Calcitonin gene-related peptide is chemotactic for human T lymphocytes

The Effects of Calcitonin Gene-Related Peptide on Bone Homeostasis and Regeneration

PURPOSE OF REVIEW

The goals of this review are two folds: (1) to describe the recent understandings on the roles of calcitonin gene-related peptide-α (CGRP) in bone homeostasis and the underlying mechanisms of related neuronal regulation and (2) to propose innovative CGRP-modulated approaches for enhancing bone regeneration in challenging bone disorders.

RECENT FINDINGS

CGRP is predominantly produced by the densely distributed sensory neuronal fibers in bone, declining with age. Under mechanical and biochemical stimulations, CGRP releases and exerts either physiological or pathophysiological roles. CGRP at physiological level orchestrates the communications of bone cells with cells of other lineages, affecting not only osteogenesis, osteoclastogenesis, and adipogenesis but also angiogenesis, demonstrating with pronounced anabolic effect, thus is essential for maintaining bone homeostasis, with tuned nerve-vessel-bone network. In addition, its effects on immunity and cell recruitment are also crucial for bone fracture healing. Binding to the G protein-coupled receptor composited by calcitonin receptor-like receptor (CRLR) and receptor activity modifying protein 1 (RAMP1) on cellular surface, CGRP triggers various intracellular signaling cascades involving cyclic adenosine monophosphate (cAMP) and cAMP response element-binding protein (CREB). Peaking at early stage post-fracture, CGRP promotes bone formation, displaying with larger callus. Then CGRP gradually decreases over time, allowing normal or physiological bone remodeling. By elevating CGRP at early stage, low-intensity pulsed ultrasound (LIPUS), electrical stimulation, and magnesium-based bio-mineral products may promisingly accelerate bone regeneration experimentally in medical conditions like osteoporosis, osteoporotic fracture, and spine fusion. Excess CGRP expression is commonly observed in pathological conditions including cancer metastatic lesions in bone and fracture delayed- or non-healing, resulting in persistent chronic pain. To date, these discoveries have largely been limited to animal models. Clinical applications are highly desirable. Compelling evidence show the anabolic effects of CGRP on bone in animals. However, further validation on the role of CGRP and the underlying mechanisms in human skeletons is required. It remains unclear if it is type H vessel connecting neuronal CGRP to osteogenesis, and if there is only specific rather than all osteoprogenitors responsible to CGRP. Clear priority should be put to eliminate these knowledge gaps by integrating with high-resolution 3D imaging of transparent bulk bone and single-cell RNA-sequencing. Last but not the least, given that small molecule antagonists such as BIBN4096BS can block the beneficial effects of CGRP on bone, concerns on the potential side effects of humanized CGRP-neutralizing antibodies when systemically administrated to treat migraine in clinics are arising.

Dental nerves: a neglected mediator of pulpitis

As one of the most densely innervated tissues, the dental pulp contains abundant nerve fibres, including sensory, sympathetic and parasympathetic nerve fibres. Studies in animal models and human patients with pulpitis have revealed distinct alterations in protein expression and histological appearance in all types of dental nerve fibres. Various molecules secreted by neurons, such as classical neurotransmitters, neuropeptides and amino acids, not only contribute to the induction, sensitization and maintenance of tooth pain, but also regulate non-neuronal cells, including fibroblasts, odontoblasts, immune cells and vascular endothelial cells. Dental nerves are particularly important for the microcirculatory and immune responses in pulpitis via their release of a variety of functional substances. Further, nerve fibres are found to be involved in dental soft and hard tissue repair. Thus, understanding how dental nerves participate in pulpitis could have important clinical ramifications for endodontic treatment. In this review, the roles of dental nerves in regulating pulpal inflammatory processes are highlighted and their implications for future research on this topic are discussed.

A promising therapeutic target for psoriasis: Neuropeptides in human skin

Psoriasis is a chronic inflammatory skin disease featured by excessive proliferation of keratinocytes, clearly defined round erythema and dry, scaly plaques, long-term inflammatory cells infiltration in skin lesions. However, the physiopathological mechanism of psoriasis is still not clearly understood. Neuropeptides, a class of peptides secreted by the nervous system, may play important roles in promoting excessive proliferation of keratinocyte, enhancing angiogenesis, vasodilation, plasma extravasation and chemotaxis of inflammatory cells during the development of psoriasis. To understand the pathogenesis of neuropeptides in psoriasis, we summarized the function of several common neuropeptides in psoriasis and hypothesize neuropeptides may serve as therapeutic potential novel targets in psoriasis.

Intimate neuro-immune interactions: breaking barriers between systems to make meaningful progress

The nervous system is often viewed as an isolated system that integrates information from the environment and host. Recently, there has been a renewed focus exploring the concept that the nervous system also communicates across biological systems. Specifically, several high profile studies have recently highlighted the importance of neuro-immune communication in the context of homeostasis, central nervous system disorders, host defense and injury. Here, we discuss the history of shared mechanisms and interconnectedness of the nervous, immune and epithelial compartments. In light of these overlapping mechanisms, it is perhaps unsurprising that neuro-immune-epithelial signaling plays a key role in regulating diverse biological phenomena. In this review, we explore recent breakthroughs in understanding neuro-immune signaling to highlight the importance of interdisciplinary approaches to biomedical research and the future development of novel therapeutics.

Autonomic nerve dysfunction and impaired diabetic wound healing: The role of neuropeptides

Lower extremity ulcerations represent a major complication in diabetes mellitus and involve multiple physiological factors that lead to impairment of wound healing. Neuropeptides are neuromodulators implicated in various processes including diabetic wound healing. Diabetes causes autonomic and small sensory nerve fibers neuropathy as well as inflammatory dysregulation, which manifest with decreased neuropeptide expression and a disproportion in pro- and anti- inflammatory cytokine response. Therefore to fully understand the contribution of autonomic nerve dysfunction in diabetic wound healing it is crucial to explore the implication of neuropeptides. Here, we will discuss recent studies elucidating the role of specific neuropeptides in wound healing.

Disruption of calcitonin gene-related peptide signaling accelerates muscle denervation and dampens cytotoxic neuroinflammation in SOD1 mutant mice

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron disease. Neuronal vacuolization and glial activation are pathologic hallmarks in the superoxide dismutase 1 (SOD1) mouse model of ALS. Previously, we found the neuropeptide calcitonin gene-related peptide (CGRP) associated with vacuolization and astrogliosis in the spinal cord of these mice. We now show that CGRP abundance positively correlated with the severity of astrogliosis, but not vacuolization, in several motor and non-motor areas throughout the brain. SOD1 mice harboring a genetic depletion of the βCGRP isoform showed reduced CGRP immunoreactivity associated with vacuolization, while motor functions, body weight, survival, and astrogliosis were not altered. When CGRP signaling was completely disrupted through genetic depletion of the CGRP receptor component, receptor activity-modifying protein 1 (RAMP1), hind limb muscle denervation, and loss of muscle performance were accelerated, while body weight and survival were not affected. Dampened neuroinflammation, i.e., reduced levels of astrogliosis in the brain stem already in the pre-symptomatic disease stage, and reduced microgliosis and lymphocyte infiltrations during the late disease phase were additional neuropathology features in these mice. On the molecular level, mRNA expression levels of brain-derived neurotrophic factor (BDNF) and those of the anti-inflammatory cytokine interleukin 6 (IL-6) were elevated, while those of several pro-inflammatory cytokines found reduced in the brain stem of RAMP1-deficient SOD1 mice at disease end stage. Our results thus identify an important, possibly dual role of CGRP in ALS pathogenesis.

Steroid Treatment Reduces Allergic Airway Inflammation and Does Not Alter the Increased Numbers of Dendritic Cells and Calcitonin Gene-Related Peptide-Expressing Neurons in Airway Sensory Ganglia

OBJECTIVES

Our previous data demonstrated that allergic airway inflammation induces migration of dendritic cells (DC) into airway sensory jugular and nodose ganglia (jugular-nodose ganglion complex; JNC). Here we investigated the effects of steroid treatment regarding the expression and migration of DC and calcitonin gene-related peptide (CGRP)-immunoreactive neurons of vagal sensory ganglia during allergic airway inflammation.

METHODS

A house dust mite (HDM) model for allergic airway inflammation was used. The mice received 0.3 mg fluticasone propionate per kilogram of body weight in the last 9 days. JNC slices were analyzed on MHC II, the neuronal marker PGP9.5, and the neuropeptide CGRP.

RESULTS

Allergic airway inflammation increased the numbers of DC and CGRP-expressing neurons in the JNC significantly in comparison to the controls (DC/neurons: HDM 44.58 ± 1.6% vs. saline 33.29 ± 1.6%, p < 0.05; CGRP-positive neurons/total neurons: HDM 30.65 ± 1.9% vs. saline 19.49 ± 2.3%, p < 0.05). Steroid treatment did not have any effect on the numbers of DC and CGRP-expressing neurons in the JNC compared to HDM-treated mice.

CONCLUSIONS

The present findings indicate an important role of DC and CGRP-containing neurons in the pathogenesis of allergic airway inflammation. However, steroid treatment did not have an effect on the population of DC and neurons displaying CGRP in the JNC, whereas steroid treatment was found to suppress allergic airway inflammation.

Tapping into the endocannabinoid system to ameliorate acute inflammatory flares and associated pain in mouse knee joints

Introduction

During the progression of rheumatoid arthritis (RA), there are frequent but intermittent flares in which the joint becomes acutely inflamed and painful. Although a number of drug therapies are currently used to treat RA, their effectiveness is variable and side effects are common. Endocannabinoids have the potential to ameliorate joint pain and inflammation, but these beneficial effects are limited by their rapid degradation. One enzyme responsible for endocannabinoid breakdown is fatty acid amide hydrolase (FAAH). The present study examined whether URB597, a potent and selective FAAH inhibitor, could alter inflammation and pain in a mouse model of acute synovitis.

Methods

Acute joint inflammation was induced in male C57BL/6 mice by intra-articular injection of 2% kaolin/2% carrageenan. After 24 hr, articular leukocyte kinetics and blood flow were used as measures of inflammation, while hindlimb weight bearing and von Frey hair algesiometry were used as measures of joint pain. The effects of local URB597 administration were then determined in the presence or absence of either the cannabinoid (CB)1 receptor antagonist AM251, or the CB2 receptor antagonist AM630.

Results

URB597 decreased leukocyte rolling and adhesion, as well as inflammation-induced hyperaemia. However, these effects were only apparent at low doses and the effects of URB597 were absent at higher doses. In addition to the anti-inflammatory effects of URB597, fatty acid amide hydrolase (FAAH) inhibition improved both hindlimb weight bearing and von Frey hair withdrawal thresholds. The anti-inflammatory effects of URB597 on leukocyte rolling and vascular perfusion were blocked by both CB1 and CB2 antagonism, while the effect on leukocyte adherence was independent of cannabinoid receptor activation. The analgesic effects of URB597 were CB1 mediated.

Conclusions

These results suggest that the endocannabinoid system of the joint can be harnessed to decrease acute inflammatory reactions and the concomitant pain associated with these episodes.

Allergic airway inflammation induces the migration of dendritic cells into airway sensory ganglia

BACKGROUND

A neuroimmune crosstalk between dendritic cells (DCs) and airway nerves in the lung has recently been reported. However, the presence of DCs in airway sensory ganglia under normal and allergic conditions has not been explored so far. Therefore, this study aims to investigate the localisation, distribution and proliferation of DCs in airway sensory ganglia under allergic airway inflammation.

METHODS

Using the house dust mite (HDM) model for allergic airway inflammation BALB/c mice were exposed to HDM extract intranasally (25 μg/50 μl) for 5 consecutive days a week over 7 weeks. With the help of the immunohistochemistry, vagal jugular-nodose ganglia complex (JNC) sections were analysed regarding their expression of DC-markers (MHC II, CD11c, CD103), the neuronal marker PGP 9.5 and the neuropeptide calcitonin gene-related peptide (CGRP) and glutamine synthetase (GS) as a marker for satellite glia cells (SGCs). To address the original source of DCs in sensory ganglia, a proliferation experiment was also carried in this study.

RESULTS

Immune cells with characteristic DC-phenotype were found to be closely located to SGCs and vagal sensory neurons under physiological conditions. The percentage of DCs in relation to neurons was significantly increased by allergic airway inflammation in comparison to the controls (HDM 51.38 ± 2.38% vs. control 28.16 ± 2.86%, p < 0.001). The present study also demonstrated that DCs were shown to proliferate in jugular-nodose ganglia, however, the proliferation rate of DCs is not significantly changed in the two treated animal groups (proliferating DCs/ total DCs: HDM 0.89 ± 0.38%, vs. control 1.19 ± 0.54%, p = 0.68). Also, increased number of CGRP-positive neurons was found in JNC after allergic sensitisation and challenge (HDM 31.16 ± 5.41% vs. control 7.16 ± 1.53%, p < 0.001).

CONCLUSION

The present findings suggest that DCs may migrate from outside into the ganglia to interact with sensory neurons enhancing or protecting the allergic airway inflammation. The increase of DCs as well as CGRP-positive neurons in airway ganglia by allergic airway inflammation indicate that intraganglionic DCs and neurons expressing CGRP may contribute to the pathogenesis of bronchial asthma. To understand this neuroimmune interaction in allergic airway inflammation further functional experiments should be carried out in future studies.

Calcitonin gene-related peptide is a key neurotransmitter in the neuro-immune axis

The question of how the neural and immune systems interact in host defense is important, integrating a system that senses the whole body with one that protects. Understanding the mechanisms and routes of control could produce novel and powerful ways of promoting and enhancing normal functions as well as preventing or treating abnormal functions. Fragmentation of biological research into specialities has resulted in some failures in recognizing and understanding interactions across different systems and this is most striking across immunology, hematology, and neuroscience. This reductionist approach does not allow understanding of the in vivo orchestrated response generated through integration of all systems. However, many factors make the understanding of multisystem cross-talk in response to a threat difficult, for instance the nervous and immune systems share communication molecules and receptors for a wide range of physiological signals. But, it is clear that physical, hard-wired connections exist between the two systems, with the key link involving sensory, unmyelinated nerve fibers (c fibers) containing the neuropeptide calcitonin gene-related peptide (CGRP), and modified macrophages, mast cells and other immune and host defense cells in various locations throughout the body. In this review we will therefore focus on the induction of CGRP and its key role in the neuroimmune axis.

Evidence for anti-inflammatory and putative analgesic effects of a monoclonal antibody to calcitonin gene-related peptide

BACKGROUND

Calcitonin gene-related peptide (CGRP) is a powerful pro-inflammatory mediator thought to play a significant role in the development of inflammation and pain. We investigated the role of CGRP in trigeminal inflammatory pain by determining the ability of a monoclonal antibody to CGRP to modify central Fos expression in response to stimulation of the inflamed ferret tooth pulp. We also assessed the effect of the antibody on pulpal inflammation.

METHODS

Ten adult ferrets were prepared under anaesthesia to allow stimulation of the upper and lower left canine pulps, recording from the digastric muscle and intravenous injections at subsequent experiments. In all animals, pulpal inflammation was induced by introducing human caries into a deep buccal cavity. Four days later animals were treated intravenously with either CGRP antibody (n=5) or vehicle (n=5). After a further 2 days animals were re-anaesthetised and the tooth pulps stimulated at 10 times jaw-opening reflex threshold. Brainstems and tooth pulps were processed immunohistochemically for Fos and the common leucocyte marker CD45, respectively.

RESULTS

Fos was expressed in ipsilateral trigeminal subnuclei caudalis (Vc) and oralis (Vo). Significantly fewer Fos-positive nuclei were present within Vc of CGRP antibody-treated animals (p=0.003 vs vehicle-treated). Mean percentage area of staining for CD45 was significantly less in antibody-treated animals (p=0.04 vs vehicle-treated).

CONCLUSIONS

This is the first direct evidence that sequestration of CGRP has anti-inflammatory and putative analgesic effects. Previous studies using this Fos model have demonstrated that it is able to predict clinical analgesic efficacy. Thus these data indicate that this antibody may have analgesic effects in dental pain and other types of inflammatory-mediated transmission, and suggest that this is in part due to peripheral anti-inflammatory effects.

CGRP1 receptor activation induces piecemeal release of protease-1 from mouse bone marrow-derived mucosal mast cells

BACKGROUND

The parasitized or inflamed gastrointestinal mucosa shows an increase in the number of mucosal mast cells (MMC) and the density of extrinsic primary afferent nerve fibers containing the neuropeptide, calcitonin gene-related peptide (CGRP). Currently, the mode of action of CGRP on MMC is unknown.

METHODS

The effects of CGRP on mouse bone marrow-derived mucosal mast cells (BMMC) were investigated by measurements of intracellular Ca(2+)[Ca(2+)](i) and release of mMCP-1.

KEY RESULTS

Bone marrow-derived mucosal mast cells responded to the application of CGRP with a single transient rise in [Ca(2+)](i). The proportion of responding cells increased concentration-dependently to a maximum of 19 ± 4% at 10(-5)mol L(-1) (mean ±SEM; C48/80 100%; EC(50)10(-8) mol L(-1) ). Preincubation with the CGRP receptor antagonist BIBN4096BS (10(-5) mol L(-1)) completely inhibited BMMC activation by CGRP [range 10(-5) to 10(-11) mol L(-1); analysis of variance (ANOVA) P < 0.001], while preincubation with LaCl(3) to block Ca(2+) entry did not affect the response (P = 0.18). The presence of the CGRP1 receptor on BMMC was confirmed by simultaneous immunofluorescent detection of RAMP1 or CRLR, the two components of the CGRP1 receptor, and mMCP-1. Application of CGRP for 1 h evoked a concentration-dependent release of mMCP-1 (at EC(50) 10% of content) but not of β-hexosaminidase and alterations in granular density indicative of piecemeal release.

CONCLUSIONS & INFERENCES

We demonstrate that BMMC express functional CGRP1 receptors and that their activation causes mobilization of Ca(2+) from intracellular stores and piecemeal release of mMCP-1. These findings support the hypothesis that the CGRP signaling from afferent nerves to MMC in the gastrointestinal wall is receptor-mediated.

Functional expression of the calcitonin receptor by human T and B cells

The calcitonin receptor (CTR) is a seven-transmembrane-domain G-protein-coupled receptor that regulates calcium metabolism and bone resorption by osteoclasts. Here we demonstrate that high levels are expressed by normal human T and B lymphocytes from tonsils and peripheral blood in relation to their activation status, as CTR(+) T cells are prone to produce IFN-gamma after TCR stimulation. The receptor is also highly expressed on B cells from chronic lymphocytic leukemia patients, thus suggesting a correlation between its expression, their proliferative extent as well as their memory, antigen-experienced phenotype. Moreover, we found that binding of the receptor with salmon calcitonin induces an increase of intracellular calcium(2+) in peripheral lymphocytes. This effect is involved in several lymphocyte immune functions, as cytosolic calcium(2+) levels regulate both cell proliferation and cytokine production. In our hands, the increase of calcium(2+) levels by CTR binding with sCT induced a dose-dependent cell proliferation. We therefore suppose that expression of this functional receptor may contribute to the modulation of cytoplasmic calcium(2+) levels needed to regulate T and B cell activation and perhaps other immune functions.

Inflammation and neuropeptides: the connection in diabetic wound healing

Abnormal wound healing is a major complication of both type 1 and type 2 diabetes, with nonhealing foot ulcerations leading in the worst cases to lower-limb amputation. Wound healing requires the integration of complex cellular and molecular events in successive phases of inflammation, cell proliferation, cell migration, angiogenesis and re-epithelialisation. A link between wound healing and the nervous system is clinically apparent as peripheral neuropathy is reported in 30-50% of diabetic patients and is the most common and sensitive predictor of foot ulceration. Indeed, a bidirectional connection between the nervous and the immune systems and its role in wound repair has emerged as one of the focal features of the wound-healing dogma. This review provides a broad overview of the mediators of this connection, which include neuropeptides and cytokines released from nerve fibres, immune cells and cutaneous cells. In-depth understanding of the signalling pathways in the neuroimmune axis in diabetic wound healing is vital to the development of successful wound-healing therapies.

Calcitonin gene-related peptide stimulates mitosis in the tip of the rat gubernaculum in vitro and provides the chemotactic signals to control gubernacular migration during testicular descent

BACKGROUND/AIMS

We investigated whether calcitonin gene-related peptide (CGRP) released from sensory genitofemoral nerve branches could stimulate rodent gubernacular growth and provide chemotactic signals for directing inguinoscrotal gubernaculum migration in vitro.

MATERIALS AND METHODS

Neonatal rat gubernacula containing a developing cremaster sac (n = 60) were removed at days 0, 2, 4, 6, 8, and 10 (n = 10 per age; n = 5 per experimental group) and placed in organ culture for 24 hours with or without added CGRP (720 nmol/L). The gubernacula were stained for bromodeoxyuridine (BrdU) immunohistochemistry. Cells were counted (3 x 100 cells) in the mesenchymal tip of the gubernaculum to find the percentage of BrdU uptake. A further group of neonatal rat gubernacula (n = 21 per group) were placed in organ culture on an agar platform with 5 agarose beads soaked in either PBS or 10(-6) mol/L CGRP placed approximately 0.8 to 1 mm on each side of the tip of the cremaster sac. After 72 hours, the position of the gubernaculum was compared with its starting position and any deviation measured.

RESULTS

Exogenous CGRP caused a significant increase in BrdU uptake in the tip of the gubernaculum in 0-day-old rats compared with control cultures. Two-way analysis of variance in the cellular proliferation pattern between gubernacula cultured +/- CGRP between 0 and 10 days showed a significant difference (P < .001). The cultures containing CGRP-impregnated beads caused significant (P < .01) deviation of the tip of the gubernaculum toward the beads, whereas the controls demonstrated no net movement of the tip.

CONCLUSIONS

These studies demonstrate that mitosis in the tip of the rat gubernaculum is significantly increased in response to CGRP in vitro. Also, CGRP may provide chemotactic signals to control inguinoscrotal gubernacular migration in the rat.

Expression and function of the calcitonin receptor by myeloma cells in their osteoclast-like activity in vitro

Malignant plasma cells exert osteoclast-like activity in vitro. We investigated the function of the calcitonin (CT) receptor (R) on myeloma cells from patients and in myeloma cell lines. Primary myeloma cells expressed high CTR levels whereas the cell lines uniformly exposed the CTR-2 variant expressed by osteoclasts. Treatment of myeloma cell lines with CT modified the intracellular Ca(2+) and cAMP levels, suggesting the activation of both PKC and PKA pathways, and abrogated their bone resorptive property as erosive pits on osteologic substrates. Thus, the expression, sensitivity and function of CTR-2 in myeloma cells emphasize their osteoclast-like behavior in vitro.

Plasma concentration of selected neuropeptides in patients suffering from psoriasis

The aim of this study was to evaluate plasma levels of substance P (SP), calcitonin gene-related peptide (CGRP), vasoactive intestinal peptide (VIP) and neuropeptide Y (NPY) during psoriasis course.

METHODS

Seventy-three patients with psoriasis and 32 healthy volunteers were included. Detailed demographic and disease anamnesis was obtained from every patient. The disease severity was assessed using the Psoriasis Area and Severity Index score. Plasma levels of SP, CGRP, VIP and NPY were measured radioimmunologically.

RESULTS

Plasma levels of SP and NPY did not significantly differ between patients with psoriasis and controls (median SP: 52.8 and 57.9 pg/ml, respectively; P = 0.32; median NPY: 8.5 and 8.2 pg/ml, respectively; P = 0.67). CGRP plasma concentration was significantly elevated in psoriatic individuals both before (median 43.1 pg/ml) and after treatment (median 45.4 pg/ml), in comparison with healthy donors (median 13.5 pg/ml; P < 0.01 and P = 0.03, respectively). Treatment did not significantly influence plasma CGRP levels (P = 0.3). Median VIP plasma concentration in psoriatics before treatment was significantly higher compared with healthy controls (medians 66.9 and 60.1 pg/ml, respectively; P = 0.04), but the therapy resulted in significant decrease in VIP plasma level (median 19.0 pg/ml; P < 0.001). In psoriatic patients significant correlations were noted between NPY and VIP (R = 0.34; P < 0.01), and VIP and CGRP plasma levels, both before (R = 0.28; P = 0.03) and after the treatment (R = 0.44; P < 0.01).

CONCLUSIONS

Based on our results and previous literature data it could be suggested that neuropeptides may be involved in the development of psoriatic lesions.

The bidirectional communication between neurons and mast cells within the gastrointestinal tract

Normal or disordered behaviour of the gastrointestinal tract is determined by a complex interplay between the epithelial barrier, immune cells, blood vessels, smooth muscle and intramurally located nerve elements. Mucosal mast cells (MMCs), which are able to detect noxious and antigenic threats and to generate or amplify signals to the other cells, are assigned a rather central position in this complex network. Signal input from MMCs to intrinsic enteric neurons is particularly crucial, because the enteric nervous system fulfils a pivotal role in the control of gastrointestinal functions. Activated enteric neurons are able to generate an alarm program involving alterations in motility and secretion. MMC signalling to extrinsic nerve fibres takes part in pathways generating visceral pain or extrinsic reflexes contributing to the disturbed motor and secretory function. Morphological and functional studies, especially studies concerning physiological stress, have provided evidence that, apart from the interaction between the enteric nervous system and MMCs, there is also a functional communication between the central nervous system and these mast cells. Psychological factors trigger neuronal pathways, which directly or indirectly affect MMCs. Further basic and clinical research will be needed to clarify in more detail whether basic patterns of this type of interactions are conserved between species including humans.

Neurogenic Aspects of Inflammation

The relationship between the inflammatory process and the nervous system is twofold. The nervous system is activated by inflammation which causes inflammatory pain and impaired motor function. Conversely, the nervous system acts back on the peripheral process. This is achieved by output systems at different levels, including primary afferent fibers (neurogenic inflammation), spinal cord (reflexes), and the brain (eg, neuroendocrine functions). This article first addresses the activation of the nociceptive system by inflammation; the second part describes the effects of the nervous system on inflamed tissue.

In vitro activation of murine DRG neurons by CGRP-mediated mucosal mast cell degranulation

Upregulation of CGRP-immunoreactive (IR) primary afferent nerve fibers accompanied by mastocytosis is characteristic for the Schistosoma mansoni-infected murine ileum. These mucosal mast cells (MMC) and CGRP-IR fibers, which originate from dorsal root (DRG) and nodose ganglia, are found in close apposition. We examined interactions between primary cultured MMC and CGRP-IR DRG neurons in vitro by confocal recording of intracellular Ca(2+) concentration ([Ca(2+)](i)). The degranulatory EC(50) for the mast cell secretagogue compound 48/80 (C48/80; 10 microg/ml) and the neuropeptides CGRP (2.10(-8) M) and substance P (SP; 3.10(-8) M) were determined by measurement of extracellular release of the granule chymase, mouse mast cell protease-1. Application of C48/80 (10 microg/ml) and CGRP and SP (both 10(-7) M) to Fluo-4-loaded MMC induced a transient rise in [Ca(2+)](i) after a lag time, indicative of mast cell degranulation and/or secretion. The CGRP response could be completely blocked by pertussis toxin (2 microg/ml), indicating involvement of G(i) proteins. Application of MMC juice, obtained by C48/80 degranulation of MMC, to Fluo-4-loaded DRG neurons induced in all neurons a rise in [Ca(2+)](i), indicative of activation. Degranulation of MMC by C48/80 in culture dishes containing Fluo-4-loaded DRG neurons also caused activation of the DRG neurons. In conclusion, these results demonstrate a bidirectional cross-talk between cultured MMC and CGRP-IR DRG neurons in vitro. This indicates that such a communication may be the functional relevance for the close apposition between MMC and CGRP-IR nerve fibers in vivo.

Vascular and cellular responses to pro-inflammatory stimuli in rat dental pulp

Dental pulp reactivity to various pro-inflammatory stimuli was independently evaluated in rats in terms of a vascular permeability increase and leukocyte recruitment. Substance P, calcitonin-gene related peptide (CGRP) and prostaglandin E(2) (in the picomol range) were applied to the exposed pulp from anesthetised animals and the plasma extravasation measured by the Evans blue content in the tissue following 10 min of administration. Leukocyte recruitment was evaluated morphometrically by counting the cell number present in serial sections of 1:3 4 microm pulp tissue 6 h after bacterial endotoxin (LPS; 0.06-1.2 microg/site) administration. Increase in pulp vascular permeability and cellular recruitment due to the injection of mentioned mediators in the skin or LPS in the peritoneal cavity were used as positive controls. Increase in vascular permeability in the pulp occurred in the same dose-range as observed in the skin, being CGRP the most active substance in both cases. However, it was necessary a higher dose of LPS (1.2 microg) to induce a similar cell recruitment in the pulp as that observed in the rat peritoneal cavity (0.3 microg). These data indicate that dental pulp reactivity presents the same pattern of increase in vascular permeability to other tissues in the rat, being CGRP the most potent mediator in this respect. In addition, they suggest the presence of CGRP receptors in the dental pulp. However, an adequate leukocyte recruitment response to bacterial endotoxin was not mounted, suggesting a deficiency in adhesion molecules in blood vessels in the rat dental pulp.

Tumour-cell migration, invasion, and metastasis: navigation by neurotransmitters

Cancer starts as a localised disease, which, if detected early, can often be treated successfully by removal of the primary tumour. A pernicious progression is the invasion of tumour cells into surrounding tissues, resulting in development of distant metastases. Because active migration of tumour cells is a prerequisite for tumour-cell invasion and metastasis, a pressing goal in tumour biology has been the elucidation of factors regulating the migratory activity of these cells. The most prominent regulatory factors are ligands to serpentine receptors-eg, chemokines and neurotransmitters. Many types of neurotransmitter receptors are expressed on tumour cells, supporting the theory that psychosocial factors are involved in the progression of cancer. Understanding how such receptors regulate migration and the availability of specific receptor antagonists could open up new avenues for chemoprevention of tumour-cell migration and metastatic development.

Role of substance P and calcitonin gene-related peptide in the regulation of interleukin-8 and monocyte chemotactic protein-1 expression in human dental pulp

AIM

To determine whether leucocyte infiltration during neurogenic inflammation in the pulp is regulated by neuropeptides via inducing the release of proinflammatory chemokines interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1) from human dental pulp.

METHODOLOGY

Cultured primary pulp cells and pulp tissue explants were stimulated with substance P (SP) and/or calcitonin gene-related peptide (CGRP). IL-8 or MCP-1, secreted from cultured cells or produced in pulp explants, was analysed by enzyme-linked immunosorbent assay.

RESULTS

Substance P induced IL-8 secretion from cultured pulp cells (approximately threefold increase over control, P < 0.05) and from pulp tissue explants (two- to three fold). SP only minimally to moderately induced MCP-1 (approximately two fold) in cultured pulp cells. While MCP-1 induction in cultured pulp cells was detected after 24 h of SP stimulation, no induction was observed in pulp tissue. CGRP did not induce IL-8, but moderately increased MCP-1 production (approximately three fold) in cultured pulp cells. There was no synergistic induction of MCP-1 by SP plus CGRP stimulation of pulp cells.

CONCLUSIONS

Substance P is a stronger inducer of IL-8 production in dental pulp than CGRP. IL-8 is more strongly induced than MCP-1 by SP, suggesting a more important role for IL-8 than MCP-1 in leucocyte infiltration during neurogenic inflammation in dental pulp.

Mast cell subsets and neuropeptides in leprosy reactions

The immunohistochemical identification of neuropeptides (calcitonin gene-related peptide, vasoactive intestinal polypeptide, substance P, alpha-melanocyte stimulating hormone and gamma-melanocyte stimulating hormone) quantification of mast cells and their subsets (tryptase/chymase-immunoreactive mast cells = TCMC and tryptase-immunoreactive mast cells = TMC) were determined in biopsies of six patients with leprosy reactions (three patients with type I reaction and three with type II). Biopsies were compared with those taken from the same body site in the remission stage of the same patient. We found a relative increase of TMC in the inflammatory infiltrate of the reactional biopsies compared to the post-reactional biopsy. Also, the total number of mast cells and the TMC/TCMC ratio in the inflammatory infiltrate was significantly higher than in the intervening dermis of the biopsies of both periods. No significant difference was found regarding neuroptide expression in the reactional and post-reactional biopsies. The relative increase of TMC in the reactional infiltrates could implicate this mast cell subset in the reported increase of the immune response in leprosy reactions.

Increased synthesis of calcitonin gene-related peptide stimulates keratinocyte proliferation in murine UVB-irradiated skin

Repeated ultraviolet (UV) irradiations have been shown to induce keratinocyte proliferation with acanthosis, stimulate the cutaneous nerve proliferation, and increase the synthesis of calcitonin gene-related peptide (CGRP). In the current study, we examined the role of CGRP in the UVB-induced proliferation of murine keratinocytes. UVB irradiation increased the number of bromodeoxyuridine (BrdU)-labeled basal keratinocytes and caused acanthosis. In addition, CGRP expression was up-regulated in the peripheral nerves of the upper dermis and lower epidermis. Repeated intradermal injections of CGRP increased the number of BrdU-labeled basal cells and caused acanthosis. Intradermal injections of capsaicin prior to UVB-irradiation inhibited the UVB-induced CGRP expression, BrdU labeling in basal keratinocytes and epidermal thickening. Intradermal injections of anti-CGRP antibody inhibited the UVB-induced BrdU labeling in basal keratinocytes, but epidermal thickening was not significantly inhibited. These results indicate that CGRP is one of the stimulators to UVB-induced keratinocyte proliferation. On the other hand, expression of substance P, another neuropeptide in the peripheral nerve, was not up-regulated by UVB irradiation.

Delayed recruitment of immunocompetent cells in denervated rat periodontal ligament following experimental tooth movement

It has previously been shown that the number of mononuclear phagocytic cells in the periodontal ligament (PDL) of orthodontically moved rat molars is significantly increased (p < or = 0.05) at 3, 7, and 14 days compared with the controls. Since these changes coincide with increased density of peptidergic nerve fibers, it was of particular interest to investigate a possible relation between the immunocompetent cells and sensory nerve fibers in the PDL of experimentally moved and denervated rat molars. Twenty-two young animals had the first right mandibular molar moved mesially, 7, 14, and 21 days after ipsilateral inferior alveolar nerve axotomy. The left side served as unoperated control. An immunohistochemical procedure was carried out on alternate, serial, cryostat sections with antibodies against CDllb (macrophages, dendritic cells) and class II major histocompatibility complex (MHC) molecules (RT1B). At 7 and 14 days, the number of CD11b+- and RT1B-expressing cells in the denervated PDL showed no significant difference compared with the contralateral side. However, at 21 days, when periodontal tissue re-innervation is established, the number of the investigated immunocompetent cells in the PDL of the denervated and experimentally moved mandibular molars demonstrated a significant difference compared with the contralateral and control molars (p < or = 0.05). It can be concluded that axotomy of the inferior alveolar nerve delays the recruitment of macrophage-like and class II MHC molecule-expressing cells in the PDL of orthodontically moved rat molars. The results further indicate that sensory nerve fibers interact with immunocompetent cells and participate in their mobilization to locally inflamed tissues.

Upregulation of COX-2 and CGRP expression in resident cells of the Borna disease virus-infected brain is dependent upon inflammation

Infection of immunocompetent adult rats with Borna disease virus (BDV) causes severe encephalitis and neural dysfunction. The expression of COX-2 and CGRP, genes previously shown to be implicated in CNS disease and peripheral inflammation, was dramatically upregulated in the cortical neurons of acutely BDV-infected rats. Neuronal COX-2 and CGRP upregulation was predominantly seen in brain areas where ED1-positive macrophages/microglia accumulated. In addition, COX-2 expression was strongly induced in brain endothelial cells and the number of COX-2 immunoreactive microglial cells was increased. In contrast, despite increased expression of viral antigens, neither COX-2 nor CGRP expression was altered in the CNS of BDV-infected rats treated with dexamethasone, or tolerant to BDV. Thus, increased CGRP and COX-2 expression in the BDV-infected brain is the result of the inflammatory response and likely to be involved in the pathogenesis of virus-induced encephalitis.

Periapical inflammatory responses and their modulation

Periapical inflammatory responses occur as a consequence of bacterial infection of the dental pulp, as a result of caries, trauma, or iatrogenic insult. Periapical inflammation stimulates the formation of granulomas and cysts, with the destruction of bone. These inflammatory responses are complex and consist of diverse elements. Immediate-type responses--including vasodilatation, increased vascular permeability, and leukocyte extravasation--are mediated by endogenous mediators, including prostanoids, kinins, and neuropeptides. Non-specific immune responses--including polymorphonuclear leukocyte and monocyte migration and activation, and cytokine production--are elicited in response to bacteria and their products. Interleukin-1 and prostaglandins in particular have been implicated as central mediators of periapical bone resorption. Chronic periapical inflammation further involves specific T- and B-cell-mediated anti-bacterial responses, and activates a network of regulatory cytokines which are produced by Th1- and Th2-type T-lymphocytes. Various naturally occurring and genetically engineered models of immunodeficiency are beginning to help elucidate those components of the immune system which protect the pulpal/periapical complex. Both specific and non-specific responses interface with and are regulated by the neural system. The modulation of these responses by immune response modifies, cytokine antagonists, and other novel therapeutic agents is discussed. As an experimental model, periapical inflammation has many advantages which permit it to be used in studies of microbial ecology and pathogenesis, host response, neuroimmunology, and bone resorption and regeneration.

Immunoreactivity of neural crest-derived cells in thymic tissue developing under the rat kidney capsule

In order to study the functional development of a thymus in an experimental model, small pieces of adult rat thymic tissue were cultured for 9 days and implanted under the kidney capsule of littermates. The tissues were examined with a panel of antibodies raised against thymic and neural factors and neural crest cells at intervals from 5 to 13 days. At 5 days post-implantation, there were groups of L1+ cells within the implants that reacted with antibodies raised against neural and neural crest cell markers. L1+ cells were highly mitotic, rounded cells measuring 8.7 +/- 0.6 micrometer in diameter. Double immunostaining with different combinations of antibodies showed that 94% of the L1+ cells were also TH+, and many were HNK-1/NCAM+, PGP 9.5+, NGF+, chromogranin A+, VIP+, S100+, CGRP+, GAD+, and A2B5+. A few were also pan-cytokeratin+. These results indicate that these cells are derived from neural crest derived cells and belong to the neuroepithelial line of development. The L1+ cells were most numerous before nerves appeared (about Day 9) and reduced in number and extent as the thymus differentiated. The neural crest cells occasionally had long cytoplasmic extensions, but it was not possible to decide if they formed the nerves that appeared in the implants. Adult thymuses also contained a population of L1+ and HNK-1/NCAM+ cells, mainly in the subcapsular cortex, the septa, and the medulla. These cells could be a source of neural crest cells able to repopulate the implant. The adult thymus may always contain a reservoir of cells potentially capable of producing neuropeptides and transmitter factors required for thymic growth and regeneration.

In vitro Leishmania major promastigote-induced macrophage migration is modulated by sensory and autonomic neuropeptides

Recruitment, migration and adherence of macrophages and their interaction with inoculated promastigotes are key steps in the initiation of the inflammatory process in cutaneous leishmaniasis. Parasite- and nervous system-derived factors might be involved in this process. In the present study the chemotactic activities of live, killed and sonicated Leishmania major promastigotes and of the promastigote culture supernatant as well as the L. major surface protease gp63 towards a murine macrophage cell line, Raw 264.7, were investigated, using the Boyden technique. The sensory neuropeptides SOM, CGRP and SP, and the autonomic neuropeptides VIP and NPY, were also investigated for possible modulatory effects on this chemotaxis, using the living promastigotes. Living promastigotes were the most efficient attractants for macrophages compared with other forms of the parasites. Prior incubation of the macrophages with the parasites completely abolished the chemotactic activity. This might indicate that the living promastigote chemotaxis is a receptor-mediated process. On the other hand, paraformaldehyde-killed promastigotes not only failed to induce macrophage chemotaxis but also inhibited it in comparison with the control. The surface protease gp63 tended to inhibit the macrophage chemotactic activity and the sonicate tended to stimulate it compared with controls. The culture supernatant had no effect, indicating that the chemoattractive factors putatively synthesized by the living promastigotes are not released to the surrounding medium. Somatostatin inhibited L. major promastigote-induced macrophage migration at a high concentration, 10(-6) M, while substance P inhibited it at both low concentrations, 10(-10) and 10(-9) M, and a high one, 10(-6) M, the last-mentioned having the greatest inhibitory effect. A stimulatory effect of calcitonin gene-related peptide was found at high concentrations, 10(-5) and 10(-6) M. Vasoactive intestinal peptide stimulated macrophage chemotactic activity at both a high, 10(-5) M, and at a low, 10(-9) M, concentration, the same concentration at which neuropeptide Y exerted its maximum inhibitory effect.

Neuropeptides and Langerhans cells

The immune system and nervous system are intimately related. In addition to neuroendocrine mechanisms, neuropeptides have a variety of effects on immune cells and are responsible at least in part for neurogenic inflammation. The presence of neuropeptides in the skin has been well documented. The influence of neuropeptides on Langerhans cells is the focus of this paper. The physical presence and effects of calcitonin gene-related peptide on Langerhans cells is emphasized. Discussion also includes the putative inflammatory and immunologic roles of vasoactive intestinal peptide, substance P, neurotensin, neuropeptide Y, and somatostatin in the skin.

Expression of the genes for alpha-type and beta-type calcitonin gene-related peptide during postnatal rat brain development

In this study we have analysed the expression of the genes for both alpha-type and beta-type calcitonin gene-related peptide (CGRP) during postnatal development of the rat brain and compared it with the expression of CGRP-like immunoreactivity. At birth both alpha-type and beta-type CGRP messenger RNA were present in the parabrachial nucleus, inferior olive and motor nuclei (except for abducens nucleus), and only alpha-type CGRP messenger RNA in some posterior thalamic nuclei. As development advanced, new nuclei started to express either only alpha-CGRP gene (superior olive, parabigeminal, sagulum, and some hypothalamic and cranial thalamic nuclei) or both genes (abducens nucleus). In the inferior olive both genes were transiently expressed. Beta-CGRP messenger RNA disappeared by postnatal day 10 and alpha-CGRP messenger RNA by postnatal day 20. During the whole postnatal development beta-CGRP gene expression predominated over that of alpha-CGRP in the trigeminal and eye motor nuclei, while in the remainder nuclei alpha-CGRP messenger RNA was either the predominant isoform or the sole one. CGRP-like immunoreactivity, which does not distinguish between alpha-type and beta-type CGRP, was detected in those nuclei containing either alpha-CGRP messenger RNA or beta-CGRP messenger RNA. However, no CGRP messenger RNA was detected in areas such as superior colliculus, lateral pontine nucleus, pars reticulata of the substantia nigra, perifornical area, or zona incerta in which CGRP-like immunoreactivity was prominent. CGRP-like immunoreactivity, but not CGRP messenger RNA, was also transiently detected by postnatal day 5 in some cells of the globus pallidus. In the adult brain, the levels of alpha- and beta-CGRP messenger RNA as well as those of CGRP-like immunoreactivity were considerably reduced. This fact, similar to that of other growth- and development-associated factors, suggests a role for CGRP as a neuron-derived neurotrophic factor. The transient expression in neurons of the inferior olive, matching the period when climbing fibres and cerebellar cortex are developing, seems to support such an idea. The results of this study show that those nuclei expressing beta-CGRP gene also express alpha-CGRP gene. However, there are a number of nuclei that only express alpha-CGRP gene. On the other hand, CGRP-like immunoreactivity is detected in some nuclei which express no CGRP messenger RNA. It suggests that such nuclei express any CGRP-related protein (identified by the antibodies against CGRP) or, if they really contain CGRP protein, this is produced from undetectable amounts (using our in situ hybridization histochemistry procedure) of CGRP messenger RNA or it comes from other nuclei that connect with them in which CGRP protein is synthesized and then transferred.

Dental innervation: functions and plasticity after peripheral injury

Oral tissues including the periodontal ligament, gingiva, and tooth pulp have a relatively dense sensory innervation and a rich vascular supply. Teeth and supporting tissues are susceptible to tissue injury and inflammation, partly due to lack of collateral blood and nerve supply and to their low compliance. This review focuses on dental nerve functions and adaptive changes in the trigeminal ganglion and tooth pulp after peripheral injuries. An overview of the peptidergic innervation of oral tissues is presented, followed by a discussion of plasticity in neuropeptide expression in trigeminal peripheral neurons after local insults to teeth and peripheral nerve injuries. The functional implications of these adaptive changes are considered, with special reference to nerve regeneration, inflammation, and hemodynamic regulation.

Immunoreactivity for the alpha-subunit of the pituitary glycoprotein hormones in pulmonary neuroendocrine cells of developing human lung and various perinatal diseases

Infant lung tissue, obtained at autopsy, was studied by immunohistochemistry for the presence of pituitary glycoprotein hormones (PGHs) in the lung. The infants, born at term or preterm, died of various causes. The results provide the first immunological evidence of the presence of the common a-subunit of the pituitary glycoprotein hormones (alphaPGH) in the lung. The immunoreactivity is located in the pulmonary neuroendocrine cells and neuroepithelial bodies. In addition, the cells labelled by alphaPGH antisera (alphaPGH cells) form a subpopulation of the neuroendocrine cells detected by anti-calcitonin immunohistochemistry (CT cells). Moreover, the number of alphaPGH cells appears to increase after neonatal pneumonia or when the number of CT cells is elevated following the development of disease. Also, the weak staining of one of the monoclonal antibodies against the specific b-subunit of thyrotropin (TSH) might, in combination with the increased detectability of a-subunits, indicate that TSH can be endogenously produced in the lung.

Does calcitonin gene-related peptide act as a chemoattractant for rat gubernacular cells?

Calcitonin gene-related peptide (CGRP) receptors are located in the cremaster muscle of the gubernaculum of rats, and causes gubernacular contraction in vitro, suggesting that CGRP plays an important role in testicular descent. It has been postulated that CGRP released from the genitofemoral nerve acts as a "chemoattractant" for gubernacular migration to the scrotum. The aim of this study is to investigate whether the gubernacular cells of rats exhibit a chemotactic response to CGRP in vitro. Chemotaxis of gubernacular cells from Sprague-Dawley rats (1 to 6 days old) was measured using blind-well chambers. The migration of cells, which passed from the upper to the lower compartment through a polycarbonate filter, were counted using microscopy. The lower compartment included 10(-11), 10(-10), 10(-9), and 10(-8) M CGRP or phosphate buffered saline (PBS) as control. The chemotactic index (CI) was defined as the ratio of migration toward CGRP versus PBS as control. There was no significant migration even at varying CGRP concentrations. Isolated rat gubernacular cells therefore did not exhibit a chemotactic response to CGRP and the role CGRP plays in testicular descent still remains unclear. This result does not exclude the possibility that the gubernaculum responds to CGRP as a whole organ rather than as individual cells.

Dynamics of the pulpo-dentin complex

Dentin has a relatively high water content due to its tubular structure. Once dentin is exposed, this intratubular water is free to move in response to thermal, osmotic, evaporative, or tactile stimuli. Fluid shifts across dentin are thought to cause sufficient shear forces on odontoblasts, nerve endings, nearby fibroblasts, and blood vessels to cause significant mechanical irritation, disruption, or damage, depending on the magnitude of the fluid shift. Even in the absence of fluid shifts, the water-filled tubules provide diffusion channels for noxious (i.e., bacterial products) substances which diffuse inward toward the pulp, where they can activate the immune system, provide chemotactic stimuli, cytokine production, and produce pain and pulpal inflammation. Viewed from this perspective, dentin is a poor barrier to external irritants. However, pulpal tissues react to these challenges by increasing the activity of nerves, blood vessels, the immune system, and interstitial fluid turnover, to make the exposed dentin less permeable either physiologically, via increased outward fluid flow, or microscopically, by lining tubules with proteins, mineral deposits, or tertiary dentin, thereby enhancing the barrier properties of dentin, and providing additional protection to pulpal tissues. These reactions involve dentin and pulp, both in the initiation of the processes and in their resolution. These responses of the dental pulp to irritation of dentin demonstrate the dynamic nature of the pulpo-dentin complex.

Effect of inferior alveolar nerve axotomy on immune cells and nerve fibres in young rat molars

Denervation has been a useful approach to the investigation of interactions between nerve fibres and the pulp-dentine complex. Information on the immunological implications of axotomy is still lacking. The effect of axotomy on CD43+, CD4+, CD11b+ and I-A antigen-expressing cells in both the distal segment of the cut inferior alveolar nerve and in the first molar pulp of young rats was evaluated. Nerve fibres immunoreactive to protein gene product (PGP) 9.5, the neuropeptides substance P and calcitonin gene-related peptide (CGRP), and neuropeptide Y were visualized also by use of the avidin-biotin peroxidase complex method. Recruitment of macrophages was found in the distal segment of the sectioned inferior alveolar nerve 2 days after axotomy, with a further increase in number during the 6-day observation period. However, in the dental pulp, the number of CD43+, CD4+, CD11b+ and I-A antigen-expressing cells was almost unaffected. An almost complete sensory denervation of the first mandibular molar pulp was obtained 2 days after axotomy. After 6 days, the mesial part of the coronal pulp still remained denervated, while regenerated nerve fibres had reached both the root pulp and the distal part of the coronal pulp. Nerve fibres immunoreactive to neuropeptide Y were slightly reduced in density 2 days after axotomy, and after 6 days the localization of neuropeptide Y-immunoreactive fibres was changed compared to the control, with fibres also distributed in the odontoblast layer close to dentine. Hence, following axotomy in young rats, an almost complete sensory denervation is achieved in the first molar, whereas nerve fibres immunoreactive to neuropeptide Y change their distribution pattern, with fibres located close to the dentine after 6 days. Due to the almost unchanged number and distribution of immunocompetent cells in the pulp after axotomy, the young rat molar pulp may represent a suitable and useful experimental model to study neuro-immune interactions.

Lateralization of T-lymphocyte responses in patients with stroke. Effect of sympathetic dysfunction?

BACKGROUND AND PURPOSE

A number of clinical observations indicate that stroke affects the course of immune-mediated diseases by lateralization of the disease manifestations, such as arthritis. The purpose of this study was to assess the impact of early stroke on lateralization of immune responsiveness.

METHODS

The delayed-type hypersensitivity (DTH) reaction to purified protein derivative was used as an in vivo measure of antigen-specific T-lymphocyte reactivity. Assessment of axon reflex vasodilation was simultaneously used to test for cutaneous sympathetic activity.

RESULTS

There were no significant differences with regard to lateralization of DTH reactivity when all stroke patients were tested. However, patients with minor stroke displayed a significant (P < .001) decrease of DTH reaction on the paretic side compared with the contralateral side. In contrast, patients with major stroke showed a significant increase (P = .022) of DTH reaction on the paretic side. Patients with left hemiparesis had a significantly greater (P = .045) DTH response on the affected side than patients with a right hemiparesis. In addition, only the patients with motor deficit but not with sensory deficit or aphasia displayed side differences in DTH responses. When electrically evoked axon reflexes were studied in relation to DTH reactions, a significant correlation (r = .64; P < .001) was found between side asymmetries of DTH responses and side asymmetries of axon reflexes in an innervated skin area. No similar relation was present in skin areas where cutaneous sympathetic activity had been blocked by regional anesthesia.

CONCLUSIONS

Early stroke lateralizes T-cell-mediated cutaneous inflammation. This effect depends on (1) the localization of the brain lesion, (2) the clinical course of the disease, and (3) the presence of motor deficit and may be mediated by (4) alteration of the cutaneous sympathetic nerve traffic.

Substance P and calcitonin gene-related peptide modulate leukocyte infiltration to mouse skin during allergic contact dermatitis

The effects of the neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP) on leukocyte infiltration during allergic contact dermatitis (ACD) in mice were studied. Concomitant topical application of SP or CGRP with the allergen oxazolone resulted in enhanced leukocyte recruitment at the sites of challenge. Immunohistochemical studies revealed that the numbers of T-helper (L3T4+) and cytotoxic (Lyt-2) lymphocytes and infiltrating macrophages (BM8+) were increased. In addition, ICAM-1 and MHC class II molecule expression by these cells was enhanced after neuropeptide application. Analysis by confocal laser scanning microscopy revealed an increase in the immunoreactivity for SP and CGRP in nerve fibres during the course of ACD. Flow cytometry studies showed that SP and CGRP did not upregulate expression of the adhesion molecules ICAM-1 and VCAM-1 by murine endothelial cell lines in vitro. This suggests that increased infiltration of leukocytes during ACD is not a consequence of direct neuropeptide-promoted upregulation of endothelial adhesion molecules in vivo. In conclusion, our observations provide evidence for a modulatory role of neuropeptides in the pathogenesis of ACD.