs regulated permeability of the blood-brain barrier, brain edema formation, and the intensity of local neutrophil infiltration. MCs were reported to play a role in the tissue plasminogen activator-mediated cerebral hemorrhages after experimental ischemic stroke, and to be involved in the expansion of hematoma and edema following intracerebral hemorrhage. Importantly, the MC-stabilizing drug cromoglycate inhibited MC-mediated adverse effects on brain pathology and improved survival of experimental animals. This brings us to a position to consider MC stabilization as a novel initial adjuvant therapy in the prevention of brain injuries in hypoxia-ischemia in new-borns, as well as in ischemic stroke and intracerebral hemorrhage in adults.

Peripheral mechanisms I: plasticity of peripheral pathways

Cough plays a vital role in protecting the lower airways from inhaled irritants, pollutants, and infectious agents. The cough reflex exhibits remarkable plasticity, such that in the context of infectious or inflammatory respiratory diseases such as asthma, chronic bronchitis, and idiopathic pulmonary fibrosis the cough reflex can become dysregulated, leading to a chronic cough. A chronic, nonproductive (dry) cough can rob sufferers of quality of life. Plasticity of the cough reflex likely involves multiple intersecting pathways within the airways, the peripheral nerves that supply them, and the central nervous system. While further studies are needed to determine the presence and relevance of many of these specific pathways in cough associated with chronic respiratory disease, the last decade has yielded unprecedented insight into the molecular identity of the ion channels and associated proteins that initiate and conduct action potentials in the primary sensory nerves involved in reflexes such as cough. We now know, for instance, that members of the transient receptor potential superfamily of nonselective cation channels function as transducers that convert specific external stimuli into neuronal activation. We also know that certain Na+ and K+ channels play specialized roles in regulating action potential discharge in irritant-sensing afferent nerves. In this chapter, we summarize the available information regarding factors that may modulate afferent neuron function acutely, via posttranslational modifications and over the longer term through neurotrophin-dependent alterations of the transcriptional programs of adult sensory neurons.

Protective autoimmunity in the nervous system

The immune system can play both detrimental and beneficial roles in the nervous system. Multiple arms of the immune system, including T cells, B cells, NK cells, mast cells, macrophages, dendritic cells, microglia, antibodies, complement and cytokines participate in limiting damage to the nervous system during toxic, ischemic, hemorrhagic, infective, degenerative, metabolic and immune-mediated insults and also assist in the process of repair after injury has occurred. Immune cells have been shown to produce neurotrophic growth factors and interact with neurons and glial cells to preserve them from injury and stimulate growth and repair. The immune system also appears to participate in proliferation of neural progenitor stem cells and their migration to sites of injury. Neural stem cells can also modify the immune response in the central and peripheral nervous system to enhance neuroprotective effects. Evidence for protective and reparative functions of the immune system has been found in diverse neurologic diseases including traumatic injury, ischemic and hemorrhagic stroke, multiple sclerosis, infection, and neurodegenerative diseases (Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis). Existing therapies including glatiramer acetate, interferon-beta and immunoglobulin have been shown to augment the protective and regenerative aspects of the immune system in humans, and other experimental interventions such as vaccination, minocycline, antibodies and neural stem cells, have shown promise in animal models of disease. The beneficent aspects of the immune response in the nervous system are beginning to be appreciated and their potential as pharmacologic targets in neurologic disease is being explored.

Interpreting crosstalk between TNF-alpha and NGF: potential implications for disease

Tumour necrosis factor-alpha (TNF-alpha) is a proinflammatory cytokine, whereas nerve growth factor (NGF) is a neurotrophin that can promote neural cell survival, differentiation and maturation. However, recent papers indicate that TNF-alpha has a pivotal role in fate decisions of neural cells in normal noninflammatory conditions, whereas NGF contributes to maintenance of inflammation. Although these observations suggest a close relationship between NGF and TNF-alpha signalling, crosstalk between these factors is not fully understood. In this Opinion article, we review recent reports regarding possible crosstalk between NGF and TNF-alpha and we propose a positive-feedback loop of their expression. We discuss the possible mechanisms by which disturbance of the crosstalk could contribute to diseases such as cancer and Alzheimer's disease.

The endogenous fatty acid amide, palmitoylethanolamide, has anti-allodynic and anti-hyperalgesic effects in a murine model of neuropathic pain: involvement of CB(1), TRPV1 and PPARgamma receptors and neurotrophic factors

Palmitoylethanolamide (PEA) is an endogenous lipid that is thought to be involved in endogenous protective mechanisms activated as a result of stimulation of inflammatory response. In spite of the well demonstrated anti-inflammatory properties of PEA, its involvement in controlling pain pathways still remains poorly characterized. On this basis, we tested the efficacy of PEA in vivo against a peculiar persistent pain, such as neuropathic one. PEA was administered i.p. to mice with chronic constriction injury of sciatic nerve (CCI) once a day for one week starting the day after the lesion. This therapeutic regimen evoked a relief of both thermal hyperalgesia and mechanical allodynia in neuropathic mice. Various selective receptor antagonists were used in order to clarify the relative contribution of cannabinoid, vanilloid and peroxisome proliferator-activated receptor to PEA-induced effects. The results indicated that CB(1), PPARgamma and TRPV1 receptors mediated the antinociception induced by PEA, suggesting that the most likely mechanism might be the so-called "entourage effect" due to the PEA-induced inhibition of the enzyme catalyzing the endocannabinoid anandamide (AEA) degradation that leads to an enhancement of its tissue levels thus increasing its analgesic action. In addition, the hypothesis that PEA might act through the modulation of local mast cells degranulation is sustained by our findings showing that PEA significantly reduced the production of many mediators such as TNFalpha and neurotrophic factors, like NGF. The findings presented here, in addition to prove the beneficial effects of PEA in chronic pain, identify new potential targets for analgesic medicine.

Neuritogenic effects of T cell-derived IL-3 on mouse splenic sympathetic neurons in vivo

To determine the role played by lymphocytes and cytokines in the growth of sympathetic neurons in vivo, the innervation and cytokine levels were examined in the spleens of SCID mice that lack T and B cells. Splenic noradrenaline, nerve growth factor (NGF), and IL-1beta levels were elevated in SCID mice. Immunohistochemical examination revealed that the density of tyrosine hydroxylase-positive (TH(+)) fibers of splenic central arteries in SCID mice was increased compared with wild-type C.B-17 mice, while SCID mice had significantly fewer TH(+) fibers in their periarteriolar lymphatic sheaths (PALS). Two weeks after SCID mice were injected with C.B-17 splenic T cells, their TH(+) fiber staining increased in the PALS. IL-3 levels increased significantly in SCID mice following T cell reconstitution, and the administration of anti-IL-3 Ab blocked the above T cell-induced increase in innervation in the PALS. Anti-IL-3 treatment also inhibited the regeneration of splenic sympathetic neurons in C.B-17 mice after they were chemically sympathetomized with 6-hydroxydopamine. Depletion of NK cells by anti-asialo GM1 promoted the splenic innervation in SCID mice, while there were no significant changes in the innervation between CD8(+) T cell-deficient beta(2)-microglobulin knockout mice and their wild type. Our results suggest that T cells (probably CD4(+) Th cells but not CD8(+) CTLs) play a role in regulating the sympathetic innervation of the spleen; this effect appeared to be mediated, at least in part, by IL-3. On the contrary, NK cells may exert an inhibitory effect on the sympathetic innervation.

Increased nerve fiber expression of sensory sodium channels Nav1.7, Nav1.8, And Nav1.9 in rhinitis

INTRODUCTION

Voltage-gated sodium channels Nav1.7, Nav1.8, and Nav1.9 are involved in nerve action potentials and have been proposed to underlie neuronal hypersensitivity. We have therefore studied their levels in allergic and nonallergic rhinitis.

MATERIALS AND METHODS

Inferior turbinate biopsies from 50 patients (n = 18 controls, n = 20 allergic, and n = 12 nonallergic rhinitis) were studied by immunohistology using antibodies to Nav1.7, Nav1.8, and Nav1.9, the structural nerve marker (protein gene product [PGP]9.5), nerve growth factor (NGF), mast cells (c-kit), macrophages (CD68), and T cells (CD3). Sodium channel-positive nerve fibers were counted per millimeter length of subepithelium, and immunoreactivity for inflammatory cell markers PGP9.5 and NGF were image analyzed.

RESULTS

All three sodium channel-immunoreactive nerve fiber numbers were significantly increased in allergic (Nav1.7, P = .0004; Nav1.8, P = .028; Nav1.9, P = .02) and nonallergic (Nav1.7, P = .006; Nav1.8, P = .019; Nav1.9, P = .0037) rhinitis. There was a significant increase of subepithelial innervation (PGP9.5, P = .01) and epithelial NGF immunoreactivity (P = .03) in nonallergic rhinitis, comparable with our previous report in allergic rhinitis. Inflammatory cell markers were significantly increased in allergic (mast cells, P = .06; macrophages, P = .044; T cells, P = .007) but not nonallergic rhinitis.

CONCLUSION

The increased levels of sensory sodium channels in allergic and nonallergic rhinitis may contribute to the hypersensitive state, irrespective of the degree of active inflammation. Selective blockers of these sodium channels, administered topically, may have therapeutic potential in rhinitis.

Exercise and brain health--implications for multiple sclerosis: Part II--immune factors and stress hormones

Part I of this review addressed the possible modulatory role of exercise on neuronal growth factors to promote brain health in neurodegenerative diseases such as multiple sclerosis (MS), which is characterized by varied patterns of inflammation, demyelination and axonal loss. Part II presents evidence that supports the potential neuroprotective effect of exercise on the modulation of immune factors and stress hormones in MS. Many current therapies used to attenuate MS progression are mediated, at least in part, through alterations in the relative concentrations of pro- and anti-inflammatory cytokines. Exercise-induced alterations in local and systemic cytokine production may also benefit immune function in health and disease. Exercise immunomodulation appears to be mediated by a complex interaction of hormones, cytokines and neural factors that may favorably influence immune variables in MS. The promising interplay between exercise and brain health in MS deserves further investigation.

Brain-derived neurotrophic factor enhances the excitability of rat sensory neurons through activation of the p75 neurotrophin receptor and the sphingomyelin pathway

Neurotrophin-mediated signalling cascades can be initiated by activation of either the p75 neurotrophin receptor (p75(NTR)) or the more selective tyrosine kinase receptors. Previously, we demonstrated that nerve growth factor (NGF) increased the excitability of sensory neurons through activation of p75(NTR) to liberate sphingosine 1-phosphate. If neurotrophins can modulate the excitability of small diameter sensory neurons through activation of p75(NTR), then brain-derived neurotrophic factor (BDNF) should produce the same sensitizing action as did NGF. In this report, we show that focally applied BDNF increases the number of action potentials (APs) evoked by a ramp of depolarizing current by reducing the rheobase without altering the firing threshold. This increased excitability results, in part, from the capacity of BDNF to enhance a tetrodotoxin-resistant sodium current (TTX-R I(Na)) and to suppress a delayed rectifier-like potassium current (I(K)). The idea that BDNF acts via p75(NTR) is supported by the following observations. The sensitizing action of BDNF is prevented by pretreatment with a blocking antibody to p75(NTR) or an inhibitor of sphingosine kinase (dimethylsphingosine), but not by inhibitors of tyrosine kinase receptors (K252a or AG879). Furthermore, using single-cell RT-PCR, neurons that were sensitized by BDNF expressed the mRNA for p75(NTR) but not TrkB. These results demonstrate that neurotrophins can modulate the excitability of small diameter capsaicin-sensitive sensory neurons through the activation of p75(NTR) and its downstream sphingomyelin signalling cascade. Neurotrophins released upon activation of a variety of immuno-competent cells may be important mediators that give rise to the enhanced neuronal sensitivity associated with the inflammatory response.

Topography and morphometry of intestinal mast cells in children with Hirschsprung's disease

Mast cells (MC) are source of many biological active compounds like cytokines, arachidonic acid derivates, proteoglicanes, prostaglandins, proteases, free oxygen radials, NGF, PAF and many more. The role of MC in pathogenesis of Hirschsprung's disease (HD) is not clear. Substances produced by MC may exert an important effect on embryology, growth, differentiation and regeneration of intestinal nervous system. Additionally, MC products modulate inflammation processes thus influencing on the clinical course of HD. Present study was established to evaluate the morphologic MC examination as a support of making diagnosis in HD. The MC topography and morphometry were evaluated in specimens collected from aganglionic colon of patients with diagnosed HD. The results were compared with corresponding data from normally innervated colon of patients suffering from constipation, and normal colon of children not presenting defecation problems. MC were visualized using indirect immunohistochemical method LSAB with mouse antibody against human tryptase. The MC visualized in submucosa and muscular layer in Hirschsprung's disease were significantly larger in comparison with control group (p<0.05). Also the number of MC/mm2 in mucosa and lamina propria in HD was significantly elevated (p<0.05). However, the MC density in submucosa was also higher but it was not high statistically significant. In muscular layer and in serosa density of MC/mm2 was not statistically significant. In the intestinal wall MC in aganglionic segment in Hirschsprung's disease are significantly activated comparing with normally innervated colon segments taken from the patients from other groups. This may confirm the role of MC both in pathogenesis of HD and in the reparation processes of bowel nervous system.

Granule formation in NGF-cultured mast cells is associated with expressions of pyruvate kinase type M2 and annexin I proteins

BACKGROUND

Nerve growth factor (NGF) is a potent mediator, which regulates characteristics of mast cells, but its biological function is not well characterized. This study aimed to screen proteins associated with the maturation of human mast cells-1 (HMC-1) or mouse bone marrow-derived mast cells (BMMCs) cultured with NGF, and to examine the functions of proteins involved.

METHODS

NGF (10 ng/ml) was added to cell culture medium every other day for 10 days for HMC-1 or twice a week for 5 weeks for BMMCs. Granule formation was determined by electron microscopy or May-Grunwald-Giemsa staining, TNF-alpha by ELISA, expressions of various proteins by two-dimensional gel electrophoresis (2-DE), siRNA transfection by Lipofectamine 2000, and the expressions of pyruvate kinase and annexin I by immunoblotting.

RESULTS

After NGF treatment, granule formation and total amounts of granular mediator, TNF-alpha increased in both mast cells. This TNF-alpha was released by calcium ionophore or by antigen/antibody reaction. Expressions of pyruvate kinase and annexin I obtained by 2-DE were confirmed by immunoblotting and siRNA-transfected HMC-1 cells. Expressions of proteins, granule formation and TNF-alpha content were blocked by both the TrkA inhibitor, K252a, and the ERK inhibitor, PD98059, but not by the PI3 kinase inhibitors, LY294002 and wortmannin.

CONCLUSION

These data suggest that pyruvate kinase and annexin I expressed by NGF contribute to granule formation containing TNF-alpha as well as other mediators in mast cells, which play a major role in allergic diseases via a TrkA/ERK pathway.

Bioconjugation of oligonucleotides for treating liver fibrosis

Liver fibrosis results from chronic liver injury due to hepatitis B and C, excessive alcohol ingestion, and metal ion overload. Fibrosis culminates in cirrhosis and results in liver failure. Therefore, a potent antifibrotic therapy is urgently needed to reverse scarring and eliminate progression to cirrhosis. Although activated hepatic stellate cells (HSCs) remain the principle cell type responsible for liver fibrosis, perivascular fibroblasts of portal and central veins as well as periductular fibroblasts are other sources of fibrogenic cells. This review will critically discuss various treatment strategies for liver fibrosis, including prevention of liver injury, reduction of inflammation, inhibition of HSC activation, degradation of scar matrix, and inhibition of aberrant collagen synthesis. Oligonucleotides (ODNs) are short, single-stranded nucleic acids, which disrupt expression of target protein by binding to complementary mRNA or forming triplex with genomic DNA. Triplex forming oligonucleotides (TFOs) provide an attractive strategy for treating liver fibrosis. A series of TFOs have been developed for inhibiting the transcription of alpha1(I) collagen gene, which opens a new area for antifibrotic drugs. There will be in-depth discussion on the use of TFOs and how different bioconjugation strategies can be utilized for their site-specific delivery to HSCs or hepatocytes for enhanced antifibrotic activities. Various insights developed in individual strategy and the need for multipronged approaches will also be discussed.

TLR4 signaling induces functional nerve growth factor receptor p75NTR on mouse dendritic cells via p38MAPK and NF-kappa B pathways

Many neuropeptides that are produced by immune cells have been shown to be involved in the pathogenesis of immunological disorders. Nerve growth factor (NGF) and its receptors are found to be widely expressed in the immune system and regulate both innate and adaptive immune responses. However, the underlying mechanisms by which NGF contributes to pathogenesis of inflammatory diseases remain to be fully understood. Dendritic cells (DCs) are potent initiator for inflammatory and immune responses upon recognization and activation of Toll-like receptors (TLRs). In this study, we demonstrated that stimulation with TLR ligand lipopolysaccharide (LPS), but not lipoteichoic acid (LTA), Poly (I:C) and CpG oligodeoxynucleotide (ODN), could significantly induce expression of NGF and NGF receptor p75(NTR) on mouse bone marrow-derived DCs (BMDCs) in vitro in dose- and time-dependent manners. The expression of NGF and NGF receptor p75(NTR) also increased on splenic DCs isolated from the mice injected with LPS in vivo. However, there was no such effect on DCs derived from TLR4-deficient mice, indicating the LPS-induced upregulation of NGF and p75(NTR) was TLR4 pathway-dependent. Furthermore, LPS-induced upregulation of NGF and p75(NTR) could be inhibited by p38MAPK inhibitor SB203580 and NF-kappaB inhibitor PDTC, suggesting TLR4-triggered activation of p38MAPK and NF-kappaB pathways are responsible for the process. Interestingly, NGF could markedly promote LPS-pretreated BMDCs to secret IL-12p40 and TNF-alpha, which could be abolished by pretreatment with p75(NTR) antagonist or the specific small interference RNA duplex targeting p75(NTR) (p75-siRNA), suggesting the inducible p75(NTR) is critical for the TLR4-initiated inflammatory effect of NGF on BMDCs. Thus, TLR4 signaling can induce expression of NGF and p75 (NTR) on DCs via activation of p38 MAPK and NF-kappaB pathways, suggesting that NGF may be involved in the pathogenesis of inflammatory diseases.

Pancreatic pain

Abdominal pain is an important clinical symptom in pancreatic diseases. There is increasing evidence that pain in chronic pancreatitis and pancreatic cancer is triggered by pancreatic neuropathy. Damage to intrapancreatic nerves seems to support the maintenance and exacerbation of neuropathic pain. In chronic pancreatitis, intrapancreatic nerves are invaded by immune cells. This observation led to the hypothesis that neuro-immune interactions play a role in the pathogenesis of chronic pancreatitis and the accompanying abdominal pain syndrome. Similarly, pancreatic cancer cells infiltrate the perineurium of local nerves, which may in part explain the severe pain experienced by the patients. Furthermore, perineural invasion extending into extrapancreatic nerves may preclude curative resection and thus often leads to local recurrence. In recent years, the involvement of a variety of neurotrophins and neuropeptides in the pathogenesis of pancreatic pain was discovered. This review summarises recent data on the mechanisms of neuropathy and pain generation in pancreatic disorders.

Growth factors and heme oxygenase-1: perspectives in physiology and pathophysiology

Growth factors are mediators of both normal homeostasis and pathophysiology through their effects on various cellular processes. Similarly, heme oxygenase-1 (HO-1) has a role in maintaining physiologic equilibrium, by which it can either alleviate or exacerbate disease, depending on several considerations, including amount, timing, and location of expression, as well as the disease setting. Thus, the synthesis and activities of growth factors and HO-1 are intricately regulated. Interestingly, several growth factors induce HO-1, and, conversely, HO-1 can regulate the expression of some growth factors. This review focuses on the influence of growth factors and HO-1 and potential physiologic effects of the growth factor(s)-HO-1 interaction.

The mast cell and allergic diseases: role in pathogenesis and implications for therapy

Mast cells have long been recognized for their role in the genesis of allergic inflammation; and more recently for their participation in innate and acquired immune responses. Mast cells reside within tissues including the skin and mucosal membranes, which interface with the external environment; as well as being found within vascularized tissues next to nerves, blood vessels and glandular structures. Mast cells have the capability of reacting both within minutes and over hours to specific stimuli, with local and systemic effects. Mast cells express the high affinity IgE receptor (FcepsilonRI) and upon aggregation of FcepsilonRI by allergen-specific IgE, mast cells release and generate biologically active preformed and newly synthesized mediators which are involved in many aspects of allergic inflammation. While mast cells have been well documented to be essential for acute allergic reactions, more recently the importance of mast cells in reacting through pattern recognition receptors in innate immune responses has become recognized. Moreover, as our molecular understanding of the mast cell has evolved, novel targets for modulation have been identified with promising therapeutic potential.

ATP plays a role in neurite stimulation with activated mast cells

Previously, we showed that nerve-mast cell cross-talk can occur bidirectionally and that substance P is a mediator to activate mast cells. Here, we have studied the mediators to activate nerves cocultured with mast cells. Addition of antigen to the cocultures of superior cervical ganglia (SCG) and rat basophilic leukemia cells (RBLs) elicited Ca(2+) response in RBLs and after a lag period induced Ca(2+) signal in SCG neurites. Pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (purinergic receptor antagonist) or apyrase (ATP-hydrolyzing enzyme) reduced the Ca(2+) signals in neurites, indicating that ATP released from activated mast cells was one of important mediators to activate nerves.

Neuroimmune interactions: potential target for mitigating or treating intestinal radiation injury

Intestinal radiation injury is characterized by breakdown of the epithelial barrier and mucosal inflammation. In addition to replicative and apoptotic cell death, radiation also induces changes in cellular function, as well as alterations secondary to tissue injury. The recognition of these "non-cytocidal" radiation effects has enhanced the understanding of normal tissue radiation toxicity, thus allowing an integrated systems biology-based approach to modulating radiation responses and providing a mechanistic rationale for interventions to mitigate or treat radiation injuries. The enteric nervous system regulates intestinal motility, blood flow and enterocyte function. The enteric nervous system also plays a central role in maintaining the physiological state of the intestinal mucosa and in coordinating inflammatory and fibroproliferative processes. The afferent component of the enteric nervous system, in addition to relaying sensory information, also exerts important effector functions and contributes critically to preserving mucosal integrity. Interactions between afferent nerves, mast cells as well as other cells of the resident mucosal immune system serve to maintain mucosal homeostasis and to ensure an appropriate response to injury. Notably, enteric sensory neurons regulate the activation threshold of mast cells by secreting substance P, calcitonin gene-related peptide and other neuropeptides, whereas mast cells signal to enteric nerves by the release of histamine, nerve growth factor and other mediators. This article reviews how enteric neurons interact with mast cells and other immune cells to regulate the intestinal radiation response and how these interactions may be modified to mitigate intestinal radiation toxicity. These data are not only applicable to radiation therapy, but also to intestinal injury in a radiological terrorism scenario.

Differential activation of dendritic cells by nerve growth factor and brain-derived neurotrophic factor

BACKGROUND

Neurotrophins are involved in inflammatory reactions influencing several cells in health and disease including allergy and asthma. Dendritic cells (DCs) play a major role in the induction of inflammatory processes with an increasing role in allergic diseases as well.

OBJECTIVE

The aim of this study was to investigate the influence of neurotrophins on DC function.

METHODS

Monocyte-derived dendritic cells were generated from allergic and non-allergic donors. Neurotrophin receptors were demonstrated by western blotting, flow cytometry and fluorescence microscopy. Activation of small GTPases was evaluated by pull-down assays. DCs were incubated with nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) and supernatants were collected for measurement of IL-4, IL-6, IL-10, IL-12p70, TNF-alpha and TGF-beta.

RESULTS

Receptor proteins were detectable by western blot, fluorescence activated cell sorting analysis and fluorescence microscopy. Signalling after neurotrophin stimulation occurred in a ligand-specific pattern. NGF led to decreased RhoA and increased Rac activation, while BDNF affected RhoA and Rac activity in a reciprocal fashion. Cells of allergics released a significantly increased amount of IL-6, while for healthy subjects a significantly higher amount of IL-10 was found.

CONCLUSION

These data indicate that DCs are activated by the neurotrophins NGF and BDNF by different pathways in a receptor-dependant manner. These cells then may initiate inflammatory responses based on allergic sensitization releasing preferred cytokines inducing tolerance or a T-helper type 2 response.

Pathophysiology of peripheral neuropathic pain: immune cells and molecules

Damage to the peripheral nervous system often leads to chronic neuropathic pain characterized by spontaneous pain and an exaggerated response to painful and/or innocuous stimuli. This pain condition is extremely debilitating and usually difficult to treat. Although inflammatory and neuropathic pain syndromes are often considered distinct entities, emerging evidence belies this strict dichotomy. Inflammation is a well-characterized phenomenon, which involves a cascade of different immune cell types, such as mast cells, neutrophils, macrophages, and T lymphocytes. In addition, these cells release numerous compounds that contribute to pain. Recent evidence suggests that immune cells play a role in neuropathic pain in the periphery. In this review we identify the different immune cell types that contribute to neuropathic pain in the periphery and release factors that are crucial in this particular condition.

New insights in the etiology and pathophysiology of irritable bowel syndrome: contribution of neonatal stress models

Irritable bowel syndrome (IBS) is one of the most common gastrointestinal disorders, characterized by abdominal pain and disturbed defecation that cannot be explained by structural abnormalities. Although IBS symptoms (visceral pain, increased gut permeability, motility alterations) are clearly established, the etiology of this pathology is loosely understood. Nevertheless, clinical studies have reported that some early abuse (physical and psychological) is often associated with IBS development. Thus, loss and separation in the family during childhood may contribute to the IBS development. The recent development of animal models has pointed out the importance of early traumatic experiences in favoring the occurrence of IBS in adult life. Among these different models, neonatal maternal deprivation (NMD), neonatal colonic irritation (inflammatory stimuli), and neonatal colonic pain (rectal distension) have been described to mimic some cardinal features of IBS. The purpose of this review is 3-fold. First, to present the different neonatal stress models. Second, to review the literature on the influence of these early traumatic experiences on the gastrointestinal tract disturbances observed in adult life. Finally, we will also present the mediators and mechanisms involved in gut dysfunction triggered by NMD and probably in IBS.

The nerve growth factor and its receptors in airway inflammatory diseases

The nerve growth factor (NGF) belongs to the neurotrophin family and induces its effects through activation of 2 distinct receptor types: the tropomyosin-related kinase A (TrkA) receptor, carrying an intrinsic tyrosine kinase activity in its intracellular domain, and the receptor p75 for neurotrophins (p75NTR), belonging to the death receptor family. Through activation of its TrkA receptor, NGF activates signalling pathways, including phospholipase Cgamma (PLCgamma), phosphatidyl-inositol 3-kinase (PI3K), the small G protein Ras, and mitogen-activated protein kinases (MAPK). Through its p75NTR receptor, NGF activates proapoptotic signalling pathways including the MAPK c-Jun N-terminal kinase (JNK), ceramides, and the small G protein Rac, but also activates pathways promoting cell survival through the transcription factor nuclear factor-kappaB (NF-kappaB). NGF was first described by Rita Levi-Montalcini and collaborators as an important factor involved in nerve differentiation and survival. Another role for NGF has since been established in inflammation, in particular of the airways, with increased NGF levels in chronic inflammatory diseases. In this review, we will first describe NGF structure and synthesis and NGF receptors and their signalling pathways. We will then provide information about NGF in the airways, describing its expression and regulation, as well as pointing out its potential role in inflammation, hyperresponsiveness, and remodelling process observed in airway inflammatory diseases, in particular in asthma.

NGF up-regulates TRPA1: implications for orofacial pain

The transient receptor potential ankyrin repeat 1 (TRPA1) channel is believed to be involved in many forms of acute and chronic hyperalgesia. Nerve Growth Factor (NGF) regulates chronic inflammatory hyperalgesia by controlling gene expression in sensory neurons, including genes involved in inflammatory hyperalgesia in the dental pulp. We hypothesized that NGF increases functional activities of the TRPA1 channel in trigeminal ganglion neurons. Here, we show that NGF induced a concentration- and time-dependent up-regulation of TRPA1 mRNA in trigeminal ganglia neurons, as detected by real-time RT-PCR and in situ hybridization. In addition, NGF evoked a time-dependent increase of mustard oil (MO)-evoked TRPA1 activation in trigeminal ganglia neurons. Collectively, these findings demonstrate that NGF participates in the functional up-regulation of TRPA1 in trigeminal ganglia neurons. These enhanced activities of TRPA1 could play an important role in the development of hyperalgesia following nerve injury and inflammation in the orofacial region.

Up-regulation of nerve growth factor and interleukin-10 in inflamed and non-inflamed intestinal segments in rats with experimental colitis

Inflammatory bowel diseases are characterized by dysregulated immune response to the normal microflora and structural and functional changes of the enteric nervous system which occur in inflamed as well as non-inflamed areas of the bowel. This study describes the changes in the expression of nerve growth factor (NGF) and interleukin-10 (IL-10) in the colon and in various segments of the small intestine in two rat models of experimental colitis induced by iodoacetamide or 2,4,6-trinitrobenzene sulfonic acid (TNBS). Levels of NGF and IL-10 were measured by ELISA in tissue homogenate sampled from duodenum, jejunum, ileum and colon at different time intervals. NGF and IL-10 increased significantly in homogenates of strips isolated from all small intestinal segments, 3-6h after iodoacetamide or TNBS administration and remained elevated until the colonic inflammation subsided. Similar but more pronounced increase occurred in areas of the colon adjacent to the ulcer. Histologic examinations revealed inflammatory changes in the colon; however, examination of sections from the small intestines did not reveal significant differences between controls and rats with colitis. The marked up-regulation of nerve growth factor and interleukin-10 in colitis suggests that they play a role in limiting or resolving inflammation and in preventing it from becoming uncontrolled. It also suggests that experimental colitis may be associated with latent inflammation in the small bowel.

The role of mast cells in atopy: what can we learn from canine models? A thorough review of the biology of mast cells in canine and human systems

Mast cell research has largely focused on the role of these cells in the early phase of allergic reactions. However, their involvement may well extend beyond this stage, and even reach across nonallergic conditions. Mast cells from different sources have helped advance our knowledge of their biology. Although in vitro and in vivo research in this area has mainly focused on humans, such studies are limited by the extent to which cells from certain human tissues and/or human patients can be collected or studied. While rodents also provide valuable models with which to further our understanding of the behaviour of mast cells and their contribution to allergy, reported differences between human and murine mast cells, and, in some instances, the limitations of in vivo rodent models of mast cell-mediated allergic conditions, preclude their use. In this review, we introduce a relatively unknown mast cell population, that of the dog. Canine mast cells display many phenotypic and functional similarities with their human counterparts, and dogs develop spontaneous and induced allergic diseases that share clinical and pathophysiological features with the human condition. Therefore, the use of canine cells can shed light on the general role of mast cells, particularly in relation to allergic diseases given the potential of in vivo dog models within this field. Here we provide a detailed review of the data reported from in vitro and in vivo studies of canine mast cells, and compare them with results obtained in human systems. We also highlight direct evidence of the mast cell contribution to canine atopy. We conclude that the dog offers useful in vitro and in vivo models in which to investigate mast cell behaviour, and that its use should be considered when undertaking studies aimed either at elucidating the role of mast cells in health and disease, or at prescreening novel therapies prior to entry into man.

Airway hyper-responsiveness in allergic asthma in guinea-pigs is mediated by nerve growth factor via the induction of substance P: a potential role for trkA

BACKGROUND

The neurotrophin nerve growth factor (NGF) has been implicated as a mediator in allergic asthma. Direct evidence that inhibition of NGF-induced activation of neurotrophin receptors leads to improvement of airway symptoms is lacking. We therefore studied the effects of inhibitors of NGF signal transduction on the development of airway hyper-responsiveness (AHR) and pulmonary inflammation in a guinea-pig model for allergic asthma.

METHODS

Airway responsiveness to the contractile agonist histamine was measured in vivo in guinea-pigs that were sensitized and challenged with ovalbumin (OVA). Inflammatory cell influx and NGF levels were determined in bronchoalveolar lavage fluid (BALF). Substance P, a key mediator of inflammation, was measured in lung tissue by radioimmunoassay, while substance P immunoreactive neurons in nodose ganglia were measured by immunohistochemistry.

RESULTS

OVA challenge induced an AHR after 24 h in OVA-sensitized guinea-pigs. This coincided with an increase in the amount of NGF in BALF. Simultaneously, an increase in the percentage of substance P immunoreactive neurons in the nodose ganglia and an increase in the amount of substance P in lung tissue were found. We used tyrosine kinase inhibitors to block the signal transduction of the high-affinity NGF receptor, tyrosine kinase A (trkA). Treatment with the tyrosine kinase inhibitors (K252a or tyrphostin AG879) both inhibited the development of AHR, and prevented the increase in substance P in the nodose ganglia and lung tissue completely whereas both inhibitors had no effect on baseline airway resistance. Neither treatment with K252a or tyrphostin AG879 changed the influx of inflammatory cells in the BALF due to allergen challenge.

CONCLUSIONS

We conclude that substance P plays a role in the induction of AHR in our model for allergic asthma which is most likely mediated by NGF. As both tyrosine kinase inhibitors AG879 and K252a show a similar inhibitory effect on airway function after allergen challenge, although both tyrosine kinase inhibitors exhibit different non-specific inhibitory effects on targets other than trkA tyrosine kinases, it is likely that the induction of substance P derived from sensory nerves is mediated by NGF via its high-affinity receptor trkA.

Relationship of serum brain-derived neurotrophic factor level with other markers of disease severity in patients with atopic dermatitis

Elevated serum levels of neurotrophins such as nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) have been reported in allergic and autoimmune diseases. The aim of this study was to assess serum levels of BDNF in patients with atopic dermatitis (AD) and to investigate the relationship of the BDNF level with other markers of disease severity. Serum BDNF concentration was significantly higher in patients with AD (n=62) compared to control subjects (n=20) (P<0.01). Stepwise multiple regression analysis showed a significant influence of the peripheral blood eosinophil counts (F=6.90) and the percentage of CD4(+)IL-4(+) (Th2) cells (F=6.61). Moreover, after remission of AD patients with conventionally treated AD patients (n=14), serum levels of BDNF, eosinophil counts and percentage of Th2 cells were decreased significantly. These results suggest that serum BDNF may be a useful marker of disease activity in AD and that both eosinophils and Th2 cells are major cellular sources of serum BDNF.

Mast cell mediators in allergic inflammation and mastocytosis

Mast cells possess an array of potent inflammatory mediators capable of inducing acute symptoms after cell activation, including urticaria, angioedema, bronchoconstriction, diarrhea, vomiting, hypotension, cardiovascular collapse, and death in few minutes. In contrast, mast cells can provide an array of beneficial mediators in the setting of acute infections, cardiovascular diseases, and cancer. The balance between the detrimental and beneficial roles of mast cells is not completely understood. Although the symptoms of acute mast cell mediator release can be reversed with epinephrine, adrenergic agonists, and mediator blockers, the continued release of histamine, proteases, prostaglandins, leukotrienes, cytokines, and chemokines leads to chronic and debilitating disease, such as mastocytosis. Identification of the molecular factors and mechanisms that control the synthesis and release of mast cell mediators should benefit all patients with mast cell activation syndromes and mastocytosis.

Pathways involved in gut mucosal barrier dysfunction induced in adult rats by maternal deprivation: corticotrophin-releasing factor and nerve growth factor interplay

Neonatal maternal deprivation (NMD) increases gut paracellular permeability (GPP) through mast cells and nerve growth factor (NGF), and modifies corticotrophin-releasing factor (CRF) and corticosterone levels. CRF, corticosterone and mast cells are involved in stress-induced mucosal barrier impairment. Consequently, this study aimed to specify whether corticosteronaemia and colonic expression of both preproCRF and CRF are modified by NMD, and to determine if altered expression may participate in the elevated GPP in connection with NGF and mast cells. Male Wistar rat pups were either separated from postnatal days 2-14, or left undisturbed with their dam. At 12 weeks of age, adult rats were treated with mifepristone (an antagonist of corticoid receptors), alpha-helical CRF((9-41)) (a non-specific CRF receptor antagonist), or SSR-125543 (CRF-R(1) receptor antagonist). We also determined corticosteronaemia and both colonic preproCRF and CRF expression. Then, control rats were treated by CRF, doxantrazole (mast cell stabilizer), BRX-537A (a mast cell activator) and anti-NGF antibody. NMD did not modify colonic CRF level but increased colonic preproCRF expression and corticosteronaemia. Peripheral CRF, via CRF-R(1) receptor, but not corticosterone, was involved in the elevated GPP observed in these rats, through a mast-cell-mediated mechanism, since the increase of GPP induced by exogenous CRF was abolished by doxantrazole. Anti-NGF antibody treatment also reduced the elevated GPP induced by CRF or BRX-537A. CRF acts through CRF-R(1) receptors to stimulate NGF release from mast cells, which participates in the elevated GPP observed in NMD adult rats. This suggests that early traumatic experience induced neuro-endocrine dysfunction, involved in alterations of gut mucosal barrier.

Nerve growth factor immunoreactivity of mast cells in acute involuted human thymus

The acute involution of the thymus is induced by either exogenous or endogenous factors, including some infections (infection type involution). The present study was focused on both detection and immunocytochemical analysis of NGF immunopositive mast cells in child thymus with acute infection-induced involution. Autopsy thymus specimens from children with infection diseases (Sepsis, Encephalomyelitis, Varicella) were examined at light and electron microscopic level and compared to normal infantile thymuses. We observed a redistribution of NGF immunopositive mast cells in infection-affected child thymus, which lobular architecture was collapsed. A positive correlation between the degree of the involutive changes, increased distribution and enhanced NGF immunoreactivity of mast cells was defined. The possible involvement of NGF immunopositive mast cells in the process of acute thymus involution is discussed.

The contribution of neurotrophins to the pathogenesis of allergic asthma

The neurotrophins nerve growth factor, brain-derived neurotrophic factor, NT-3 (neurotrophin 3) and NT-4 are known for regulating neuron development, function and survival. Beyond this, neurotrophins were found to exert multiple effects on non-neuronal cells such as immune cells, smooth muscle and epithelial cells. In allergic asthma, airway inflammation, airway obstruction, AHR (airway hyperresponsiveness) and airway remodelling are characteristic features, indicating an intensive interaction between neuronal, structural and immune cells in the lung. In allergic asthma patients, elevated neurotrophin levels in the blood and locally in the lung are commonly observed. Additionally, structural cells of the lung and immune cells, present in the lung during airway inflammation, were shown to be capable of neurotrophin production. A functional relationship between neurotrophins and the main features of asthma was revealed, as airway obstruction, airway inflammation, AHR and airway remodelling were all shown to be stimulated by neurotrophins. The aim of the present review is to provide an overview of neurotrophin sources and target cells in the lung, concerning their possible role as mediators between structural cells, immune cells and neurons, connecting the different features of allergic asthma.

Non-adenine based purines accelerate wound healing

Wound healing is a complex sequence of cellular and molecular processes that involves multiple cell types and biochemical mediators. Several growth factors have been identified that regulate tissue repair, including the neurotrophin nerve growth factor (NGF). As non-adenine based purines (NABPs) are known to promote cell proliferation and the release of growth factors, we investigated whether NABPs had an effect on wound healing. Full-thickness, excisional wound healing in healthy BALB/c mice was significantly accelerated by daily topical application of NABPs such as guanosine (50% closure by days 2.5′.8). Co-treatment of wounds with guanosine plus anti-NGF reversed the guanosine-promoted acceleration of wound healing, indicating that this effect of guanosine is mediated, at least in part, by NGF. Selective inhibitors of the NGF-inducible serine/threonine protein kinase (protein kinase N), such as 6-methylmercaptopurine riboside abolished the acceleration of wound healing caused by guanosine, confirming that activation of this enzyme is required for this effect of guanosine. Treatment of genetically diabetic BKS.Cg-m+/+lepr db mice, which display impaired wound healing, with guanosine led to accelerated healing of skin wounds (25% closure by days 2.8′.0). These results provide further confirmation that the NABP-mediated acceleration of cutaneous wound healing is mediated via an NGF-dependent mechanism. Thus, NABPs may offer an alternative and viable approach for the treatment of wounds in a clinical setting.

The NK1 Receptor Antagonist SR140333 Inhibits Capsaicin-Induced ERK Phosphorylation in Sensory Neurons

Primary sensory neurons respond to a vigorous excitation via the capsaicin receptor/TRPV1 cation channel by a phosphorylation of the Jak/STAT pathway as measured by phospho-STAT3, and of the Ras/Raf-MAPK pathway as measured by phospho-MAPK/ERK1/2. In the present investigation a possible involvement of NK1 receptors in the capsaicin-induced activation of these signal transduction pathways was investigated by protein extraction and Western immunoblotting. Phospho-MAPK/ERK1/2 and phospho-STAT3 were determined in the dorsal root ganglia (DRG) and in the sciatic nerve of rats at 3 and 6 h following a systemic capsaicin treatment without or with the pretreatment of the selective NK1 receptor antagonist SR140333 (1 mg/kg s.c.; 3 h before capsaicin). Capsaicin evoked a threefold increase in phospho-ERK in the sciatic nerve and a two- to threefold increase in the DRG at 3 h and 6 h after the treatment. SR140333 markedly attenuated the capsaicin-induced increase in phosphorylated ERK. In the sciatic nerve the difference was significant at each individual time point (3 and 6 h, p < 0.001). In the DRG the difference was significant when the data at 3 h and 6 h were combined (p < 0.05), but not when individual time points were considered. Capsaicin evoked a four- to fivefold increase in phospho-STAT3 in the sciatic nerve and a twofold increase in the DRG at 3 and 6 h after the treatment. SR140333 less markedly attenuated the capsaicin-induced increase in phosphorylated STAT3: whereas in the sciatic nerve the difference was significant when the data at 3 h and 6 h were combined (p < 0.05), no such treatment effect of SR140333 was observed in the DRG. The expression of TRPV1 mRNA, a specific marker of capsaicin-sensitive small sensory neurons, was investigated by RT-PCR 4 days after the capsaicin treatment. Treatment of rats with SR140333 had no influence on the long-term downregulation of TRPV1 mRNA by capsaicin. Based on the present results and previous findings it can be postulated that the capsaicin-induced ERK phosphorylation in sensory neurons is not a direct effect by capsaicin, but that rather substance P release from the stimulated sensory neurons with an NK1-mediated nerve growth factor (NGF) production is involved.

Plasticity of peripheral mechanisms of cough

The cough reflex pathway is characterized by a remarkable plasticity often resulting in a persistent and uncontrollable urge to cough during airway inflammation. In many instances cough becomes up regulated to the extent that ceases to fulfill its defensive role in protecting the airways. The exact mechanisms underlying this plasticity are unknown and likely involves a variety of factors influencing the function of the peripheral and central nervous system. This review outlines the evidence of increased cough sensitivity during airway disease. This is followed by a discussion of the peripheral mechanisms involved including the potential role of inflammatory mediators, neutrophins and changes in the airway mucosal structure. A greater understanding of the mechanisms leading to enhanced cough should lead to the development of more effective therapeutic strategies.

Molecular, genetic, and cellular pathogenesis of neurofibromas and surgical implications

Neurofibromatosis 1 (NF1) is a common autosomal dominant disease characterized by complex and multicellular neurofibroma tumors. Significant advances have been made in the research of the cellular, genetic, and molecular biology of NF1. The NF1 gene was identified by positional cloning. The functions of its protein product, neurofibromin, in RAS signaling and in other signal transduction pathways are being elucidated, and the important roles of loss of heterozygosity and haploinsufficiency in tumorigenesis are better understood. The Schwann cell was discovered to be the cell of origin for neurofibromas, but understanding of a more complicated interplay of multiple cell types in tumorigenesis, specifically recruited heterogeneous cell types such as mast cells and fibroblasts, has important implications for surgical therapy of these tumors. This review summarizes the most recent NF1 and neurofibroma literature describing the pathogenesis and treatment of nerve sheath tumors. Understanding the biological underpinnings of tumorigenesis in NF1 has implications for future surgical and medical management of neurofibromas.

Regulation of early and delayed radiation responses in rat small intestine by capsaicin-sensitive nerves

PURPOSE

Mast cells protect against the early manifestations of intestinal radiation toxicity, but promote chronic intestinal wall fibrosis. Intestinal sensory nerves are closely associated with mast cells, both anatomically and functionally, and serve an important role in the regulation of mucosal homeostasis. This study examined the effect of sensory nerve ablation on the intestinal radiation response in an established rat model.

METHODS AND MATERIALS

Rats underwent sensory nerve ablation with capsaicin or sham ablation. Two weeks later, a localized segment of ileum was X-irradiated or sham irradiated. Structural, cellular, and molecular changes were examined 2 weeks (early injury) and 26 weeks (chronic injury) after irradiation. The mast cell dependence of the effect of sensory nerve ablation on intestinal radiation injury was assessed using c-kit mutant (Ws/Ws) mast cell-deficient rats.

RESULTS

Capsaicin treatment caused a baseline reduction in mucosal mast cell density, crypt cell proliferation, and expression of substance P and calcitonin gene-related peptide, two neuropeptides released by sensory neurons. Sensory nerve ablation strikingly exacerbated early intestinal radiation toxicity (loss of mucosal surface area, inflammation, intestinal wall thickening), but attenuated the development of chronic intestinal radiation fibrosis (collagen I accumulation and transforming growth factor beta immunoreactivity). In mast cell-deficient rats, capsaicin treatment exacerbated postradiation epithelial injury (loss of mucosal surface area), but none of the other aspects of radiation injury were affected by capsaicin treatment.

CONCLUSIONS

Ablation of capsaicin-sensitive enteric neurons exacerbates early intestinal radiation toxicity, but attenuates development of chronic fibroproliferative changes. The effect of capsaicin treatment on the intestinal radiation response is partly mast cell dependent.

Nerve Growth Factor Translates Stress Response and Subsequent Murine Abortion via Adhesion Molecule-Dependent Pathways1

Spontaneous abortion is a frequent threat affecting 10%-25% of human pregnancies. Psychosocial stress has been suggested to be attributable for pregnancy losses by challenging the equilibrium of systems mandatory for pregnancy maintenance, including the nervous, endocrine, and immune system. Strong evidence indicates that stress-triggered abortion is mediated by adhesion molecules, i.e., intercellular adhesion molecule 1 (ICAM1) and leukocyte function associated molecule 1, now being referred to as integrin alpha L (ITGAL), which facilitate recruitment of inflammatory cells to the feto-maternal interface. The neurotrophin beta-nerve growth factor (NGFB), which has been shown to be upregulated in response to stress in multiple experimental settings including in the uterine lining (decidua) during pregnancy, increases ICAM1 expression on endothelial cells. Here, we investigated whether and how NGFB neutralization has a preventive effect on stress-triggered abortion in the murine CBA/J x DBA/2J model. We provide experimental evidence that stress exposure upregulates the frequency of abortion and the expression of uterine NGFB. Further, adhesion molecules ICAM1 and selectin platelet (SELP, formerly P-Selectin) and their ligands ITGAL and SELP ligand (SELPL, formerly P selectin glycoprotein ligand 1) respectively increase in murine deciduas in response to stress. Subsequently, decidual cytokines are biased toward a proinflammatory and abortogenic cytokine profile. Additionally, a decrease of pregnancy protective CD8alpha(+) decidual cells is present. Strikingly, all such uterine stress responses are abrogated by NGFB neutralization. Hence, NGFB acts as a proximal mediator in the hierarchical network of immune rejection by mediating an abortogenic environment comprised of classical signs of neurogenic inflammation.

How exposures to biologics influence the induction and incidence of asthma

A number of environmental factors can affect the development and severity of allergy and asthma; however, it can be argued that the most significant inhaled agents that modulate the development of these conditions are biologics. Sensitization to environmental allergens is an important risk factor for the development of asthma. Innate immune responses are often mediated by receptors on mononuclear cells whose primary ligands arise from microorganisms. Many pathogens, especially viruses, target epithelial cells and affect the host immune response to those pathogens. The acquired immune response to an allergen is influenced by the nature of the innate immune system. Products of innate immune responses to microbes promote T(H)1-acquired responses. In the absence of T(H)1 responses, T(H)2 responses can dominate. Central to T(H)1/T(H)2 balance is the composition of contaminants that derive from microbes. In this review we examine the biology of the response to allergens, viruses, and bacterial products in the context of the development of allergy and asthma.

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

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

Human lung fibroblast response to NGF, IL-1beta, and dexamethsone

It has been shown that lung mast cells, eosinophils, and fibroblasts are receptive to the action of nerve growth factor (NGF) and that NGF is released in to the bloodstream of subjects affected by allergic inflammatory response. The role of NGF in lung inflammatory disorders is unclear because there is evidence suggesting that NGF can be involved in both proinflammatory and anti-inflammatory responses. Lung fibroblasts play a marked role in inflammation. In this study we investigated the effect of NGF, interleukin 1beta (II-1beta), and dexamethasone (DEX) on human lung fibroblasts in vitro. We found that II-1beta, but not NGF, promotes fibroblasts' survival and that NGF stimulates trkA receptor expression, down regulates TFG-alpha, and has no effect on TNF-beta immunoreactivity. Moreover, DEX exerts different effects on NGF release by fibroblasts pre-exposed to II-1gamma. Our findings suggest that the NGF released by lung fibroblast during inflammation is not associated with the increase of proinflammatory factors such as TNF-alpha and II-1beta.

Hair growth inhibition by psychoemotional stress: a mouse model for neural mechanisms in hair growth control

Stress has long been discussed controversially as a cause of hair loss. However, solid proof of stress-induced hair growth inhibition had long been missing. If psychoemotional stress can affect hair growth, this must be mediated via definable neurorendocrine and/or neuroimmunological signaling pathways. Revisiting and up-dating relevant background data on neural mechanisms of hair growth control, we sketch essentials of hair follicle (HF) neurobiology and discuss the modulation of murine hair growth by neuropeptides, neurotransmitters, neurotrophins, and mast cells. Exploiting an established mouse model for stress, we summarize recent evidence that sonic stress triggers a cascade of molecular events including plasticity of the peptidergic peri- and interfollicular innervation and neuroimmune crosstalk. Substance P (SP) and NGF (nerve growth factor) are recruited as key mediators of stress-induced hair growth-inhibitory effects. These effects include perifollicular neurogenic inflammation, HF keratinocyte apoptosis, inhibition of proliferation within the HF epithelium, and premature HF regression (catagen induction). Intriguingly, most of these effects can be abrogated by treatment of stressed mice with SP-receptor neurokinin-1 receptor (NK-1) antagonists or NGF-neutralizing antibodies - as well as, surprisingly, by topical minoxidil. Thus there is now solid in vivo-evidence for the existence of a defined brain- HF axis. This axis can be utilized by psychoemotional and other stressors to prematurely terminate hair growth. Stress-induced hair growth inhibition can therefore serve as a highly instructive model for exploring the brain-skin connection and provides a unique experimental model for dissecting general principles of skin neuroendocrinology and neuroimmunology well beyond the HF.

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.