Stimulation of phagocytic function in mouse macrophages by neurotensin and neuromedin N

B-type allatostatin regulates immune response of hemocytes in mud crab Scylla paramamosain

B-type allatostatins (AST-B) are neuropeptides that have important physiological roles in arthropods, they have also been identified in a number of crustacean species. Recent research on neuroendocrine-immune (NEI) regulatory system in invertebrates has exploded, it reveals that the NEI network plays an indispensable role in optimizing the immune response and maintaining homeostasis. Herein, mud crab Scylla paramamosain provides a primitive and ancient model to study crosstalk between the neuroendocrine and immune systems. In this study, qRT-PCR analysis showed that the nervous system was the main production site for Sp-AST-B mRNA in S. paramamosain, while its receptor gene (Sp-AST-BR) mRNA could be detected in all the analyzed tissues including hemocytes. This reveals that AST-B might act as a pleiotropic neuropeptide. In situ hybridization further confirmed that granular cells of hemocyte subpopulations express Sp-AST-BR. Time-course analysis revealed that bacteria-analog LPS or virus-analog Poly (I:C) challenge significantly induced Sp-AST-B expression in the thoracic ganglion, and the expression of Sp-AST-BR in hemocytes were also positively changed. Furthermore, mud crabs treated with a synthetic AST-B peptide significantly increased the mRNA levels of AST-BR, nuclear factor-κB (NF-κB) transcription factor (Dorsal and Relish), pro-inflammatory cytokine (IL-16) and immune-effector molecules, and also dramatically enhanced the nitric oxide (NO) production and phagocytic activity in hemocytes. Meanwhile dsRNA-mediated knockdown of Sp-AST-B remarkably suppressed the NO concentrations, phagocytic activity and the expression of immune related genes, resulting in markedly impaired ability of crabs to inhibit bacterial proliferation in vivo. Combined, these data demonstrate that AST-B induced innate immune in the mud crab.

The effect of neurotensin in human keratinocytes--implication on impaired wound healing in diabetes

Diabetic foot ulcers are an important complication of diabetes mellitus characterized by chronic, non-healing ulcers resulting from poor proliferation and migration of fibroblasts and keratinocytes, thus impairing a correct re-epithelialization of wounded tissues. This healing process can be modulated by neuropeptides released from peripheral nerves; however, little is known regarding the role of neurotensin (NT) as a modulator of human keratinocyte function under hyperglycemic conditions. Therefore, this work is focused on the effect of NT in human keratinocytes, under normal and hyperglycemic conditions at different functional levels, namely NT receptors, cytokine, and growth factor expression, as well as proliferation and migration. Human keratinocyte cells were maintained at either 10/30 mM glucose and treated with or without NT (10 nM). The results show that NT did not affect keratinocyte viability. In addition, NT and all NT receptor expression levels were significantly reduced by hyperglycemia; however, NT treatment stimulated expression of NT and neurotensin receptor 2 (NTR2) while neurotensin receptor 1 (NTR1) and neurotensin receptor 3 (NTR3) expression levels were unchanged. Keratinocyte proliferation was not affected by NT and hyperglycemia, while cell migration was reduced by NT treatment. These results demonstrated that hyperglycemic conditions strongly impaired endogenous NT and NTR2 expression in keratinocytes. Despite the addition of exogenous NT to stimulate the endogenous NT and NTR2 expression, these changes do not translate into functional modifications on keratinocytes, particularly in terms of migration, proliferation, and production of cytokines or growth factors. These results suggest that NT production by keratinocytes may exert a paracrine effect on other skin cells, namely fibroblasts, macrophages, and dendritic cells for correct wound healing.

Neurotensin modulates the migratory and inflammatory response of macrophages under hyperglycemic conditions

Diabetic foot ulcers (DFUs) are characterized by an unsatisfactory inflammatory and migratory response. Skin inflammation involves the participation of many cells and particularly macrophages. Macrophage function can be modulated by neuropeptides; however, little is known regarding the role of neurotensin (NT) as a modulator of macrophages under inflammatory and hyperglycemic conditions. RAW 264.7 cells were maintained at 10/30 mM glucose, stimulated with/without LPS (1 μg/mL), and treated with/without NT(10 nM). The results show that NT did not affect macrophage viability. However, NT reverted the hyperglycemia-induced impair in the migration of macrophages. The expression of IL-6 and IL-1β was significantly increased under 10 mM glucose in the presence of NT, while IL-1β and IL-12 expression significantly decreased under inflammatory and hyperglycemic conditions. More importantly, high glucose modulates NT and NT receptor expression under normal and inflammatory conditions. These results highlight the effect of NT on cell migration, which is strongly impaired under hyperglycemic conditions, as well as its effect in decreasing the proinflammatory status of macrophages under hyperglycemic and inflammatory conditions. These findings provide new insights into the potential therapeutic role of NT in chronic wounds, such as in DFU, characterized by a deficit in the migratory properties of cells and a chronic proinflammatory status.

Golgi-to-phagosome transport of acid sphingomyelinase and prosaposin is mediated by sortilin

Sortilin, also known as neurotensin receptor 3 (NTR3), is a transmembrane protein with a dual function. It acts as a receptor for neuromediators and growth factors at the plasma membrane, but it has also been implicated in binding and transport of some lysosomal proteins. However, the role of sortilin during phagosome maturation has not been investigated before. Here, we show that in macrophages, sortilin is mainly localized in the Golgi and transported to latex-bead phagosomes (LBPs). Using live-cell imaging and electron microscopy, we found that sortilin is delivered to LBPs in a manner that depends on its cytoplasmic tail. We also show that sortilin participates in the direct delivery of acid sphingomyelinase (ASM) and prosaposin (PS) to the phagosome, bypassing fusion with lysosomal compartments. Further analysis confirmed that ASM and PS are targeted to the phagosome by sortilin in a Brefeldin-A-sensitive pathway. Analysis of primary macrophages isolated from Sort1(-/-) mice indicated that the delivery of ASM and PS, but not pro-cathepsin D, to LBPs was severely impaired. We propose a pathway mediated by sortilin by which selected lysosomal proteins are transported to the phagosome along a Golgi-dependent route during the maturation of phagosomes.

Biology of neurotensin: revisited study

The tridecapeptide neurotensin (NT) acts in the mammalian brain as a primary neurotransmitter or neuromodulator of classical neurotransmitters. Morphological and functional in vitro and in vivo studies have demonstrated the existence of close interactions between NT and dopamine both in limbic and in striatal brain regions. Additionally, biochemical and neurochemical evidence indicates that in these brain regions NT also plays a crucial role in the regulation of the aminoacidergic signalling. Immune cells, such as lymphocytes, macrophages and mast cells are reported to be activated by neuropeptides, such as neurotensin; this activation leads to cytokine and immunoglobulin production. In addition, neurotensin increases calcium level and the production of nitric oxide. Therefore neurotensin is deeply involved in immunity and inflammation but its real function still remains to be elucidated.

Functional ryanodine receptors are expressed by human microglia and THP-1 cells: Their possible involvement in modulation of neurotoxicity

Ryanodine receptors (RyRs) are intracellular Ca(2+) channels that mediate the release of calcium from internal stores and therefore play an important role in Ca(2+) signaling and homeostasis. Three RyR isoforms have been described thus far, and various areas of brain are known to express each of them. It is well established that neurons can express different RyR isoforms, but it is not known whether microglial cells do so. In the present study we showed that cultured human microglia from both fetal and adult brain specimens express mRNA for RyR1 and RyR2, whereas RyR3 mRNA can be detected only in fetal microglial cells. Calcium spectrofluorometry showed that high levels of the RyR agonist 4-chloro-m-cresol (4-CmC, 1-5 mM) induced elevation of intracellular Ca(2+) concentration ([Ca(2+)](i)) in both types of cultured human microglial cells. This effect was attenuated by the RyR antagonist 1,1'-diheptyl-4,4'-bipyridinium dibromide (DHBP, 10 microM). Neurotoxicity of conditioned medium from human microglia and THP-1 monocytic cells stimulated with a combination of interferon-gamma (IFN-gamma) with either lipopolysaccharide (LPS) or alpha-synuclein was diminished by DHBP. It was also diminished by 4-CmC at concentrations approximately 100-fold lower than those used to stimulate intracellular Ca(2+) release. These data indicate that human microglial cells express functional RyRs and that selective RyR ligands exert antineurotoxic action on this cell type. Therefore, RyR ligands may represent a novel class of compounds that have utility in reducing microglial-mediated inflammation, which is believed to contribute to the pathogenesis of a number of neurodegenerative disorders including Alzheimer's disease and Parkinson's disease.

Role of neuropeptides in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic, relapsing condition involving complex interactions between genes and the environment. The mechanisms triggering the initial attack and relapses, however, are not well understood. In the past several years the enteric nervous system (ENS) has been implicated in the pathophysiology of IBD. Both the ENS and the central nervous system (CNS) can amplify or modulate aspects of intestinal inflammation through secretion of neuropeptides that serve as a link between the ENS and CNS. Neuropeptides are defined as any peptide released from the nervous system that serves as an intercellular signaling molecule. Neuropeptides thought to play a potentially key role in IBD include substance P, corticotropin-releasing hormone, neurotensin, vasoactive intestinal peptide, mu-opioid receptor agonists, and galanin. This review focuses on the role of these neuropeptides in the pathophysiology of IBD and discusses the cell types and mechanisms involved in this process. The available evidence that neuropeptide blockade may be considered a therapeutic approach in both Crohn's disease and ulcerative colitis will also be discussed.

The in vitro influences of neurotensin on the motility characteristics of human U373 glioblastoma cells

Astrocytic tumours are associated with dismal prognoses due to their pronounced ability to diffusely invade the brain parenchyma. Various neuropeptides, including gastrin, are able to modulate tumour astrocyte migration. While neurotensin has been shown to influence the proliferation of glioma cells and the migratory ability of a large set of other cell types, its role in glioma cell migration has never been investigated. Neurotensin-induced modifications to the motility features of human U373 glioblastoma cells therefore constitute the topic of the present study. We evidenced that three subtypes of neurotensin receptors (NTR1, NTR2 and NTR3) are expressed in U373 glioblastoma cells, at least as far as their mRNAs are concerned. Treating U373 tumour cells with 10 nM neurotensin markedly modified the morphological patterns of these cells and also profoundly altered the organization of their actin cytoskeletons. Pull-down assays revealed that neurotensin induced the activation in U373 cells of both Rac1 and Cdc42 but not RhoA. Scratch wound assays evidenced that neurotensin (0.1 and 10 nM) very significantly inhibited wound colonization by U373 cells cultured in the absence of serum. In addition, quantitative phase-contrast videomicroscopy analyses showed that neurotensin decreases the motility levels of U373 glioblastoma cells when these cells are cultured on plastic. In sharp contrast, neurotensin stimulates the motility of U373 cells when they are cultured on laminin, which is a pro-adhesive extracellular matrix component ubiquitously secreted by glioma cells. Our data thus strongly suggest that, in addition to gastrin, neurotensin is a neuropeptide capable of modulating tumour astrocyte migration into the brain parenchyma.

Effects of NT on gastrointestinal motility and secretion, and role in intestinal inflammation

It is well established that interactions of neuropeptides with several cell types at various parts of the intestine are critically involved in intestinal pathophysiology. Among them, neurotensin has been identified as an important mediator in the development and progress of several gastrointestinal functions and disease conditions, exerting its effects by interacting with specific receptors that exert direct and indirect effects on nerves, epithelial cells, and cells of the immune and inflammatory systems. This review summarizes our recent understanding on the participation of neurotensin in the physiology and pathophysiology of the small and large intestine, and discusses various mechanisms that could be involved in these actions.

Neurotensin enhances nitric oxide generation via the JAK2-STAT1 pathway in murine macrophage Raw264.7 cells during costimulation with LPS and IFNgamma

Neurotensin has been known to be implicated in immune function, but its molecular mechanisms remain largely unclear. In this study, we report that neurotensin increased the intracellular calcium levels of murine macrophage Raw264.7 cells, and that this calcium increase disappeared in the presence of either U73122, a PLC inhibitor, or SR48692, a neurotensin receptor antagonist. Also, the production of nitric oxide (NO) during costimulation with lipopolysaccharide (LPS) and interferon gamma (IFNgamma) was potentiated by exposure to neurotensin, whereas neurotensin itself had no ability to induce NO generation. The up-regulation of NO generation was correlated with the induction of inducible NO synthase (iNOS). In addition, the activities of janus activated kinase 2 (JAK2)-signal transducer and activated transcription 1 (STAT1) and the migration capacity of macrophage were increased as the result of costimulation of neurotensin with LPS and IFNgamma, and pretreatment of either U73122 or SR48692 attenuated these phenomenon. Moreover, the neurotensin-mediated enhancement of NO generation and migration were observed in the wild-type JAK2 transfected cells, but not in the dominant negative JAK2 transfected cells. Together, these results demonstrate that neurotensin can effect enhancement in LPS/IFNgamma-induced NO generation and migration capacity, via the JAK2-STAT1 pathway.

Nitric oxide released by accessory cells mediates the gastrin-releasing peptide effect on murine lymphocyte chemotaxis

Several neuropeptides, including gastrin-releasing peptide (GRP), modulate the immune response, specifically lymphocyte chemotaxis. In the present work the effect of GRP on the chemotaxis of murine lymphocytes from different immune locations in both, total leukocyte populations and populations depleted of adherent cells have been studied. Specificity of the GRP effect on chemotaxis using an antagonist of the GRP receptor, as well as the implication of nitric oxide (NO), using inhibitors of NO synthase and donors of NO, were investigated. The effects of GRP stimulating the chemotaxis of lymphocytes from peritoneum, axillary nodes and spleen and decreasing the chemotaxis from thymus were receptor-specific and disappeared in lymphocytes from populations depleted of adherent cells. NO synthase inhibitors blocked the GRP effect on lymphocyte chemotaxis, and this action was reversed in the presence of l-arginine. Thus, the effect of GRP on murine lymphocyte chemotaxis appears to be mediated by NO secreted by adherent cells.

Insulin-like growth factor (IGF) induced proliferation of human lung fibroblasts is enhanced by neurotensin

Fibroblasts are key cells in tissue repair and important contributors to the inflammatory response. Insulin-like growth factors (IGFs) have been shown to participate in growth, in immune responses and in tissue repair where they stimulate cell growth. Neurotensin (NT) has been suggested to participate in inflammation and in tissue repair and is an autocrine or paracrine growth factor for several cancer cell types. Here we show that IGF-induced proliferation of fibroblasts is enhanced by NT in a concentration and type 1 NT-receptor dependent manner. This action of NT was blocked by inhibitors of phospholipase C and protein kinase C but not by inhibitors of phosphoinositide-3-kinase. An inhibitor of MEK 1/2 significantly reduced the proliferative effects of the IGFs but NT's ability to enhance IGF-induced proliferation was not effected. The ability of NT to enhance IGF-induced proliferation did not involve an autocrine factor. These results suggest that interactions between NT and the IGFs may contribute to the regulation of fibroblasts in for example, inflamed or injured tissues.

Neurotensin and the neurotensin receptor-3 in microglial cells

Microglia motility plays a crucial role in response to lesion or exocytotoxic damage of the cerebral tissue. The neuropeptide neurotensin elicited the migration of the human microglial cell line C13NJ by a mechanism dependent on both phosphatidylinositol-3 kinase (PI3 kinase) and mitogen-activated protein (MAP) kinases pathways. The effect of neurotensin on cell migration was blocked by the neurotensin receptor-3 propeptide, a selective ligand of this receptor. The type I neurotensin receptor-3 was the only known neurotensin receptor expressed in these microglial cells, and its activation led to the phosphorylation of both extracellular signaling-regulated kinases Erk1/2 and Akt. Furthermore, the effect of neurotensin on cell migration was preceded by a profound modification of the F-actin cytoskeleton, particularly by the rapid formation of numerous cell filopodia. Both the motility and the filopodia appearance induced by neurotensin were totally blocked by selective inhibitors of MAP kinases or PI3 kinase pathways. In the murine microglial cell line N11, the neurotensin receptor-3 is also the only neurotensin receptor expressed, and its activation by neurotensin leads to the phosphorylation of both Erk1/2 and Akt. In these cells, neurotensin induces the gene expression of several cytokines/chemokines, including MIP-2, MCP-1, interleukin-1beta and tumor necrosis factor-alpha. This induction is dependent on both protein kinases pathways. We observed that the effect of neurotensin on the cytokine/chemokine expression is also inhibited by the neurotensin receptor-3 propeptide. This is the demonstration that the neurotensin receptor-3 is functional and mediates both the migratory action of neurotensin and its induction of chemokines/cytokines expression.

Neurotensin receptor-3/sortilin mediates neurotensin-induced cytokine/chemokine expression in a murine microglial cell line

We show that the type I neurotensin receptor-3 (also called sortilin) is the only known neurotensin receptor expressed in a murine microglial cell line and that its activation leads to phosphorylation of both extracellular signaling-regulated (Erk1/2) and Akt kinases. Using semiquantitative reverse-transcriptase (RT) PCR, we demonstrate that neurotensin induces gene expression of several cytokines/chemokines including macrophage inflammatory protein (MIP)-2, monocyte chemotactic protein (MCP)-1, interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha. This induction is dependent on both phosphatidylinositol 3-kinase and mitogen-activated protein kinases pathways. We observe that the effect of neurotensin on cytokine/chemokine expression is inhibited by the neurotensin receptor-3 propeptide, a selective ligand of this receptor. These results demonstrate that the neurotensin receptor-3 is functional in microglial cells where it mediates the induction of chemokines/cytokines expression by neurotensin.

The effect of neurotensin on insulin-induced proliferation of human fibroblasts

Neurotensin has been shown to influence growth in a number of cancerous and non-cancerous cells and to enhance the proliferative effects of growth factors without itself inducing proliferation. Here we show that neurotensin potentiates the proliferative effects of insulin on IMR90 human fibroblasts in a concentration and neurotensin receptor type 1-dependent manner. This potentiating effect of neurotensin was blocked by inhibitors of phospholipase C and protein kinase C, was accompanied by an increase in the level of soluble inositol phosphates and did not involve an autocrine factor. These results show that neurotensin can enhance insulin-dependent proliferation of human fibroblasts and suggest a possible role for neurotensin in tissue growth and repair.

Involvement of the neurotensin receptor-3 in the neurotensin-induced migration of human microglia

Microglia motility plays a crucial role in response to lesion or exocytotoxic damage of the cerebral tissue. We used two in vitro assays, a wound-healing model and a chemotaxis assay, to show that the neuropeptide neurotensin elicited the migration of the human microglial cell line C13NJ by a mechanism dependent on both phosphatidylinositol 3-kinase (PI 3-kinase) and mitogen-activated protein (MAP) kinase pathways. The effect of neurotensin on cell migration was blocked by the neurotensin receptor-3 propeptide, a selective ligand of this receptor. We demonstrate, by using RT-PCR, photoaffinity labeling, and Western blot analysis, that the type I neurotensin receptor-3 was the only known neurotensin receptor expressed in these microglial cells and that its activation led to the phosphorylation of both extracellular signal-regulating kinases 1/2 and Akt. Furthermore, the effect of neurotensin on cell migration was preceded by a profound modification of the F-actin cytoskeleton, particularly by the rapid formation of numerous cell filopodia. Both the motility and the filopodia appearance induced by neurotensin were totally blocked by selective inhibitors of MAP kinases or PI 3-kinase pathways. This demonstrates that the neurotensin receptor-3 is functional and mediates the migratory actions of neurotensin.

Functional characterization of neurotensin receptors in human cutaneous T cell lymphoma malignant lymphocytes

Cutaneous T cell lymphomas are a clonal proliferation of CD4+ T lymphocytes primarily involving the skin. Mycosis fungoides is an epidermotropic CD4+ cutaneous T cell lymphoma, and a more aggressive form, Sezary syndrome, occurs when the malignant cells become nonepidermotropic. The role of neuropeptides in the growth and chemotaxis capacity of cutaneous T cell lymphoma cells remains unknown. In this report, we found that cutaneous T cell lymphoma cells, similarly to normal resting or activated peripheral lymphocytes, were able to bind neurotensin. We used an interleukin-2-dependent cutaneous T cell lymphoma malignant T cell line derived from cutaneous T cell lymphoma lesions in order to study the role of neurotensin in the proliferation and migration of these malignant cells. First, we determined that the malignant cells expressed neurotensin receptors on their cell membrane. Functional results indicated that neurotensin did not stimulate the growth of the cell line. In contrast, this neuropeptide inhibited the proliferation of the tumor cells in response to exogenous interleukin-2. Furthermore, we found that neurotensin enhanced both spontaneous and chemoattractant-induced migration of the malignant cells. This suggests that neurotensin in skin can play a role in the disease by locally limiting the growth of the cutaneous T cell lymphoma tumor cells in response to cytokines and by enhancing their chemotaxis capacity.

Inhibitory neuropeptide receptors on macrophages

The immune response, both in innate and adaptive immunity, is controlled at several levels, including signaling from the central nervous system. Neuropeptides released within the lymphoid organs modulate the immune response, either as stimulators or inhibitors. The subject of this review is the description of macrophage-expressed receptors of inhibitory neuropeptides. We describe the inhibitory effects on macrophage function for several neuropeptides, the receptors that mediate those activities, and the molecular mechanisms initiated by some of these receptors in terms of transduction pathways and transcriptional factors.

Modulation of human polymorphonuclear leukocyte adherence by cyanopeptide toxins

The oligopeptides microcystins and nodularins are the most common and abundant cyanotoxins present in diverse water systems. They cause different illnesses in animal and humans, sometimes leading to death, and are responsible for severe environmental problems. Here we demonstrate that both microcystin-LR and N. spumigena nodularin (Nod) significantly enhance the early spontaneous adherence of peripheral polymorphonuclear leukocytes (PMNs) over the concentration range 10(-11)-10(-9) M. However, neither of them affect significantly the late spontaneous adherence or the early or late PMN-stimulated adherence (when cells are treated with formyl-methionyl-leucyl-phenylalanine). Since PMN adherence is a key step in the immune response, our data clearly indicate for the first time the immunomodulatory capacity of cyanopeptide toxins. The low concentrations at which the adherence modulation occurs are similar to the physiological concentrations for natural mammalian peptide hormones. Such concentrations are well below those recommended by other authors and World Health Organization in terms of risk assessment as safe for drinking water (8x10(-10) to 10(-9) M).

Changes with ageing in the modulation of murine lymphocyte chemotaxis by CCK-8S, GRP and NPY

The general immunodepression found in ageing organisms may be related to changes in the neuroimmune network. In the present study, the migration capacity of lymphocytes from BALB/c mice of three different ages: young (12 +/- 2 weeks), adult (24 +/- 2 weeks) and old (72 +/- 2 weeks), has been assayed in vitro in response to three neuropeptides: sulfated cholecystokinin octapeptide (CCK-8s), gastrin-releasing peptide (GRP) and neuropeptide Y (NPY) in a physiological range of concentrations (10(-8)-10(-12) M). The capacity of migration to a chemical gradient or chemotaxis was studied by the Boyden's technique using f-met-leu-phe at 10(-8) M as chemoattractant. The results show a different response of lymphocytes to the different neuropeptides, as wells as to age, concentrations and locations studied. However, some similarities were found, for instance the three neuropeptides inhibited chemotaxis in thymus. The stimulatory effects that GRP and NPY exerted in young and adult mice were not observed in old animals. CCK-8s inhibited the chemotaxis in every organ studied, with the effect being more striking in old mice. Our conclusion is that stimulatory effects of the neuropeptides disappear or become inhibitory with ageing.

Effect of cholecystokinin and gastrin on human peripheral blood lymphocyte functions, implication of cyclic AMP and interleukin 2

The effects in vitro of sulphated and desulphated cholecystokinin (CCK)-8, and of gastrin-17 and gastrin-34 were studied at concentrations from 10(-14) M to 10(-6) M on several functions of human peripheral blood lymphocytes, i.e.: adherence to substrate, mobility (spontaneous and directed by a chemical gradient or chemotaxis), and spontaneous and phytohaemagglutinin (PHA)-mediated proliferation. All peptides, at concentrations from 10(-10) M to 10(-8) M, inhibited significantly the mobility capacity and PHA-induced proliferation, and increased the adherence and spontaneous proliferation. A dose-response relationship was observed, with a maximum response of lymphocyte functions at 10(-10) M. These peptides induced a significant increase of intracellular cAMP levels at 30 and 60 sec. Because lymphoproliferation requires production of interleukin 2 (IL-2) by lymphocytes, we also measured the IL-2 production in the presence of the CCK and gastrin peptides, finding that this production was higher than in the respective controls. When peptides were added to samples containing PHA, the IL-2 production was significantly decreased with respect to samples incubated with PHA alone. These results suggest that the CCK and gastrin peptides are negative modulators of lymphocyte mobility (spontaneous mobility and chemotaxis), causing an inhibition of these activities through an increase of intracellular cAMP levels, and of PHA-induced lymphoproliferation, which is mediated by a diminution of the IL-2 production by lymphocytes.

Inhibition of human neutrophil functions by sulfated and nonsulfated cholecystokinin octapeptides

The effects of CCK-8s and desulfated CCK-8 at concentrations ranging from 10(-14) to 10(-6) M were studied in vitro on several functions of human peripheral neutrophils: adherence to substrate, mobility (spontaneous and directed by a chemical gradient or chemotaxis), ingestion of inert particles (latex beads) or cells (Candida albicans), and production of superoxide anion measured by the nitroblue tetrazolium reduction test. The effect of CCK-8s on intracellular levels of cAMP was investigated as well as the implication of calcium in the action of CCK-8s on phagocytic function using stimulants and inhibitors of both intracellular and extracellular calcium channels. The two peptides, at concentrations from 10(-12) to 10(-8) M, inhibited significantly both mobility and ingestion capacities and increased adherence to substrate. A dose-response relationship was observed with a maximum inhibition of neutrophil functions at 10(-10) M, CCK-8s and desulfated CCK-8 induced in these cells a significant, but transient, increase of cAMP levels at 60 s. Moreover, CCK-8s was found to inhibit completely the stimulation of latex bead phagocytosis in neutrophils produced by the calcium ionophore A23187. These results suggest that CCK-8 is a negative modulator of several neutrophil functions and that the inhibition of these activities could be carried out through an increase of the intracellular cAMP levels and a decrease of the extracellular calcium input.

Changes of neurotensin and endotoxin in rats with intestinal ischemia

AIM: To investigate the changes of neurotensin (NT) and endotoxin in rats with segmental intestinal ischemia.

METHODS: The distal ileal mesenteric arteries in rats were ligated to make segmental intestinal ischemia models. At the 2^nd, 6^th and 12^th hours after intestinal ischemia, endotoxin levels in portal blood were tested by limulus lysate test and NT levels in plasma from the heart and in intestine tissues (ischemia and peri-ischemia areas) were assayed by radioimmunoassay. Histological changes of the mucosa were examined under light and electron microscopes.

RESULTS: NT levels decreased significantly in intestinal ischemia and peri-ischemia areas (34.07 ± 5.93 vs 40.14 ± 5.38, P < 0.05; 7.47 ± 1.38 vs 40.14 ± 5.38, P < 0.01), especially lower in ischemia area (34.07 ± 5.93 vs 7.47 ± 1.38, P < 0.05. However, NT level increased obviously in plasma (0.76 ± 0.16 vs 0.47 ± 0.10, P < 0.05). Levels of endotoxin elevated obviously in portal blood (389.0 ± 105.0 vs 55.1 ± 6.7, P < 0.01), and the mucosa was injured both in ischemia and peri-ischemia areas.

CONCLUSION: Intestinal ischemia injures intestinal mucosa and leads to decrease of intestinal NT level, which is accelerated by endotoxemia and increase of blood NT level.

Pituitary adenylate cyclase-activating polypeptide (PACAP38) modulates lymphocyte and macrophage functions: stimulation of adherence and opposite effect on mobility

The effects of pituitary adenylate cyclase-activating polypeptide (PACAP38) in a concentration range from 10(-13) to 10(-6) M were studied, in vitro, on two functions of peritoneal rat lymphocytes and macrophages: adherence and mobility (spontaneous and chemotaxis). The results show that PACAP38 raised the adherence of the two cell types, increased the mobility of macrophages and decreased the mobility of lymphocytes. The maximal effects were observed at 10(-10) M in macrophages and at 10(-9) M in lymphocytes. Moreover, incubation with increasing concentrations of phorbol myristate acetate (PMA), a protein kinase C (PKC) activator, resulted in a progressive enhancement of adherence and chemotaxis of both macrophages and lymphocytes. In contrast, retinal, a PKC inhibitor, significantly decreased these capacities. Incubation of macrophages with both PMA and PACAP38 did not have a synergistic effect on chemotaxis and adherence whereas, with lymphocytes, adherence was increased and chemotaxis was partially decreased. On the other hand, incubation with forskolin (an enhancer of intracellular cyclic AMP [cAMP] levels) caused inhibition and stimulation of chemotaxis and adherence, respectively, in both cell types. PACAP38 prevented the inhibitory effect of forskolin on chemotaxis of macrophages but not of lymphocytes, whereas the simultaneous presence of PACAP38 and forskolin was synergistic for adherence of both peritoneal cells. In addition, PACAP38 was chemoattractant for macrophages but not for lymphocytes. Furthermore, a VIP receptor antagonist was able to partially reverse the modulatory effects of PACAP38 on lymphocytes, but not on macrophages. These data suggest that PACAP38 exerts its action through the binding to type I PACAP receptors and PKC activation in macrophages and through the elevation of intracellular cAMP levels by binding to type II PACAP receptors in lymphocytes. The present work reveals an additional link between neuropeptides and the immune system and suggests that the peptide PACAP modulates the immunological function of macrophages and lymphocytes.

Enhancement of phagocytosis by corticostatin I (CSI) in cultured mouse peritoneal macrophages

Corticostatin I (CSI) is one of the corticostatic peptides which inhibit ACTH-stimulated steroidogenesis. To clarify the function of CSI on the immune system, the effect of CSI on phagocytosis by peritoneal macrophages was examined by means of flow cytofluorometry. In the presence of Ca2+ and Mg2+, CSI enhanced phagocytosis of latex beads in a dose-dependent manner. Unstimulated phagocytosis in physiological solution consisted of Ca2+ and Mg(2+)-dependent and -independent phagocytosis. Divalent cations-independent phagocytosis was sensitive to CSI. Present results suggest that the enhancement of phagocytosis by CSI may be one of the mechanisms modulating the immune response regarding infection and inflammation. Present study also showed that one of defensin HNP-1 enhanced phagocytosis.

Neuroendocrine system and immune responses after confinement

A confinement experiment in a normobaric diving chamber was undertaken to obtain more understanding of the effects of confinement and isolation on human psychology and physiology. Pre- and post-confinement blood samples were obtained from four test subjects and five control subjects for the analysis of plasma proteins, hormone levels and immune responses. The absence of significant changes in the immune responses correlates with the absence of major changes in neurohormones and other hormones such as cortisol, prolactin, growth hormone, insulin-like growth factor 1, triiodothyronin, thyrotrophin and 1,25-dihydroxyvitamin D. It is increasingly recognized that the immune system is not an independent physiological system, but a system that interacts multidirectionally with other organs and body functions. It seems that the conditions of this confinement experiment were not stressful from a psychological point of view. The presence of a female crew member had probably a positive effect on group behavior of the test subjects. In conclusion, the data suggest that confinement for 60 days in a small habitat without particularly stressful situations has no significant impact on a variety of neuroimmunological parameters.

Pituitary adenylate cyclase-activating polypeptide (PACAP-38) stimulates rat peritoneal macrophage functions

The present study shows that PACAP-38, in a dose-dependent manner, increased in vitro two steps of the phagocytic process in rat peritoneal macrophages: ingestion of inert particles (latex beads) and production of superoxide anion as measured by nitroblue tetrazolium reduction. The most effective concentration of PACAP-38 was 10(-10) M. Similarly, PMA, an activator of protein kinase C (PKC), increased the phagocytic activity in a dose-dependent manner, whereas retinal, a PKC inhibitor, decreased the activity. Macrophages incubated with forskolin, an enhancer of intracellular cAMP levels, produced an inhibitory effect on both phagocytic functions. The maximum stimulation of the phagocytic activity by PACAP-38 was not further enhanced by addition of PMA, suggesting that the enhancement of the phagocytic activity by PACAP-38 and PMA is mediated by a common signaling pathway. In addition, retinal as well as forskolin inhibited partially the stimulatory effect that PACAP-38 produced in the macrophage functions studied. Furthermore, this study showed that a VIP receptor antagonist was unable to suppress the stimulatory effect of PACAP-38. These results could prove that PACAP-38 stimulates the phagocytosis and production of superoxide anion in macrophages through PKC activation by binding to type I PACAP receptor.

VIP modulation of immune cell functions

Neuropeptides have recently been shown to modulate the immune response. Vasoactive intestinal peptide (VIP) released from nerve endings and from immune cells modulates the mobility and adherence of lymphocytes and macrophages, phagocytic cell functions (phagocytosis and free radical production), the lymphocyte proliferative response, lymphokine and immunoglobulin production and the natural killer cell activity, with opposite effects in vitro on these immune cell functions. The VIP receptor heterogeneity and the different action mechanisms of VIP-mediated immunoregulation could explain, at least in part, the different VIP effects observed on lymphoid and phagocytic cells. The evidence supports the theory that VIP acts not as an inhibitor, but as a modulator of immune functions, as previously thought, and that this neuropeptide may play a relevant role in vivo.

Modulation of murine peritoneal macrophage functions by gastrin

The effect in vitro of gastrin-17 and gastrin-34 was studied at concentrations from 10(-12) to 10(-6) M on several functions of resting peritoneal macrophages from BALB/c mice: adherence to substrate, mobility (spontaneous and directed by chemical gradient or chemotaxis), and ingestion of inert particles (latex beads) or cells (Candida albicans). Both gastrins, at concentrations from 10(-10) to 10(-8) M, inhibited significantly all functions studied with the exception of adherence, which was increased. A dose-response relationship was observed, with a maximum inhibition of macrophage functions found at 10(-9) M. These peptides induced in murine macrophages a significant increase of cAMP levels at 60 and 120 s. Adenosine, an adenylate cyclase inhibitor, significantly increased the ingestion of latex beads, whereas the combined presence of adenosine and either G-17 or G-34 produced similar values to those of control samples without adenosine or gastrin. These results suggest that gastrin is a negative modulator of several macrophage functions, and that the inhibition of these activities is carried out through an increase of intracellular cAMP levels.

Expression of vasoactive intestinal peptide binding sites in rat peritoneal macrophages is stimulated by inflammatory stimulus

Vasoactive intestinal peptide (VIP) binding to resident and stimulated-rat peritoneal macrophages was studied. No specific VIP binding was obtained with resident rat peritoneal macrophages. In contrast, VIP bound specifically to casein-elicited macrophages. The Scatchard analysis of binding data was consistent with the presence of two classes of VIP binding sites, but may represent a receptor site and internalized VIP. Both specific VIP binding and number of specific high affinity binding sites for VIP augmented progressively after sodium caseinate injection, reaching maximum at days 4-5. Macrophages obtained 1 day after injection showed a minimal specific VIP binding (0.3 +/- 0.1% of total), but cells obtained 4 days after injection showed a maximal binding to the peptide (3.1+/-0.2% of total). The number of high affinity binding sites per cell raised also progressively after sodium caseinate injection: 2650+/-301 at day 2, 4939 +/-723 at day 3, 6684+/-903 at day 4 and 9636+/-1626 at day 5 (P = 0.0035). The number of low affinity binding sites per cell exhibited the same changes. In contrast, the Kd values of both high and low affinity VIP binding sites did not vary significantly (P>0.05). These results demonstrate that VIP binding sites are only displayed by stimulated macrophages, suggesting that VIP binding sites could be considered to be a pre-activation marker in macrophages and could be used to recognize inflammatory or stimulated macrophages.

Enhancement of phagocytosis in mouse macrophages by pituitary adenylate cyclase activating polypeptide (PACAP) and related peptides

The effects of pituitary adenylate cyclase activating polypeptide (PACAP) and related peptides on phagocytosis of fluorescent latex beads by mouse peritoneal macrophages were examined using flow cytometry (FCM). PACAP38, PACAP27 and vasoactive intestinal peptide (VIP) enhanced phagocytosis in a dose-dependent manner. Relative potencies of related peptides at a concentration of 10(-6) M were PACAP38 > PACAP27 > VIP > secretin > glucagon > (peptide with NH2-terminal histidine and COOH-terminal methionine amide, in short PHM). PACAP(6-38) was as effective as PACAP38. PACAP(6-27) enhanced phagocytosis more effectively than did PACAP27. PACAP(28-38) slightly enhanced phagocytosis. The present result suggest that PACAP38 is one of the mediators that the nervous system uses to modulate the immune system.

Enhancement of phagocytosis by dynorphin A in mouse peritoneal macrophages

The effects of the opioid peptide dynorphin A (DynA) on phagocytosis in peritoneal macrophages was examined by flow cytometry (FCM). DynA enhanced phagocytosis in a dose-dependent manner. Leucine-enkephalin (Leu-Enk), methionine-enkephalin (Met-Enk), beta-neo-endorphin (beta Neo-End), DynA(9-17) and DynA(13-17) had no such activity. Alpha-Neo-endorphin (alpha Neo-End), dynorphin B (DynB), DynA(1-13) and DynA(6-17) enhanced phagocytosis less effectively than DynA. Naloxone did not inhibit the enhancement of phagocytosis induced by DynA. Unstimulated control phagocytosis was partially suppressed in Ca2+-free EGTA-containing solution and even in this solution DynA enhanced phagocytosis. However, the enhancement by DynA was suppressed in EGTA- and BAPTA-AM-containing Ca2+-free solution. The present study showed that enhancement of phagocytosis by DynA was independent of extracellular Ca2+ ([Ca2+]o) and dependent on intracellular Ca2+ ([Ca2+]i). The present results support DynA being one of the mediators from the nervous system that modulates the immune system.

Inhibition of murine peritoneal macrophage functions by sulfated cholecystokinin octapeptide

The effect in vitro of the sulfated octapeptide form of cholecystokinin, CCK-8, at concentrations from 10(-12) M to 10(-6) M on several functions of resting peritoneal macrophages from BALB/c mice: adherence to substrate, mobility (spontaneous and directed by chemical gradient or chemotaxis), ingestion of inert particles (latex beads) or cells (Candida albicans), and production of superoxide anion measured by nitroblue tetrazolium reduction was studied. CCK-8, at concentrations from 10(-10) M to 10(-8) M, inhibited significantly all functions studied with the exception of adherence to substrate, which was increased. A dose-response relationship was observed, with a maximum inhibition of macrophage functions found at 10(-8) M. This neuropeptide induced in murine macrophages a significant, but transient, increase of cAMP levels at 60 sec. On the contrary, CCK-8 produced a slight but significant decrease of protein kinase C (PKC) activity at 5 min of incubation. These results suggest that CCK-8 is a negative modulator of several macrophage functions, and that the inhibition of these activities is carried out through an increase of intracellular cAMP levels and a decrease in PKC activity.

Inhibitory effect of vasoactive intestinal peptide (VIP) on phagocytosis in mouse peritoneal macrophages

The effect of VIP on phagocytosis in peritoneal macrophages was examined by means of flow cytometry (FCM). This assay revealed that VIP suppressed phagocytosis in a dose-dependent manner. VIP(1-12) did not suppress phagocytosis. VIP(10-28) was more suppressive than VIP(1-28). A known VIP-antagonist (N-Ac-Tyr1,D-Phe2)-growth hormone-releasing factor (GRF) (1-29)-NH2 suppressed phagocytosis less than VIP. Control phagocytosis was partially suppressed in Ca(2+)-free solution. Phagocytosis was suppressed by VIP further in Ca(2+)-free solution than in the normal solution. Phagocytosis was suppressed in a known phosphodiesterase inhibitor IBMX-containing solution. The degree of suppression by VIP was the same in the presence or the absence of IBMX. These results suggest that VIP suppresses extracellular Ca(2+)-dependent and -independent phagocytosis, that the C-terminal fragment of VIP is essential for VIP action, that the suppression is mediated by cAMP and that the inhibition of macrophage phagocytosis by VIP is one of the mechanisms which modulates immune responses by the nervous system.

Suppression of phagocytosis by adrenocorticotropic hormone in murine peritoneal macrophages

Phagocytosis of latex beads by peritoneal macrophages was examined by means of flow cytometry (FCM). This assay revealed that adrenocorticotropic hormone (ACTH) suppressed phagocytosis in a dose-dependent manner. ACTH (1-24) was more suppressive than ACTH (1-39). Control phagocytosis was partially suppressed in Ca(2+)-free solution. Phagocytosis was suppressed by ACTH in this solution to the same degree as in the normal solution. Suppression by ACTH was reduced in phosphodiesterase inhibitor-containing solution. These results suggest that (1) ACTH suppresses extracellular Ca(2+)-dependent and -independent phagocytosis, (2) the suppression is not mediated by cAMP and (3) the inhibition of macrophage phagocytosis by ACTH is one of the mechanisms that modulate immune responses in stressful situations.

Expression of VIP receptors in mouse peritoneal macrophages: functional and molecular characterization

Receptors for VIP in mouse peritoneal macrophages (MPM) were examined using [125I]labeled VIP as ligand. The receptor binding was rapid, reversible, saturable, specific, and dependent on time, pH, temperature and cell concentration. At 15 degrees C, the stoichiometric data suggested the presence of two classes of VIP receptors with Kd values of 1.05 +/- 0.2 and 66.4 +/- 11.0 nM and binding capacities of 19.2 +/- 2.8 and 706.6 +/- 172.0 fmol VIP/10(6) cells. The interaction showed a high degree of specificity, as suggested by competition experiments with various peptides structurally related to VIP as follows: VIP > helodermin > rGRF > PHI >> secretin. Glucagon, pancreastatin, somatostatin, insulin, and octapeptide of cholecystokinin (CCK 26-33) were ineffective at concentrations as high as 1 microM. VIP was a potent and efficient stimulator of cyclic AMP production in MPM. The stimulation was observed at a concentration as low as 0.01 nM VIP. Half-maximal stimulation (ED50) was observed at 1.0 +/- 0.2 nM VIP, and maximal stimulation (three-fold above basal levels) was obtained between 0.1-1 microM. The cyclic AMP system of mouse peritoneal macrophages showed a high specificity for VIP. The order of potency observed in inducing cyclic AMP production was VIP > helodermin > rGRF > PHI >> secretin. Glucagon, insulin, pancreastatin, somatostatin and octapeptide of cholecystokinin did not modify cyclic AMP levels at concentrations as high as 1 microM.(ABSTRACT TRUNCATED AT 250 WORDS)

Chemoattractant capacity of bombesin, gastrin-releasing peptide and neuromedin C is mediated through PKC activation in murine peritoneal leukocytes

Bombesin-like peptides have been recently shown to regulate immune functions. In the present work, we have studied their action as chemoattractants for murine peritoneal macrophages and lymphocytes. The results showed a significant increase in the number of cells that migrate when they are exposed to a gradient of bombesin, gastrin-releasing peptide (GRP) or neuromedin C (from 10(-8) to 10(-12) M). The most effective of the three neuropeptides studied was GRP, even more than formyl-Met-Leu-Phe peptide (FMLP), an established leukocyte chemoattractant. GRP action was mediated through specific cell receptors as it was significantly reduced in presence of a competitive and specific bombesin receptor antagonist. In the presence of retinal, a protein kinase C (PKC) inhibitor, the chemoattractant capacity of GRP was considerably reduced. In order to investigate further the mechanism of action involved in the GRP effect, we measured PKC activity. Peritoneal cells incubated with GRP experimented an increase in PKC activity to the same extent of that produced by the PKC activator phorbol myristate acetate (PMA). These data prove that bombesin-like peptides are potent chemoattractants for murine peritoneal macrophages and lymphocytes, and that their action is at least in part mediated through PKC activation.

Vasoactive intestinal peptide modulation of adherence and mobility in rat peritoneal lymphocytes and macrophages

In this work, the effects of vasoactive intestinal peptide (VIP) in a concentration range from 10(-13) to 10(-7) M were studied in vitro on two common activities of peritoneal rat lymphocytes and macrophages: adherence and mobility (spontaneous and chemotaxis). The results show that VIP stimulated the adherence of the two cells studied, and increased the macrophage mobility but decreased this activity in lymphocytes. Moreover, a specific protein kinase C (PKC) activator such as phorbol myristate acetate (PMA, 50 ng/ml) also stimulated significantly the adherence and chemotaxis of both macrophages and lymphocytes. By contrast, a PKC inhibitor, retinal (2 x 10(-5) M), decreased significantly these capacities. Macrophages incubated with both VIP and PMA in relation to those incubated with VIP or PMA showed an increase in adherence and chemotaxis, whereas in lymphocytes adherence was also increased but chemotaxis decreased. The incubation with forskolin (10(-5) M), an enhancer of intracellular cAMP levels, produced an inhibitory effect of the chemotaxis activity in both types of cells. VIP prevented this inhibitory effect of forskolin in macrophages but not in lymphocytes. In addition, VIP was chemoattractant for macrophages but not for lymphocytes. The present study proves that VIP proves that VIP has a coronary effect on the two principal and representative types of immune cells in the rat peritoneum: lymphocytes and macrophages, stimulating macrophage chemotaxis through PKC activation and inhibiting lymphocyte chemotaxis through adenylate cyclase activation.

Stimulation by vasoactive intestinal peptide (VIP) of phagocytic function in rat macrophages. Protein kinase C involvement

The action of vasoactive intestinal peptide (VIP) on macrophages has not yet been studied, although there are studies that show an inhibitory action of VIP on lymphocyte functions. The present study shows that VIP in a range from 10(-12) to 10(-7) M increased significantly the phagocytosis and digestion capacities of rat peritoneal macrophages. The most effective concentration of VIP was 10(-9) M followed by 10(-8) M. With respect to the phagocytic capacity, the ingestion of cells (Candida albicans) or inert particles (latex beads) was stimulated significantly with all the concentrations used. The digestion capacity was analyzed through the production of superoxide anion, measured by the reduction of nitroblue tetrazolium (NBT). As with phagocytic capacity, superoxide anion production was increased by VIP in non-stimulated macrophages (incubated without latex beads) and even more in stimulated cells (incubated in the presence of latex beads). The study of the mechanism of action of this neuropeptide showed that protein kinase C (PKC) was activated in the presence of VIP concentrations from 10(-10) to 10(-8) M in a similar way to that found with a specific PKC activator such as phorbol myristate acetate (PMA, 50 ng/ml). PMA also stimulated significantly the phagocytosis and digestion capacities of rat macrophages. By contrast, a PKC inhibitor, retinal (20 microM), decreased significantly the phagocytosis and digestion capacities. These data show that VIP could stimulate these macrophage functions through PKC activation.