Effect of substance P on histamine secretion from gut mucosa in inflammatory bowel disease

Mas-related G protein-coupled receptors in gastrointestinal dysfunction and inflammatory bowel disease: A review

Inflammatory bowel disease (IBD) is a chronic debilitating condition, hallmarked by persistent inflammation of the gastrointestinal tract. Despite recent advances in clinical treatments, the aetiology of IBD is unknown, and a large proportion of patients are refractory to pharmacotherapy. Understanding IBD immunopathogenesis is crucial to discern the cause of IBD and optimise treatments. Mas-related G protein-coupled receptors (Mrgprs) are a family of approximately 50 G protein-coupled receptors that were first identified over 20 years ago. Originally known for their expression in skin nociceptors and their role in transmitting the sensation of itch in the periphery, new reports have described the presence of Mrgprs in the gastrointestinal tract. In this review, we consider the impact of these findings and assess the evidence that suggests that Mrgprs may be involved in the disrupted homeostatic processes that contribute to gastrointestinal disorders and IBD. LINKED ARTICLES: This article is part of a themed issue Therapeutic Targeting of G Protein-Coupled Receptors: hot topics from the Australasian Society of Clinical and Experimental Pharmacologists and Toxicologists 2021 Virtual Annual Scientific Meeting. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.14/issuetoc.

Histamine-producing bacteria and their role in gastrointestinal disorders

INTRODUCTION

Gut microbiota produces thousands of metabolites, which have a huge impact on the host health. Specific microbial strains are able to synthesize histamine, a molecule with a crucial role in many physiologic and pathologic mechanisms of the host. This function is mediated by the histidine decarboxylase enzyme (HDC) that converts the amino acid histidine to histamine.

AREAS COVERED

This review summarizes the emerging data on histamine production by gut microbiota, and the effect of bacterial-derived histamine in different clinical contexts, including cancer, irritable bowel syndrome, and other gastrointestinal and extraintestinal pathologies. This review will also outline the impact of histamine on the immune system and the effect of probiotics that can secrete histamine. Search methodology: we searched the literature on PubMed up to February 2023.

EXPERT OPINION

The potential of modulating gut microbiota to influence histamine production is a promising area of research, and although our knowledge of histamine-secreting bacteria is still limited, recent advances are exploring their diagnostic and therapeutical potential. Diet, probiotics, and pharmacological treatments directed to the modulation of histamine-secreting bacteria may in the future potentially be employed in the prevention and management of several gastrointestinal and extraintestinal disorders.

Infliximab Inhibits Colitis Associated Cancer in Model Mice by Downregulating Genes Associated with Mast Cells and Decreasing Their Accumulation

Inflammatory bowel diseases (IBDs), such as Crohn’s disease or ulcerative colitis, can be treated with anti TNF-alpha (TNF-α) antibodies (Abs), but they also put patients with IBDs at risk of cancer. We aimed to determine whether the anti TNF-α Ab induces colon cancer development in vitro and in vivo, and to identify the genes involved in colitis-associated cancer. We found that TNF-α (50 ng/mL) inhibited the proliferation, migration, and invasion of HCT8 and COLO205 colon cancer cell lines and that anti TNF-α Ab neutralized TNF-α inhibition in vitro. The effects of anti TNF-α Ab, infliximab (10 mg/kg) were investigated in mouse models of colitis-associated cancer induced by intraperitoneally injected azoxymethane (AOM: 10 mg/kg)/orally administered dextran sodium sulfate (DSS: 2.5%) (AOM/DSS) in vivo. Infliximab significantly attenuated the development of colon cancer in these mice. Microarray analyses and RT-qPCR revealed that mast cell protease 1, mast cell protease 2, and chymase 1 were up-regulated in cancer tissue of AOM/DSS mice; however, those mast cell related genes were downregulated in cancer tissue of AOM/DSS mice with infliximab. These results suggested that mast cells play a pivotal role in the development of cancer associated with colitis in AOM/DSS mice.

Mast Cell Mediated Regulation of Small Intestinal Chloride Malabsorption in SAMP1/YitFc Mouse Model of Spontaneous Chronic Ileitis

In Inflammatory Bowel Disease (IBD), malabsorption of electrolytes (NaCl) results in diarrhea. Inhibition of coupled NaCl absorption, mediated by the dual operation of Na:H and Cl:HCO₃ exchangers on the brush border membrane (BBM) of the intestinal villus cells has been reported in IBD. In the SAMP1/YitFcs (SAMP1) mice model of spontaneous ileitis, representing Crohn’s disease, DRA (Downregulated in Adenoma) mediated Cl:HCO₃ exchange was shown to be inhibited secondary to diminished affinity of the exchanger for Cl. However, NHE3 mediated Na:H exchange remained unaffected. Mast cells and their secreted mediators are known to be increased in the IBD mucosa and can affect intestinal electrolyte absorption. However, how mast cell mediators may regulate Cl:HCO₃ exchange in SAMP1 mice is unknown. Therefore, the aim of this study was to determine the effect of mast cell mediators on the downregulation of DRA in SAMP1 mice. Mast cell numbers and their degranulation marker enzyme (β-hexosaminidase) levels were significantly increased in SAMP1 mice compared to control AKR mice. However, treatment of SAMP1 mice with a mast cell stabilizer, ketotifen, restored the β-hexosaminidase enzyme levels to normal in the intestine, demonstrating stabilization of mast cells by ketotifen. Moreover, downregulation of Cl:HCO₃ exchange activity was restored in ketotifen treated SAMP1 mice. Kinetic studies showed that ketotifen restored the altered affinity of Cl:HCO₃ exchange in SAMP1 mice villus cells thus reinstating its activity to normal. Further, RT-qPCR, Western blot and immunofluorescence studies showed that the expression levels of DRA mRNA and BBM protein, respectively remained unaltered in all experimental conditions, supporting the kinetic data. Thus, inhibition of Cl:HCO₃ exchange resulting in chloride malabsorption leading to diarrhea in IBD is likely mediated by mast cell mediators.

Changes in the expression of substance P in nerve fibres of the colonic mucosa in dogs suffering from inflammatory bowel disease

Due to its difficult diagnosis and complicated treatment, inflammatory bowel disease (IBD) in dogs is a challenge for the veterinarian. Several aspects connected with pathological changes during IBD still remain unknown. Since one of these aspects is the participation of intestinal innervation in the evolution of the disease, the aim of this study was to demonstrate changes in the number and distribution of intramucosal colonic nerve fibres immunoreactive to substance P (SP) arising as the disease progresses. SP is one of the most important neuronal factors in intestinal innervation which, among other tasks, takes part in the conduction of pain stimuli. Using routine immunofluorescence technique, the density of nerve fibres containing SP was evaluated within mucosal biopsy specimens collected from the descending colon of healthy dogs and animals suffering from IBD of varying severity. The results of the study indicate that during severe IBD the number of nerve fibres containing SP located in the colonic mucosal layer increases in comparison to control animals. The number of SP-positive intramucosal nerves amounted to 10.99 ± 2.11 nerves per observation field in healthy dogs, 14.62 ± 2.86 in dogs with mild IBD, 14.80 ± 0.91 in dogs with moderate IBD and 19.03 ± 6.11 in animals with severe IBD. The observed changes were directly proportional to the intensity of the disease process. These observations may suggest a role of this neuronal substance in pathological processes occurring during IBD. Although the exact mechanism of the observed changes has not been completely explained, the results obtained in this investigation may contribute to improving the diagnosis and treatment of this disease, as well as the staging of canine IBD in veterinary practice.

Intestinal Mucosal Mast Cells: Key Modulators of Barrier Function and Homeostasis

The gastrointestinal tract harbours the largest population of mast cells in the body; this highly specialised leukocyte cell type is able to adapt its phenotype and function to the microenvironment in which it resides. Mast cells react to external and internal stimuli thanks to the variety of receptors they express, and carry out effector and regulatory tasks by means of the mediators of different natures they produce. Mast cells are fundamental elements of the intestinal barrier as they regulate epithelial function and integrity, modulate both innate and adaptive mucosal immunity, and maintain neuro-immune interactions, which are key to functioning of the gut. Disruption of the intestinal barrier is associated with increased passage of luminal antigens into the mucosa, which further facilitates mucosal mast cell activation, inflammatory responses, and altered mast cell⁻enteric nerve interaction. Despite intensive research showing gut dysfunction to be associated with increased intestinal permeability and mucosal mast cell activation, the specific mechanisms linking mast cell activity with altered intestinal barrier in human disease remain unclear. This review describes the role played by mast cells in control of the intestinal mucosal barrier and their contribution to digestive diseases.

Mast cells within cellular networks

Mast cells are highly versatile in terms of their mode of activation by a host of stimuli and their ability to flexibly release a plethora of biologically highly active mediators. Within the immune system, mast cells can best be designated as an active nexus interlinking innate and adaptive immunity. Here we try to draw an arc from initiation of acute inflammatory reactions to microbial pathogens to development of adaptive immunity and allergies. This multifaceted nature of mast cells is made possible by interaction with multiple cell types of immunologic and nonimmunologic origin. Examples for the former include neutrophils, eosinophils, T cells, and professional antigen-presenting cells. These interactions allow mast cells to orchestrate inflammatory innate reactions and complex adaptive immunity, including the pathogenesis of allergies. Important partners of nonimmunologic origin include cells of the sensory neuronal system. The intimate association between mast cells and sensory nerve fibers allows bidirectional communication, leading to neurogenic inflammation. Evidence is accumulating that this mast cell/nerve crosstalk is of pathophysiologic relevance in patients with allergic diseases, such as asthma.

Mast Cells Exert Anti-Inflammatory Effects in an IL10-/- Model of Spontaneous Colitis

Mast cells are well established as divergent modulators of inflammation and immunosuppression, but their role in inflammatory bowel disease (IBD) remains to be fully defined. While previous studies have demonstrated a proinflammatory role for mast cells in acute models of chemical colitis, more recent investigations have shown that mast cell deficiency can exacerbate inflammation in spontaneous colitis models, thus suggesting a potential anti-inflammatory role of mast cells in IBD. Here, we tested the hypothesis that in chronic, spontaneous colitis, mast cells are protective. We compared colitis and intestinal barrier function in IL10^−/− mice to mast cell deficient/IL10^−/− (double knockout (DKO): Kit^Wsh/Wsh × IL10^−/−) mice. Compared with IL10^−/− mice, DKO mice exhibited more severe colitis as assessed by increased colitis scores, mucosal hypertrophy, intestinal permeability, and colonic cytokine production. PCR array analyses demonstrated enhanced expression of numerous cytokine and chemokine genes and downregulation of anti-inflammatory genes (e.g., Tgfb2, Bmp2, Bmp4, Bmp6, and Bmp7) in the colonic mucosa of DKO mice. Systemic reconstitution of DKO mice with bone marrow-derived mast cells resulted in significant amelioration of IL10^−/−-mediated colitis and intestinal barrier injury. Together, the results presented here demonstrate that mast cells exert anti-inflammatory properties in an established model of chronic, spontaneous IBD. Given the previously established proinflammatory role of mast cells in acute chemical colitis models, the present findings provide new insight into the divergent roles of mast cells in modulating inflammation during different stages of colitis. Further investigation of the mechanism of the anti-inflammatory role of the mast cells may elucidate novel therapies.

Concurrent Ulcerative Colitis and Neurofibromatosis Type 1: The Question of a Common Pathway

Patients with neurofibromatosis type 1 (NF1) are prone to the development of gastrointestinal stromal tumors, which may present clinically with hematochezia, obstruction, or abdominal pain. These symptoms are also commonly associated with the presentation of ulcerative colitis (UC). Within the past 5 years, there have been 2 reports of concurrent NF1 and UC and a common pathophysiologic pathway involving mast cells has been postulated. We present the case of a 15-year-old boy with a known history of NF1 who presented with 3 months of hematochezia and loose stools. A colonoscopy revealed pancolitis and histology demonstrating acute cryptitis, focal crypt abscesses, and architectural distortion consistent with UC. Due to the paucity of reported cases, the findings of both diseases in the same individual could reasonably be discounted as coincidence. However, in light of increasing reports of concurrent NF1 and UC, advances in characterizing the microenvironment within neurofibromas, and recent findings regarding potential shared genetic susceptibility, it is increasingly possible that the proposed common pathway is accurate. Our case adds to the literature and underscores the need for further investigation.

Tachykinin peptide, substance P, and its receptor NK-1R play an important role in alimentary tract mucosal inflammation during cytotoxic therapy

The alimentary tract mucosal inflammation has been a topic of concern in oncology; though many modalities of treatment have been proposed for mucosal inflammation, the contributing adverse effects have severely affected the quality of life of patients. This review focuses on the importance of neurogenic peptide, Substance P and its receptor NK-1R in modulating the cascades of events in mucosal inflammation during cytotoxic therapy. There are various preclinical and clinical models showing increased expression of Substance P/NK-1R in ionizing radiation and chemotherapy, but only very few preclinical studies to our knowledge have highlighted or examined its role in mucosal inflammation. Hence, the importance of neuropeptide involved in the inflammatory events in mucosal inflammation in cytotoxic therapy could be a major breakthrough for future research purposes and treatment. The factors contributing to the severity of tissue reactions have been multietiogenic; thus, resultant treatment also has to be directed toward multiple contributing factors. This review also focuses on the significance of care strategy to be adopted in alimentary tract mucositis when multietiogenic factors are taken into consideration.

Histamine and gut mucosal immune regulation

Histamine is a biogenic amine with extensive effects on many cell types, mediated by the activation of its four receptors (H1R-H4R). Distinct effects are dependent on receptor subtypes and their differential expression. Within the gastrointestinal tract, histamine is present at relatively high concentrations, particularly during inflammatory responses. In this review, we discuss the immunoregulatory influence of histamine on a number of gastrointestinal disorders, including food allergy, scombroid food poisoning, histamine intolerance, irritable bowel syndrome, and inflammatory bowel disease. It is clear that the effects of histamine on mucosal immune homeostasis are dependent on expression and activity of the four currently known histamine receptors; however, the relative protective or pathogenic effects of histamine on inflammatory processes within the gut are still poorly defined and require further investigation.

Innate immunity modulation by the IL-33/ST2 system in intestinal mucosa

Innate immunity prevents pathogens from entering and spreading within the body. This function is especially important in the gastrointestinal tract and skin, as these organs have a large surface contact area with the outside environment. In the intestine, luminal commensal bacteria are necessary for adequate food digestion and play a crucial role in tolerance to benign antigens. Immune system damage can create an intestinal inflammatory response, leading to chronic disease including inflammatory bowel diseases (IBD). Ulcerative colitis (UC) is an IBD of unknown etiology with increasing worldwide prevalence. In the intestinal mucosa of UC patients, there is an imbalance in the IL-33/ST2 axis, an important modulator of the innate immune response. This paper reviews the role of the IL-33/ST2 system in innate immunity of the intestinal mucosa and its importance in inflammatory bowel diseases, especially ulcerative colitis.

CRF induces intestinal epithelial barrier injury via the release of mast cell proteases and TNF-α

BACKGROUND AND AIMS

Psychological stress is a predisposing factor in the onset and exacerbation of important gastrointestinal diseases including irritable bowel syndrome (IBS) and the inflammatory bowel diseases (IBD). The pathophysiology of stress-induced intestinal disturbances is known to be mediated by corticotropin releasing factor (CRF) but the precise signaling pathways remain poorly understood. Utilizing a porcine ex vivo intestinal model, the aim of this study was to investigate the mechanisms by which CRF mediates intestinal epithelial barrier disturbances.

METHODOLOGY

Ileum was harvested from 6-8 week-old pigs, mounted on Ussing Chambers, and exposed to CRF in the presence or absence of various pharmacologic inhibitors of CRF-mediated signaling pathways. Mucosal-to-serosal flux of 4 kDa-FITC dextran (FD4) and transepithelial electrical resistance (TER) were recorded as indices of intestinal epithelial barrier function.

RESULTS

Exposure of porcine ileum to 0.05-0.5 µM CRF increased (p<0.05) paracellular flux compared with vehicle controls. CRF treatment had no deleterious effects on ileal TER. The effects of CRF on FD4 flux were inhibited with pre-treatment of tissue with the non-selective CRF(1/2) receptor antagonist Astressin B and the mast cell stabilizer sodium cromolyn (10(-4) M). Furthermore, anti-TNF-α neutralizing antibody (p<0.01), protease inhibitors (p<0.01) and the neural blocker tetrodotoxin (TTX) inhibited CRF-mediated intestinal barrier dysfunction.

CONCLUSION

These data demonstrate that CRF triggers increases in intestinal paracellular permeability via mast cell dependent release of TNF-α and proteases. Furthermore, CRF-mast cell signaling pathways and increases in intestinal permeability require critical input from the enteric nervous system. Therefore, blocking the deleterious effects of CRF may address the enteric signaling of mast cell degranulation, TNFα release, and protease secretion, hallmarks of IBS and IBD.

Antimicrobial anxiety: the impact of stress on antimicrobial immunity

Leukocytes and epithelial cells are fundamental to antimicrobial immunity. Their antimicrobial responses are an evolutionarily conserved component of the innate immune system and are influenced by the host's response to external stimuli. The efficacy of host defense via antimicrobial responses derives from the ability of AMPs to rapidly identify and eradicate foreign microbes and activate proinflammatory pathways, and from the capacity of later innate and adaptive immune responses to amplify protection through distinct biochemical mechanisms. Recent advances in neuroimmunology have identified a direct link between the neuroendocrine and immune systems, where environmental stimuli are generally believed to promote a transient effect on the immune system in response to environmental challenges and are presumably brought back to baseline levels via neuroendocrine pathways. Stress is an environmental stimulus that flares from a variety of circumstances and has become engrained in human society. Small bouts of stress are believed to enhance the host's immune response; however, prolonged periods of stress can be detrimental through excess production of neuroendocrine-derived mediators that dampen immune responses to invasive pathogens. Elucidation of the mechanisms behind stress-induced immune modulation of antimicrobial responses will ultimately lead to the development of more effective therapeutic interventions for pathologic conditions. It is the intent of this review to broaden the existing paradigm of how stress-related molecules dampen immune responses through suppression of antimicrobial mechanisms, and to emphasize that bacteria can use these factors to enhance microbial pathogenesis during stress.

Stress-induced barrier disruption of rat follicle-associated epithelium involves corticotropin-releasing hormone, acetylcholine, substance P, and mast cells

BACKGROUND

The follicle-associated epithelium (FAE) is specialized in uptake and sampling of luminal antigens and bacteria. We previously showed that stress increased FAE permeability in rats. An increased uptake may alter antigen exposure in Peyer's patches leading to intestinal disease. The aim of this study was to elucidate mechanisms involved in the acute stress-induced increase in FAE permeability.

METHODS

Rats were pretreated i.p. with corticotropin-releasing hormone receptor (CRH-R) antagonist, neurokinin receptor 1 (NK-1R) antagonist, atropine, the mast cell stabilizer doxantrazole (DOX), or NaCl, and submitted to 1-h acute water avoidance stress. FAE tissues were mounted in Ussing chambers for measurements of permeability to (51)Cr-EDTA, horseradish peroxidase (HRP) and chemically killed Escherichia coli K-12. Further, FAE segments were exposed in vitro in chambers to CRH, substance P (SP), carbachol, and DOX. Neurotransmitter- and receptor distribution was studied by immunohistochemistry.

KEY RESULTS

Stress-induced increases in uptake across FAE of HRP and E. coli were reduced by DOX, CRH-R antagonist and atropine, whereas the NK-1R antagonist decreased (51)Cr-EDTA permeability. Exposure to CRH and carbachol increased HRP and E. coli passage, whereas SP increased bacterial and (51)Cr-EDTA permeability. DOX counteracted all of these effects. Immunohistochemistry revealed CRH, acetylcholine, SP, and their receptors on mast cells within the Peyer's patches, subepithelial dome, and adjacent villi.

CONCLUSIONS & INFERENCES

Corticotropin-releasing hormone and acetylcholine signaling affect mainly transcellular permeability while SP seems more selective toward the paracellular pathways. Our findings may be of importance for the understanding of the pathogenesis of stress-related intestinal disorders.

The effect of hypnosis on systemic and rectal mucosal measures of inflammation in ulcerative colitis

OBJECTIVES

Hypnotherapy is effective in several diseases with a psychosomatic component. Our aim was to study the effects of one session of hypnosis on the systemic and rectal mucosal inflammatory responses in patients with active ulcerative colitis (UC).

METHODS

In total, 17 patients with active UC underwent a 50-min session of gut-focused hypnotherapy. Before and after each procedure, the systemic inflammatory response was assessed by serum interleukin (IL)-6 and IL-13 concentrations, tumor necrosis factor-alpha (TNF-alpha) and IL-6 production by lipopolysaccharide (LPS)-stimulated whole blood, leukocyte count, natural killer (NK) cell number, platelet activation, and platelet-leukocyte aggregate formation. Rectal inflammation was assessed by mucosal release of substance P (SP), histamine, IL-13 and TNF-alpha, reactive oxygen metabolite production, and mucosal blood flow. Eight patients with active UC underwent a control procedure.

RESULTS

Hypnosis decreased pulse by a median 7 beats per minute (bpm) (P= 0.0008); it also reduced the median serum IL-6 concentration by 53% (P= 0.001), but had no effect on the other systemic variables assessed. Hypnosis reduced rectal mucosal release of SP by a median 81% (P= 0.001), histamine by 35% (P= 0.002) and IL-13 by 53% (P= 0.003), and also, blood flow by 18% (P= 0.0004). The control protocol had no effect on any of the variables assessed.

CONCLUSIONS

Hypnosis reduced several components of the systemic and mucosal inflammatory response in active ulcerative colitis toward levels found previously in the inactive disease. Some of these effects may contribute to the anecdotally reported benefits of hypnotherapy and provide a rationale for controlled trials of hypnotherapy in UC.

Review article: gastrointestinal sensory and motor disturbances in inflammatory bowel disease - clinical relevance and pathophysiological mechanisms

BACKGROUND

It is well known that inflammation has a profound impact on the neuromuscular apparatus of the gastrointestinal tract during the inflammatory insult and in periods of remission, at the site of inflammation and at distance from this site. The importance of this interaction is illustrated by the higher prevalence of functional gut disorders in patients with inflammatory bowel disease.

AIMS

To document the epidemiological and clinical significance of functional alterations of gut motility and sensitivity in patients with inflammatory bowel disease and to formulate potential pathophysiological mechanisms.

RESULTS AND CONCLUSIONS

Functional gut disorders occur frequently in patients with inflammatory bowel disease, both during inflammatory episodes and in periods of remission, and have a major impact on their quality of life. The clinical manifestations of these motility and sensitivity disorders vary and are often difficult to treat, mainly because therapeutic guidelines and specific diagnostic tests to distinguish inflammatory bowel disease from functional gut disorders are lacking. Chronic bowel inflammation results in a complicated interaction between neuroendocrine serotonin-predominant cells of the mucosa, inflammatory cells (particularly mast cells) in the submucosa, the intrinsic and extrinsic innervation and the muscular apparatus including the interstitial cells of Cajal. The outcome of this interaction is a perturbation of gastrointestinal motor function, both locally and at distance from the site of inflammation and during both acute inflammation and remission.

Fecal levels of leukocyte markers reflect disease activity in patients with ulcerative colitis

OBJECTIVE

A prominent feature of inflammatory bowel disease (IBD) is the presence of inflammatory cells in the gut mucosa, and which contribute to the ongoing inflammatory process. The aim of the study was to evaluate fecal neutrophil, eosinophil, mast cell and macrophage markers in the assessment of disease activity in patients with ulcerative colitis (UC).

METHODS

Twenty-eight patients with active UC; 4 with proctitis, 16 with left-side colitis and 8 with total colitis, were included in the study. Patient history, endoscopy and histopathology were examined and fecal and serum samples were evaluated at inclusion and after 4 and 8 weeks of treatment. Fecal samples were analysed for myeloperoxidase (MPO), eosinophil protein X (EPX), mast cell tryptase, IL-1beta and TNF-alpha using immunoassays. Blood samples were analysed for MPO, EPX, C-reactive protein, orosomucoid and leucocyte counts.

RESULTS

Fecal MPO and IL-1beta levels were elevated in all patients at inclusion despite different disease extensions. Striking reductions in fecal levels of MPO, EPX, tryptase and IL-1beta were observed after 4 weeks of treatment in 20/28 patients with complete remission after 8 weeks. No further reductions were seen in 20/27 patients at 8 weeks. Endoscopic score correlated to IL-1beta at all visits (p<0.01), to MPO at visits 2 and 3 (p<0.05, p<0.001), EPX at visit 2 (p<0.05) and tryptase at visit 3 (p<0.01). Levels of fecal markers also related to histological indices of the disease.

CONCLUSIONS

Measurements of fecal MPO, EPX and IL-1beta could be objective complements to endoscopical and histopathological evaluations in the daily care of patients with UC.

Reduced immunostaining for c-kit receptors in mucosal mast cells in inflammatory bowel disease

BACKGROUND AND AIM

The deleterious effects of stress in inflammatory bowel disease (IBD) have been attributed to activation of the brain-gut axis (BGA) and its end effectors, mast cells (MC). We previously showed that cold pressor stress test (CPT) results in increased activation and degranulation (but not increased proliferation) of mucosal MC, mitochondrial damage to epithelial cells and mucosal protein oxidation in both healthy controls and IBD patients. These changes are more marked in IBD patients. This increased activation of MC in IBD could be due to (i) greater activation of the BGA or (ii) inherited or acquired abnormalities in mucosal MC. In the current study we investigated the latter possibility.

METHODS

To assess the effects of stress on mucosal MC in patients with IBD, seven controls and 15 subjects with inactive IBD underwent 5 consecutive days of CPT to activate the BGA. Endoscopic mucosal biopsies of the distal sigmoid colon were taken during unprepared sigmoidoscopy before the first CPT and after the last CPT, and formalin-fixed samples were stained for both MC granules (MCg) and for the c-kit receptor, which is present on MC membranes (MCm). Mast cell degranulation was assessed using electron microscopy.

RESULTS

Mast cell granule staining suggested that IBD subjects do not have a significantly different number of MC compared with controls, either before or after stress. Mast cell membrane staining, in contrast, suggested that MC c-kit immunostaining was significantly reduced - at both baseline (P = 0.01) and post stress (P = 0.04) samples - in IBD patients compared to controls. MC c-kit immunostaining was independent of stress-induced MC degranulation. There was no significant change in MC number as a result of the stress intervention using either staining method in both groups.

CONCLUSION

These data support our previous report that the size of the mucosal MC population in patients with inactive IBD is not altered by disease or by stress, yet MC in IBD are different (fewer c-kit receptors) and respond differently (greater activation) than MC in control subjects. It remains to be seen whether this abnormality is an inherited or acquired one and to identify its role and mechanism in tissue injury in the pathogenesis of IBD.

Mast cells and nerves tickle in the tummy: implications for inflammatory bowel disease and irritable bowel syndrome

Mast cells are well known as versatile cells capable of releasing and producing a variety of inflammatory mediators upon activation and are often found in close proximity of neurons. In addition, inflammation leads to local activation of neurons resulting in the release neuropeptides, which also play an important immune modulatory role by stimulation of immune cells. In intestinal disorders like inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS), the number of mast cells is known to be much higher than in the normal intestine. Moreover, both these disorders are also reported to be associated with alterations in neuropeptide content and in neural innervation. Mutual association between mast cells and enteric nerves has been demonstrated to be increased in pathophysiological conditions and contribute to spreading and amplification of the response in IBD and IBS. In this review the focus lies on studies appointed to the direct interaction between mast cells and nerves in IBD, IBS, and animal models for these disorders so far.

Combination therapy using fexofenadine, disodium cromoglycate, and a hypoallergenic amino acid-based formula induced remission in a patient with steroid-dependent, chronically active ulcerative colitis

Corticosteroids and 5-aminosalicylic acid are the primary standard therapy for inflammatory bowel disease. Recent immunologic data implicate an involvement of mast cell activation followed by increased histamine secretion and elevated tissue concentrations of histamine in the pathogenesis of ulcerative colitis. In the present case, the clinical course of a 35-year-old man with steroid-dependent chronic active ulcerative colitis, who did not respond to high-dose steroids, antibiotics, or azathioprine during 3 years, is reported. Clinical disease activity and established serological markers were recorded during 6 weeks of unsuccessful therapy and during the next 6 weeks, as a new nonsedative antihistaminergic drug, a mast cell stabilizer, and an hypoallergenic diet were implemented in addition to conventional therapy. Induction of remission was achieved within 2 weeks after treatment with fexofenadine, disodium cromoglycate, and an amino acid-based formula. Clinical disease activity, stool frequency, leukocytes, c-reactive protein, and orosomucoid levels in serum decreased rapidly. Daily steroid administration could be gradually reduced along with 6 weeks of this treatment. This report suggests that histamine and mast cell activity may be important pathophysiological factors responsible for persistent clinical and mucosal inflammatory activity in ulcerative colitis despite the use of steroids. In ulcerative colitis, patients unresponsive to conventional treatment, therapeutic considerations should also include an antiallergic approach when further signs of atopy or intestinal hypersensitivity are present.

Role of neuropeptides in inflammatory bowel disease

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

Mucosal mast cells are pivotal elements in inflammatory bowel disease that connect the dots: Stress, intestinal hyperpermeability and inflammation

Mast cells (MC) are pivotal elements in several physiological and immunological functions of the gastro-intestinal (GI) tract. MC translate the stress signals that has been transmitted through brain gut axis into release of proinflammatory mediators that can cause stimulation of nerve endings that could affect afferent nerve terminals and change their perception, affect intestinal motility, increase intestinal hyperpermeability and, in susceptible individuals, modulate the inflammation. Thus, it is not surprising that MC are an important element in the pathogenesis of inflammatory bowel disease and non inflammatory GI disorders such as IBS and mast cell enterocolitis.

Functional characteristics of the porcine colonic epithelium following transportation stress and Salmonella infection

OBJECTIVE

Stressful life events and infections contribute to gut disorders such as irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD). We used a pig model to analyse whether this could be linked to altered mediator sensitivity of the epithelial lining.

MATERIAL AND METHODS

Uninfected control pigs or pigs with subclinical Salmonella (S.) typhimurium DT 104 infection were killed either without (ConRest, InfRest) or with prior 8-h transportation (ConTrans, InfTrans). Short-circuit current (I(sc)), tissue conductance (G(t)) and release of mast cell mediators were monitored in isolated colonic epithelia mounted in Ussing chambers. Epithelia were exposed to histamine (100 microM, mucosally), substance P (SP; 1 microM, serosally), calcimycin A23187 (1 microM, serosally) and theophylline (10 mM, bilaterally). Transepithelial flux of histamine and colonic activities of histamine N-methyltransferase (HMT) and diamine oxidase (DAO) were determined.

RESULTS

S. infection decreased baseline I(sc), G(t) and histamine fluxes, while transportation had no effect on these values. Mucosal histamine increased I(sc) only in ConTrans pigs. This was not associated with increased mucosal-to-serosal flux of histamine but with a 2-fold increased DAO activity. Serosal SP increased I(sc) only in transported animals, but the increase was six times higher in ConTrans versus InfTrans pigs. Effectiveness of SP was not dependent on the release of histamine or prostaglandin D2. A23187 and theophylline elicited increases in I(sc) that were not different between treatments.

CONCLUSIONS

Transportation stress facilitates secretory responses of the colonic epithelium to SP and luminal histamine. This is suppressed by subclinical S. infection. Effects of S. infection on porcine colon resemble, in part, the known effects of an oral S. endotoxin application.

Effect of Mast Cell Degranulation on Chicken Ileal Ion Transport In Vitro

Histamine is a primary mediator of the inflammatory response in mammals. Degranulation of intestinal mast cells results in the release of mast cell mediators such as histamine. Histamine stimulates epithelial ion transport in a range of mammalian tissues via specific histamine receptors. The aim of this study was to assess a potential role of tissue mast cells and of exogenous histamine in the regulation of ion transport in avian mucosa. Broiler chicken ileal histamine release and secretory responses to mast cell degranulation were determined in vitro with the use of ELISA and Ussing chamber techniques. Pharmacological degranulation of mucosal mast cells using compound 48/80 (15 microg/mL) resulted in histamine release and an immediate-onset transient increase in transmural short-circuit current. The response to compound 48/80 was subject to tachyphylaxis and was significantly reduced in the presence of the histamine H(1) antagonist mepyramine, but was unaffected by the cyclooxygenase inhibitor piroxicam. Prior incubation with the mast cell stabilizer ketotifen prevented compound 48/80-induced increase in transmural short-circuit current. In conclusion, degranulation of avian intestinal mast cells would appear to result in histamine release that stimulates epithelial ion transport via histamine H(1) receptor activation. Although prostaglandin E(2) is a potent secretagogue in the avian small intestine epithelium, prostanoid production appears to have little role to play in mast cell-mediated epithelial ion transport.

Increase in substance P precursor mRNA in noninflamed small-bowel sections in patients with Crohn's disease

BACKGROUND

Neuropeptides, such as substance P (SP), are mediators of neurogenic inflammation and play an important role in inflammatory disorders. To further investigate the role of the SP pathway in inflammatory bowel disease (IBD), we analyzed the following in normal intestinal tissue specimens and in tissue specimens from patients with Crohn's disease (CD) and ulcerative colitis (UC): neurokinin receptor-1 (NK-1R); its isoforms (NK-1R-L and NK-1R-S); its ligand SP, encoded by preprotachykinin-A (PPT-A); and the SP-degradation enzyme, neutral endopeptidase (NEP).

METHODS

Real-time quantitative reverse transcription-polymerase chain reaction was used to simultaneously determine the expression of NK-1R-L, NK-1R-S, and PPT-A. Protein levels of NK-1R and NEP were determined by immunoblot analysis.

RESULTS

In noninflamed small-bowel tissue samples of CD patients, PPT-A mRNA expression was significantly increased, whereas there was no difference between inflamed or noninflamed UC and normal intestinal tissue samples. Examining subgroups of diverse intestinal segments from CD and UC samples with various levels of inflammation revealed no differences in NK-1R-L and NK-1R-S mRNA expression, whereas there was a tendency toward overall lower NK-1R-S mRNA copy numbers. Immunoblot analysis showed upregulation of NK-1R protein levels in cases of IBD, with more pronounced enhancement in cases of CD than in UC. For NEP, there were no differences in protein levels in normal, CD, and UC intestinal tissues.

COMMENTS

These observations suggest a contribution of SP and its receptor, NK-1R, in the local inflammatory reaction in IBD and particularly in ileal CD. Moreover, significant upregulation of PPT-A mRNA in the noninflamed ileum of these patients suggests an influence of inflamed intestines on their healthy counterparts.

Immunomodulatory properties of substance P: the gastrointestinal system as a model

Communication between nerves and immune and inflammatory cells of the small and large intestine plays a major role in the modulation of several intestinal functions, including intestinal motility, ion transport, and mucosal permeability. Neuroimmune interactions at intestinal sites have been associated with the pathophysiology of infectious and enterotoxin-mediated diarrhea and intestinal inflammation, including inflammatory bowel disease (IBD). During the past 20 years the neuropeptide substance P (SP) has been identified as an important mediator in the development and progress of intestinal inflammation by binding to its high-affinity neurokinin-1 receptor (NK-1R). This peptide, released from enteric nerves, sensory neurons, and inflammatory cells of the lamina propria during intestinal inflammation, participates in gut inflammation by interacting, directly or indirectly, with NK-1R expressed on nerves, epithelial cells, and immune and inflammatory cells, such as mast cells, macrophages, and T cells. SP-dependent activation of these cells leads to the release of cytokines and chemokines as well as other neuropeptides that modulate diarrhea, inflammation, and motility associated with the pathophysiology of several intestinal disease states. The recent development of specific nonpeptide NK-1R antagonists and NK-1R-deficient mice helped us understand the functional importance of the SP-NK-1R system in mediating intestinal neuroimmune interactions and to identify the particular cells and signaling pathways involved in this response. This review summarizes our understanding on the immunomodulatory properties of SP and its receptor in the intestinal tract with particular focus on their involvement in intestinal physiology as well as in the pathophysiology of several intestinal disease states at the in vivo and cell signaling level.

The autonomic nervous system and inflammatory bowel disease

Crohn's disease and ulcerative colitis, collectively known as inflammatory bowel disease (IBD), are chronic, recurring, inflammatory conditions of the intestine. The precise mechanisms underlying the pathogenesis of IBD are not yet clear but they are believed to involve a number of precipitating factors, most notably genetic susceptibility and environmental influences. The autonomic nervous system (ANS) has long been known as a critical regulator of intestinal function and much evidence now exists to suggest that it also plays an important role in the development of IBD. Dramatic changes in the ANS in IBD are apparent from the cellular to the molecular level ultimately leading to altered communication between the ANS and effector cells of the intestine. This review aims to synthesize the current understanding of the pathogenesis of IBD with a particular emphasis on the role that the ANS plays in the progression of these diseases.

Beneficial effect of tachykinin NK1 receptor antagonism in the development of hapten-induced colitis in mice

The gastro-intestinal tract is highly innervated by both intrinsic and extrinsic sensory nerves and this neuronal component is thought to play a role in local inflammatory responses. This in vivo study was designed to determine the function of substance P and the tachykinin NK1 receptor in the pathogenesis of inflammatory bowel disease by the use of the specific antagonist RP 67580. The dinitrofluorobenzene (DNFB)-induced colonic hypersensitivity model is associated with increased levels of substance P in the colon. The tachykinin NK1 receptor antagonist RP 67580 was used to investigate the role of substance P on the development of diarrhea, mast cell infiltration and activation, colonic tissue damage, hypertrophy of colonic lymphoid structures and leukocyte infiltration. The formation of watery diarrhea could completely be abrogated by treatment with RP 67580 in DNFB-sensitized animals 72 h after challenge. Antagonizing the tachykinin NK1 receptor in these animals also resulted in significantly reduced colonic patch hypertrophy, leukocyte recruitment and tissue damage. Total levels of substance P in the colon of DNFB-sensitized mice treated with the inactive enantiomer of the tachykinin NK1 receptor antagonist were significantly higher compared to DNFB-sensitized mice treated with RP 67580 72 h after challenge. Although RP 67580 was capable of reducing the total number of mast cells present in the colon, mast cell activation was not affected by this treatment. In conclusion, in this chemically-induced immunological model for inflammatory bowel disease we demonstrated an important role for tachykinin NK1 receptors, and its ligand substance P, in the development of colitis downstream from mast cell activation.

The effect of acute psychologic stress on systemic and rectal mucosal measures of inflammation in ulcerative colitis

BACKGROUND & AIMS

Recent studies suggest that life events and chronic stress increase the risk of relapse in inflammatory bowel disease. Our aim was to study the effects of acute psychologic stress on systemic and rectal mucosal inflammatory responses in patients with inactive ulcerative colitis (UC).

METHODS

Twenty-five patients with inactive UC and 11 healthy volunteers (HV) underwent an experimental stress test. Ten patients with UC and 11 HV underwent a control procedure. Before and after each procedure, systemic inflammatory response was assessed by serum interleukin (IL)-6 and IL-13 concentrations, tumor necrosis factor (TNF)-alpha and IL-6 production by lipopolysaccharide (LPS)-stimulated whole blood, leukocyte count, natural killer (NK) cell numbers, platelet activation, and platelet-leukocyte aggregate (PLA) formation. In patients with UC, rectal mucosal inflammation was assessed by TNF-alpha, IL-13, histamine and substance P release, reactive oxygen metabolite (ROM) production, mucosal blood flow (RMBF) and histology.

RESULTS

Stress increased pulse (P < .0001) and systolic BP (P < .0001). In UC, stress increased LPS-stimulated TNF-alpha and IL-6 production by 54% (P = .004) and 11% (P = .04), respectively, leukocyte count by 16% (P = .01), NK cell count by 18% (P = .0008), platelet activation by 65% (P < .0001), PLA formation by 25% (P = .004), mucosal TNF-alpha release by 102% (P = .03), and ROM production by 475% (P = .001) and reduced rectal mucosal blood flow by 22% (P = .05). The control protocol did not change any of the variables measured. There were no differences between the responses of the patients with UC and HV.

CONCLUSIONS

Acute psychologic stress induces systemic and mucosal proinflammatory responses, which could contribute to exacerbations of UC in ordinary life.

Heightened responses to stressors in patients with inflammatory bowel disease

OBJECTIVES

Several studies suggest that stressful situations (stressors) worsen the course of inflammatory bowel disease (IBD), but the mechanism is not known. Based on several lines of evidence, we hypothesized that psychosocial stress activates the brain-gut axis (BGA) and mucosal mast cells (MC), and activated MC produce proinflammatory cytokines. To test this hypothesis, we determined whether stressor-induced activation of BGA is exaggerated in IBD patients.

METHODS

Stress was induced in 15 IBD patients who were in remission (inactive IBD) and in seven controls by a widely used stressor, the cold pressor test (CPT), daily for five consecutive days. Induction of stress was confirmed objectively by measurement of stress hormones (serum cortisol and ACTH), and hemodynamic parameters and subjectively by questionnaire. Activation of the BGA by this stressor was assessed by evaluating colonic mucosal MC histology and degranulation, using electron microscopy (EM). The effects of the stressor on the intestinal mucosa were assessed by changes in inflammatory cell histology, epithelial mitochondria (EM), and oxidative tissue injury (assays for protein oxidation).

RESULTS

In both study groups, the stressor resulted in (1) increased levels of stress hormones, (2) the expected changes in hemodynamic parameters, (3) activation and degranulation of MC, (4) mitochondrial damage to epithelial cells, and (5) mucosal protein oxidation. These changes were more marked in IBD patients.

CONCLUSIONS

The heightened response to the stressors and the greater epithelial damage in IBD patients suggests that stress-induced activation of the BGA and of mucosal MC is important in the initiation and/or flare up of IBD.

Roles of histamine and its receptors in allergic and inflammatory bowel diseases

Mast cell has a long history of being recognized as an important mediator-secreting cell in allergic diseases, and has been discovered to be involved in IBD in last two decades. Histamine is a major mediator in allergic diseases, and has multiple effects that are mediated by specific surface receptors on target cells. Four types of histamine receptors have now been recognized pharmacologically and the first three are located in the gut. The ability of histamine receptor antagonists to inhibit mast cell degranulation suggests that they might be developed as a group of mast cell stabilizers. Recently, a series of experiments with dispersed colon mast cells suggested that there should be at least two pathways in man for mast cells to amplify their own activation-degranulation signals in an autocrine or paracrine manner. In a word, histamine is an important mediator in allergic diseases and IBD, its antagonists may be developed as a group of mast cell stabilizers to treat these diseases.

Substance P and other neuropeptides do not induce mediator release in isolated human intestinal mast cells

Neuropeptides such as substance P (SP) and related peptides are supposed to act as mast cell agonists, and thus as mediators of neuroimmune interactions. The data supporting this hypothesis were obtained mostly from rodent experiments. Here, we studied for the first time the effect of SP and other peptides on mediator release in human intestinal mast cells, either unpurified or enriched to 85-99% purity. We found that SP at 0.1-100 micromol L(-1), or other peptides including neurokinin A and B, calcitonin gene-related peptide, vasoactive intestinal peptide and serotonin at 1 micromol L(-1) do not induce release of mediators such as histamine, sulphidoleukotrienes, and tumour necrosis factor alpha. The peptides also failed to cause mediator release in mast cells isolated from inflamed tissue derived from Crohn's disease. Using reverse transcriptase-polymerase chain reaction, flow cytometry and immunohistochemistry, we could show that human intestinal mast cells do not express the tachykinin receptors NK-1, NK-2, or NK-3 under basal conditions. However, upon stimulation by immunoglobulin E (IgE) receptor-crosslinking, which induces an extensive mediator release reaction, a subpopulation of mast cells clearly expressed NK-1, the SP receptor. In conclusion, our data show that SP and other neuropeptides do not act as secretagogues in human intestinal mast cells that have not been pre-activated by IgE receptor-crosslinking.

Activated mast cells in proximity to colonic nerves correlate with abdominal pain in irritable bowel syndrome

BACKGROUND & AIMS

The mechanisms underlying abdominal pain perception in irritable bowel syndrome (IBS) are poorly understood. Intestinal mast cell infiltration may perturb nerve function leading to symptom perception. We assessed colonic mast cell infiltration, mediator release, and spatial interactions with mucosal innervation and their correlation with abdominal pain in IBS patients.

METHODS

IBS patients were diagnosed according to Rome II criteria and abdominal pain quantified according to a validated questionnaire. Colonic mucosal mast cells were identified immunohistochemically and quantified with a computer-assisted counting method. Mast cell tryptase and histamine release were analyzed immunoenzymatically. Intestinal nerve to mast cell distance was assessed with electron microscopy.

RESULTS

Thirty-four out of 44 IBS patients (77%) showed an increased area of mucosa occupied by mast cells as compared with controls (9.2% +/- 2.5% vs. 3.3 +/- 0.8%, respectively; P < 0.001). There was a 150% increase in the number of degranulating mast cells (4.76 +/- 3.18/field vs. 2.42 +/- 2.26/field, respectively; P = 0.026). Mucosal content of tryptase was increased in IBS and mast cells spontaneously released more tryptase (3.22 +/- 3.48 pmol/min/mg vs. 0.87 +/- 0.65 pmol/min/mg, respectively; P = 0.015) and histamine (339.7 +/- 59.0 ng/g vs. 169.3 +/- 130.6 ng/g, respectively; P = 0.015). Mast cells located within 5 microm of nerve fibers were 7.14 +/- 3.87/field vs. 2.27 +/- 1.63/field in IBS vs. controls (P < 0.001). Only mast cells in close proximity to nerves were significantly correlated with severity and frequency of abdominal pain/discomfort (P < 0.001 and P = 0.003, respectively).

CONCLUSIONS

Colonic mast cell infiltration and mediator release in proximity to mucosal innervation may contribute to abdominal pain perception in IBS patients.

Key role of mast cells and their major secretory products in inflammatory bowel disease

Historically, mast cells were known as a key cell type involved in type I hypersensitivity. Until last two decades, this cell type was recognized to be widely involved in a number of non-allergic diseases including inflammatory bowel disease (IBD). Markedly increased numbers of mast cells were observed in the mucosa of the ileum and colon of patients with IBD, which was accompanied by great changes of the content in mast cells such as dramatically increased expression of TNF-α, IL-16 and substance P. The evidence of mast cell degranulation was found in the wall of intestine from patients with IBD with immunohistochemistry technique. The highly elevated histamine and tryptase levels were detected in mucosa of patients with IBD, strongly suggesting that mast cell degranulation is involved in the pathogenesis of IBD. However, little is known of the actions of histamine, tryptase, chymase and carboxypeptidase in IBD. Over the last decade, heparin has been used to treat IBD in clinical practice. The low molecular weight heparin (LMWH) was effective as adjuvant therapy, and the patients showed good clinical and laboratory response with no serious adverse effects. The roles of PGD2, LTC4, PAF and mast cell cytokines in IBD were also discussed. Recently, a series of experiments with dispersed colon mast cells suggested there should be at least two pathways in man for mast cells to amplify their own activation-degranulation signals in an autocrine or paracrine manner. The hypothesis is that mast cell secretogogues induce mast cell degranulation, release histamine, then stimulate the adjacent mast cells or positively feedback to further stimulate its host mast cells through H₁ receptor. Whereas released tryptase acts similarly to histamine, but activates mast cells through its receptor PAR-2. The connections between current anti-IBD therapies or potential therapies for IBD with mast cells were discussed, implicating further that mast cell is a key cell type that is involved in the pathogenesis of IBD. In conclusion, while pathogenesis of IBD remains unclear, the key role of mast cells in this group of diseases demonstrated in the current review implicates strongly that IBD is a mast cell associated disease. Therefore, close attentions should be paid to the role of mast cells in IBD.

Functional and morphologic characterization of eosinophils in the lower intestinal mucosa of patients with food allergy

OBJECTIVE

The aim of this study was to characterize the functional and morphologic features of eosinophils in the intestinal mucosa of patients with food allergy.

METHODS

Eighteen patients with food allergy and 11 controls took part in this study. In every patient, corresponding biopsy samples obtained during colonoscopy were quantitatively assessed by immunohistochemical methods (EPO-I) and subjected to mucosa oxygenation using eosinophilic cationic protein (ECP). Initial basal release, spontaneous and anti-IgE-dependent release, and the total ECP content of mucosal biopsies were studied.

RESULTS

Morphologically, mucosal eosinophils in patients with food allergy have distinct features, occur in larger amounts, and show a distinct distribution pattern (i.e., intraepithelial, lamina propria, and submucosa). Their initial basal release is similar to that of controls, but stimulation of the IgE receptor with anti-IgE results in 40-fold activation (p < 0.001). In food allergy patients, the density of eosinophils, the presence of intraepithelial eosinophils, and the rate of degranulation showed a highly significant correlation to the initial basal release of ECP by mucosal tissue (Kendall tau = 0.619, 0.381, and 0.609, respectively; p < 0.05 for all) but not to their capability to be stimulated with anti-IgE.

CONCLUSIONS

Eosinophils of the lower intestine of patients with food allergy show characteristic features with regard to morphology, distribution, and functional behavior to IgE receptor stimulation. Immunostaining of eosinophil peroxidase (EPO) detects important characteristic features that are missed with conventional hematoxylin-eosin staining.

Urinary excretion of N-methylhistamine as a marker of disease activity in inflammatory bowel disease

OBJECTIVE

Mast cells are thought to participate in the pathogenesis of inflammatory bowel disease (IBD). In this study, urinary excretion of N-methylhistamine (UMH), a stable metabolite of the mast cell mediator histamine, was evaluated as an indicator of disease activity in patients with IBD.

METHODS

Urinary excretion of UMH (microg/mmol creatinine x m2 body surface area) was measured by radioimmunoassay in 55 controls, 56 patients with Crohn's disease, and in 36 patients with ulcerative colitis. Excretion rates were correlated with clinical, serological, and endoscopic disease activity, disease extent, and location.

RESULTS

Urinary excretion of UMH was found to be significantly elevated in IBD. Patients with active Crohn's disease (7.1 +/- 4.2, p = 0.002 vs controls) and active ulcerative colitis (8.1 +/- 4.8, p = 0.02 vs controls) had higher rates of UMH excretion than patients in remission (6.3 +/- 3.8 and 5.2 +/- 2.3, respectively) or controls (4.6 +/- 1.9). In Crohn's disease and ulcerative colitis, a significant correlation of UMH excretion with clinical disease activity was obtained (Crohn's Disease Activity Index r2 = 0.58, Clinical Activity Index r2 = 0.57, p < 0.0001). Serologically, orosomucoid showed the best positive correlation with disease activity (Crohn's Disease Activity Index r2 0.80, Clinical Activity Index r2 = 0.86, p < 0.0001), but UMH excretion was found to reflect disease activity more accurately than C-reactive protein (Crohn's Disease Activity Index r2 = 0.46, Clinical Activity Index r2 = 0.42, p < 0.0001). No association between UMH excretion and disease type or localization could be found in Crohn's disease. However, UMH excretion correlated strongly with endoscopic severity of inflammation in Crohn's disease (Crohn's Disease Endoscopic Index of Severity r2 = 0.70, p < 0.0001) or disease extent in ulcerative colitis.

CONCLUSIONS

Urinary excretion of the histamine metabolite UMH is enhanced in IBD. It appears to represent an integrative parameter to monitor clinical and endoscopic disease activity in IBD, which appears to be influenced most likely by mediators released from histamine-containing cells, such as intestinal mast cell subtypes.

Nerve-mast cell (RBL) interaction: RBL membrane ruffling occurs at the contact site with an activated neurite

Mast cell-neurite interaction serves as a model for neuroimmune interaction. We have shown that neurite-mast cell communication can occur via substance P interacting with neurokinin (NK)-1 receptors on the mucosal mast cell-like cell, the rat basophilic leukemia (RBL) cell. Neurite (murine superior cervical ganglia) and RBL cell [expressing the granule-associated antigen CD63-green fluorescent protein (GFP) conjugate] cocultures were established and stimulated with bradykinin (BK; 10 nM) or scorpion venom (SV; 10 pg/ml), both of which activate only neurites. Cell activation was assessed by confocal imaging of Ca2+ (cells preloaded with fluo 3), and analyses of RBL CD63-GFP+ granule movement were conducted. Neurite activation by BK or SV was followed by RBL Ca2+ mobilization, which was inhibited by an NK-1 receptor antagonist (NK-1 RA). Moreover, membrane ruffling was observed on RBL pseudopodial extensions in contact with the activated neurite, but not on noncontacting pseudopodia. RBL membrane ruffling was inhibited by NK-1 RA, but not NK-2 RA, and was accompanied by a significant increase in granule movement (0.13 +/- 0.04 vs. 0.05 +/- 0.01 microm/s) that was most evident at the point of neurite contact: many of the granules moved toward the plasmalemma. This is the first documentation of such precise (restricted to the membrane's contact site) transfer of information between nerves and mast cells that could allow for very subtle in vivo communication between these two cell types.

Substance P-stimulated interleukin-8 expression in human colonic epithelial cells involves Rho family small GTPases

Interaction of the neuropeptide substance P (SP) and its neurokinin-1 receptor (NK-1R) plays an important role in the pathophysiology of intestinal inflammation. SP is known to stimulate production of interleukin (IL)-6 and IL-8 in the U-373-MG human astrocytoma cell line via activation of p38 MAPK (mitogen-activated protein kinase) and nuclear factor (NF)-kappaB, respectively. However, the signalling mechanisms by which SP-NK-1R interaction induces NF-kappaB activation and IL-8 expression are still not clear. In this study we demonstrate that SP stimulates IL-8 secretion and IL-8 promoter activity in the NCM460 non-transformed human colonic epithelial cell line transfected with NK-1R cDNA. Our results indicate that inhibition of endogenous Rho family proteins (RhoA, Rac1 and Cdc42) by their respective dominant negative mutants significantly decreases SP-induced IL-8 secretion and IL-8 promoter activity. We also demonstrate that SP rapidly activates RhoA, Rac1 and Cdc42 and that co-expression of the dominant negative mutants of RhoA, Rac1 and Cdc42 in NK-1R cDNA-transfected NCM460 cells significantly inhibits SP-induced NF-kappaB-dependent gene expression. These results demonstrate that Rho family small GTPases RhoA, Rac1 and Cdc42 are novel signal transducers for SP-stimulated IL-8 expression.

Inflammatory mediators in gastrointestinal defense and injury

Inflammation of the mucosal layer of the gastrointestinal (GI) tract is not only a feature almost always associated with ulceration of those tissues, but it also plays an important role in both the production and healing of the lesions. The mediators that coordinate inflammatory responses also have the capability to alter the resistance of the mucosa to injury induced by noxious substances, while others render the mucosa more susceptible to injury. In this article, we provide a review of the inflammatory mediators that modulate GI mucosal defense. Among the mediators discussed are nitric oxide, the eicosanoids (prostaglandins, leukotrienes, and thromboxanes), neuropeptides, cytokines, and proteinases. Many of these mediators are considered potential therapeutic targets for the treatment of ulcerative diseases of the digestive tract.

Mast cell distribution and activation in chronic pancreatitis

Chronic pancreatitis (CP) is characterized by mononuclear inflammatory cell infiltration and replacement of the destroyed parenchyma by fibrous tissue. Recently, mast cells have been implicated in chronic inflammatory processes with fibrous tissue deposition. Therefore, the number and distribution of mast cells and their state of activation were evaluated in 12 normal specimens and in 46 specimens of CP with different causes (alcoholic, tropical, and idiopathic). Furthermore, the presence of stem cell factor (SCF), the main mast cell growth factor, and of its receptor, c-kit, was also assessed. In CP tissues, mast cells were localized both in the fibrotic areas and in the residual acinar parenchyma. The total number of mast cells was significantly higher in CP than in the normal pancreas (P < .0001) and correlated positively with the extent of fibrosis and the intensity of inflammation. Immunoglobulin E (IgE)-dependent mast cell activation was higher in CP than in the normal pancreas. No differences in mast cell number or IgE positivity were found among the 3 causes of CP. SCF-and c-kit immunoreactive mast cells were mostly localized in fibrous tissue and around regenerating ducts, which were also positive for c-kit but were negative for SCF. These results suggest that mast cells, activated by an IgE-dependent mechanism and/or by an SCF-c-kit autocrine loop, are a relevant component of the inflammatory infiltrate in CP, independent of the underlying cause. Their localization near degenerating acini and regenerating ducts might indicate that they play a crucial role in tissue destruction and remodeling in CP.

Analysis of single-cell cultures by immunoaffinity capillary electrophoresis with laser-induced fluorescence detection

Neuropeptide regulation of immunological activity is becoming an important issue in both basic and clinical sciences, necessitating the need for analysis to be performed at the single-cell level. A microsampling procedure has been developed for studying secretion of biologically important peptides from neuropeptide-stimulated lymphocytes, based on microdialysis sampling coupled to immunoaffinity capillary electrophoresis (ICE), with laser-induced fluorescence (LIF) detection using a fibre-optic spectrometer and diode laser excitation. The system demonstrated a limit of detection in the high attomole (10(-18) mol/L) range with pure standards and was capable of monitoring secretion from a single cell over time. Using this system it was possible to differentiate the effects of four neuropeptides on both T and B cell release of regulatory cytokines. CD4(+) lymphocytes demonstrated a 7.5-fold increase in cytokine secretion over baseline following stimulation with substance P (SP) and calcitonin gene-related peptide (CGRP). B cells responded to CGRP and vasoactive intestinal peptide (VIP) stimulation (5.5-fold increase), but not to SP. These changes took place 12--20 h post-stimulation and, once the peak secretion had been reached, remained at that level for the duration of the experiment. This system demonstrates the ability to perform high sensitivity measurements on microsamples of biological fluids.

Increased response of blood eosinophils to various chemotactic agents in quiescent Crohn disease

BACKGROUND

The number of eosinophils is increased in the mucosae of the digestive and the respiratory tracts in Crohn disease, even clinically quiescent. The mechanisms underlying this panmucosal eosinophilia are unknown.

METHODS

The response of blood eosinophils to various chemotactic agents was assessed in 15 patients with clinically quiescent Crohn disease. The results were compared with 15 healthy controls. After purification, eosinophils were placed in Boyden microchambers and the chemotactic effect of PAF (10(-7) M), RANTES (50 ng/ml), IL-5 (0-20 ng/ml), IL-8 (0-50 ng/ml), Eotaxin (0-50 ng/ml) was evaluated. The number of eosinophils in induced sputum of these Crohn disease patients and controls was also assessed and the correlation between chemotaxis and eosinophil count in induced sputum was studied.

RESULTS

PAF and RANTES induced a chemotactic effect both in Crohn disease patients and controls. The chemotactic index was significantly higher in Crohn than controls for PAF (2.09+/-0.24 versus 1.37+/-0.14; P < 0.05) but not RANTES. With IL-5, IL-8 and Eotaxin, there was no detectable chemotactic effect in controls while in Crohn, we observed a significant dose-dependent chemotactic effect. Furthermore, with Eotaxin 50 ng/ml, the chemotactic index was significantly higher in Crohn disease patients than controls (2.42+/-0.18 versus 1.56+/-0.28; P < 0.05). A significant increase in sputum eosinophil count and a significant decrease in sputum macrophage count in Crohn disease were observed. However, there was no correlation between eosinophil chemotaxis and sputum eosinophil count in individual patients.

CONCLUSION

There is an increased response of blood eosinophils to various chemotactic agents, mainly PAF and Eotaxin, in clinically quiescent Crohn disease. This may participate in the mucosal infiltration by eosinophils in this disease.