Modulation of the immune response by tachykinins

Tachykinin-related peptides modulate immune-gene expression in the mealworm beetle Tenebrio molitor L

Tachykinins (TKs) are a group of conserved neuropeptides. In insects, tachykinin-related peptides (TRPs) are important modulators of several functions such as nociception and lipid metabolism. Recently, it has become clear that TRPs also play a role in regulating the insect immune system. Here, we report a transcriptomic analysis of changes in the expression levels of immune-related genes in the storage pest Tenebrio molitor after treatment with Tenmo-TRP-7. We tested two concentrations (10^-8 and 10^-6 M) at two time points, 6 and 24 h post-injection. We found significant changes in the transcript levels of a wide spectrum of immune-related genes. Some changes were observed 6 h after the injection of Tenmo-TRP-7, especially in relation to its putative anti-apoptotic action. Interestingly, 24 h after the injection of 10^-8 M Tenmo-TRP-7, most changes were related to the regulation of the cellular response. Applying 10^-6 M Tenmo-TRP-7 resulted in the downregulation of genes associated with humoral responses. Injecting Tenmo-TRP-7 did not affect beetle survival but led to a reduction in haemolymph lysozyme-like antibacterial activity, consistent with the transcriptomic data. The results confirmed the immunomodulatory role of TRP and shed new light on the functional homology between TRPs and TKs.

Neurokinin receptors and their implications in various autoimmune diseases

Neurokinin receptors belong to the GPCRs family and are ubiquitously expressed throughout the nervous and immune systems. Neurokinin receptors in coordination with neurokinins playing an important role in many physiological processes, including smooth muscle contraction, secretion, proliferation, and nociception. They also contribute to various disease conditions such as inflammatory bowel disease, rheumatoid arthritis, multiple sclerosis, psoriasis, and cancer. Neurokinin receptors antagonist are potent and highly selective and showing success in treating chemotherapy-induced nausea and vomiting. In this review, discuss the various neurokinin receptor expression on immune cells and their importance in various inflammatory and autoimmune diseases and their therapeutic importance.

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The Neurokinin receptor is an important regulatory mechanism to control the neuronal and immune systems.

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Various neurokinin receptors (NK1R, NK2R, and NK3R) are expressed in neurons and cells of the immune system.

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Substance P (SP) controls the differentiation and function of immune cells.

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SP-NK1R receptor signaling shows substantial cross-talk between neuronal and immune systems in inflammation and autoimmunity.

The immunomodulatory effects of tachykinins and their receptors

Tachykinins (TKs) are a family of neuropeptides mainly expressed by neuronal and non-neuronal cell types, especially immune cells. Expression of TKs receptors on immune cell surfaces, their involvement in immune-related disorders, and therefore, understanding their immunomodulatory roles have become of particular interest to researchers. In fact, the precise understanding of TKs intervention in the immune system would help to design novel therapeutic approaches for patients suffering from immune disorders. The present review summarizes studies on TKs function as modulators of the immune system by reviewing their roles in generation, activation, development, and migration of immune cells. Also, it discusses TKs involvement in three main cellular mechanisms including inflammation, apoptosis, and proliferation.

Biological and Pharmacological Aspects of the NK1-Receptor

The neurokinin 1 receptor (NK-1R) is the main receptor for the tachykinin family of peptides. Substance P (SP) is the major mammalian ligand and the one with the highest affinity. SP is associated with multiple processes: hematopoiesis, wound healing, microvasculature permeability, neurogenic inflammation, leukocyte trafficking, and cell survival. It is also considered a mitogen, and it has been associated with tumorigenesis and metastasis. Tachykinins and their receptors are widely expressed in various human systems such as the nervous, cardiovascular, genitourinary, and immune system. Particularly, NK-1R is found in the nervous system and in peripheral tissues and are involved in cellular responses such as pain transmission, endocrine and paracrine secretion, vasodilation, and modulation of cell proliferation. It also acts as a neuromodulator contributing to brain homeostasis and to sensory neuronal transmission associated with depression, stress, anxiety, and emesis. NK-1R and SP are present in brain regions involved in the vomiting reflex (the nucleus tractus solitarius and the area postrema). This anatomical localization has led to the successful clinical development of antagonists against NK-1R in the treatment of chemotherapy-induced nausea and vomiting (CINV). The first of these antagonists, aprepitant (oral administration) and fosaprepitant (intravenous administration), are prescribed for high and moderate emesis.

The role of neurokinin-1 receptor in the microenvironment of inflammation and cancer

The recent years have witnessed an exponential increase in cancer research, leading to a considerable investment in the field. However, with few exceptions, this effort has not yet translated into a better overall prognosis for patients with cancer, and the search for new drug targets continues. After binding to the specific neurokinin-1 (NK-1) receptor, the peptide substance P (SP), which is widely distributed in both the central and peripheral nervous systems, triggers a wide variety of functions. Antagonists against the NK-1 receptor are safe clinical drugs that are known to have anti-inflammatory, analgesic, anxiolytic, antidepressant, and antiemetic effects. Recently, it has become apparent that SP can induce tumor cell proliferation, angiogenesis, and migration via the NK-1 receptor, and that the SP/NK-1 receptor complex is an integral part of the microenvironment of inflammation and cancer. Therefore, the use of NK-1 receptor antagonists as a novel and promising approach for treating patients with cancer is currently under intense investigation. In this paper, we evaluate the recent scientific developments regarding this receptor system, its role in the microenvironment of inflammation and cancer, and its potentials and pitfalls for the usage as part of modern anticancer strategies.

The neuronal influence on tumor progression

Nerve fibers accompany blood and lymphatic vessels all over the body. An extensive amount of knowledge has been obtained with regard to tumor angiogenesis and tumor lymphangiogenesis, yet little is known about the potential biological effects of "neoneurogenesis". Cancer cells can exploit the advantage of the factors released by the nerve fibers to generate a positive microenvironment for cell survival and proliferation. At the same time, they can stimulate the formation of neurites by secreting neurotrophic factors and axon guidance molecules. The neuronal influence on the biology of a neoplasm was initially described several decades ago. Since then, an increasing amount of experimental evidence strongly suggests the existence of reciprocal interactions between cancer cells and nerves in humans. Moreover, researchers have been able to demonstrate a crosstalk between cancer cells and nerve fibers as a strategy for survival. Despite all these evidence, a lot remains to be done in order to clarify the role of neurotransmitters, neuropeptides, and their associated receptor-initiated signaling pathways in the development and progression of cancer, and response to therapy. A global-wide characterization of the neurotransmitters or neuropeptides present in the tumor microenvironment would provide insights into the real biological influences of the neuronal tissue on tumor progression. This review is intended to discuss our current understanding of neurosignaling in cancer and its potential implications on cancer prevention and therapy. The review will focus on the soluble factors released by cancer cells and nerve endings, their biological effects and their potential relevance in the treatment of cancer.

Morphine-induced early delays in wound closure: involvement of sensory neuropeptides and modification of neurokinin receptor expression

Dose-limiting side effects of centrally acting opioid drugs have led to the use of topical opioids to reduce the pain associated with chronic cutaneous wounds. However, previous studies indicate that topical morphine application impairs wound healing. This study was designed to elucidate the mechanisms by which morphine delays wound closure. Rats were depleted of sensory neuropeptides by treatment with capsaicin, and full-thickness 4-mm diameter wounds were excised from the intrascapular region. Wounds were treated topically twice daily with 5mM morphine sulfate, 1mM substance P, 1mM neurokinin A, or 5mM morphine combined with 1mM substance P or neurokinin A and wound areas assessed. During closure, wound tissue was taken 1, 3, 5, and 8 days post-wounding from control and morphine-treated rats and immunostained for neurokinin receptors and markers for macrophages, myofibroblasts, and vasculature. Results obtained from capsaicin-treated animals demonstrated a significant delay in the early stages of wound contraction that was reversed by neuropeptide application. Treatment of capsaicin-treated rats with topical morphine did not further delay wound closure, suggesting that topical opioids impair wound closure via the inhibition of peripheral neuropeptide release into the healing wound. Morphine application altered neurokinin-1 and neurokinin-2 receptor expression in inflammatory and parenchymal cells essential for wound healing in a cell-specific manner, demonstrating a direct effect of morphine on neurokinin receptor regulation within an array of cells involved in wound healing. These data provide evidence indicating a potentially detrimental effect of topical morphine application on the dynamic wound healing process.

The peptide molecular links between the central nervous and the immune systems

The central nervous system (CNS) and the immune system were for many years considered as two autonomous systems. Now, the reciprocal connections between them are generally recognized and very well documented. The links are realized mainly by various immuno- and neuropeptides. In the review the influence of the following immunopeptides on CNS is presented: tuftsin, thymulin, thymopoietin and thymopentin, thymosins, and thymic humoral factor. On the other side, the activity in the immune system of such neuropeptides as substance P, neurotensin, some neurokinins, enkephalins, and endorphins is discussed.

Pharmacological effects of fermented red pepper

The pharmacological effects were investigated of fermented red pepper (HF-S), which consisted of 14.7% carbohydrate, 1.5% lipid, 4.9% protein, 0.3% ash, 78.2% moisture content, with 0.15% capsaicin and 0.06% dihydrocapsaicin. Oral administration of 0.25 mL HF-S for 3 weeks produced significant changes of the perirenal fat pad weight compared with the HF-control group, suggesting a suppressive effect on lipid accumulation and a significant decrease in the risk of arteriosclerosis. The HF-S (0.25 mL) group also showed a lower plasma TG, TC level and atherogenic index than that of the HF-control. In addition, the HF-S (0.25 mL) group showed a marked increase in the production of glutathione, which is the major endogenous antioxidant, and a decrease in the production of lipid peroxide as the product of chemical damage by oxygen free radicals. It is assumed that the effect of HF-S might relate to high glutathione production on the suppression of lipid peroxidation. HF-S stimulated not only the proliferation of macrophages (as high as the positive control, LPS at 1000 microg/mL) but also mitogenic activity (1.2-fold of LPS at 100 microg/mL).

Involvement of tachykinin NK1 receptor in the behavioral and immunological responses to swimming stress in mice

This study investigated the influence of a selective tachykinin NK(1) receptor antagonist FK888 on the performance of mice in the elevated plus-maze test and on peripheral blood count after central treatment with substance P (SP) compared to animals submitted to a swim stress session. Percentage of time spent on open arms was significantly reduced by SP treatment as well as the percentage of entries into open arms and the number of head-dipping, indicating an anxiogenic-like profile of action to SP, as previously described. Nevertheless, SP did not affect the peripheral blood counting. The swim stress also promoted a marked reduction in the exploration of the open arms of the plus-maze as well as in the number of leukocytes, most notably lymphocytes. FK888 alone showed the reverse effect, i.e. an anxiolytic-like profile, increasing the frequency of entries and the time spent in the open arms, but did not affect the blood parameters used as an index of the immune system activity. Nevertheless, FK888 (100 pmol) inhibited the anxiogenic-like profile of SP and swimming stress and also prevented the effect promoted by the swimming stress on the immunological parameters, i.e., the reduction in the number of peripheral leukocytes. These findings are discussed in terms of the interaction between the CNS and the immune system and the involvement of the tachykininergic system.

Capsaicin-sensitive nerves regulate the metabolic response to abdominal sepsis

BACKGROUND

Both the systemic release of inflammatory mediators and activation of the neuroendocrine axis by sensory afferent nerves (SANs) have been implicated as initiators of the metabolic response to infection. In this study, we investigate the role of SANs as mediators of protein catabolism and the insulin-like growth factor (IGF) axis during abdominal sepsis using capsaicin (Cap) to selectively destroy nociceptive sensory axons.

METHODS

Four groups of male Sprague-Dawley rats were studied: Control, Control+Cap, Sepsis, and Sepsis+Cap. Rats were injected with Cap (75 mg/kg) on day 1 and (50 mg/kg) on day 2 to destroy SANs. Time-matched control and septic rats were pair-fed and injected with vehicle on the same schedule. Controls underwent sham laparotomy, while septic rats had a fecal-agar pellet inoculated with Escherichia coli and Bacteroides fragilis implanted in the peritoneal cavity. Blood and tissues were harvested 5 days after the induction of sepsis. Plasma IGF-I, IGFBP-1, and -3 were measured by radioimmunoassay and Western blot analysis. IGF-I, acid-labile subunit (ALS), IGFBP-1 and -3 mRNA levels were determined by Northern blot analysis.

RESULTS

Mortality was 40% in septic rats vs 0% in the sepsis+Cap group. Capsaicin had no effect on muscle mass, protein content, or the IGF system in control rats. However, sepsis-induced reductions in gastrocnemius mass (25%) and protein content (35%) were ameliorated by capsaicin. The sepsis-induced decrease in hepatic IGF-I mRNA and circulating IGF-I (26%), as well as the 4-fold increase in plasma IGFBP-1 and hepatic IGFBP-1 mRNA were prevented by capsaicin.

CONCLUSIONS

Capsaicin-sensitive nerves mediate mortality, the catabolism of skeletal muscle, and selected elements of the IGF system during abdominal sepsis. The results suggest an important role for nociceptive SANs and the neuroendocrine system in mediating the host response to abdominal infection.

Developmental pattern of tachykinins during aging in several organs: effect of exogenous melatonin

Mammalian neurokinin A (NKA) and substance P (SP) are neuropeptides widely distributed in the body; they are potential regulators of the basal blood flow and therefore of the function of many organs and tissues. In the present investigation, we studied the age-dependent changes in NKA and SP in ovary, liver, pancreas and spleen as well as the role of exogenous melatonin on these changes. Female rats of 5, 15 or 25 months of age were studied. In the ovary, NKA concentrations did not change during aging. SP concentrations in the control group were significantly higher (P<0.01) in old rats than in the other two age groups studied. Melatonin treatment resulted in reduced concentrations as compared with those of the control old rats. In the pancreas, NKA and SP concentrations increased during aging, the young rats showing significantly lower values (P<0.01) than middle-aged and old rats for NKA and significantly lower (P<0.01) than the old rats for SP. After melatonin treatment the differences in NKA concentrations disappeared and SP decreased in middle-aged as compared with those in old rats. In the liver, NKA and SP concentrations in the control and melatonin-treated groups did not differ significantly for the three age groups studied. Splenic NKA in control and melatonin-treated groups increased from young to middle-age up to old ages. SP concentrations showed similar values at all ages except in melatonin-treated old rats; in these animals there were significantly higher concentrations than in young melatonin-treated rats. The effect of melatonin was mainly observed on the ovary and pancreas in old rats, with a reduction in the concentrations as compared with those observed in the young groups.

Calcitonin gene-related peptide partially reverses decreased production of chemokines KC and MIP-2 following murine sepsis

The secretion of calcitonin gene-related peptide (CGRP) and the chemokines KC and MIP-2 are increased in the animal models of endotoxemic and septic shock. We tested whether CGRP could modulate KC and MIP-2 secretion from different sources of macrophages after murine sepsis induced by cecal ligation and puncture (CLP). Macrophages were obtained from the peritoneal exudate and lung of female BALB/c mice 16 h after CLP and plated in culture with CGRP and/or LPS for 12 h. The results showed that peritoneal macrophage production of the chemokines (KC, MIP-2) and cytokines (TNF-alpha, IL-6) was markedly decreased in CLP mice. Alveolar macrophages did not display decreased cytokine/chemokines production after CLP. CGRP (0.1 nM-10 nM) partially reversed this decreased production of LPS-induced KC and MIP-2 from peritoneal macrophages. These results suggest that CGRP might be intimately involved in recruitment of neutrophils by promoting local production of the chemokines KC and MIP-2 in murine sepsis.

Comparison of calcitonin gene-related peptide release from rat lymphocytes and dorsal root ganglia neurons

Calcitonin gene-related peptide (CGRP), a neuropeptide contained in primary sensory neurons, has been demonstrated to be synthesized and released by rat lymphocytes in our previous studies. In this study, the release properties and molecular characteristics of CGRP such as immunoreactivity (CGRP-LI) from lymphocytes were compared with those from dorsal root ganglia (DRG) neurons by using CGRP-specific RIA, reverse-phase HPLC, and RT-PCR. Con A and IL-2 could trigger CGRP-LI release from lymphocytes in a time-dependent manner. After 3 days stimulation with 4 microg/ml Con A, the level of CGRP-LI released by lymphocytes was increased from 77.4 +/- 9.6 pg/10(8) cells to 191.1 +/- 13.6 pg/10(8) cells and increased further to 374.5 +/- 38.3 pg/10(8) cells after 5 days. Stimulation with 750 U/ml human IL-2 recombinant (rhIL-2) caused a significantly elevated CGRP-LI release from 75.4 +/- 6.5 pg/10(8) cells to 266.2 +/- 16.2 pg/10(8) cells after 3 days and to 469.1 +/- 43.2 pg/10(8) cells after 5 days. Con A and IL-2 also augmented CGRP mRNA expression in lymphocytes. In the tested period (1-5 days), Con A and rhIL-2 had no stimulating effect on CGRP release from DRG neurons. In contrast, a high concentration of potassium and LPS could induce an acute release of CGRP from DRG neurons, but not from lymphocytes. Lymphocyte-released CGRP-LI was shown to coelute with synthetic rat CGRP (rCGRP) and DRG neuron-released CGRP by reverse-phase HPLC. In addition, to displace (125)I-CGRP from CGRP antibody by lymphocyte-released CGRP-LI was similar to that by synthetic rCGRP. These data suggest that lymphocyte- and nerve-derived CGRP-LI are similar in terms of immunological characteristics, molecular size, and polarity. However, lymphocytes secrete CGRP-LI in response to different stimuli compared to nerve-derived CGRP.

Circulating sensory peptide levels within 24 h of human bone fracture

We designed this study to examine the circulatory levels of wound modulatory peptides [substance P (SP), calcitonin gene related peptide (CGRP] in patients with muscle injuries with bone fractures and within 24 h of the injury. The peripheral plasma levels of these sensory nerve peptides were measured on hospital admission (OA) and 24 h post-injury (PI), using ELISA technique. Mean (s.d) ng/liter of CGRP was higher in patients OA (270 +/- 199), and PI (205 +/- 176); than the controls (3 +/- 81) P < 0.05. Substance P also increased in the patients OA: 101 +/- 50; PI: 46 +/- 3 than controls [8 +/- 9] P < 0.001. Elastase (predictor of posttraumatic complication) was examined and there was no significant differences between patients and control samples (P = NS). This study shows that sensory nerve peptides are increased in bone fracture related injuries up to 24 h after injury. An intact nociceptor system of primary afferent sensory nerves is important for the initiation of the inflammatory process and successful tissue repair as dysfunction of this system could be a contributing factor for a delayed wound healing.

Involvement of substance P and central opioid receptors in morphine modulation of the CHS response

Morphine administration prior to challenge with the antigen 2,4-dinitro-fluorobenzene increases the contact hypersensitivity (CHS) response in rats. The present study extended these findings by showing that central, but not systemic, administration of N-methylnaltrexone antagonized the morphine-induced enhancement of the CHS response. The importance of the neuroimmune mediator substance P was shown via the attenuation of the morphine-induced enhancement following both systemic and topical administration of the NK-1 antagonist WIN51,708. Taken together, the findings of the present study provide new data showing that central opioid receptors and peripheral substance P are involved in the morphine-induced enhancement of the CHS response.

Impairment of rat thymocyte differentiation and functions by neonatal capsaicin treatment is associated with induction of apoptosis

The direct and indirect interaction between the nervous system and its transmitters with the immune system was evaluated in the rat by using the neurotoxin capsaicin (Caps). In the present study we investigated the effect of Caps administration to neonatal rats on thymocyte subpopulation distribution and functions at different times after treatment. Caps treatment results in a marked reduction of thymus weight and cellularity. As shown by immunofluorescence and FACS analysis, profound depletion of double negative (DN), double positive (DP), and single positive (SP) CD4(+) cells was already evident at day 7 after treatment and persisted until day 28. Reduced numbers of SP CD8(+) cells were observed only at later time points. Analysis of TCR phenotype indicates that CD5(+) TCR gamma/delta(+) are particularly sensitive to neonatal Caps treatment. Caps-induced thymocyte depletion was associated with reduced proliferation in response to T cell mitogens. Moreover, in situ TUNEL reaction and agarose gel electrophoresis indicate that neonatal Caps treatment induces apoptosis of thymus cells. Morphological analysis reveals the presence of apoptotic cells in the subcapsular thymus cortical region. Overall our results suggest that Caps when administered at birth, profoundly affects T cell differentiation, likely through its ability to activate apoptotic cell death program.

Co-increase of nerve fibers and HLA-DR- and/or factor-XIIIa-expressing dendritic cells in dentinal caries-affected regions of the human dental pulp: an immunohistochemical study

Neuro-immune interaction has been suggested to play some modulatory role in the immunodefense of the dentin/pulp complex. In this study, we performed a simultaneous immunohistochemical observation of neural elements and pulpal dendritic cells (PDCs) on human carious teeth, to obtain morphological evidence for neuro-immune interaction in response to dentinal tubule-derived carious stimuli. Human third molars bearing a pulp-exposure-free caries lesion were studied. Immunoperoxidase staining was performed with anti-HLA-DR, anti-coagulation factor XIIIa, and anti-CD14 as PDC markers, and anti-low-affinity nerve growth factor receptor (NGFR), anti-protein gene products 9.5, and anti-calcitonin gene-related peptide as nerve markers. The carious teeth usually exhibited localized accumulation of both PDCs and nerve fibers immunoreactive to each marker, in the para-odontoblastic region corresponding to the pulpal end of carious dentinal tubules. Semi-quantitative digital densitometry revealed that pixel numbers corresponding to factor-XIIIa- and NGFR-immunoreactivity were significantly higher in the carious regions than those in the non-carious regions of the same teeth as well as those in the corresponding regions of intact teeth. Classification of specimens with respect to caries depth showed that the co-increase was most apparent in teeth with superficial caries. The increase of PDCs was less pronounced in carious teeth with reparative dentin. These findings suggest that both pulpal nerves and PDCs respond promptly and actively to dentinal tubule-derived carious stimuli. The synchronized accumulation of the two structures suggests an increased opportunity for neuro-immune interaction that may be of significance in the modulation of pathological processes in the dental pulp.

Hyperosmolar saline induces airway resistance changes and neuropeptide release: a comparison with the effect of capsaicin, potassium and histamine

BACKGROUND

Healthy subjects do not show any bronchoconstricting response to inhalation of hypertonic saline, in contrast to subjects with symptoms of asthma. There is evidence indicating that these airway reactions may be related to stimulation of sensory nerves.

MATERIALS AND METHODS

We investigated the effects of hyperosmolar solutions on the changes in airway resistance as well as on release of neuropeptides from an isolated and perfused guinea pig lung model.

RESULTS

We observed that hyperosmolar saline (HS), capsaicin, potassium and histamine induced different patterns of response in airway resistance and neuropeptide release. HS 3.6% induced a biphasic response in airway resistance. Initially a minor relaxation, 4 +/- 1 cmH2O mL-1 min (P < 0.05), followed by a contraction, 22 +/- 3 cmH2O mL-1 min (P < 0.01). This was associated with release of calcitonin gene-related peptide (CGRP) 7.7 +/- 1.9 fmol mL-1 g (P < 0.01), but not of neurokinin A (NKA), a known bronchoconstrictor. Mannitol, at the same osmolarity as HS 3.6%, did not elicit a change in airway resistance, CRGP or NKA release. Capsaicin at 10-6 mol L-1 and potassium at 70 mmol L-1 induced a profound increase in airway tone (50 +/- 9 and 42 +/- 8 cmH2O mL-1 min respectively; P < 0.01) and elevation of both CGRP (6.4 +/- 1.9 and 3.9 +/- 1.1 fmol mL-1 g respectively; P < 0.05) and NKA (3.3 +/- 1.0 and 1.0 +/- 0.2 fmol mL-1 respectively; P < 0.05). Histamine increased the airway resistance by 42 +/- 8 cmH2O mL-1 min (P < 0.01) but had no effect on either CGRP or NKA release.

CONCLUSIONS

In healthy guinea pigs, hyperosmolar saline 3.6% initially caused relaxation of the airways followed by contraction and induced release of CGRP-LI. This was not seen with mannitol at the same osmolarity as for the hyperosmolar saline.

Identification and characterization of immunoreactive calcitonin gene-related peptide from lymphocytes of the rat

There is accumulating evidence that the immune system can produce neuropeptides. In the light of these facts, we obtained direct evidences to prove that T lymphocytes also synthesize and secrete calcitonin gene-related peptide (CGRP), a neuropeptide localized within primary sensory nerves. By using CGRP specific RIA, CGRP-like immunoreactivity (LI) was found in the extracts of rat lymphocytes from thymus and mesenteric lymph node. The intracellular concentration of lymphocyte-derived CGRP-LI of rat thymus and mesenteric lymph node was 745+/-39 and 447+/-33 fg/10(6) cells, respectively. CGRP-LI in lymphocytes was shown to co-elute with synthetic rat CGRP and sensory neuron-derived CGRP by reverse-phase HPLC. In addition, the CGRP-LI located in the T lymphocytes was also shown by immunocytochemical method examined by electron microscopy. The CGRP mRNA detected by RT-PCR was also present in these lymphocytes and was also identified to be the same one in sensory neurons. These data suggest that CGRP is synthesized and secreted in T lymphocytes of both thymus and lymph node in the rat, and this is identified to be the same one in neuronal tissue. Lymphocyte-derived CGRP may act in an autocrine/paracrine mode and play an important role in certain physiological and pathophysiological conditions.

Age and species-dependent differences in the neurokinin B system in rat and human brain

Neurokinin B and its cognate neurokinin-3 receptor are expressed more in the forebrain than in brain stem structures but little is known about the primary function of this peptide system in the central processing of information. In general, few studies have specifically addressed age-related changes of tachykinins, notably the changes in number and/or distribution of the neurokinin B-expressing and neurokinin-3 receptor-bearing neurons. Data on functions and changes of neurokinins in physiological aging are limited and apply mainly to the substance P/neurokinin-1 receptor system. In the present study, we analyzed neurokinin B/neurokinin-3 receptor system in young (5 months) versus middle aged (15 months) and old rats (23-25 months) and also in aging human brains. For the majority of the immunohistochemically examined regions of the rat brain, there was no statistically significant change in neuronal number and size of the neurokinin B and neurokinin-3 receptor staining. In the adult human brain, there was no age-associated change of the number or size of neurokinin-B-positive neurons. However, we found a major decline in number of neurokinin-3 receptor-expressing neurons between young/middle aged (30 years to 69 years) versus old (70 years and older) adults. Interestingly, numbers of neurokinin-3 receptor-positive microglia increased whereas the neurokinin-3 receptor-positive astrocytes remained unchanged in both aging rat and human brains. Finally, in addition to assessing the morphological and quantitative changes of the neurokinin B/neurokinin-3 receptor system in the rat and human brain, we discuss functional implications of the observed interspecies differences.

Neurokinin type-1 receptor antagonist inhibits enhancement of T cell functions by substance P in normal and neuromanipulated capsaicin-treated rats

Substance P (SP) plays a major role in the regulation of the interaction between immune and nervous systems. SP administration stimulates Con A-induced proliferation of spleen and peripheral blood lymphocytes from normal and neonatally capsaicin treated rats, which correlated with enhanced IL-2 production and expression of activation antigens such as IL-2 receptor alpha chain (CD25) and RT1B MHC class II molecule. Moreover, SP markedly increased the percentage of CD5+ and CD4+ T lymphocytes in the peripheral blood of capsaicin-treated rats. Concomitant administration of SP with the non-peptide Neurokinin-1 receptor (NK1R) antagonist SR140333 completely inhibited the SP-mediated augmentation of Con A-induced PBL proliferation and IL-2 production as well as of CD4+ CD25+ and CD4+ RT1B+ T cell numbers in normal and capsaicin-treated rats. SR 140333 also blocked the increased percentage of peripheral blood CD4+ T cells induced by SP in capsaicin-treated rats.

Comparative effects of nonpeptide tachykinin receptor antagonists on experimental gut inflammation in rats and guinea-pigs

Previous studies have shown tachykinins implicated in gut inflammation. The aim of this work was to evaluate the effect of treatments with tachykinin NK1, NK2, and NK3 selective receptor antagonists on the development of gut inflammation induced by trinitrobenzenesulfonic acid (TNBS) in rats and guinea-pigs. On day 0, rats and guinea-pigs received an intraluminal instillation of TNBS/ethanol (40 mg/kg). Each group was daily treated with intraperitoneally injected NK1 (SR 140333; 0.3 mg/kg/day), NK2 (SR 48968; 5 mg/kg/day), or NK3 (SR 142801; 1, 5, or 10 mg/kg/day) receptor antagonists or their vehicle. On day 4, inflammatory levels were evaluated by measuring gut permeability, myeloperoxidase activity, macro- and microscopic damage scores. In TNBS treated rats, daily administration of SR 140333 (0.3 mg/kg/day) and SR 48968 (5 mg/kg/day) reduced colonic inflammation. In TNBS treated guinea-pigs, daily administration of SR 48968 (5 mg/kg/day) and SR 142801 (at 5 and 10 mg/kg/day) attenuated significantly ileal injury. These results suggest that non-peptide tachykinin receptor antagonists are potent anti-inflammatory agents on gut inflammation in rats and guinea-pigs. However, their activity depends upon the animal species and type of receptor considered.

Substance P enhances cytokine-induced vascular cell adhesion molecule-1 (VCAM-1) expression on cultured rheumatoid fibroblast-like synoviocytes

Rheumatoid arthritis (RA) is an autoimmune disease characterized by inflammation of the synovial membrane of multiple joints. This inflammatory microenvironment allows fibroblast-like synoviocytes (FLS) to express or enhance several adhesion or costimulatory molecules. This phenotypic shift, under proinflammatory cytokines, seems to be related to functional consequences for antigen presentation to T cells. The sensory neuropeptide substance P (SP), present at high levels, is able to act on FLS proliferation and enzyme secretion. These data led us to investigate whether SP could also provoke a phenotypic change of FLS. Using flow cytometry and a three-step cellular ELISA method, we determined whether SP has an influence on the expression of MHC class II, intercellular adhesion molecule-1 (ICAM-1), VCAM-1, LFA-3, CD40, B7.1 or B7.2 molecules on RA FLS incubated with interferon-gamma (IFN-gamma) or IL-1beta or tumour necrosis factor-alpha (TNF-alpha) with or without SP. Our results indicate that SP potentiates the effect of proinflammatory cytokines on the expression of VCAM-1 on RA FLS. We verified the presence of specific SP (NK1) receptor mRNA. Using reverse transcription-polymerase chain reaction, we showed that RA FLS of patients express NK1 receptor mRNA. These results suggest that SP increase of cytokine-induced VCAM-1 expression acts via this specific SP receptor. Thus, during chronic inflammation RA FLS are at the interface between the immune and the nervous systems.

Immune defense mechanisms of the dental pulp

Defense reactions of the dentin/pulp complex involve a variety of biological systems, in which the immune system plays a pivotal role. The knowledge of the organization and function of pulpal immunocompetent cells has been sparse, but in recent years a significant body of information of immune mechanisms in general has provided a footing for substantial new knowledge of the immune mechanisms of the dental pulp. The identification of pulpal dendritic cells (DCs) has generated research activities which have led to a concept of how an antigenic challenge may evoke a pulpal inflammatory response. Although DCs are not able to identify foreign antigens specifically, they provide necessary signals to activate T-lymphocytes which in turn will orchestrate other immunocompetent cells to mount the local immune defense of the dental pulp. The purpose of this review is to accent the organization and function of pulpal DCs and other tissue and cellular components and to provide a basis for how they may interact to instigate pulpal defense mechanisms.

Structural and functional association between substance P- and calcitonin gene-related peptide-immunoreactive nerves and accessory cells in the rat dental pulp

Defense mechanisms of the dentin/pulp complex involve a variety of biological systems in which immunocompetent cells, the nervous system, and the vascular supply play important roles. In the present study, pulpal accessory cells were examined regarding (i) their structural relationship to nerves and (ii) how the functional capacities of these cells were affected by neuropeptides. Micro-anatomic association was investigated in the normal rat molar pulp with the use of double-immunofluorescence staining and dual-channel confocal laser scanning microscopy. Examinations of confocal laser scanning microscopic images from single focal planes revealed the presence of apparent contacts between thin, varicose nerve fibers and immunocompetent cells, indicating proximity between these two structures. The close associations were most frequently observed in the para-odontoblastic region of the coronal pulp, where more than 70% of class II antigen-expressing (OX6+) cells showed proximity to nerve fibers immunoreactive to calcitonin gene-related peptide. The corresponding figure for substance P was about 50%. ED2+ macrophages closely associated with nerves were less frequently observed. Functional studies conducted in vitro demonstrated that 10(-9) to 10(-7) mol/L of substance P significantly increased (p < 0.05), while 10(-7) to 10(-6) mol/L of calcitonin gene-related peptide suppressed (p < 0.01) proliferation of purified T-lymphocytes stimulated with sub-optimal concentrations of concanavalin A in the presence of rat incisor pulpal cells as accessory cells. These data suggest that pulpal sensory nerve fibers and their products may have an influence upon the immune defense of the dental pulp.

Application of [(125)I]-[Tyr8]-substance P prepared by the chloramine-T method to receptor-binding experiments after subsequent reduction with mercaptoethanol and purification by reversed-phase liquid chromatography

Radiolabeling of [Tyr8]-substance P ([Tyr8]-SP) with the (125)I-isotope was performed by use of the chloramine-T technique. The primary formed radiolabeled product, having been quantitatively converted to the corresponding sulfoxide yielding [(125)I]-[Tyr8]-(Met11-->O)-SP completely lacked any binding to proteins rich in SP receptor populations. However, after reductive treatment with mercaptoethanol for about 2 h, a complete reconstitution of the Met11 thioether structure was observed. The reduced peptide, consisting of [(125)I]-[Tyr8]-(Met11)-SP was separated from its by-products by reversed-phase high-performance liquid chromatography on octadecylsilyl silica gel with 100 mM triethyl ammonium formate buffer containing 22% acetonitrile (pH 2.2). The labeled SP derivative prepared by this two-step synthesis was obtained in 73% overall yield related to the [Tyr8]-SP starting material and exhibited a specific activity of 1.9-10(6) Ci/M. In contrast to [(125)I]-[Tyr8]-->(Met11-->O)-SP, satisfactory receptor-binding was now observed with the [(125)I]-->[Tyr8]-(Met11)-SP derivative.

Capsaicin-induced inhibition of mitogen and interleukin-2-stimulated T cell proliferation: its reversal by in vivo substance P administration

The direct and indirect interaction between the nervous and the immune systems was evaluated in the rat using the neurotoxin capsaicin. Capsaicin treatment of neonatal rats (50 mg/kg at 2 days of age), results in a marked inhibition of mitogen and hrIL-2-induced cell proliferation both in the spleen and peripheral blood. Inhibition is already evident on day 15 after treatment and persists until day 90 in the spleen; at this time a return to control levels is observed in peripheral blood. The inhibition of proliferative response strongly correlates with a decreased number of CD5+ and CD4+ T cells as evaluated by immunofluorescence and FACS analysis. Moreover, continuous in vivo SP administration stimulates mitogen and hrIL-2-induced proliferative response and completely reverts the capsaicin-induced inhibition of lymphocyte proliferation in the spleen.

Substance P receptor antagonist inhibits murine IgM expression in developing schistosome granulomas by blocking the terminal differentiation of intragranuloma B cells

Schistosome granulomas make substance P (SP). CP96,345 is a nonpeptide SP receptor antagonist active in vivo. Granulomas that form in the presence of SP receptor blockade produce little IgM as compared to normal lesions. The objective of this study was to determine how CP96,345 modulates granuloma IgM production. Schistosome ova were embolized to the lungs of infected mice to induce granulomas of synchronous age. Animals received CP96,345 (50 mg/kg/day) for 4 days following egg embolization. Then granulomas were isolated from tissue and dispersed into single-cell preparations. The dispersed granuloma cells were cultured in vitro to measure IgM and cytokine secretion. Also, granuloma B cells were studied using an IgM ELISPOT assay and flow cytometry. As expected, mice treated with CP96,345 formed granulomas that secreted little IgM. Granulomas from CP96,345-treated mice, as compared to buffer-treated animals, contained few IgM-secreting B lymphocytes, but had appropriate numbers of B cells expressing surface IgM. Also decreased was the capacity of the granulomas to make IFN-gamma, IL-4, IL-5 and IL-6. CP96,345 treatment did not affect splenocyte IgM or cytokine synthesis. These data suggest that CP96,345 inhibits granuloma IgM secretion by blocking intragranuloma B cell maturation at a terminal stage of B cell differentiation. Moreover, SP receptor antagonist affects a variety of cytokine circuits that could influence IgM B cell maturation in vivo.

Sample preparation, high-performance liquid chromatographic separation and determination of substance P-related peptides

This review deals with the determination of low levels of substance P and peptide fragments derived from the undecapeptide, i.e. covers the whole amount of so-called substance P-like immunoreactivity (SPLI) in biological samples. First an overview of the most currently used sample pretreatment procedures is given, followed by a description of the most effective high-performance liquid chromatographic (HPLC) separation methods. Special attention is paid to the choice of the appropriate column and the possible pitfalls encountered in separation of fmol amounts of peptide material. Subsequently the most important techniques of detection are discussed. This section primarily focuses on the coupling of HPLC with radioimmunoassay (RIA), which is indispensable for detection of components in the fmol range at present. Finally, some aspects of preparation and chromatographic separation of radiolabelled antigens for use in RIA are discussed.

Functional characterization of the human neurokinin receptors NK1, NK2, and NK3 based on a cellular assay system

The neurokinin receptor family is known to modulate phospholipase C activity. In order to find new compounds modulating the activity of these receptors we have developed a cellular screening system that measures the biological activity of receptors coupled to the IP3/DAG signal transduction pathway via the transcriptional activation of a reporter gene. For the establishment of neurokinin test cell lines the reporter cell line A20, stably transformed with the luciferase gene under the control of a promoter containing TPA response elements (TRE), which did not respond to neurokinin agonists, was used. Stable test cell lines were developed by transfecting the reporter cell line A20 with the genes for the human neurokinin receptors NK1, NK2 or NK3, respectively. In these cell lines, expression of luciferase was inducible by substance P, neurokinin A and neurokinin B, respectively. The order of potency of the three neurokinins substance P, neurokinin A and neurokinin B was consistent with published data and results from ligand binding studies performed with the NK1 and NK2 test cell lines. The agonistic effect of the neurokinins could be inhibited in a dose-dependent manner by simultaneous addition of neurokininspecific antagonists like the non-peptide antagonists CP-99,994 and SR 48968.

In vivo inhibition of the rat primary antibody response to antigenic stimulation by somatostatin

Somatostatin inhibits in vitro lymphocyte proliferative responses from a variety of species including human, mouse and rat. The immunoinhibitory effects of somatostatin are thought to involve binding to specific cell surface somatostatin receptors on immunocompetent cells. This report describes an in vivo immunoinhibitory effect of somatostatin on the rat popliteal lymph node lymphocyte primary antibody response to sheep red blood cell (SRBC) stimulation. Infusion of somatostatin immediately following SRBC injection into the hind feet of rats had a dose-related inhibitory effect. At the highest concentration used, 10 mumol/L, the level of inhibition was similar to that previously described following neonatal capsaicin treatment of rats. This suggests that neonatal capsaicin treatment may lead to decreased primary antibody responses to SRBC by a selective effect on tachykinin containing nerves and a lesser effect on somatostatin containing nerves. The immunoinhibitory effect of somatostatin was reversed by co-infusion of neurokinin A but not substance P, both of which have been shown to stimulate this response. This suggests the possibility that multiple tachykinin receptors are involved in the modulation of the SRBC primary antibody response in vivo. These results present evidence for an in vivo immunomodulatory role of somatostatin.