Functional relationship between mast cells and C-sensitive nerve fibres evidenced by histamine H3-receptor modulation in rat lung and spleen

Expression pattern and prognostic potential of histamine receptors in epithelial ovarian cancer

PURPOSE

Despite recent advances in the treatment of ovarian cancer (OC), long-term remissions remain scarce. For a targeted approach, prognostic markers are indispensable for predicting survival and treatment response. Given their association with multiple hallmarks of cancer, histamine receptors (HR) are emerging as promising candidates. Here, we investigate their expression pattern and prognostic value in OC.

METHODS

Specimens of 156 epithelial OC patients were collected during cytoreductive surgery at the Department of Obstetrics and Gynecology, LMU, between 1990 and 2002 and combined in a tissue microarray. Immunohistochemical staining of the HR H1, H2, H3 and H4 was quantified by an immunoreactive score and linked with clinico-pathological data by Spearman's correlation. Via ROC curve analysis, optimal cut-off values for potential prognostic markers were defined. Overall survival (OS) was visualized in Kaplan-Maier curves and significances determined by log-rank testing. A Cox regression model was applied for multivariate analysis.

RESULTS

HR H3 and H4 expression was restricted to the cytosol of OC cells, while H1 was also present in the nucleus. A significant association between HR H1, H3 and H4 expression with several clinico-pathological parameters was revealed. In addition, HR H1 and H3 expression correlated positively, HR H4 expression negatively with OS. In addition, HR H3 was identified as independent prognostic marker for OS. HR H2 expression had no prognostic value.

CONCLUSIONS

HR H1, H3 and H4 could serve as potential predictors for OS of OC patients. Further research is warranted to elucidate their pathophysiologic role and their predictive and therapeutic potential in OC.

TRPV1 in Pain and Itch

Transient receptor potential vanilloid type 1 (TRPV1) is a nonselective cation channel that is intensively expressed in the peripheral nerve system and involved in a variety of physiological and pathophysiological processes in mammals. Its activity is of great significance in transmitting pain or itch signals from peripheral sensory neurons to the central nervous system. The alteration or hypersensitivity of TRPV1 channel is well evidenced under various pathological conditions. Moreover, accumulative studies have revealed that TRPV1-expressing (TRPV1⁺) sensory neurons mediate the neuroimmune crosstalk by releasing neuropeptides to innervated tissues as well as immune cells. In the central projection, TRPV1⁺ terminals synapse with the secondary neurons for the transmission of pain and itch signalling. The intense involvement of TRPV1 and TRPV1⁺ neurons in pain and itch makes it a potential pharmaceutical target. Over decades, the basis of TRPV1 channel structure, the nature of its activity, and its modulation in pathological processes have been broadly studied and well documented. Herein, we highlight the role of TRPV1 and its associated neurons in sensing pain and itch. The fundamental understandings of TRPV1-involved nociception, pruriception, neurogenic inflammation, and cell-specific modulation will help bring out more effective strategies of TRPV1 modulation in treating pain- and itch-related diseases.

Peripheral Mechanisms of Itch

Itch is a universally experienced sensation, and chronic itch can be as diabolically debilitating as pain. Recent advances have not only identified the neuronal itch sensing circuitry, but also have uncovered the intricate interactions between skin and immune cells that work together with neurons to identify itch-inducing irritants. In this review, we will summarize the fundamental mechanisms of acute itch detection in the skin, as well as highlight the recent discoveries relating to this topic.

Histamine in cancer immunology and immunotherapy. Current status and new perspectives

Cancer is the second leading cause of death globally and its incidence and mortality are rapidly increasing worldwide. The dynamic interaction of immune cells and tumor cells determines the clinical outcome of cancer. Immunotherapy comes to the forefront of cancer treatments, resulting in impressive and durable responses but only in a fraction of patients. Thus, understanding the characteristics and profiles of immune cells in the tumor microenvironment (TME) is a necessary step to move forward in the design of new immunomodulatory strategies that can boost the immune system to fight cancer. Histamine produces a complex and fine-tuned regulation of the phenotype and functions of the different immune cells, participating in multiple regulatory responses of the innate and adaptive immunity. Considering the important actions of histamine-producing immune cells in the TME, in this review we first address the most important immunomodulatory roles of histamine and histamine receptors in the context of cancer development and progression. In addition, this review highlights the current progress and foundational developments in the field of cancer immunotherapy in combination with histamine and pharmacological compounds targeting histamine receptors.

Itch: A Paradigm of Neuroimmune Crosstalk

Although the medical definition of itch has been in existence for 360 years, only in the last 20 years have we begun to understand the basic mechanisms that underlie this unique sensation. Therapeutics that specifically target chronic itch as a pathologic entity are currently still not available. Recent seminal advances in itch circuitry within the nervous system have intersected with discoveries in immunology in unexpected ways to rapidly inform emerging treatment strategies. The current review aims to introduce these basic concepts in itch biology and highlight how distinct immunologic pathways integrate with recently identified itch-sensory circuits in the nervous system to inform a major new paradigm of neuroimmunology and therapeutic development for chronic itch.

Histamine and histidine decarboxylase: Immunomodulatory functions and regulatory mechanisms

Histamine is a bioactive monoamine that is synthesized by the enzymatic activity of histidine decarboxylase (HDC) in basophils, mast cells, gastric enterochromaffin‐like (ECL) cells and histaminergic neuronal cells. Upon a series of cellular stimuli, these cells release stored histamine, which elicits allergies, inflammation, and gastric acid secretion and regulates neuronal activity. Recent studies have shown that certain other types of myeloid lineage cells also produce histamine with HDC induction under various pathogenic stimuli. Histamine has been shown to play a series of pathophysiological roles by modulating immune and inflammatory responses in a number of disease conditions, whereas the mechanistic aspects underlying induced HDC expression remain elusive. In the present review, we summarize the current understanding of the regulatory mechanism of Hdc gene expression and the roles played by histamine in physiological contexts as well as pathogenic processes. We also introduce a newly developed histaminergic cell‐monitoring transgenic mouse line (Hdc‐BAC‐GFP) that serves as a valuable experimental tool to identify the source of histamine and dissect upstream regulatory signals.

The Return of the Mast Cell: New Roles in Neuroimmune Itch Biology

The mast cell-nerve unit classically has represented a fundamental neuroimmune axis in the development of itch because of the traditional prominence of histamine as a pruritogen. However, it is appreciated increasingly that most chronic itch disorders are likely nonhistaminergic in nature, provoking the hypothesis that other novel effector itch mechanisms derived from mast cells are important. In this review, we present an overview of classical mast cell biology and put these concepts into the context of recent advances in our understanding of the regulation and function of the mast cell-nerve unit in itch biology.

Histamine receptors and cancer pharmacology: an update

In the present review, we will discuss the recent advances in the understanding of the role of histamine and histamine receptors in cancer biology. The controversial role of the histaminergic system in different neoplasias including gastric, colorectal, oesophageal, oral, pancreatic, liver, lung, skin, blood and breast cancers will be reviewed. The expression of histamine receptor subtypes, with special emphasis on the histamine H4 receptor, in different cell lines and human tumours, the signal transduction pathways and the associated biological responses as well as the in vivo treatment of experimental tumours with pharmacological ligands will be described. The presented evidence demonstrates that histamine regulates cancer-associated biological processes during cancer development in multiple cell types, including neoplastic cells and cells in the tumour micro-environment. The outcome will depend on tumour cell type, the level of expression of histamine receptors, signal transduction associated with these receptors, tumour micro-environment and histamine metabolism, reinforcing the complexity of cancer disease. Findings show the pivotal role of H4 receptors in the development and progression of many types of cancers, and considering its immunomodulatory properties, the H4 receptor appears to be the most promising molecular therapeutic target for cancer treatment within the histamine receptor family. Furthermore, the H4 receptor is differentially expressed in tumours compared with normal tissues, and in most cancer types in which data are available, H4 receptor expression is associated with clinicopathological characteristics, suggesting that H4 receptors might represent a novel cancer biomarker. LINKED ARTICLES: This article is part of a themed section on New Uses for 21st Century. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.3/issuetoc.

Role of Histamine in Modulating the Immune Response and Inflammation

Inflammatory mediators, including cytokines, histamine, bradykinin, prostaglandins, and leukotrienes, impact the immune system, usually as proinflammatory factors. Other mediators act as regulatory components to establish homeostasis after injury or prevent the inflammatory process. Histamine, a biogenic vasoactive amine, causes symptoms such as allergies and has a pleiotropic effect that is dependent on its interaction with its four histamine receptors. In this review, we discuss the dualistic effects of histamine: how histamine affects inflammation of the immune system through the activation of intracellular pathways that induce the production of inflammatory mediators and cytokines in different immune cells and how histamine exerts regulatory functions in innate and adaptive immune responses. We also evaluate the interactions between these effects.

The Role of Histamine and Histamine Receptors in Mast Cell-Mediated Allergy and Inflammation: The Hunt for New Therapeutic Targets

Histamine and its receptors (H1R–H4R) play a crucial and significant role in the development of various allergic diseases. Mast cells are multifunctional bone marrow-derived tissue-dwelling cells that are the major producer of histamine in the body. H1R are expressed in many cells, including mast cells, and are involved in Type 1 hypersensitivity reactions. H2R are involved in Th1 lymphocyte cytokine production. H3R are mainly involved in blood–brain barrier function. H4R are highly expressed on mast cells where their stimulation exacerbates histamine and cytokine generation. Both H1R and H4R have important roles in the progression and modulation of histamine-mediated allergic diseases. Antihistamines that target H1R alone are not entirely effective in the treatment of acute pruritus, atopic dermatitis, allergic asthma, and other allergic diseases. However, antagonists that target H4R have shown promising effects in preclinical and clinical studies in the treatment of several allergic diseases. In the present review, we examine the accumulating evidence suggesting novel therapeutic approaches that explore both H1R and H4R as therapeutic targets for histamine-mediated allergic diseases.

Role of the Histamine H3 Receptor in the Central Nervous System

The G_i/o protein-coupled histamine H₃ receptor is distributed throughout the central nervous system including areas like cerebral cortex, hippocampus and striatum with the density being highest in the posterior hypothalamus, i.e. the area in which the histaminergic cell bodies are located. In contrast to the other histamine receptor subtypes (H₁, H₂ and H₄), the H₃ receptor is located presynaptically and shows a constitutive activity. In detail, H₃ receptors are involved in the inhibition of histamine release (presynaptic autoreceptor), impulse flow along the histaminergic neurones (somadendritic autoreceptor) and histamine synthesis. Moreover, they occur as inhibitory presynaptic heteroreceptors on serotoninergic, noradrenergic, dopaminergic, glutamatergic, GABAergic and perhaps cholinergic neurones. This review shows for four functions of the brain that the H₃ receptor represents a brake against the wake-promoting, anticonvulsant and anorectic effect of histamine (via postsynaptic H₁ receptors) and its procognitive activity (via postsynaptic H₁ and H₂ receptors). Indeed, H₁ agonists and H₃ inverse agonists elicit essentially the same effects, at least in rodents; these effects are opposite in direction to those elicited by brain-penetrating H₁ receptor antagonists in humans. Although the benefit for H₃ inverse agonists for the symptomatic treatment of dementias is inconclusive, several members of this group have shown a marked potential for the treatment of disorders associated with excessive daytime sleepiness. In March 2016, the European Commission granted a marketing authorisation for pitolisant (Wakix^R) (as the first representative of the H₃ inverse agonists) for the treatment of narcolepsy.

Expression and function of histamine and its receptors in atopic dermatitis

Background

Atopic dermatitis constitutes a most burdensome chronic inflammatory skin disease. Standard treatment is cumbersome and often targets its main symptom, pruritus, only insufficiently.

Findings

Recent advances in our understanding of the role of histamine and its four receptors suggest new approaches which target the histamine receptors alone or as combination therapies to more efficiently combat pruritus and inflammation in atopic dermatitis.

Conclusions

With this review, we provide an overview on histamine and the expression of its four receptors on skin resident and nonresident cells. Furthermore, we summarize recent studies which suggest anti-histamine therapy to efficiently combat pruritus and inflammation in atopic dermatitis and discuss possible approaches to incorporate these findings into more effective treatment strategies for atopic dermatitis in childhood.

Nα -Methyl Histamine Safety and Efficacy in Migraine Prophylaxis: Phase III Study

Background:

The histamine catabolite, Nα-methylhistamine, possesses a selective affinity for H3 receptors. For this reason, we considered evaluating the efficacy of this histaminergic H3 agonist in migraine prophylactic treatment.

Objective:

To study the therapeutic potential of the subcutaneous administration of Nα-methylhistamine in migraine prophylaxis, in a Phase III clinical pharmacological study.

Methods:

Using a controlled double-blind, placebo controlled clinical trial for 12 weeks, 60 patients with migraine, who fit the criteria established by the International Headache Society, were selected. The efficacy of subcutaneous administration of Nα-methylhistamine 1 to 3 ng twice a week against placebo was studied, evaluating the outcome of headache intensity, frequency, duration, and analgesic intake.

Results:

Comparison between the groups treated with placebo (n=30) and Nα-methylhistamine (n=30), on data collected for the 4th, 8th and 12th weeks of treatment, revealed that Nα-methylhistamine exerted a significant (p<0.0001) reduction (compared to placebo) in intensity, frequency, and duration of migraine attacks, as well as on the use of analgesic intake. No significant (p>0.05) adverse experiences or side effects developed in either group.

Conclusions:

The present study provides evidence of the efficacy of Nα-methylhistamine, given subcutaneously at doses of 1 to 3 ng twice a week, offering a new therapeutic alternative and laying the clinical and pharmacological groundwork for the use of histaminergic H3-agonists in migraine prophylaxis, which may specifically inhibit the neurogenic edema response involved in migraine pathophysiology.

N Alpha Methyl Histamine Versus Propranolol in Migraine Prophylaxis

Objectives:

To compare the efficacy and tolerability of the subcutaneous administration of N alpha methyl histamine versus oral propranolol in the treatment of migraine prophylaxis.

Background:

N alpha methyl histamine has a selective affinity for H3 receptors and could constitute a new therapeutic drug in migraine prophylaxis.

Methods:

Sixty patients with migraine were selected and enrolled in a 12-week double-blind controlled clinical trial to evaluate the efficacy of subcutaneous administration of N-alpha methyl histamine (1 to 3 ug twice a week ) n=30, compared to administration of 120 mg/day of oral propranolol n=30. the variables were: headache intensity, frequency of attacks, duration of migraine attacks and analgesic intake.

Results:

fifty five patients completed the study. the data collected during the 4th week of treatment revealed that N alpha methyl histamine and propranolol caused a significantly (p<0.01) greater reduction between the basal values and final values of every variable studied.

Conclusions:

Both N alpha methyl histamine and propranolol are similarly effective in reducing or eliminating the headache in migraine prophylaxis. low doses of N-alpha methyl histamine injected subcutaneously may represent a novel and effective therapeutic alternative in migraine patients and may lay the clinical and pharmacological groundwork for the use of H3 receptor agonist in migraine prophylaxis.

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

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

Subcutaneous histamine versus botulinum toxin type A in migraine prophylaxis: a randomized, double-blind study

OBJECTIVES

To compare the efficacy and tolerability of the subcutaneous administration of histamine and botulinum toxin type A (BoNTA) in migraine prophylaxis.

BACKGROUND

Histamine has a selective affinity for H3 receptors and it may specifically inhibit the neurogenic edema response involved in migraine pathophysiology.

METHODS

One hundred patients with migraine were selected in a 12-week double-blind controlled clinical trial to evaluate the efficacy of subcutaneous administration of histamine (1-10 ng twice a week) n = 50, compared with administration of 50 U of BoNTA (one injection cycle) n = 50.

RESULTS

The data collected during the 4th week of treatment revealed a significant decrease in all parameters studied, in histamine and BoNTA (P < 0.001). After 4 weeks of treatment, but one injection cycle of 50 U BoNTA had only a 40-day period of efficacy.

CONCLUSIONS

This randomized study demonstrated that both histamine and BoNTA are similarly effective and well tolerated in reducing or eliminating headache in migraine prophylaxis. Low doses of histamine applied subcutaneously may represent a novel and effective therapeutic alternative in migraine patients and lay the clinical and pharmacological groundwork for the use of H3 agonist in migraine prophylaxis.

Regulation of the immune response and inflammation by histamine and histamine receptors

Histamine is a biogenic amine with extensive effects on many cell types, including important immunologic cells, such as antigen-presenting cells, natural killer cells, epithelial cells, and T and B lymphocytes. Histamine and its 4 receptors represent a complex system of immunoregulation with distinct effects dependent on receptor subtypes and their differential expression. These are influenced by the stage of cell differentiation, as well as microenvironmental influences, leading to the selective recruitment of effector cells into tissue sites accompanied by effects on cellular maturation, activation, polarization, and effector functions, which lead to tolerogenic or proinflammatory responses. In this review we discuss the regulation of histamine secretion, receptor expression, and differential activation of cells within both the innate and adaptive immune responses. It is clear that the effects of histamine on immune homeostasis are dependent on the expression and activity of the 4 currently known histamine receptors, and we also recognize that 100 years after the original identification of this biogenic amine, we still do not fully understand the complex regulatory interactions between histamine and the host immune response to everyday microbial and environmental challenges.

Workshop: tuning the 'cough center'

The Workshop considered the mechanisms whereby the 'cough center' could be tuned by various afferent inputs. There were particular presentations on the effects of inputs from the nose, mouth, respiratory tract and lungs, cerebral cortex, somatic tissues and the pharynx. From all these sites cough induced from the lungs could be increased or decreased in its strength or modified in its pattern. Thus 'tuning' of cough could be due to the interaction of afferent inputs, or to the sensitization or desensitization of brainstem neural pathways. The pattern of response depended on the 'type' of cough being studied and, in some instances, on the timing of the sensory input into the brainstem. Cough inputs could also affect various 'non-cough' motor outputs from the brain, although this was not the main theme of the Workshop. The main conclusion was that cough is not a stereotyped output from the medullary 'cough center', but that its pattern and strength depend on many afferent inputs acting on the 'cough center'.

Airway mast cells in a rhesus model of childhood allergic airways disease

Asthma is a leading cause of morbidity in children. Risk factors include chronic exposure to allergens and air pollution. While chronically activated mast cells contribute to the pathophysiology of asthma in part through their proteases such as chymase and tryptase, previous studies of airway mast cell abundance and distribution in asthmatics have been inconsistent. To determine whether repeated episodic exposures to environmental pollutants during postnatal lung development alter airway mast cell abundance and distribution, we exposed infant rhesus monkeys to a known human allergen, house dust mite antigen (HDMA), and/or a known environmental pollutant, ozone (O(3)), and quantitatively compared the abundance of tryptase- or chymase-positive mast cells in three airway levels. Mast cells are resident in multiple compartments of the airway wall in infant rhesus monkeys raised from birth in filtered air. Tryptase- and chymase-positive cells were most abundant in trachea and least in terminal bronchioles. The majority of tryptase-positive and almost all chymase-positive cells were in extracellular matrix and smooth muscle bundles. Chronic exposure to HDMA elevated the abundance of both tryptase- and chymase-positive cells in the trachea and intrapulmonary bronchi. Neither exposure to O(3) nor HDMA + O(3) increased mast cell accumulations in the airway wall. We conclude that during postnatal airway development (1) mast cells are a resident airway cell population even in the absence of toxic air contaminants; (2) aeroallergen exposure alters large airway mast cell distribution and abundance, increasing chymase-positive mast cells; and (3) this response is attenuated by exposure to oxidant air pollutants.

Subcutaneous histamine versus topiramate in migraine prophylaxis: a double-blind study

BACKGROUND

Histamine has a selective affinity for H3 receptors and it may specifically inhibit the neurogenic edema response involved in migraine pathophysiology.

OBJECTIVE

To evaluate the therapeutic potential of subcutaneous administration of histamine in migraine prophylaxis, compared with oral administration of topiramate.

METHODS

Ninety patients with migraine were selected in a 12-week double-blind controlled clinical trial to evaluate the efficacy of subcutaneous administration of histamine (1-10 ng twice a week) compared with oral administration of topiramate (100 mg daily dose). The variables studied were: headache intensity, frequency, duration, analgesic intake and Migraine Disability Assessment.

RESULTS

The data collected during the 12 weeks of treatment revealed that headache symptoms improved in both the histamine and topiramate groups, which was evident within the first month after the initiation of treatment, with statistically significant (p < 0.001) reductions in headache frequency (50%), Migraine Disability Assessment score (75%), intensity of pain (51%), duration of migraine attacks (45%), as well as in the use of rescue medication (52%).

CONCLUSION

The present study provides evidence of the efficacy of subcutaneously applied histamine and orally administered topiramate in migraine prophylaxis. Subcutaneously applied histamine may represent a novel and effective therapeutic alternative in resistant migraine patients.

Are pruritus and scratching the cough of the skin?

Pruritus is not the equivalent of the cough of the skin, but itch and scratch can certainly be defined as such. In physiological conditions, they share the same function: to exclude a foreign body. Itch/scratching and cough could be selective responses for the same diseases, mainly atopic diseases, and their pathophysiology is similar (role of C fibers and mast cells; role of histamine, substance P and tachykinins). This is an intriguing analogy rather than a pathophysiological identity. It may be inappropriate for many disease settings. Itch and cough can be triggered or enhanced by stress. This similarity is very interesting because it could give rise to many new research ideas.

Presynaptic receptors for dopamine, histamine, and serotonin

Presynaptic receptors for dopamine, histamine and serotonin that are located on dopaminergic, histaminergic and sertonergic axon terminals, respectively, function as autoreceptors. Presynaptic receptors also occur as heteroreceptors on other axon terminals. Auto- and heteroreceptors mainly affect Ca(2+) -dependent exocytosis from the receptor-bearing nerve ending. Some additionally subserve other presynaptic functions.Presynaptic dopamine, histamine and serotonin receptors are involved in various (patho)physiological conditions. Examples are the following:Dopamine autoreceptors play a role in Parkinson's disease, schizophrenia and drug addiction. Dopamine heteroreceptors affecting the release of acetylcholine and of amino acid neurotransmitters in the basal ganglia are also relevant for Parkinson's disease. Peripheral dopamine heteroreceptors on postganglionic sympathetic terminals influence heart rate and vascular resistance through modulation of noradrenaline release. Blockade of histamine autoreceptors increases histamine synthesis and release and may support higher CNS functions such as arousal, cognition and learning. Peripheral histamine heteroreceptors on C fiber and on postganglionic sympathetic fiber terminals diminish neuropeptide and noradrenaline release, respectively. Both inhibititory effects are beneficial in myocardial ischemia. The inhibition of neuropeptide release also explains the antimigraine effects of some agonists of presynaptic histamine receptors. Upregulation of presynaptic serotonin autoreceptors is probably involved in the pathogenesis of major depression. Correspondingly, antidepressant treatments can be linked with a reduced density of 5-HT autoreceptors. 5-HT Heteroreceptor activation diminishes acetylcholine and GABA release and may therefore increase anxiety. In the periphery, presynaptic 5-HT heteroreceptor agonists shorten migraine attacks by inhibition of the release of neuropeptides from trigeminal afferents, apart from their constrictive action on meningeal vessels.

Subcutaneous histamine versus sodium valproate in migraine prophylaxis: a randomized, controlled, double-blind study

Histamine has a selective affinity for H3-receptors and it may specifically inhibit the neurogenic edema response involved in migraine pathophysiology. The objective of this study was to evaluate the therapeutic potential of subcutaneous administration of histamine in migraine prophylaxis, compared with oral administration of sodium valproate, in an open clinical trial. Ninety-two patients with migraine were selected under criteria established by the International Headache Society and enrolled in a 12-week double-blind controlled clinical trial to evaluate the efficacy of subcutaneous administration of histamine (1-10 ng twice a week; n = 46) compared with oral administration of sodium valproate (500 mg daily dose; n = 46). The variables studied were headache intensity, frequency, duration, analgesic intake and migraine disability assessment (MIDAS). Two-tailed Student's t- test was used to compare means and the Mann-Whitney U and anova tests were used. The data collected during the 4th, 8th and 12th weeks of treatment revealed that histamine caused a significantly greater reduction (P < 0.001) in intensity and duration of migraine attacks as well as in analgesic intake. No difference was detected in the frequency of attacks or in MIDAS. The present study provides evidence of the superior efficacy of histamine applied subcutaneously in migraine prophylaxis when compared with sodium valproate taken orally. Subcutaneously applied histamine may represent a novel and effective therapeutic alternative in resistant migraine patients.

Renin: at the heart of the mast cell

Cardiac mast cells proliferate in cardiovascular diseases. In myocardial ischemia, mast cell mediators contribute to coronary vasoconstriction, arrhythmias, leukocyte recruitment, and tissue injury and repair. Arrhythmic dysfunction, coronary vasoconstriction, and contractile failure are also characteristic of cardiac anaphylaxis. In coronary atherosclerosis, mast cell mediators facilitate cholesterol accumulation and plaque destabilization. In cardiac failure, mast cell chymase causes myocyte apoptosis and fibroblast proliferation, leading to ventricular dysfunction. Chymase and tryptase also contribute to fibrosis in cardiomyopathies and myocarditis. In addition, mast cell tumor necrosis factor-alpha promotes myocardial remodeling. Cardiac remodeling and hypertrophy in end-stage hypertension are also induced by mast cell mediators and proteases. We recently discovered that cardiac mast cells contain and release renin, which initiates local angiotensin formation. Angiotensin causes coronary vasoconstriction, arrhythmias, fibrosis, apoptosis, and endothelin release, all demonstrated mechanisms of mast-cell-associated cardiac disease. The effects of angiotensin are further amplified by the release of norepinephrine from cardiac sympathetic nerves. Our discovery of renin in cardiac mast cells and its release in pathophysiological conditions uncovers an important new pathway in the development of mast-cell-associated heart diseases. Several steps in this novel pathway may constitute future therapeutic targets.

Modification of formalin-induced nociception by different histamine receptor agonists and antagonists

The present study evaluated the effects of different histamine receptor agonists and antagonists on the nociceptive response in the mouse formalin test. Intracerebroventricular (20-40 microg/mouse i.c.v.) or subcutaneous (1-10 mg/kg s.c.) injection of HTMT (H(1) receptor agonist) elicited a dose-related hyperalgesia in the early and late phases. Conversely, intraperitoneal (20 and 30 mg/kg i.p.) injection of dexchlorpheniramine (H(1) receptor antagonist) was antinociceptive in both phases. At a dose ineffective per se, dexchlorpheniramine (10 mg/kg i.p.) antagonized the hyperalgesia induced by HTMT (40 mug/mouse i.c.v. or 10 mg/kg s.c.). Dimaprit (H(2) receptor agonist, 30 mg/kg i.p.) and ranitidine (H(2) receptor antagonist, 20 and 40 mg/kg i.p.) reduced the nociceptive responses in the early and late phases. No significant change in the antinociceptive activity was found following the combination of dimaprit (30 mg/kg i.p.) with ranitidine (10 mg/kg i.p.). The antinociceptive effect of dimaprit (30 mg/kg i.p.) was prevented by naloxone (5 mg/kg i.p.) in the early phase or by imetit (H(3) receptor agonist, 25 mg/kg i.p.) in both early and late phases. The histamine H(3) receptor agonist imetit was hyperalgesic following i.p. administration of 50 mg/kg. Imetit-induced hyperalgesia was completely prevented by treatment with a dose ineffective per se of thioperamide (H(3) receptor antagonist, 5 mg/kg i.p.). The results suggest that histamine H(1) and H(3) receptor activations increase sensitivity to nociceptive stimulus in the formalin test.

Immunohistochemical localization of histamine H3 receptors in rodent skin, dorsal root ganglia, superior cervical ganglia, and spinal cord: potential antinociceptive targets

Activation of histamine H3 receptors (H3Rs) reduces inflammation and nociception, but the existence of H3Rs on peripheral innervation has never been demonstrated. Here we use antibodies to locate H3Rs in whisker pads, hairy and glabrous hind paw skin, dorsal root ganglia (DRGs), and spinal cords of rats, wild type mice, and H3R knockout (H3KO) mice. Although H3Rs have been hypothesized to be on C and sympathetic fibers, H3R-like immunoreactivity (H3R-LI) was only detected on presumptive periarterial A delta fibers and on A beta fibers that terminated in Meissner's corpuscles and as lanceolate endings around hair follicles. The H3R-positive periarterial fibers were thin-caliber and coexpressed immunoreactivity for calcitonin gene-related peptide (CGRP), substance P, acid sensing ion channel 3, and 200 kDa neurofilament protein (NF). H3R-LI was also detected on epidermal keratinocytes and Merkel cells, but not on Merkel endings, C fibers, any other A delta fibers, or sympathetic fibers. In DRGs, H3R-LI was preponderantly on medium to large neurons coexpressing NF-LI and mostly CGRP-LI. In dorsal horn, CGRP-positive fibers with and without H3R-LI ramified extensively in lamina II; many of the former formed a plexus in lamina V. Low levels of H3R-LI were also present on A beta fibers penetrating superficial and into deeper laminae. The distribution of H3R-LI was similar in rats and wild type mice, but was eliminated or strongly reduced in A delta fibers and A beta fibers, respectively, in H3KO mice. Taken with recently published behavioral results, the present findings suggest that periarterial, peptidergic, H3R-containing A delta fibers may be sources of high threshold mechanical nociception.

Histamine receptors are hot in immunopharmacology

In addition to its well-characterized effects in the acute allergic inflammatory responses, histamine has been demonstrated to affect chronic inflammation and regulate several essential events in the immune response. Histamine can selectively recruit the major effector cells into tissue sites and affect their maturation, activation, polarization, and other functions leading to chronic inflammation. Histamine also regulates dendritic cells, T cells and B cells, as well as related antibody isotype responses. In addition, acting through its receptor 2, histamine positively interferes with the peripheral antigen tolerance induced by T regulatory cells in several pathways. The diverse effects of histamine on immune regulation appear to be due to differential expression and regulation of 4 types of histamine receptors and their distinct intracellular signals. In addition, differences in affinities of these receptors for histamine is highly decisive for the biological effects of histamine and drugs that target histamine receptors. This article highlights recent discoveries in histamine immunobiology and discusses their relevance in allergic inflammation.

Nasal allergic response mediated by histamine H3 receptors in murine allergic rhinitis

BACKGROUND

Histamine is one of the most important chemical mediators causing nasal allergic symptoms, and H1 receptor antagonist have been used as the treatment first choice in nasal allergy. The presence of H3 receptors has also been determined in the human nasal mucosa, but few studies have investigated the involvement of H3 receptors in nasal allergy.

OBJECTIVE

We used a murine allergic model to investigate the presence of nasal mucosa H3 receptor mRNA and any H3 receptor agonist or antagonist influences on clinical nasal allergic symptoms.

METHODS

H3 receptor mRNA in nasal mucosa was investigated by reverse-transcription polymerase chain reaction. OVA-sensitized mice were given an intraperitoneal injection of H3 receptor agonist or antagonist, and clinical nasal allergic symptoms were scored over 10 minutes after nasal provocation of OVA. Inhibition of nasal allergic symptoms was also examined using an H1 receptor antagonist alone and using a both an H3 receptor agonist and an H1 receptor antagonist.

RESULTS

H3 receptor mRNA was identified in the murine nasal mucosa. The H3 receptor agonist (R)-alpha-metylhistamine significantly inhibited clinical nasal allergic symptoms of OVA-sensitized mice. The H3 receptor agonist and H1 receptor antagonist inhibited clinical nasal allergic symptoms in the murine allergic model more strongly than the single drug.

CONCLUSION

The foregoing results indicate that H3 receptors are involved in modulation of nasal allergy. H3 receptor agonists can also be useful as a novel therapeutic approach in nasal allergy. Both H3 receptor agonist and H1 receptor antagonist may be more effective than a single drug.

Histamine in allergic inflammation and immune modulation

Histamine, originally considered as a mediator of acute inflammatory and immediate hypersensitivity responses has also been demonstrated to affect chronic inflammation and regulate several essential events in the immune response. On the other hand, various cytokines control histamine synthesis, release and expression of histamine receptors (HRs). The cells involved in the regulation of immune response and hematopoiesis express HRs and also secrete histamine, which can selectively recruit the major effector cells into tissue sites and affect their maturation, activation, polarization and effector functions leading to chronic inflammation. Histamine, acting through its receptor type 2, positively interferes with the peripheral antigen tolerance induced by T regulatory cells in several pathways. Histamine also regulates antigen-specific Th1 and Th2 cells, as well as related antibody isotype responses. The diverse effects of histamine on immune regulation are due to differential expression and regulation of four HRs and their distinct intracellular signals. In addition, differences in affinities of these receptors are highly decisive on the biological effects of histamine and agents that target HRs. This article highlights the findings leading to a change of perspective in histamine immunobiology.

Histamine-cytokine connection in immunity and hematopoiesis

A number of recent studies have led to a reappraisal of the functional capacities of histamine in immunity and hematopoiesis. This change of perspective was provided by the following findings: (1) the evidence for multiple cellular sources of histamine, differing from mature basophils and mast cells by their ability to newly synthesize and liberate the mediator without prior storage, (2) the discovery of a novel histamine receptor (H4R), preferentially expressed on hematopoietic and immunocompetent cells, (3) the potential intracellular activity of histamine through cytochrome P450 and (4) the demonstration of a histamine-cytokine cross-talk. Indeed, cytokines not only modulate the degranulation process of histamine but also control its neosynthesis by the histamine-forming enzyme, histidine decarboxylase (HDC), at transcriptional and post-transcriptional levels. In turn, histamine intervenes in the intricate cytokine network, regulating cytokine production by immune cells through distinct receptors signaling distinct biological effects. This type of regulation is particularly relevant in the context of TH1/TH2 differentiation, autoimmunity and tumor immunotherapy.

Genes of tolerance

Activation-induced cell death, anergy and/or immune response modulation by T-regulatory cells (T(Reg)) are essential mechanisms of peripheral T-cell tolerance. There is growing evidence that anergy, tolerance and active suppression are not entirely distinct, but rather, represent linked mechanisms possibly involving the same cells and multiple suppressor mechanisms. Skewing of allergen-specific effector T cells to T(Reg) cells appears as a crucial event in the control of healthy immune response to allergens and successful allergen-specific immunotherapy. The T(Reg) cell response is characterized by abolished allergen-induced specific T-cell proliferation and suppressed T helper 1 (Th1)- and Th2-type cytokine secretion. In addition, mediators of allergic inflammation that trigger cAMP-associated G-protein coupled receptors, such as histamine receptor 2 may contribute to peripheral tolerance mechanisms. The increased levels of interleukin-10 (IL-10) and transforming growth factor-beta (TGF-beta) that are produced by T(Reg) cells potently suppress immunoglobulin E (IgE) production, while simultaneously increasing production of noninflammatory isotypes IgG4 and IgA, respectively. In addition, T(Reg) cells directly or indirectly suppress effector cells of allergic inflammation such as mast cells, basophils and eosinophils. In conclusion, peripheral tolerance to allergens is controlled by multiple active suppression mechanisms. It is associated with regulation of antibody isotypes and effector cells to the direction of a healthy immune response and opens a window for novel therapies of allergic diseases.

Histamine H3 receptors regulate vascular permeability changes in the skin of mast cell-deficient mice

The participation of histamine H(3) receptors in the regulation of skin vascular permeability changes in mast cell-deficient mice was studied. Although intradermal injection of histamine H(3) antagonists, iodophenpropit and clobenpropit, at a dose of 100 nmol/site caused significant increases in skin vascular permeability in both mast cell-deficient (WBB6F1 W/W(v)) and wild-type (WBB6F1 +/+) mice, this response was significantly lower in mast cell-deficient mice than in the wild-type controls. Histamine also caused dose-related increases in skin vascular permeability in both wild-type and mast cell-deficient mice. Significant effects were observed at doses of 10 and 100 nmol/site, and no significant difference in skin vascular permeability was observed between mast cell-deficient and wild-type mice. However, histamine contents of dorsal skin in mast cell-deficient mice were significantly lower than in wild-type mice. In addition, the H(1) antagonists diphenhydramine and chlorpheniramine and the NK(1) antagonists, L-732,138 and L-733,060, were able to antagonize H(3) antagonist-induced skin vascular permeability. These results indicated that blockade of H(3) receptors by H(3) antagonists induce skin vascular permeability through mast cell-dependent mechanisms. In addition, histamine and, to a lesser extent substance P are involved in the reaction.

Pruritus-associated response mediated by cutaneous histamine H3 receptors

BACKGROUND

Histamine is one of the most common chemical mediators causing pruritus, and H1 receptor antagonists have been used as a first choice in its treatment. On the other hand, although the presence of H3 receptors has been identified in the skin, few studies have investigated the involvement of H3 receptors on pruritus.

OBJECTIVE

The purpose of this study was to examine whether H3 receptor agonist or antagonist influences the incidence of scratching behaviour in ICR or mast cell-deficient WBB6F1-W/WV mice.

METHODS

The mice were given an intradermal injection of H3 receptor agonist or antagonist into the rostral part of the back, and the occurrence of scratching behaviour at the injected site by the hind paws was counted over 60 min.

RESULTS

H3 receptor antagonists, thioperamide and AQ0145 significantly increased the incidence of scratching behaviour in ICR mice. H3 receptor agonist, (R)-alpha-methylhistamine, had no effect. On the other hand, (R)-alpha-methylhistamine significantly inhibited thioperamide or AQ0145-induced scratching behaviour. In addition, both thioperamide and AQ0145 elicited scratching behaviour in mast cell-deficient WBB6F1-W/WV mice.

CONCLUSION

From these results, it may be concluded that H3 receptors are involved in the modulation of pruritus in the skin, and mast cells are not essential in this response. In addition, H3 receptor agonists can be useful as a novel therapeutic approach against pruritus.

NEUROPEPTIDES AND NEUROGENIC MECHANISMS IN ORAL AND PERIODONTAL INFLAMMATION

It is generally accepted that the nervous system contributes to the pathophysiology of peripheral inflammation, and a neurogenic component has been implicated in many inflammatory diseases, including periodontitis. Neurogenic inflammation should be regarded as a protective mechanism, which forms the first line of defense and protects tissue integrity. However, severe or prolonged noxious stimulation may result in the inflammatory response mediating injury rather than facilitating repair. This review focuses on the accumulating evidence suggesting that neuropeptides have a pivotal role in the complex cascade of chemical activity associated with periodontal inflammation. An overview of neuropeptide synthesis and release introduces the role of neuropeptides and their interactions with other inflammatory factors, which ultimately lead to neurogenic inflammation. The biological effects of the neuropeptides substance P (SP), calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP), and neuropeptide Y (NPY) are summarized, and evidence for their involvement in the localized inflammatory lesions which characterize periodontitis is presented. In this context, the role of CGRP in bone metabolism is described in more detail. Recent research highlighting the role of the nervous system in suppressing pain and inflammation is also discussed.

Gastric mucosal mast cells are increased in Helicobacter pylori-negative functional dyspepsia

BACKGROUND & AIMS

Mast cells might be involved in pathogenesis of functional dyspepsia because they can release a wide range of potent mediators, capable of altering gastric nerve and muscle function. This study aimed to determine whether mast cell numbers were increased in the gastric mucosa of patients with functional dyspepsia compared to control subjects.

METHODS

Biopsy samples were taken from the antrum and corpus of 111 patients: 20 asymptomatic control subjects, 62 patients with Rome criteria functional dyspepsia (33 Helicobacter pylori positive, 29 H. pylori negative), and 29 inflammatory control subjects (H. pylori positive). Mast cells were detected immunohistochemically by using a mouse monoclonal antibody specific for tryptase. Quantification was performed with light microscopy, and results were expressed as mast cells/mm(2) +/- standard error of mean.

RESULTS

Mast cells were significantly increased in H. pylori negative functional dyspepsia samples compared to normal control samples in the antrum (230.1 +/- 11.3 vs. 94.8 +/- 8.4, P < 0.001) and corpus (264.1 +/- 27.1 vs. 123.9 +/- 11.5, P = 0.001). Mast cells were also significantly increased in the antrum of patients with H. pylori positive functional dyspepsia compared to asymptomatic control subjects (166.5 +/- 17.0 vs. 94.8 +/- 8.4, P < 0.03). However, there was no significant difference between mast cell numbers in patients with H. pylori positive functional dyspepsia compared to inflammatory control subjects.

CONCLUSIONS

Mast cells are increased in functional dyspepsia, independently of inflammation. This might contribute to the pathogenesis of functional dyspepsia by altering signaling in the brain-gut axis.

Histamine in the immune regulation of allergic inflammation

Histamine was the first mediator implicated in mechanisms of allergy, asthma, and anaphylactic shock because it has been discovered to mimic several features of these diseases. In addition to its well-characterized effects in the acute inflammatory and allergic responses, it was recently demonstrated that histamine regulates several essential events in the immune response. Histamine affects the maturation of immune system cells and alters their activation, polarization, chemotaxis, and effector functions. Histamine also regulates antigen-specific T(H)1 and T(H)2 cells, as well as related antibody isotype responses. Histamine binds to 4 different G protein-coupled receptors that transduce signals to cells through distinct pathways. The expression of these receptors on different cells and cell subsets is regulated, and apparently, the diverse effects of histamine on immune regulation are due to differential expression of 4 histamine receptors and their distinct intracellular signals. This article highlights novel discoveries in histamine immunobiology and discusses clinical findings or disease models that indicate immune regulation by histamine.

Involvement of histamine H3 receptors in scratching behaviour in mast cell-deficient mice

BACKGROUND

Although the roles of histamine H3 receptors have been studied in several tissues such as the brain, lung, spleen, colon and peripheral sensory nerve endings, the involvement of H3 receptors in skin responses particularly in relation to scratching behaviour are not well documented.

OBJECTIVES

This work was performed to study the effects of histamine H3 antagonists on scratching behaviour in mast cell-deficient mice.

METHODS

Histamine H3 antagonists iodophenpropit and clobenpropit, histamine and substance P were injected intradermally into the rostral part of the back of mast cell-deficient (WBB6F1 W/Wv) and wild-type (WBB6F1+/+) mice and scratching behaviour was measured for 60 min. The effects of H1 antagonists on scratching behaviour induced by H3 antagonists were also investigated.

RESULTS

Intradermal injection of iodophenpropit and clobenpropit at doses of 10 and 100 nmol per site caused significant increases in scratching behaviour in both mast cell-deficient and wild-type mice. Histamine also caused a dose-related increase in the incidence of scratching behaviour, and a significant effect was observed at a dose of 100 nmol per site in both mast cell-deficient and wild-type mice. Substance P was also effective in causing scratching behaviour in both mast cell-deficient and wild-type mice. However, histamine H1 antagonists diphenhydramine and chlorphenamine failed to inhibit H3 antagonist-induced scratching behaviour in both types of mice.

CONCLUSIONS

Our results indicated that intradermal injection of H3 antagonists induces scratching behaviour and that chemical mediators other than histamine seem to be involved in the response.

Nalpha-methylhistamine safety and efficacy in migraine prophylaxis: phase I and phase II studies

OBJECTIVE

To study the therapeutic potential of the subcutaneous administration of Nalpha-methylhistamine in migraine prophylaxis.

BACKGROUND

The histamine catabolite, Nalpha-methylhistamine, possesses a selective affinity for H3 receptors. We consequently considered it viable to conduct a clinical pharmacological study to evaluate the safety and efficacy of this histaminergic H3 agonist in migraine prophylactic treatment, which specifically may inhibit the neurogenic edema response involved in migraine pathophysiology.

METHODS

Phase I.-In a clinical trial of 30 healthy volunteers, the effects of the subcutaneous administration of Nalpha-methylhistamine and placebo were studied to assess undesirable symptomatic effects. Phase II.-In a clinical open study, we evaluated the efficacy of Nalpha-methylhistamine in reducing headache intensity, frequency, and duration; and in decreasing analgesic intake in 18 patients with migraine.

RESULTS

Phase I.-None of the variables studied showed significant differences (P>.05), and no secondary effects were observed at doses below 10 ng. Phase II.-Nalpha-methylhistamine, at doses of 1 to 3 ng, significantly reduced (P<.0001) the frequency, intensity, and duration of migraine attacks, as well as the need for rescue analgesics. However, at doses greater than 3 ng, patients experienced intense headache.

CONCLUSIONS

The present study provides evidence of the safety and efficacy of Nalpha-methylhistamine applied subcutaneously at doses of 1 to 3 ng twice a week.

Parallel development of blood vessels and mast cells in the lateral geniculate nuclei

The present study examined quantitatively developmental changes of the vasculature in the dorsal (dLGN) and the ventral (vLGN) lateral geniculate nuclei together with concomitant changes in the number of mast cells (MCs), known for their role in angiogenesis. Vascular network, marked after transcardial perfusion of India ink, and MCs detected with conventional histochemical techniques were examined at postnatal days (P) 1, 8, 14, 21, 31, 90 and 300 of Wistar rats. Quantitative analysis by means of an image analysis system showed age-dependent changes in both vascular parameters [vascular area and relative frequency (%) of capillaries and medium- and large-diameter vessels] and mast cells number in the developing dLGN and vLGN. Despite quantitative differences in the vascularization and MC infiltration between the two nuclei at some age points, MC number, vascular area and the percentage frequency of capillaries exhibited similar developmental time courses, especially up to the end of the first postnatal month. Both MC number and the capillary frequency reached maximal levels at P31 and declined thereafter, following a massive or a partial, respectively, decrease up to P300.

Modulatory effect of two novel CGRP receptor antagonists on nasal vasodilatatory responses to exogenous CGRP, capsaicin, bradykinin and histamine in anaesthetised pigs

Calcitonin gene-related peptide (CGRP) is a 37-amino acid peptide and potent vasodilatator agent located in sensory C fibres. Several functional studies suggest that CGRP could be involved in the vasodilatation of different vascular beds during neurogenic inflammation. We have studied, in pentobarbital anaesthetised pigs, the antagonistic effect of local intra-arterial (i.a.) pretreatment with the analogues CGRP 8-37, [D31, P34, F35]CGRP 27-37 and [N31, P34, F35]CGRP 27-37 on the vasodilatation of the nasal vascular bed induced by exogenous CGRP, capsaicin, bradykinin (BK) and histamine. The attenuating effect of CGRP 8-37 analogue on exogenous CGRP-induced vasodilatation, previously described in other in vivo animal models, was confirmed in the pig nasal mucosa. It also interfered with BK-and, to a lesser extent, with capsaicin-and histamine-induced decrease in vascular resistance. CGRP 27-37 analogues reduced the duration of CGRP-, capsaicin- and BK-induced vasodilatation by more than 50%. Peak values of vasodilatation were attenuated by more than 25% overall. Attenuation of histamine-induced decrease in vascular resistance was less pronounced. It is concluded that CGRP 27-37 analogues antagonise the action of exogenous CGRP, capsaicin, BK and histamine by attenuating their vasodilatation effect, both in intensity and duration. These results strongly suggest that BK- and histamine-induced vasodilatation is partly mediated by CGRP. CGRP 8-37 and 27-37 appear to be potential contributors to the study of CGRP and its physiological role in neurogenic inflammation. In addition, they may have putative therapeutic applications in the treatment of rhinitic patients suffering from chronic nasal obstruction.

Mast cell density and substance P-like immunoreactivity during the initiation and progression of lung lesions in ovine Mannheimia (Pasteurella) haemolytica pneumonia

To determine the density of mast cells (MCs) and the extent of substance P (SP) immunoreactivity during initiation and progression of pneumonic pasteurellosis (PP), 18 lambs were inoculated intrabronchially with Mannheimia (Pasteurella) haemolytica or saline, and lung tissue was collected at 1, 15 and 45 days post-inoculation (n=3, each group). Additionally, the left (non-inoculated) contralateral lungs in bacteria-inoculated animals were collected as controls. At 1 day after bacterial inoculation the lungs had typical M. haemolytica lesions. These pneumonic lesions had fewer numbers of MCs and reduced histamine content. Macrophages infiltrating some of the inflamed areas were strongly immunoreactive for SP. At 15 days, MCs remained scarce at sites where lung damage persisted, i.e. pyogranulomatous foci, but were increased in number in areas of interstitial damage. Pulmonary ganglion neurons were strongly immunoreactive for SP. By 45 days the fibrosing changes became more defined as pleural fibrosis, fibrosing alveolitis, alveolar epithelial hyperplasia and bronchiolitis obliterans. These lungs had increased numbers of MCs, but histamine content was not different from saline- and non-inoculated left lungs. Substance P immunoreactivity occurred only in nerves and was scarce and mild. This work demonstrates that MC density decreases initially with PP, but increases with progression of PP. SP fibres tend to be decreased during the initiation and at 45 days of PP, but other cells, such as macrophages and neuronal ganglion cells, produce substance P during progression of PP and thereby constitute an additional source of substance P.

New agents for the medical treatment of interstitial cystitis

Interstitial cystitis (IC) is a painful, sterile, disorder of the urinary bladder characterised by urgency, frequency, nocturia and pain. IC occurs primarily in women but also in men with recent findings indicating that chronic, abacterial prostatitis may be a variant of this condition. The prevalence of IC has ranged from about 8 - 60 cases/100,000 female patients depending on the population evaluated. About 10% of patients have severe symptoms that are associated with Hunner's ulcers on bladder biopsy; the rest could be grouped in those with or without bladder inflammation. Symptoms of IC are exacerbated by stress, certain foods and ovulatory hormones. Many patients also experience allergies, irritable bowel syndrome (IBS) and migraines. There have been various reports indicating dysfunction of the bladder glycosaminoglycan (GAG) protective layer and many publications showing a high number of activated bladder mast cells. Increasing evidence suggests that neurogenic inflammation and/or neuropathic pain is a major component of IC pathophysiology. Approved treatments so far include intravesical administration of dimethylsulphoxide (DMSO) or oral pentosanpolysulphate (PPS). New treatments focus on the combined use of drugs that modulate bladder sensory nerve stimulation (neurolytic agents), inhibit neurogenic activation of mast cells, or provide urothelial cytoprotection, together with new drugs with anti-inflammatory activity.

Effects of BP 2-94, a selective H(3)-receptor agonist, on blood flow and vascular permeability of the rat mandibular incisor pulp

Pulpal blood-flow changes were monitored by laser Doppler flowmetry after electrical stimulation of the mandibular incisor. Stimuli of 10 s (50 microA, 2 ms, 20 Hz) were applied to the incisors of untreated animals and longer stimulations (5 min) were applied in animals treated with the alpha-blocker phenoxybenzamine. Changes in vascular permeability in the dental pulp were measured by Evans blue extravasation following resection of the superior cervical ganglion. In these groups, a selective agonist of H(3) receptors, BP2-94 (1.5 and 15 mg/kg), and an H(3)-antagonist ciproxifan (1 mg/kg) were administered. The effects of these drugs were compared with those obtained from animals treated only with the vehicle (methylcellulose 1%). Basal pulpal blood-flow was not affected significantly by BP2-94 or ciproxifan. The vasoconstriction induced in the group of intact rats by electrical stimulation of 10 s is decreased in amplitude and duration at the higher dose of BP2-94 by 58 and 40%, respectively (P<0.05, n=5). In the sympathectomized animals, plasma extravasation was significantly increased at 15 mg/kg BP2-94 (+100%, P<0.01, n=5). These results suggest that H(3) receptors may participate in the regulation of changes in vessel contraction and permeability provoked by electrical stimulation of the dental pulp. However, the non-selective effects of the H(3) agonists reacting on adrenergic sites and H(1) receptors could explain a part of the results.

Dihydrocapsaicin treatment depletes peptidergic nerve fibers of substance P and alters mast cell density in the respiratory tract of neonatal sheep

In the present study we administered dihydrocapsaicin (DHC) to neonatal lambs to deplete C-fibers of neuropeptides. We measured the density of substance P (SP)-fibers in nasal septum to assess the effectiveness of the treatment at 3, 9, and 21 days. The numbers of mast cells in the upper and lower respiratory tract were determined at the same time points and histamine content was determined from lung tissue. DHC treatment depleted SP-fibers for up to the 21 day time point. This depletion was estimated as 85% in comparison with controls. In vehicle-treated lambs, the density of SP-fibers decreased progressively with age, but not to the degree of DHC-treated lambs whose SP-fibers were depleted from the initial 3-day measurement. In both, vehicle- and DHC-treated lambs, numbers of mast cells increased progressively with time; however, the density of mast cells was augmented in the entire respiratory tract of DHC-treated animals. Apparently, DHC treatment exerts a single and initial effect in increasing mast cells whereas time maintains a continuous influence; both factors exert their influence independently. Despite large numbers of mast cells in DHC-treated animals, histamine content in the lung had similar levels as controls. Our study provides fundamental data for a better understanding of conditions that may influence defense mechanisms dependent on the mast cell-nerve axis in the respiratory tract.