Release of histamine from rat mast cells by acetylcholine

Neuroimmune communication of the cholinergic system in gut inflammation and autoimmunity

Neuroimmune communication in the body forms a bridge between two central regulatory systems of the body, i.e., nervous and immune systems. The cholinergic system is a crucial modulatory neurotransmitter in the central and peripheral nervous system. It includes the neurotransmitter acetylcholine (ACh), the enzyme required for the synthesis of ACh (choline acetyltransferase, ChAT), the enzyme required for its degradation (acetylcholinesterase, AChE), and cholinergic receptors (Nicotinic acetylcholine receptors and muscarinic acetylcholine receptors). The cholinergic system in neurons is well known for its role in cognitive function, sensory perception, motor control, learning, and memory processes. It has been shown that the non-neuronal cholinergic system (NNCS) is present in various tissues and immune cells and forms a neuroimmune communications system. In the present review, we discussed the NNCS on immune cells, its role in homeostasis and inflammatory reactions in the gut, and how it can be exploited in treating inflammatory responses.

Degranulation and expression of cytokines were modulated by diazinon in activated mast cells

Diazinon is an organophosphorus (OP) insecticides used in agriculture, home gardening and indoor pest control in Japan. It can activate macrophages and induce pro-inflammatory responses and has been reported to cause airway hyper-reactivity, suggesting the possibility of asthma exacerbation from exposure to OP insecticides. Despite the correlation between insecticide use and the pathogenesis of allergic diseases, there have been no reports on the effects of diazinon on mast cell function. Therefore, in this study, we investigated the effects of diazinon on mast cell function in rat basophilic leukemia (RBL)-2H3 cells. Surprisingly, we found that diazinon inhibited mast cell activation, although the degree of inhibition varied with concentration. Diazinon induced reactive oxygen species (ROS) generation and HO-1 expression at a concentration of 150 µM without affecting cell viability. Diazinon inhibited A23187-mediated degranulation and Tnf and Il4 expression in RBL-2H3 cells but did not affect calcium influx. Suppression of degranulation by diazinon was reversed when the culture supernatant was removed. As a signaling event downstream of calcium influx, diazinon inhibited the phosphorylation of extracellular signal-regulated kinase (ERK) induced by A23187, whereas the phosphorylation of p38 had little effect. IgE cross-linking-mediated degranulation as well as the induction of Tnf and IL4 expression was significantly inhibited by diazinon, while diazinon had little effect on calcium influx. In conclusion, diazinon inhibited mast cell activation, including degranulation and cytokine expression. When evaluating the in vivo effects of diazinon, its potential to inhibit mast cell activation should be considered in the pathophysiology and development of allergic diseases in terms of basic and clinical aspects, respectively, although the effect of diazinon varies depending on the cell type.

Mast cells in the autonomic nervous system and potential role in disorders with dysautonomia and neuroinflammation

Mast cells (MC) are ubiquitous in the body, and they are critical for not only in allergic diseases but also in immunity and inflammation, including having potential involvement in the pathophysiology of dysautonomias and neuroinflammatory disorders. MC are located perivascularly close to nerve endings and sites such as the carotid bodies, heart, hypothalamus, the pineal gland, and the adrenal gland that would allow them not only to regulate but also to be affected by the autonomic nervous system (ANS). MC are stimulated not only by allergens but also many other triggers including some from the ANS that can affect MC release of neurosensitizing, proinflammatory, and vasoactive mediators. Hence, MC may be able to regulate homeostatic functions that seem to be dysfunctional in many conditions, such as postural orthostatic tachycardia syndrome, autism spectrum disorder, myalgic encephalomyelitis/chronic fatigue syndrome, and Long-COVID syndrome. The evidence indicates that there is a possible association between these conditions and diseases associated with MC activation. There is no effective treatment for any form of these conditions other than minimizing symptoms. Given the many ways MC could be activated and the numerous mediators released, it would be important to develop ways to inhibit stimulation of MC and the release of ANS-relevant mediators.

Understanding food allergy through neuroimmune interactions in the gastrointestinal tract

Food allergies are adverse immune reactions to food proteins in the absence of oral tolerance, and the incidence of allergies to food, including peanut, cow's milk, and shellfish, has been increasing globally. Although advancements have been made toward understanding the contributions of the type 2 immune response to allergic sensitization, crosstalk between these immune cells and neurons of the enteric nervous system is an area of emerging interest in the pathophysiology of food allergy, given the close proximity of neuronal cells of the enteric nervous system and type 2 effector cells, including eosinophils and mast cells. At mucosal sites, such as the gastrointestinal tract, neuroimmune interactions contribute to the sensing and response to danger signals from the epithelial barrier. This communication is bidirectional, as immune cells express receptors for neuropeptides and transmitters, and neurons express cytokine receptors, allowing for the detection of and response to inflammatory insults. In addition, it seems that neuromodulation of immune cells including mast cells, eosinophils, and innate lymphoid cells is critical for amplification of the type 2 allergic immune response. As such, neuroimmune interactions may be critical targets for future food allergy therapies. This review evaluates the contributions of local enteric neuroimmune interactions to the underlying immune response in food allergy and discusses considerations for future investigations into targeting neuroimmune pathways for treatment of food allergies.

α7- and α9-Containing Nicotinic Acetylcholine Receptors in the Functioning of Immune System and in Pain

Nicotinic acetylcholine receptors (nAChRs) present as many different subtypes in the nervous and immune systems, muscles and on the cells of other organs. In the immune system, inflammation is regulated via the vagus nerve through the activation of the non-neuronal α7 nAChR subtype, affecting the production of cytokines. The analgesic properties of α7 nAChR-selective compounds are mostly based on the activation of the cholinergic anti-inflammatory pathway. The molecular mechanism of neuropathic pain relief mediated by the inhibition of α9-containing nAChRs is not fully understood yet, but the role of immune factors in this process is becoming evident. To obtain appropriate drugs, a search of selective agonists, antagonists and modulators of α7- and α9-containing nAChRs is underway. The naturally occurring three-finger snake α-neurotoxins and mammalian Ly6/uPAR proteins, as well as neurotoxic peptides α-conotoxins, are not only sophisticated tools in research on nAChRs but are also considered as potential medicines. In particular, the inhibition of the α9-containing nAChRs by α-conotoxins may be a pathway to alleviate neuropathic pain. nAChRs are involved in the inflammation processes during AIDS and other viral infections; thus they can also be means used in drug design. In this review, we discuss the role of α7- and α9-containing nAChRs in the immune processes and in pain.

Impaired sweating in patients with cholinergic urticaria is linked to low expression of acetylcholine receptor CHRM3 and acetylcholine esterase in sweat glands

Background

Cholinergic urticaria (CholU), a frequent form of chronic inducible urticaria, is characterized by itchy wheals and angioedema in response to sweating. As of now, the rate and pathophysiological relevance of impaired sweating in patients with CholU are ill-defined.

Aim

To assess in CholU patients the rate and extent of impaired sweating and its links to clinical and pathophysiological features of CholU.

Patients and methods

We assessed sweating in patients with CholU (n = 13) subjected to pulse-controlled ergometry (PCE) provocation testing. Pre- and post-PCE biopsies of lesional (L) and non-lesional (NL) skin were analyzed for the expression of acetylcholine receptor M3 (CHRM3) and acetylcholine esterase (ACh-E) by quantitative histomorphometry and compared to those of healthy control subjects (HCs). CholU patients were assessed for disease duration and severity as well as other clinical features.

Results

Of the 13 patients with CholU, 10 showed reduced sweating in response to PCE provocation, and 3 had severely reduced sweating. Reduced sweating was linked to long disease duration and high disease severity. CholU patients with impaired sweating responses showed reduced sweat gland epithelial expression of CHRM3 and ACh-E.

Conclusion

Reduced sweating is common in CholU patients, especially in those with long-standing and severe disease, and it can be severe. Reduced expression of CHRM3 and ACh-E may be the cause or consequence of CholU in patients with impaired sweating, and this should be explored by further studies.

Cholinergic Urticaria, an Effective and Safe "Off Label" Use of Dupilumab: A Case Report with Literature Review

Cholinergic Urticaria (CholU) is a form of generalized urticaria induced by an increase in core body temperature that activates the sweat reflex. Clinically it is characterized by localized and highly itchy wheals with surrounding erythema and can occur in response to exercise, hot baths and/or emotional stress. Dupilumab is a fully human monoclonal antibody specifically designed to simultaneously inhibit the activity of interleukin-4 (IL-4) and interleukin-13 (IL-13), which play a key role in the inflammation cascade of type 2. We report the case of a 26-year-old man suffering from CholU for 3 years, unresponsive to standard treatment in which off-label therapy was undertaken with Dupilumab, 600 mg subcutaneous as a loading dose and then 300 mg every 15 days. The daily Visual Analogue Scale (VAS) score was used to assess the efficacy of the therapy. Already after the first two administrations, the patient no longer had CholU episodes and resumed regular sporting activity, with a marked improvement in the quality of life. A possible mechanism of Dupilumab in reducing the manifestations of CholU is the blocking of the IL-4 pathway and the expression of the high-affinity IgE receptor (FcεR1) on B cells, mast cells (MCs) and basophils. By decreasing the production of FcεR1, the adhesion of IgE to the surface of MCs decreases with consequent reduction of MCs activation and histamine release. Further experience and large-scale studies may be needed to establish whether Dupilumab can be a therapeutic alternative in CholU, especially in patients who do not respond to standard treatment.

PACAP38- and VIP-induced cluster headache attacks are not associated with changes of plasma CGRP or markers of mast cell activation

BACKGROUND

Pituitary adenylate cyclase-activating polypeptide-38 (PACAP38) and vasoactive intestinal polypeptide can provoke cluster headache attacks in up to half of cluster headache patients in their active phase. At present, it is unknown whether provoked attacks are mediated via calcitonin gene-related peptide or mast cell activation.

METHODS

All enrolled patients with cluster headache were randomly allocated to receive a continuous infusion of either PACAP38 (10 pmol/kg/min) or vasoactive intestinal polypeptide (8 pmol/kg/min) over 20 min. We collected clinical data and measured plasma levels of calcitonin gene-related peptide and markers of mast cell activation (tryptase and histamine) at fixed time points: at baseline (T₀), at the end of the infusion (T₂₀), 10 min after the infusion (T₃₀), and 70 min after the infusion (T₉₀).

RESULTS

Blood was collected from episodic cluster headache patients in active phase (n = 14), episodic cluster headache patients in remission (n = 15), and chronic cluster headache patients (n = 15). At baseline, plasma levels of calcitonin gene-related peptide, tryptase, and histamine were not different among the three study groups. Plasma levels of calcitonin gene-related peptide (p = 0.7074), tryptase (p = 0.6673), or histamine (p = 0.4792) remained unchanged during provoked attacks compared to attack-free patients.

CONCLUSION

Cluster headache attacks provoked by either PACAP38 or vasoactive intestinal polypeptide were not accompanied by alterations of plasma calcitonin gene-related peptide, tryptase or histamine. The provoked attacks may not be mediated by calcitonin gene-related peptide or mast cell activation.Trial Registration: The study is registered at ClinicalTrials.gov (NCT03814226).

OnabotulinumtoxinA injection towards the SPG for treating symptoms of refractory chronic rhinosinusitis with nasal polyposis: a pilot study

BACKGROUND AND OBJECTIVE

The main objective of this prospective, open, uncontrolled pilot study was to investigate the safety of administering onabotulinumtoxinA (BTA) towards the sphenopalatine ganglion (SPG) in 10 patients with refractory chronic rhinosinusitis with nasal polyposis (CRSwNP) using a novel injection tool, the MultiGuide^®.

MATERIAL AND METHODS

A one-month baseline period was followed by bilateral injections of 25 U BTA in the SPG and a follow-up of 12 weeks. The primary outcome was adverse events (AE), and the main efficacy outcome was a 50% reduction in visual analogue scale (VAS) symptoms for nasal obstruction and rhinorrhea in months 2 and 3 post-treatment compared to baseline.

RESULTS

We registered 13 AEs, none of which were serious, however, one patient experienced diplopia which moderately affected his daily activities. The symptoms slowly improved and resolved 4 weeks after injection. Five patients were treatment responders with at least 50% median reduction in the nasal obstruction, and four were treatment responders concerning rhinorrhea.

CONCLUSIONS

Injection of BTA toward the SPG using the MultiGuide^® in patients with CRSwNP appears to be safe but with a potential for moderately disabling side effects. The study indicates a beneficial effect on nasal obstruction.

Acquired Idiopathic Generalized Anhidrosis (AIGA) and Its Complications: Implications for AIGA as an Autoimmune Disease

Acquired idiopathic generalized anhidrosis (AIGA) is a rare disorder in which systemic anhidrosis/hypohidrosis occurs without causative dermatological, metabolic or neurological disorder. Most cases of AIGA have been reported in Asia, especially in Japan, but there have been only a few reports in Europe and the United States. Severe AIGA may result in heatstroke and can reduce quality of life due to restriction of exercise and outdoor works. AIGA is often accompanied by cholinergic urticaria (CholU), and it is thought that AIGA and CholU with anhidrosis/hypohidrosis belong to the same spectrum of the disease. However, the pathophysiology of AIGA has not yet been clarified. Decreased expression of cholinergic receptor M3 on the epithelial cells of eccrine sweat glands is often accompanied by T cell infiltration around eccrine apparatus, suggesting an immunological mechanism of disordered perspiration. AIGA is occasionally associated with various complications indicative of autoimmune disorders. The association of autoimmune complications further suggests that AIGA is an autoimmune disorder. Studies on complications may lead to a better understanding of the pathophysiology of AIGA.

Neuro-Immune Modulation Effects of Sacral Nerve Stimulation for Visceral Hypersensitivity in Rats

Background: Visceral hypersensitivity (VH) is one of the underlying pathophysiologies of irritable bowel syndrome. Mast cell overactivation has been found to be one of the main causes of VH. We investigated the effects and mechanisms of actions of sacral nerve stimulation (SNS) on visceral pain in a rodent model of VH.

Methods: The VH was established by an intrarectal infusion of AA in 10-day-old pups. Rats were chronically implanted with electrodes for SNS and recording electromyogram (EMG) and electrocardiogram. The acute study was performed in 2-randomized sessions with SNS (14 Hz, 330 μs, 40% motor threshold or MT, 30 min) or sham-SNS. Later on, rats were randomized into SNS/sham-SNS groups and a chronic study was performed with 2 h-daily SNS or sham-SNS for 21 days. Visceromotor reflexes were assessed by abdominal EMG and withdrawal reflex (AWR). Colon tissues were collected to study colonic acetylcholine (ACh), the enteric neurons (ChAT, nNOS, and PGP9.5), mast cells activity [Tryptase, prostaglandins E2 (PGE2), and cyclooxygenases-2 (COX2)] and pain markers [nerve growth factor (NGF) and Sub-P].

Key Results: Sacral nerve stimulation significantly improved visceromotor reflexes assessed by the EMG and AWR, compared with sham-SNS. SNS normalized the protein expressions of ChAT and nNOS and regulated mast cells activity by downregulating Tryptase, COX2, and PGE2. Neonatal AA administration upregulated NGF and Sub-P; chronic SNS significantly decreased these pain biomarkers. Concurrently, chronic SNS increased ACh in colon tissues and vagal efferent activity.

Conclusions: Sacral nerve stimulation reduces VH in rats and this ameliorating effect might be attributed to the suppression of mast cell overactivation in the colon tissue via the modulation of autonomic nervous system functions.

Acetylcholine-induced whealing in cholinergic urticaria - What does it tell us?

BACKGROUND

Cholinergic urticaria (CholU) is characterized by the occurrence of itchy wheals induced by sweating. Intradermal injections of acetylcholine (ACh) have been proposed to help with diagnosing CholU and subgrouping of patients, but controlled studies are largely missing.

OBJECTIVE

To compare the rates of positive ACh test results in well characterized CholU patients and controls and to identify clinical features of CholU linked to ACh reactivity.

METHODS

Acetylcholine was injected intradermally into 38 CholU patients and 73 matched healthy controls. Wheal and flare skin responses were assessed after 15 and 30 min and correlated with clinical features of CholU.

RESULTS

At 15 min after intradermal injections of ACh, wheal and flare responses were significantly more frequent in CholU patients than healthy controls, wheals: 34 % vs.15% (P = 0.028); flares: 50 % vs.18 % (P <0.001). Also, wheals were 37 % and flares 172 % larger and of longer duration in CholU patients than in healthy controls (both P < 0.01). CholU patients with ACh-induced wheals (ACh⁺) had larger flare but not wheal responses in response to histamine than those without (ACh^-; P = 0.011). Also, ACh-induced wheal responses were significantly correlated with sweating (r = 0.54, P = 0.046) in CholU patients. Finally, wheal responses lasted longer in ACh⁺ than in ACh^- patients (P = 0.03).

CONCLUSION

Intradermal ACh testing does not allow for the identification of CholU patients due to its low sensitivity. ACh-induced wheals, in patients with CholU, is linked to sweating and longer lasting symptoms. Intradermal ACh testing is an interesting tool for mechanistic studies in CholU.

Cholinergic System and Its Therapeutic Importance in Inflammation and Autoimmunity

Neurological and immunological signals constitute an extensive regulatory network in our body that maintains physiology and homeostasis. The cholinergic system plays a significant role in neuroimmune communication, transmitting information regarding the peripheral immune status to the central nervous system (CNS) and vice versa. The cholinergic system includes the neurotransmitter\ molecule, acetylcholine (ACh), cholinergic receptors (AChRs), choline acetyltransferase (ChAT) enzyme, and acetylcholinesterase (AChE) enzyme. These molecules are involved in regulating immune response and playing a crucial role in maintaining homeostasis. Most innate and adaptive immune cells respond to neuronal inputs by releasing or expressing these molecules on their surfaces. Dysregulation of this neuroimmune communication may lead to several inflammatory and autoimmune diseases. Several agonists, antagonists, and inhibitors have been developed to target the cholinergic system to control inflammation in different tissues. This review discusses how various molecules of the neuronal and non-neuronal cholinergic system (NNCS) interact with the immune cells. What are the agonists and antagonists that alter the cholinergic system, and how are these molecules modulate inflammation and immunity. Understanding the various functions of pharmacological molecules could help in designing better strategies to control inflammation and autoimmunity.

Direct and indirect action modes of acetylcholine in cholinergic urticaria

Cholinergic urticaria (CholU) manifests small, itchy and/or painful wheals occurring upon perspiration and mechanically involving acetylcholine (Ach). Although a considerable number of studies have been conducted, the pathomechanisms underlying perspiration-associated release of histamine remain to be elucidated. We have proposed that CholU can be categorized into two major subtypes: Ach-indirectly induced, sweat allergic type and Ach-directly induced, depressed sweating type. In the former type, Ach evokes perspiration, and some sweat antigen(s) leaking from the sweat ducts to the dermis may stimulate mast cells to release histamine. In this scenario, the ducts might be damaged or obstructed for sweat leakage, and patients frequently exhibit positive autologous sweat skin test, representing "sweat allergy (hypersensitivity)". On the other hand, the latter Ach-mast cell directly interacting type, typically seen as "CholU with anhidrosis and/or hypohidrosis (CUAH)", eccrine sweat gland epithelial cells lack cholinergic receptor M3 expression. The expression of cholinergic receptors is completely absent in the anhidrotic areas and only slightly expressed in the hypohidrotic areas. In the hypohidrotic area, where pinpoint wheal occurs, it is hypothesized that released Ach cannot be completely trapped by cholinergic receptors of eccrine glands and overflows to the adjacent mast cells, leading to wheal formation. Thus, sweat allergy is not a requirement in this depressed sweating type. Although some additional complications, such as angioedema, anaphylaxis, and cold urticaria, have been documented, these two types represent the modes of action of Ach in this enigmatic urticaria.

Vasopressin augments TNBS-induced colitis through enteric neuronal V1a receptor-mediated COX-2-dependent prostaglandin release from mast cells in mice

BACKGROUND

Inflammatory bowel disease (IBD) is a functional disorder with chronic and relapsing clinical features. Vasopressin (VP) is a hormone responsible for water and stress homeostasis and also regulates gastrointestinal inflammation and motility. We explored whether VP was related to IBD pathogenesis and its possible pathway.

METHODS

Colitis was induced by 2,4,6-trinitrobenzenesulfonic acid (TNBS) in mice. The disease activity and colonic damage were evaluated through a scoring system. Locations of the V_1a receptor were revealed by immunochemistry method in colon. Ussing chamber technique was performed for the electrophysiological characterization by using rat ileum. The (Arg⁸ )-Vasopressin (AVP)-evoked short-circuit current (Isc) was recorded in the presence of conivaptan (V_1a and V₂ receptor antagonist), tolvaptan (V_1b receptor antagonist), tetrodotoxin (TTX), atropine, cyclooxygenase (COX) inhibitors (indomethacin, nonspecific COX antagonist; SC560, COX-1 antagonist; NS560, COX-2 antagonist), and a stabilizer of mast cell (cromolyn sodium), respectively.

KEY RESULTS

TNBS resulted in the obvious loss of body weight and tissue damages in mice. AVP significantly aggravated the TNBS-induced colitis, which was attenuated by conivaptan but not tolvaptan. V_1a receptors were found immunopositive in neurons among the enteric nervous system. AVP evoked a pulsatile response in Isc. Its amplitude, frequency, and cycle duration were around 8-15 µA/cm² , 10-11 mHz, and 1.5 minutes, respectively. Notably, the AVP-evoked change in Isc was abolished by TTX, atropine, conivaptan, indomethacin, NS560, and cromolyn sodium, respectively.

CONCLUSIONS AND INFERENCES

VP-V_1a receptor played the proinflammatory role in TNBS-induced colitis by promoting COX-2-dependent prostaglandin release from mucosal mast cells, which was mediated by the cholinergic pathway.

Modulation of the extraneuronal cholinergic system on main innate response leukocytes

The expression of elements of the cholinergic system has been demonstrated in non-neuronal cells, such as immune cells, where acetylcholine modulates innate and adaptive responses. However, the study of the non-neuronal cholinergic system has focused on lymphocyte cholinergic mechanisms, with less attention to its role of innate cells. Considering this background, the aims of this review are 1) to review information regarding the cholinergic components of innate immune system cells; 2) to discuss the effect of cholinergic stimuli on cell functions; 3) and to describe the importance of cholinergic stimuli on host immunocompetence, in order to set the base for the design of intervention strategies in the biomedical field.

Cholinergic Modulation of Type 2 Immune Responses

In recent years, the bidirectional relationship between the nervous and immune system has become increasingly clear, and its role in both homeostasis and inflammation has been well documented over the years. Since the introduction of the cholinergic anti-inflammatory pathway, there has been an increased interest in parasympathetic regulation of both innate and adaptive immune responses, including T helper 2 responses. Increasing evidence has been emerging suggesting a role for the parasympathetic nervous system in the pathophysiology of allergic diseases, including allergic rhinitis, asthma, food allergy, and atopic dermatitis. In this review, we will highlight the role of cholinergic modulation by both nicotinic and muscarinic receptors in several key aspects of the allergic inflammatory response, including barrier function, innate and adaptive immune responses, and effector cells responses. A better understanding of these cholinergic processes mediating key aspects of type 2 immune disorders might lead to novel therapeutic approaches to treat allergic diseases.

Hyperosmolarity evokes histamine release from ileum mucosa by stimulating a cholinergic pathway

Changes in extracellular osmolarity lead to alteration in cellular volume. In the study, we examined the effects of hyperosmolarity on short-circuit currents (Isc) in the rat ileum using the Ussing chamber technique. Mucosal exposure to 20 mM glucose evoked a decrease of I_SC in the rat ileum, which was antagonized by the stretch-activated channel blocker GdCl3, TTX and atropine, respectively. In contrast, it was not blocked by phlorizin, a Na⁺-glucose cotransporter SGLT1 inhibitor. Furthermore, the unabsorbed substances, such as sucrose, lactulose or urea, also induced a decrease of I_SC in rat ileum. ELISA results revealed that 20 mM glucose stimulated the release of histamine from rat ileum mucosa, which was attenuated by TTX. In addition, the glucose-induced I_SC was depressed by pyrilamine, a histamine H₁ receptor blocker (H₁ antagonist) whereas it was not affected by ranitidine (H₂ antagonist), clobenpropit (H₃ antagonists) or JNJ7777120 (H₄ antagonist), respectively. The ion substitution experiments suggest that the changes of Na⁺ and HCO₃^- ion flux underlie the glucose-induced I_SC. In conclusion, osmotic stimulus decreased the basal I_SC of rat ileum by evoking histamine release from ileum mucosa. The changes of Na⁺ and HCO₃^- ion transport are involved in the glucose-evoked decrease of basal I_SC.

Neuroendocrinology of mast cells: Challenges and controversies

Mast cells (MC) are hemotopoietically derived tissue immune cells that are ubiquitous in the body, including neuroendocrine organs such as the hypothalamus, pineal, pituitary, ovaries, pancreas and uterus where their action is not well understood. Mast cells have historically been associated with allergies because of their rich content of histamine and tryptase, but more recently with regulation of immunity and inflammation due to their synthesis and release of numerous cytokines and chemokines. Mast cells are located perivascularly and express numerous receptors for diverse ligands such as allergens, pathogens, neurotransmitters, neuropeptides and hormones including acetylcholine, calcitonin gene-related peptide (CGRP), corticosteroids, corticotropin-releasing hormone (CRH), β-endorphin, epinephrine, 17β-oestradiol, gonadotrophins, hemokinin-A (HKA), leptin, melatonin, neurotensin (NT), parathyroid hormone (PTH), substance P (SP) and vasoactive intestinal peptide (VIP). Moreover, MC can synthesize and release most of their neurohormonal triggers, including adrenocorticotropin hormone (ACTH), CRH, endorphins, HKA, leptin, melatonin, NT, SP and VIP. Animal experiments have shown that diencephalic MC increase in number during courting in doves, while stimulation of brain and nasal MC leads to activation of the hypothalamic-pituitary-adrenal (HPA) axis. Recent evidence indicates that MC reactivity exhibits diurnal variations, and it is interesting that melatonin appears to regulate MC secretion. However, the way MC change their phenotype or secrete specific molecules selectively at different pathophysiological settings still remains unknown. Mast cells developed over 500 million years ago and may have served as the original prototype neuroimmunoendocrine cell and then evolved into a master regulator of such interactions, especially as most of the known diseases involve neuroinflammation that worsens with stress.

Atopic predisposition in cholinergic urticaria patients and its implications

BACKGROUND

Cholinergic urticaria (CholU) is a frequent chronic urticaria disorder with itchy weal and flare-type skin reactions in response to physical exercise or passive warming. A higher frequency of atopy among CholU patients has been reported, but the significance of this observation is unclear.

OBJECTIVE

To assess the prevalence and relevance of atopy in CholU patients.

MATERIALS AND METHODS

Thirty CholU patients were assessed for atopic skin diathesis (atopic predisposition) by use of the Erlangen Atopy Score and divided into atopic and non-atopic predisposed CholU individuals. Both groups were assessed for disease severity (CholUSI) and activity (CholUAS7), quality of life impairment [Dermatology Life Quality Index (DLQI) and CU-Q₂ OL], seasonal exacerbation, total and specific serum IgE and comorbidities.

RESULTS

CholU patients were found to exhibit high rates of atopic predisposition (57%), with higher prevalence and scores in female than in male patients. High Erlangen Atopy Scores were linked to high CholU severity, activity and impact on QoL. Atopic predisposed CholU patients show different seasonal exacerbation patterns, IgE specificity and comorbidity profiles as compared to non-atopic CholU patients.

CONCLUSION

Atopic predisposition and cholinergic urticaria appear to be linked more closely than previously thought, which suggests shared pathogenetic mechanisms. Atopic patients with cholinergic urticaria have more severe disease and poorer quality of life than those who do not. Thus, all cholinergic urticaria patients should be assessed for atopic predisposition.

The parasympathetic nervous system as a regulator of mast cell function

Often considered as the archetype of neuroimmune communication, much of our understanding of the bidirectional relationship between the nervous and immune systems has come from the study of mast cell-nerve interaction. Mast cells play a role in resistance to infection and are extensively involved in inflammation and subsequent tissue repair. Thus, the relationship between mast cells and neurons enables the involvement of peripheral and central nervous systems in the regulation of host defense mechanisms and inflammation. Recently, with the identification of the cholinergic anti-inflammatory pathway, there has been increased interest in the role of the parasympathetic nervous system in regulating immune responses. Classical neurotransmitters and neuropeptides released from cholinergic and inhibitory NANC neurons can modulate mast cell activity, and there is good evidence for the existence of parasympathetic nerve-mast cell functional units in the skin, lung, and intestine that have the potential to regulate a range of physiological processes.

Combining small-volume metabolomic and transcriptomic approaches for assessing brain chemistry

The integration of disparate data types provides a more complete picture of complex biological systems. Here we combine small-volume metabolomic and transcriptomic platforms to determine subtle chemical changes and to link metabolites and genes to biochemical pathways. Capillary electrophoresis–mass spectrometry (CE–MS) and whole-genome gene expression arrays, aided by integrative pathway analysis, were utilized to survey metabolomic/transcriptomic hippocampal neurochemistry. We measured changes in individual hippocampi from the mast cell mutant mouse strain, C57BL/6 Kit^W-sh/W-sh. These mice have a naturally occurring mutation in the white spotting locus that causes reduced c-Kit receptor expression and an inability of mast cells to differentiate from their hematopoietic progenitors. Compared with their littermates, the mast cell-deficient mice have profound deficits in spatial learning, memory, and neurogenesis. A total of 18 distinct metabolites were identified in the hippocampus that discriminated between the C57BL/6 Kit^W-sh/W-sh and control mice. The combined analysis of metabolite and gene expression changes revealed a number of altered pathways. Importantly, results from both platforms indicated that multiple pathways are impacted, including amino acid metabolism, increasing the confidence in each approach. Because the CE–MS and expression profiling are both amenable to small-volume analysis, this integrated analysis is applicable to a range of volume-limited biological systems.

Pathogenesis of cholinergic urticaria in relation to sweating

Cholinergic urticaria (CU) has clinically characteristic features, and has been frequently described in the literature. However, despite its comparatively old history, the pathogenesis and classification remains to be clarified. CU patients are occasionally complicated by anhidrosis and/or hypohidrosis. This reduced-sweat type should be included in the classification because the therapeutic approaches are different from the ordinary CU. It is also well-known that autologous sweat is involved in the occurrence of CU. More than half of CU patients may have sweat hypersensitivity. We attempt to classify CU and address the underlying mechanisms of CU based on the published data and our findings. The first step for classification of CU seems to discriminate the presence or absence of hypersensitivity to autologous sweat. The second step is proposed to determine whether the patients can sweat normally or not. With these data, the patients could be categorized into three subtypes: (1) CU with sweat hypersensitivity; (2) CU with acquired anhidrosis and/or hypohidrosis; (3) idiopathic CU. The pathogenesis of each subtype is also discussed in this review.

Evaluation of different combined regimens in the treatment of cholinergic urticaria

BACKGROUND

: Cholinergic urticaria is uncommon and accounts for 10% of all young adults. To date, there is no effective therapy for cholinergic urticaria.

OBJECTIVE

: To determine the therapeutic efficacy of different drug combinations in the treatment of cholinergic urticaria.

PATIENTS AND METHODS

: The participants included in the study are in the age range of 16 to 29 years, with cholinergic urticaria of any duration as diagnosed by physicians. Patients were recruited from Asthma and Allergy Centers in Baghdad and Tikrit. The selected patients were divided randomly into 3 groups according to the treatment protocol. All patients completed screening before treatment.

RESULTS

: The study indicated that cholinergic urticaria was completely controlled in 30.4% of patients (group A) receiving 4 mg of chlorpheniramine maleate, half hour before the exercise, plus chlordiazopoxide (5 mg) and clindium bromide (2.5 mg) tablets, 3 times daily. However, cure rate was higher (83.1%) in patients (group B) receiving 4 mg of chlorpheniramine maleate (histadine), 3 times daily, plus 25 mg of maprotiline HCl (ludiomil), once daily at night. Furthermore, the complete cure rate was 85.4% in patients (group C) receiving 4 mg of chlorpheniramine maleate (histadine)3 times daily, plus 200 mg of cimetidine (tagadine), 3 times daily. The frequency of relapse was higher in group A (89%) as compared with group B (68.4%) and group C (23.5%) (P < 0.0001).

CONCLUSIONS

: Combination of H1 and H2 antagonists was more effective based on complete control of cholinergic urticaria with lower relapsing rate. However, a future placebo-controlled clinical trial taking in consideration higher H1 antagonists than we used is warranted.

Gustatory itching: an unusual complication following superficial parotidectomy

OBJECTIVE

We report the previously undocumented complication of gustatory itching following superficial parotidectomy.

METHOD

Case report and review of the English literature concerning Frey's syndrome, complications of superficial parotidectomy and the pathophysiology of itching.

RESULTS

A 49-year-old woman developed gustatory itching following a superficial parotidectomy. Her symptoms were satisfactorily managed with topical and oral antihistamine preparations. We propose a neurophysiological pathway involving acetylcholine and histamine to explain this phenomenon.

CONCLUSION

To our knowledge, this is the first documented case of gustatory itching following superficial parotidectomy. The use of antihistamine preparations appears to effectively manage this symptom, without the need for invasive procedures.

New concepts of hive formation in cholinergic urticaria

Patients with cholinergic urticaria (CU) show a number of small, short-lasting hives when their body core temperature increases, usually during sweating following exercise or bathing. The precise mechanism(s) of hive formation in CU has been unclear except for the involvement of acetylcholine. We recently reported that most CU patients show immediate-type skin responses to their own sweat, whereas the rest of CU patients have positive autologous serum skin tests (ASSTs). The former group produced satellite wheals following acetylcholine injection, whereas the latter group produced hives in conjunction with hair follicles. We propose two subtypes of CU: 1) a sweat-hypersensitivity type with strong hypersensitivity to autologous sweat, nonfollicular hives, development of satellite wheals, and lack of positive ASST; and 2) a follicular type with follicular hives and positive ASST, but no hypersensitivity to autologous sweat or satellite wheals. We discuss the mechanisms of hive formation in these subtypes.

Nicotinic acetylcholine receptors on basophils and mast cells

Anaphylaxis in response to drugs administered during anaesthesia is a rare but potentially catastrophic event. The anaesthetic drugs most commonly associated with anaphylaxis are neuromuscular blocking agents. As these drugs act on the nicotinic acetylcholine receptor of the neuromuscular junction, potentiation of anaphylaxis by a nicotinic receptor on basophils and mast cells is plausible. The aim of this study was to investigate whether nicotinic acetylcholine receptors are present on a human basophil and mast cell lines as their presence may suggest a mechanism of associated anaphylaxis. Nicotinic receptors were demonstrated on a basophil and a mast cell line using an alpha-bungarotoxin-fluorescein conjugate by flow cytometry and by both conventional and confocal microscopic techniques. The identity of this receptor was confirmed by reverse transcriptase PCR and quantitative PCR.

Cutaneous and pulmonary reactivity in cholinergic urticaria

Cutaneous and pulmonary reactions to mediators of inflammation were studied in twenty-one patients with cholinergic urticaria, in twenty patients with other types of urticaria, and in seventeen healthy controls. Compared with controls and patients with moderate disease, patients severely affected by cholinergic urticaria or other types of urticaria developed larger weals at sites of injection with histamine (9 X 10(-7) M), but not with compound 48/80 (0.1%), acetylcholine (7 X 10(-5) M), kallikrein (4 X 10(-10) M). On bronchial challenge with acetylcholine (7 X 10(-5) M), pulmonary resistance increased markedly only in severely affected cholinergic urticaria patients. There was no correlation between cutaneous and pulmonary reactivity in individual subjects. Patients with cholinergic urticaria therefore demonstrate features of heightened skin reactivity (shared by patients with other urticarias) and an increased bronchial reactivity (as found in latent asthmatics).

Corticotropin-releasing hormone induces skin vascular permeability through a neurotensin-dependent process

Many skin disorders are associated with increased numbers of activated mast cells and are worsened by stress; however, the mechanism underlying these processes is not understood. Corticotropin-releasing hormone (CRH) is secreted under stress from the hypothalamus, but also in the skin, where it induces mast cell activation and vascular permeability. We investigated the effect of CRH in a number of animal models by using i.v. Evans blue extravasation as a marker of vascular permeability. Intradermal CRH is among the most potent peptides at 100 nM, its effect being nearly comparable to that of neurotensin (NT). Pretreatment of skin injection sites with the NT receptor antagonist SR48692 blocks CRH-induced vascular permeability, which is diminished in NT-/- mice, implying that NT is necessary for the effect of CRH. CRH and NT precursor mRNA are shown to be expressed in both dorsal root ganglia and skin, whereas the latter also expresses mRNA for prohormone convertase 5, an enzyme that cleaves pro-NT into its active form. We also show that the effect of both CRH and NT is absent in W/W(v) mast cell-deficient mice; however, only a fraction of skin mast cells express CRH receptors, as shown by FACS analysis of CRH receptor (CRHR) and c-kit double-positive disaggregated mouse skin mast cells. These findings suggest that CRH induces skin vascular permeability through NT acting on mast cells and that both peptides should be considered in the pathogenesis of skin disorders exacerbated by stress.

The distribution of mast cells in the human area postrema

The topography and phenotype of mast cells in the human area postrema, together with correlation between mast-cell density and microvessel density (MVD), were analysed in 16 brains. Transverse serial sections of formalin-fixed, paraffin-embedded brainstems were stained with toluidine blue and alcian blue/safranin stainings, and with anti-tryptase and anti-CD31 monoclonal antibodies. The mean (+/- SD) numbers of mast cells per section were 1.3 +/- 0.8 and 1.2 +/- 0.7 with toluidine blue and alcian blue/safranin, respectively, whereas anti-tryptase monoclonal antibody showed a mean of 5.1 +/- 2.4 cells. Mast cells were alcian blue- and safranin-positive in 56%, because of the coexistence of low-sulphated (blue-staining) and high-sulphated (red-staining) granules. No significant linear correlation between mast-cell density (4.9 mm(-2)) and MVD (114.5 mm(-2)) was found (r(2) = 0.19, P = 0.09). Mast cells were frequently located close to blood vessels (55%) (33% to venules, 22% to arterioles), indicating that their products play a role in the regulation of blood flow and in vessel permeability in the area postrema. Mast cells were located subependymally in 44% and close to the dorsal aspect of the nucleus of the tractus solitarius in 31%, suggesting a subregional distribution.

Catecholaminergic and acetylcholine esterase containing nerves of cranial and spinal dura mater in humans and rodents

The innervation of cranial and spinal dura mater in humans and rodents was studied by examining several dural zones (vascular, perivascular, intervascular) in different regions. Characterization and distribution of dural acetylcholinesterase-positive nerve fibers, catecholaminergic nerve fibers, and mast cells are analyzed and discussed. The results of chemical and surgical sympathectomy as well as the relationships between catecholaminergic nerve fibers and mast cells are studied. Our results are discussed in the light of possible implications in the physiopathology of dural algic syndromes including cephalalgia and spinal pain.

Cholinergic urticaria associated with acquired generalized hypohidrosis: report of a case and review of the literature

Acquired generalized hypohidrosis/anhidrosis is a rare condition of unknown pathogenesis, while idiopathic cholinergic urticaria is relatively common. We report the case of a 19-year-old male with cholinergic urticaria and acquired generalized hypohidrosis, and review previously published similar cases of this association.

Long-term superior cervical sympathectomy induces mast cell hyperplasia and increases histamine and serotonin content in the rat dura mater

Nerve fibres and mast cells are often described in close morphological and functional interactions in various organs such as the dura mater. The respective roles of mast cell activation and sympathetic impairment in cluster headache and migraine attacks have been repeatedly suggested. We have thus investigated the long-term effects of sympathectomy on mast cell morphology and content in the rat dura mater. Fifteen to 60 days after either sham, unilateral or bilateral superior cervical ganglionectomy, dura were removed for either histochemical or biochemical analysis. In the first case, they were fixed and mast cell heparin was stained by fluorescein isothiocyanate-conjugated avidin. Microscopic examination was followed by digital acquisitions using a tomographic process to assess mast cell density in the whole depth of the dura mater. Unilateral ganglionectomy induced a progressive and significant increase in mast cell density 15-60 days post-surgery in contralateral hemi-dura and 30 days post-surgery in ipsilateral hemi-dura. This increase was significant in both dura 60 days after bilateral ganglionectomy. Following perfusion with saline, we also examined the content of histamine and serotonin, pre-formed amines stored in mast cell granules. Biochemical analysis of dura serotonin and histamine content using high-pressure liquid chromatography and radioenzymatic assays, respectively, revealed under all conditions a serotonin tissue concentration lower than that of histamine. After sham ganglionectomy, the dura serotonin content increased from 15 to 60 days post-surgery, whereas the histamine content remained stable over the same period. After unilateral ganglionectomy, the histamine content increased progressively and significantly 30-60 days post-surgery in both hemi-dura, whereas the serotonin content became significantly different from that of sham only 60 days post-surgery in the ipsilateral dura. After bilateral ganglionectomy, the histamine level significantly increased in both hemi-dura 15-60 days post-surgery, whereas the serotonin level had significantly increased at 60 days post-surgery. These results clearly demonstrate, for the first time, a long-term trophic effect of sympathetic nerve degeneration on mast cells in the dura mater. Since mast cell activation has been described previously on the painful side of cluster headache patients during attack periods, we propose that the sympathetic impairment reported in these patients could be prominent, directly or indirectly inducing mast cell hyperplasia and changes in amine contents in the tissue concerned.

Vagus-mediated activation of mucosal mast cells in the stomach: effect of ketotifen on gastric mucosal lesion formation and acid secretion induced by a high dose of intracisternal TRH analogue

TRH analogue, RX 77368, injected intracisternally (i.c.) at high dose (3 microg/rat) produces gastric mucosal lesion formation through vagal-dependent pathway. The gastric mucosal hyperemia induced by i.c. RX 77368 was shown to be mediated by muscarinic vagal efferent fibres and mast cells. Furthermore, electrical vagal stimulation was observed to induce gastric mucosal mast cell degranulation. The aim of the study was to assess the influence of ketotifen, a mast cell stabilizer, on RX 77368-induced gastric lesion formation and gastric acid secretion. RX 77368 (3 microg, i.c.) or vehicle (10 microL, i.c.) was delivered 240 min prior to the sacrifice of the animals. Ketotifen or vehicle (0.9% NaCl, 0.5 mL) was injected intraperitoneally (i.p.) at a dose of 10 mg x kg(-1) 30 min before RX 77368 injection. The extent of mucosal damage was planimetrically measured by a video image analyzer (ASK Ltd., Budapest) device. In the gastric acid secretion studies, the rats were pretreated with ketotifen (10 mg x kg(-1), i.p.) or vehicle (0.9% NaCl, 0.5 mL, i.p.), 30 min later pylorus-ligation was performed and RX 77368 (3 microg, i.c.) or vehicle (0.9% NaCl, 10 microL, i.c.) was injected. The rats were killed 240 min after i.c. injection, and the gastric acid secretion was measured through the titration of gastric contents with 0.1 N NaOH to pH 7.0. RX 77368 (3 microg, i.c.) resulted in a gastric mucosal lesion formation involving 8.2% of the corpus mucosa (n = 7). Ketotifen elicited an 85% inhibition on the development of mucosal lesions (n = 7, P < 0.001) whereas ketotifen alone had no effect on the lesion formation in the mucosa (n = 7). The RX 77368 induced increase of gastric acid secretion was not influenced by ketotifen pretreatment in 4-h pylorus-ligated animals. Central vagal activation induced mucosal lesion formation is mediated by the activation of mucosal mast cells in the stomach. Mast cell inhibition by ketotifen does not influence gastric acid secretion induced by i.c. TRH analogue in 4-h pylorus-ligated rats.

Gastric submucosal microdialysis: a method to study gastrin- and food-evoked mobilization of ECL-cell histamine in conscious rats

Rat stomach ECL cells are rich in histamine and chromogranin A-derived peptides, such as pancreastatin. Gastrin causes the parietal cells to secrete acid by flooding them with histamine from the ECL cells. In the past, gastric histamine release has been studied using anaesthetized, surgically manipulated animals or isolated gastric mucosa, glands or ECL cells. We monitored gastric histamine mobilization in intact conscious rats by subjecting them to gastric submucosal microdialysis. A microdialysis probe was implanted into the submucosa of the acid-producing part of the stomach (day 1). The rats had access to food and water or were deprived of food (48 h), starting on day 2 after implantation of the probe. On day 4, the rats received food or gastrin (intravenous infusion), and sampling of microdialysate commenced. Samples (flow rate 1.2 microl min(-1)) were collected every 20 or 60 min, and the histamine and pancreastatin concentrations were determined. The serum gastrin concentration was determined in tail vein blood. Exogenous gastrin (4-h infusion) raised microdialysate histamine and pancreastatin dose-dependently. This effect was prevented by gastrin receptor blockade (YM022). Depletion of ECL-cell histamine by alpha-fluoromethylhistidine, an irreversible inhibitor of the histamine-forming enzyme, suppressed the gastrin-evoked release of histamine but not that of pancreastatin. Fasting lowered serum gastrin and microdialysate histamine by 50%, while refeeding raised serum gastrin and microdialysate histamine and pancreastatin 3-fold. We conclude that histamine mobilized by gastrin and food intake derives from ECL cells because: 1) Histamine and pancreastatin were released concomitantly, 2) histamine mobilization following gastrin or food intake was prevented by gastrin receptor blockade, and 3) mobilization of histamine (but not pancreastatin) was abolished by alpha-fluoromethylhistidine. Hence, gastric submucosal microdialysis allows us to monitor the mobilization of ECL-cell histamine in intact conscious rats under various experimental conditions not previously accessible to study. While gastrin receptor blockade lowered post-prandial release of ECL-cell histamine by about 80%, unilateral vagotomy reduced post-prandial mobilization of ECL-cell histamine by about 50%. Hence, both gastrin and vagal excitation contribute to the post-prandial release of ECL-cell histamine.

Acute immobilization stress triggers skin mast cell degranulation via corticotropin releasing hormone, neurotensin, and substance P: A link to neurogenic skin disorders

Many skin disorders, such as atopic dermatitis and psoriasis, worsen during stress and are associated with increased numbers and activation of mast cells which release vasoactive, nociceptive, and proinflammatory mediators. Nontraumatic acute psychological stress by immobilization has been shown to induce mast cell degranulation in the rat dura and colon. Moreover, intradermal injection of corticotropin-releasing hormone (CRH) or its analogue urocortin (10(-5)-10(-7) M) induced skin mast cell degranulation and increased vascular permeability. Here, we investigated the effect of acute immobilization stress on skin mast cell degranulation by light microscopy and electron microscopy. Immobilization for 30 min resulted (P < 0.05) in degranulation of 40.7 +/- 9.1% of skin mast cells compared to 22.2 +/- 7.3% in controls killed by CO(2) or 17.8 +/- 2.4% in controls killed by pentobarbital. Pretreatment intraperitoneally (ip) with antiserum to CRH for 60 min prior to stress reduced (P < 0.05) skin mast cell degranulation to 21.0 +/- 3. 3%. Pretreatment with the neurotensin (NT) receptor antagonist SR48692 reduced (P < 0.05) mast cell degranulation to 12.5 +/- 3.4%, which was significantly (P < 0.05) below control levels. In animals treated neonatally with capsaicin to deplete their sensory neurons of their neuropeptides, such as substance P (SP), mast cell degranulation due to immobilization stress was reduced to about 15%. This is the first time that stress has been shown to trigger skin mast cell degranulation, an action not only dependent on CRH, but apparently also involving NT and SP. These findings may have implications for the pathophysiology and possible therapy of neuroinflammatory skin disorders such as atopic dermatitis, neurogenic pruritus, or psoriasis, which are induced or exacerbated by stress.

Modulatory effect of imetit, a histamine H3 receptor agonist, on C-fibers, cholinergic fibers and mast cells in rabbit lungs in vitro

The pharmacological mechanisms involved in the interactions between C-fibers, cholinergic fibers and mast cells were investigated in tracheally perfused rabbit lungs by measuring the simultaneous release of substance P and histamine in lung effluents. The amounts of substance P and histamine released in lung superfusates were measured by radioimmunoassay (RIA) after administration of capsaicin and carbachol. Capsaicin (10(-4) M) induced a simultaneous increase in substance P (273 +/- 56% of baseline) and histamine (460 +/- 138%) release. Similarly, carbachol (10(-4) M) caused an increase in the release of both substance P (367 +/- 111%) and histamine (1379 +/- 351%). The effect of capsaicin was prevented by pretreating the lungs with the tachykinin NK1 receptor antagonist SR 140333 (10(-7) M), and atropine (10(-6) M). SR 140333 prevented the carbachol-induced release of substance P but not of histamine. Exogenous substance P induced an increase in histamine release (136 +/- 7%) which was significantly greater in lungs perfused with the neutral endopeptidase inhibitor, thiorphan (10(-5) M) (272 +/- 35%). This effect was prevented by atropine (10(-6) M). Pretreatment of lungs with imetit (5 x 10(-8) M), a selective H3 receptor agonist, prevented the capsaicin-induced release of both mediators. Imetit also blocked the carbachol-induced release of substance P but not of histamine. Exogenous substance P-evoked histamine release was inhibited by imetit. Therefore, it can be concluded that substance P released through the action of capsaicin can activate cholinergic fibers, leading to cholinoceptor stimulation with subsequent activation of C-fibers and mast cells. While the presence of presynaptic H3 receptors modulating substance P-induced acetylcholine release was only surmised, the existence of modulating histamine H3 receptors on C-fibers was confirmed.

Altered expression of bladder mast cell growth factor receptor (c-kit) in interstitial cystitis

OBJECTIVES

To investigate the presence of mast cell growth factor receptors (c-kit) on bladder mast cells in interstitial cystitis (IC), a bladder condition occurring primarily in women. IC is characterized by pain, urgency, frequency, and mucosal microhemorrhages discernible with cystoscopy under general anesthesia. One of the prevailing theories to explain IC pathophysiology is the increased number of bladder mast cells, many of which are activated in at least a subgroup of IC patients. Stem cell factor (SCF), also known as c-kit ligand, is now recognized as the key molecule responsible for mast cell proliferation and is known to exert its action through specific surface receptors.

METHODS

Bladder specimens from patients with IC, identified by the criteria established by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), and control patients were obtained during diagnostic cystoscopy and were immediately fixed in 4% paraformaldehyde. They were then examined by immunohistochemistry for the unique proteolytic mast cell enzyme tryptase or the presence of c-kit, or both.

RESULTS

Bladders of IC patients contained a higher number of mast cells than control patients. However, mast cells in IC patients expressed fewer c-kit on their surface than those in control patients. These results could be explained if the c-kit were occupied by endogenous SCF or were downregulated, possibly by internalization after ligand-receptor interactions, making them inaccessible to immunocytochemical detection.

CONCLUSIONS

Bladder mastocytosis and/or activation of mast cells, in at least a subpopulation of IC patients, may be explained by increased stimulation of mast cells by SCF. These results could be explained either by a mutation leading to constitutive activation of c-kit or overproduction of c-kit ligand leading to bladder mast cell proliferation in IC.

Contractile responses of proximal and distal trachea segments isolated from rats subjected to immunological stimulation: role of connective tissue mast cells

1. Anaphylaxis-induced contractions of proximal and distal tracheal segments isolated from 14-day ovalbumin (OA)-sensitized rats were studied. 2. OA-induced contractions in distal segments were significantly greater than those observed in proximal segments. 3. Pretreatment of the rats with compound 48/80 or with sodium cromoglycate (SCG) aerosolization significantly reduced OA-induced contractions of trachea distal segments, whereas the contractions of proximal segments were reduced only by compound 48/80. 4. Mepacrine reduced and indomethacin increased the OA-induced contractions in all tracheal segments. Nor-dihydroguaiaretic acid increased the OA-induced contractions in distal tracheal segments, whereas dazoxiben inhibited the contractions in these same segments; neither of these drugs had any effect on the contractions in proximal tracheal segments. 5. The depletion of connective tissue mast cells and subsequent in vitro treatment with indomethacin increased the OA-induced contractions in both segments. 6. We conclude that the contractions of tracheal muscle from OA-sensitized rats depends on the topographic and anatomical origin of the airway tissue. 7. Mediators released by connective tissue mast cells in proximal and distal segments play a pivotal role in this response and may account for variations in the intensity of contraction seen after the addition of OA.

Cerebral dura mater and cephalalgia: relationships between mast cells and catecholaminergic nerve fibers in the rat

The aim of the present study was to examine whether mast cells have the same variations as the related catecholaminergic nerve fibers. Chemical sympathectomy or surgical removal of right superior cervical ganglion induced a rapid decrease of fluorescence in both nerve fibers and mast cells, as confirmed by quantitative analysis (nerve fibers 19 +/- 1.1 vs 1.3 +/- 0.6; mast cell 10.8 +/- 1.9 vs 2.1 +/- 0.3). The results of quantitative analysis after nerve fiber stimulation (electrical), however, showed an increase of the fluorescence in both the nerve fibers and the mast cells (nerve fibers 43.4 +/- 2.4; mast cells 18.6 +/- 1.6). Moreover, we found that the basal zone is more innervated (regarding catecholaminergic nerve fibers) than the apical one, and that the fluorescence level decreases passing from the vasal zone to the perivasal and intervasal zones. Further studies are needed in order to clarify the role of fluorescent nerve fibers and mast cells of cerebral dura mater in cephalalgia.

Release of mast cell mediators into the jejunum by cold pain stress in humans

BACKGROUND & AIMS

The central nervous system regulates gut functions via complex interactions between the enteric nervous and immune systems. The aim of this study was to investigate whether mast cell mediators are released into the human jejunal lumen during stress.

METHODS

A closed-segment perfusion technique was used to investigate jejunal release of tryptase, histamine, prostaglandin D2, and water flux in response to the cold pressor test in 8 healthy subjects and 9 patients with food allergy. In 6 food-allergic patients, jejunal biochemical responses to cold pain stress were compared with those induced by food intraluminal challenge.

RESULTS

Cold pain stress elevated heart rate and blood pressure and increased luminal release of mast cell mediators and jejunal water secretion in both groups. Stress-induced release of tryptase and histamine, but not of prostaglandin D2 and water flux, was greater in food-allergic patients than in healthy volunteers. In food-allergic patients, jejunal biochemical responses induced by cold pain stress were similar to those induced by antigen challenge.

CONCLUSIONS

These results show the ability of the central nervous system to modulate intestinal mast cell activity and suggest that mast cells have a role in stress-related gut dysfunction.

Ketotifen prevents gastric hyperemia induced by intracisternal thyrotropin-releasing hormone at a low dose

The thyrotropin-releasing hormone (TRH) analog, RX 77368, (p-Glu-His-(3,3'-dimethyl)-Pro-NH2) injected intracisternally (i.c.) at low doses increases gastric mucosal blood flow through vagal cholinergic and calcitonin gene-related peptide dependent pathways. The influence of the mast cell stabilizer, ketotifen, on i.c. injection of RX 77368 (1.5 ng)-induced changes in gastric mucosal blood flow (hydrogen gas-clearance technique), gastric acid secretion and mean arterial pressure was studied in urethane-anesthetized rats. RX 77368 increased gastric blood flow by 131% and systemic arterial pressure by 11 mm Hg and decreased gastric mucosal vascular resistance by 54% whereas acid secretion was not altered within the 30 min period post injection. Ketotifen had no effect on these basal parameters but abolished i.c. RX 77368-induced increased gastric mucosal blood flow and decreased gastric vascular resistance. These data suggest that mast cells may be part of the peripheral mechanisms involved in vagal gastric hyperemia induced by TRH analog injected i.c. at a low dose.