Formation of contacts between mast cells and sympathetic neurons in vitro

Release of histamine from dural mast cells by substance P and calcitonin gene-related peptide

The aim of the present study was to examine if the neuropeptides substance P (SP), calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY) and vasoactive intestinal peptide (VIP) can stimulate histamine release from mast cells in the dura mater and thereby play a role in cranial vasoregulation and local neurogenic inflammation. Dura mater mast cells were compared with peritoneal mast cells in the rat. Histamine was released from dura mater mast cells by compound 48/80, SP and CGRP but from peritoneal mast cells only by compound 48/80 and SP. NPY and VIP released quite small amounts of histamine from dural mast cells. The release of SP and CGRP from rat dura mater mast cells was blocked by the receptor antagonists FK888 and CGRP8-37 respectively, suggesting receptor mediated release mechanisms. None of the stimuli released histamine from human or porcine dural mast cells, possibly because the sampling procedure injures and incapacitates the cells.

Carbachol-induced bladder mast cell activation: augmentation by estradiol and implications for interstitial cystitis

OBJECTIVES

Interstitial cystitis (IC) is a painful, sterile bladder disorder that occurs primarily in women, many of whom also experience allergies with symptoms that worsen perimenstrually. Increased numbers of activated bladder mast cells have recently been implicated in the pathophysiology of IC. These mast cells express high-affinity estrogen receptors and are located close to increased bladder nerves, many of which contain the neuropeptide substance P (SP). We therefore investigated whether the neurotransmitter acetylcholine (ACh) and SP could activate bladder mast cells and whether estradiol could influence this effect.

METHODS

Bladder pieces from male Sprague-Dawley rats were perfused with carbachol (the stable analogue of ACh), SP, or the mast cell secretagogue compound 48/80 (C48/80) with or without preincubation with beta-estradiol. The effect of carbachol was also investigated after pretreatment with the muscarinic antagonist atropine. Mast cell activation was assessed by release of 3H-serotonin and morphologic evidence of secretion by light and electron microscopy.

RESULTS

Carbachol triggered rat bladder mast cell serotonin release in a dose-dependent manner, an effect increased by tissue pretreatment with estradiol and blocked by atropine. The effect of carbachol was accompanied by ultrastructural evidence of mast cell activation and was stronger than that obtained by either C48/ 80 or SP.

CONCLUSIONS

Bladder mast cell activation is neurogenically mediated and augmented by estradiol, findings that could possibly explain the painful symptoms of IC and its prevalence in women, as well as the worsening of symptoms perimenstrually.

Murine and human mast cell express acetylcholinesterase

Expression of catalytically active protein was detected in a murine mast cell line. The primary type of AChE mRNA produced by these cells was found to be the brain and muscle type by PCR amplification of alternative exons from the 3' of mast cells AChE cDNA. AChE was further found to be expressed in the HMC-1 the human mast cell precursor line. Furthermore, utilizing the single cell RT-PCR method we detected AChE mRNA expression in Fc epsilon RI-positive single cells derived from human colonic mucosal biopsies. Our findings predict the involvement of mast cell AChE in neuronal-mast cell interactions.

Inotropic effects of histamine on developing chick heart: release of transmitters from autonomic nerve terminals

Inotropic effects of histamine were examined in isolated ventricular preparations from late embryonic and hatched chick hearts. In 19 day-old embryonic preparations, histamine had little effect on the contractile force. In preparations from 1 to 2 day-old hatched chick, histamine produced a transient decrease in contractile force followed by a sustained increase. The negative and positive responses were antagonized by atropine and propranolol, respectively, but not by histamine antagonists terfenadine, cimetidine or thioperamide. Acetylcholine produced positive inotropic responses in the embryo while negative responses were observed after hatching. In myocardium of hatched chicks, compound 48/80, which releases histamine from mast cells, produced a transient decrease in contractile force followed by a sustained increase with a similar magnitude and time course to the case of exogenously applied histamine. The negative and positive responses were inhibited by atropine and propranolol, respectively, but not by terfenadine, cimetidine or thioperamide, which was similar to the case with the responses to histamine. The present results suggest that histamine, either applied exogenously or released from myocardial store sites, produces negative and positive inotropic responses in hatched chick myocardium which are due to release of acetylcholine and norepinephrine, respectively, from autonomic nerve terminals.

Chronotropic and inotropic effects of histamine in developing chick heart: differential mechanisms before and after hatching

Chronotropic and inotropic effects of histamine were examined in isolated atrial and ventricular preparations from embryonic and hatched chicken hearts. Histamine produced positive chronotropic and inotropic responses both in embryonic and hatched hearts. The responses to histamine in middle embryonic myocardia, which were observed in the micromolar range, were antagonized by H2 antagonists but not by H1, H3 antagonists and propranolol. Isobutyl-methylxantine, an inhibitor of phosphodiesterase, produced a leftward shift of the concentration-response curve for the chronotropic effect of histamine in the embryo. The responses to histamine in myocardia from hatched chicks, which were observed in the milimolar range, appeared concurrently with the responses to tyramine during development and were antagonized by beta adrenoceptor antagonists but not by any of the histamine antagonists. The positive inotropic response to histamine in hatched ventricular preparations were greatly attenuated by reserpine pretreatment or in the presence of desipramine. Thus, we demonstrated that exogenously applied histamine produces positive chronotropic and inotropic responses in developing chicken hearts and that the mechanisms are different between embryonic and hatched chicks: direct action on H2 receptors in the embryonic heart and release of norepinephrine from sympathetic nerve terminals in hatched hearts.

Accumulation and degranulation of mast cells in experimental neuromas

Mast cell accumulation and degranulation occur within the endoneurium of injured peripheral nerves. We investigated the time course of mast cell accumulation and degranulation in experimental neuromas of the sciatic nerve in rats. Mast cell accumulation and degranulation were significant only after the first week following neuroma creation and were prominent at 14 days within the neuroma stump. Mast cell degranulation could account for microvascular changes within neuromas after the first week following injury.

The interaction between mast cells and nerves in the gastrointestinal tract

Study of the neuroimmune system typifies the new integrative approach to biological systems. Numerous spatial associations between mast cells and nerves have been described, and data are accumulating on the functional aspects of this relationship. Here, Derek McKay and John Bienenstock review the bidirectional communication between mast cells and nerves as a homeostatic unit in the regulation of gut physiology and host defense.

Effect of isolation stress on brain mast cells and brain histamine levels in rats

The effects of the chronic social stress of isolation on changes in brain mast cells (MC), the hypothalamic histamine content and the activity of the hypothalamic-pituitary adrenal (HPA) axis were investigated in rats. Social stress of isolation markedly reduced the total number of brain mast cells, most significantly by 90% in the first day. The extent of MC degranulation, 36-67%, in stressed rats did not significantly differ from that in control animals, 45-58%. Isolation stress substantially, though not significantly, increased the hypothalamic histamine content. The serum corticosterone levels in isolated rats did not significantly differ from the control levels. These results indicate that social stress of isolation considerably diminishes the number of brain MC and suggest that histamine which might be liberated from these cells does not significantly influence the HPA activity.

Mast cells synthesize, store, and release nerve growth factor

Mast cells and nerve growth factor (NGF) have both been reported to be involved in neuroimmune interactions and tissue inflammation. In many peripheral tissues, mast cells interact with the innervating fibers. Changes in the behaviors of both of these elements occur after tissue injury/inflammation. As such conditions are typically associated with rapid mast cell activation and NGF accumulation in inflammatory exudates, we hypothesized that mast cells may be capable of producing NGF. Here we report that (i) NGF mRNA is expressed in adult rat peritoneal mast cells; (ii) anti-NGF antibodies clearly stain vesicular compartments of purified mast cells and mast cells in histological sections of adult rodent mesenchymal tissues; and (iii) medium conditioned by peritoneal mast cells contains biologically active NGF. Mast cells thus represent a newly recognized source of NGF. The known actions of NGF on peripheral nerve fibers and immune cells suggest that mast cell-derived NGF may control adaptive/reactive responses of the nervous and immune systems toward noxious tissue perturbations. Conversely, alterations in normal mast cell behaviors may provoke maladaptive neuroimmune tissue responses whose consequences could have profound implications in inflammatory disease states, including those of an autoimmune nature.

Smooth muscle from aganglionic bowel in Hirschsprung's disease impairs neuronal development in vitro

Hirschsprung's disease results from the congenital absence of enteric neurons in human distal colon. The reason for aganglionosis is unknown but may reflect an unfavourable microenvironment for neuronal development. We asked if smooth muscle cells from the anganglionic region could affect neuronal development in vitro. Neurons from neonatal mouse superior cervical ganglia were added to cultures of smooth muscle obtained from normal or aganglionic regions of five patients with Hirschsprung's disease. Although neurons initially showed more rapid attachment to aganglionic smooth muscle, this was equal by 60 min and thereafter. Progressive increase in the diameter of the nerve cell body was characteristic of normal maturation in vitro. This was consistently inhibited by 15-22% in neurons grown on aganglionic muscle compared with normal controls over the 6-day test period (P < 0.05). This phenomenon was preserved when the smooth muscle cells were lysed by brief exposure to distilled water before initiation of co-culture (16-18% inhibition; P < 0.05). These data imply that smooth muscle of the aganglionic colon is less favourable for neuronal development than the normally innervated region and suggest a membrane-linked factor. Clearly, this persists in postnatal life and in vitro and may reflect an abnormality of cellular interaction causing Hirschsprung's disease.

Ionizing radiation reduces neurally evoked electrolyte transport in rat ileum through a mast cell-dependent mechanism

BACKGROUND/AIMS

Mechanisms of neuroimmune regulation of intestinal electrolyte transport under pathophysiological conditions are unclear. This study investigated the effect of ionizing radiation on ileal electrolyte transport.

METHODS

Rats were exposed to 10 Gy gamma-radiation and were killed 2, 24, and 48 hours later. Ileal segments were either mounted in Ussing chambers and exposed to electrical field stimulation, prostaglandin E2, leukotriene D4, or theophylline, or they were assayed for biochemical indices of inflammation. Other segments were processed for routine histological screening, mast cell counts, or immunohistochemical analysis of the distribution of vasoactive intestinal polypeptide or substance P immunoreactivity.

RESULTS

Basal short-circuit current was unchanged 2, 24, or 48 hours postirradiation. However, there was a reduction of tissue responsiveness to electrical field stimulation, prostaglandin E2, and theophylline but not to leukotriene D4. Decreased responsiveness at 2-hours postirradiation was blocked by pretreatment with the H1 antagonist pyrilamine. Tissue myeloperoxidase activity and 5-hydroxytryptamine content were not altered postirradiation, but tissue histamine and mucosal mast cells were significantly reduced at 24 and 48 hours. There were no significant changes in villus-crypt architecture until 48 hours postirradiation. There was no significant alteration in the distribution of immunoreactive vasoactive intestinal polypeptide or substance P.

CONCLUSIONS

Ionizing radiation reduced the transport response to neural stimulation. The effect correlated temporally with decreased mast cells and histamine, suggesting a functional role for previously reported mast cell-nerve interactions.

Nerve growth factor and autoimmune diseases

The initiation of a humoral immune response to a foreign antigen is a complex biologic process involving the interaction of many cell types and their secreted products. Autoimmune diseases, which are characterized by an abnormal activation of the immune system, probably result from the failure of normal self-tolerance mechanisms. The etiology of such illnesses, however, is far from being understood. While there have been extensive studies on the participation of the immune and endocrine systems in autoimmune diseases, few have dealt with nervous system-mediated immunoregulation in such situations. Evidence continues to grow suggesting that nerve growth factor (NGF), first identified for its activity in promoting the growth and differentiation of sensory and sympathetic neurons, may exert a modulatory role on neuroimmunoendocrine functions of vital importance in the regulation of homeostatic processes. Newly detected NGF-responsive cells belong to the hemopoietic-immune system and to populations in the brain involved in neuroendocrine functions. NGF levels are elevated in a number of autoimmune states, along with increased accumulation of mast cells. NGF and mast cells both appear to be involved in neuroimmune interactions and tissue inflammation. Moreover, mast cells themselves synthesize, store, and release NGF, proposing that alterations in normal mast cell behaviors may provoke maladaptive neuroimmune tissue responses whose consequences could have profound implications in inflammatory disease states, including those of an autoimmune nature. This review focuses on these cellular events and presents a working model which attempts to explain the close interrelationships of the neuroendocrinoimmune triade via a modulatory action of NGF.

Proliferation of mast cells in the smooth muscle of denervated rat jejunum

Mast cell hyperplasia and changes in phenotypic characteristics subsequent to myenteric and extrinsic denervation of a segment of rat jejunum were studied. The myenteric plexus and extrinsic nerves were ablated by serosal application of the cationic surfactant benzyldimethyltetradecylammonium chloride. There was a four-fold increase in the number of mast cells in the smooth muscle layers 15 days after denervation. This increase was sustained for at least 90 days after treatment. No increase in mast cell number was observed in the villus-crypt axis of the jejunum. Berberine sulfate fluorescent detection of heparin-containing mast cells demonstrated that a change in mast cell phenotype occurred between 20 and 90 days after the denervation procedure. The fact that myeloperoxidase activity was the same in denervated and control tissue within 5 days of denervation demonstrates the lack of a chronic inflammatory reaction. Our results suggest that mast cells might play a role in the gut wall re-modeling processes.

Interactions of mast cells with the nervous system ?Recent advances

This article reviews recent advances in the understanding of mast cell-nervous system interactions. It is drawn largely from work published within the last ten years, and discusses the anatomical and biochemical evidence of a functional connection between mast cells and the nervous system, and the implications that such a relationship may have for normal and abnormal physiological functioning. Mast cells are found at varying levels of association with the nervous system; in CNS parenchyma (mainly thalamus), in connective tissue coverings (e.g. meninges, endoneurium), and in close apposition to peripheral nerve endings in a variety of tissues. There is, as yet, no clearly defined role for mast cells in nervous system function, or vice-versa, and it seems most likely that their interactions fulfil mutually modulatory roles. By extension, pathological situations where one of the partners in this relationship is overly stimulated may lead to a dysregulation of the other, and contribute to disease symptomatology.

Sympathetic nerve contact alters membrane resistance of cells of the RBL-2H3 mucosal mast cell line

Indirect evidence links sensory nerves with mast cells (MC) in inflammatory reactions of airway, skin, and intestine. Isolated MC secrete histamine, serotonin, and other inflammatory mediators in response to neuropeptides such as substance P (SP) in vitro. To obtain direct evidence of nerve/MC interactions, we used a tissue culture model involving the co-culture of murine sympathetic neurons and rat basophilic leukemia (RBL) cells (homologous to mucosal MC). An electrophysiologic analysis of the consequences of neuron/RBL cell contacts showed that neurite contact with RBL cells reduced the control input resistance (Ro) of 61.8 +/- 3.2 (n = 110) M omega to 22.4 +/- 4.8 (n = 13) M omega (P less than 0.01) without change in the membrane potential. Time course studies showed that Ro of RBL cells with neurite contact was always lower by 30 to 54% than adjacent RBL cells lacking such contact. This effect was not seen in RBL cells cultured on rat fibroblasts. Direct application of SP, bradykinin, and somatostatin, but not acetylcholine, noradrenaline, or the putative neurotransmitter ATP, could partly mimic the effect of neurite contact. Therefore, neurotransmitter release from sympathetic neurons in contact with RBL cells may decrease RBL cell membrane resistance, possibly leading to activation.