Mast cells in ulcerative colitis. Quantitative and ultrastructural studies

Adverse Food Reactions in Inflammatory Bowel Disease: State of the Art and Future Perspectives

Limited knowledge is available about the relationship between food allergies or intolerances and inflammatory bowel disease (IBD). Clinicians frequently encounter patients who report food allergies or intolerances, and gastroenterologists struggle distinguishing between patients with organic disorders and those with functional disorders, which the patients themselves may associate with specific dietary components. This task becomes even more arduous when managing patients with significant underlying organic conditions, like IBD. The aim of this review is to summarize and emphasize any actual associations between food allergies and intolerances and inflammatory diseases, such as ulcerative colitis and Crohn's disease. Through a narrative disceptation of the current literature, we highlight the increased prevalence of various food intolerances, including lactose, fructose, histamine, nickel, and non-celiac gluten sensitivity, in individuals with IBD. Additionally, we explore the association between increased epithelial barrier permeability in IBD and the development of food sensitization. By doing so, we aim to enhance clinicians' awareness of the nutritional management of patients with IBD when facing complaints or evidence of food allergies or intolerances.

Evidence-based pathogenesis and treatment of ulcerative colitis: A causal role for colonic epithelial hydrogen peroxide

In this comprehensive evidence-based analysis of ulcerative colitis (UC), a causal role is identified for colonic epithelial hydrogen peroxide (H₂O₂) in both the pathogenesis and relapse of this debilitating inflammatory bowel disease. Studies have shown that H₂O₂ production is significantly increased in the non-inflamed colonic epithelium of individuals with UC. H₂O₂ is a powerful neutrophilic chemotactic agent that can diffuse through colonic epithelial cell membranes creating an interstitial chemotactic molecular “trail” that attracts adjacent intravascular neutrophils into the colonic epithelium leading to mucosal inflammation and UC. A novel therapy aimed at removing the inappropriate H₂O₂ mediated chemotactic signal has been highly effective in achieving complete histologic resolution of colitis in patients experiencing refractory disease with at least one (biopsy-proven) histologic remission lasting 14 years to date. The evidence implies that therapeutic intervention to prevent the re-establishment of a pathologic H₂O₂ mediated chemotactic signaling gradient will indefinitely preclude neutrophilic migration into the colonic epithelium constituting a functional cure for this disease. Cumulative data indicate that individuals with UC have normal immune systems and current treatment guidelines calling for the suppression of the immune response based on the belief that UC is caused by an underlying immune dysfunction are not supported by the evidence and may cause serious adverse effects. It is the aim of this paper to present experimental and clinical evidence that identifies H₂O₂ produced by the colonic epithelium as the causal agent in the pathogenesis of UC. A detailed explanation of a novel therapeutic intervention to normalize colonic H₂O₂, its rationale, components, and formulation is also provided.

Quantitative Analysis of Intramucosal Mast Cells in Irritable Bowel Syndrome: A Comparison With Inflammatory Bowel Disease in Remission

GOAL

We aimed to study the density of intramucosal mast cells in histologically normal colonic mucosa biopsied from patients with a clinical diagnosis of irritable bowel syndrome (IBS).

BACKGROUND

Mast cell activation has been thought to implicate in the pathogenesis of inflammatory bowel disease (IBD). Whether it serves a role in the pathogenesis of IBS remains controversial.

STUDY

A total of 127 colonoscopic mucosal biopsies were immunohistochemically stained, including 51 IBS, 66 IBD, and 10 normal control samples. Intact mast cells were quantified in 3 high power fields (HPF) in areas showing the highest density.

RESULTS

CD117 was sensitive in detecting mast cells in colonic mucosa. The mast cell counts in all biopsies ranged from 2 to 60 per HPF (mean=17.5±7.2). The density of intramucosal mast cells were similar among IBS, IBD and normal control groups (P=0.6733). IBD in remission versus IBS (17.1±8.0 vs. 18.1±7.0; P=0.4804), Crohn disease versus ulcerative colitis (17.1±10.4 vs. 17.2±5.2; P=0.9463), IBS with diarrhea versus without diarrhea (19.5±6.3 vs. 16.8±6.9; P=0.1404). Forty biopsies (31.5%) showing ≥20 mast cells per HPF appeared to equally distribute among various disease groups (P=0.7283).

CONCLUSIONS

There is no significant difference in the number of intramucosal mast cells between IBS and IBD that show normal colonic biopsies. In IBS patients, the number of intramucosal mast cell does not correlate with symptoms. The mast cell count (≥20/HPF) is not a reliable criterion for the diagnosis of IBS or for the distinction between patients with IBS and those with IBD in remission.

Urinary and faecal N-methylhistamine concentrations do not serve as markers for mast cell activation or clinical disease activity in dogs with chronic enteropathies

Background

This study sought to correlate faecal and urinary N-methylhistamine (NMH) concentrations with resting versus degranulated duodenal mast cell numbers in dogs with chronic enteropathies (CE), and investigate correlations between intestinal mast cell activation and clinical severity of disease as assessed by canine chronic enteropathy clinical activity index (CCECAI), and between urinary and faecal NMH concentrations, mast cell numbers, and histopathological scores. Twenty-eight dogs with CE were included. Duodenal biopsies were stained with haematoxylin and eosin (H&E), toluidine blue, and by immunohistochemical labelling for tryptase. Duodenal biopsies were assigned a histopathological severity score, and duodenal mast cell numbers were counted in five high-power fields after metachromatic and immunohistochemical staining. Faecal and urinary NMH concentrations were measured by gas chromatography–mass spectrometry.

Results

There was no correlation between the CCECAI and faecal or urinary NMH concentrations, mast cell numbers, or histopathological score – or between faecal or urinary NMH concentration and mast cell numbers. Post hoc analysis revealed a statistically significant difference in toluidine blue positive mast cells between two treatment groups (exclusion diet with/without metronidazole versus immunosuppression (IS)), with higher numbers among dogs not requiring IS.

Conclusion

Faecal and urinary NMH concentrations and duodenal mast cell numbers were not useful indicators of severity of disease as assessed by the CCECAI or histological evaluation. The number of duodenal mast cells was higher in dogs that did not need IS, i.e. in dogs responding to an exclusion diet (with/without metronidazole), than in dogs requiring IS. Further studies comparing the role of mast cells in dogs with different forms of CE are needed.

Non-pulmonary allergic diseases and inflammatory bowel disease: A qualitative review

While the etiological underpinnings of inflammatory bowel disease (IBD) are highly complex, it has been noted that both clinical and pathophysiological similarities exist between IBD and both asthma and non-pulmonary allergic phenomena. In this review, several key points on common biomarkers, pathophysiology, clinical manifestations and nutritional and probiotic interventions for both IBD and non-pulmonary allergic diseases are discussed. Histamine and mast cell activity show common behaviors in both IBD and in certain allergic disorders. IgE also represents a key immunoglobulin involved in both IBD and in certain allergic pathologies, though these links require further study. Probiotics remain a critically important intervention for both IBD subtypes as well as multiple allergic phenomena. Linked clinical phenomena, especially sinonasal disease and IBD, are discussed. In addition, nutritional interventions remain an underutilized and promising therapy for modification of both allergic disorders and IBD. Recommending new mothers breastfeed their infants, and increasing the duration of breastfeeding may also help prevent both IBD and allergic diseases, but requires more investigation. While much remains to be discovered, it is clear that non-pulmonary allergic phenomena are connected to IBD in a myriad number of ways and that the discovery of common immunological pathways may usher in an era of vastly improved treatments for patients.

Mast cell proteases as protective and inflammatory mediators

Proteases are the most abundant class of proteins produced by mast cells. Many of these are stored in membrane-enclosed intracellular granules until liberated by degranulating stimuli, which include cross-linking of high affinity IgE receptor F(c)εRI by IgE bound to multivalent allergen. Understanding and separating the functions of the proteases is important because expression differs among mast cells in different tissue locations. Differences between laboratory animals and humans in protease expression also influence the degree of confidence with which results obtained in animal models of mast cell function can be extrapolated to humans. The inflammatory potential of mast cell proteases was the first aspect of their biology to be explored and has received the most attention, in part because some of them, notably tryptases and chymases, are biomarkers of local and systemic mast cell degranulation and anaphylaxis. Although some of the proteases indeed augment allergic inflammation and are potential targets for inhibition to treat asthma and related allergic disorders, they are protective and even anti-inflammatory in some settings. For example, mast cell tryptases may protect from serious bacterial lung infections and may limit the "rubor" component of inflammation caused by vasodilating neuropeptides in the skin. Chymases help to maintain intestinal barrier function and to expel parasitic worms and may support blood pressure during anaphylaxis by generating angiotensin II. In other life-or-death examples, carboxypeptidase A3 and other mast cell peptidases limit systemic toxicity of endogenous peptideslike endothelin and neurotensin during septic peritonitis and inactivate venom-associated peptides. On the other hand, mast cell peptidase-mediated destruction of protective cytokines, like IL-6, can enhance mortality from sepsis. Peptidases released from mast cells also influence nonmast cell proteases, such as by activating matrix metalloproteinase cascades, which are important in responses to infection and resolution of tissue injury. Overall, mast cell proteases have a variety of roles, inflammatory and anti-inflammatory, protective and deleterious, in keeping with the increasingly well-appreciated contributions of mast cells in allergy, tissue homeostasis and innate immunity.

Immunoreactivity for CD25 in gastrointestinal mucosal mast cells is specific for systemic mastocytosis

Systemic mastocytosis (SM) is characterized by the accumulation of neoplastic mast cells in bone marrow and other organs. Gastrointestinal (GI) symptoms are common in both SM and cutaneous mastocytosis [urticaria pigmentosa (UP)], and are usually caused by the release of histamine and other inflammatory mediators. Occasionally, neoplastic mast cells may also directly infiltrate the GI tract. Previous studies have suggested that enumeration of the mast cells in GI biopsies may help establish the diagnosis of SM. However, mast cells have been reported to be increased in various inflammatory diseases, and mast cell density has not been systematically evaluated in other GI disorders. Recently, expression of CD25 by mast cells in bone marrow has been shown to be specific for SM. The purpose of this study was (1) to quantitate and compare mast cells in mucosal biopsies from patients with SM involving the GI tract, UP with GI symptoms, and a control group of diverse inflammatory disorders, and (2) to determine whether immunostaining for CD25 can be used to distinguish neoplastic from reactive mast cells in GI biopsies. Seventeen GI biopsies from 6 patients with SM; 17 GI biopsies from 5 patients with UP; and 157 control cases including 10 each normal stomach, duodenum, terminal ileum, and colon, Helicobacter pylori gastritis, bile reflux gastropathy, peptic duodenitis, celiac disease, Crohn disease, ulcerative colitis, lymphocytic colitis, and collagenous colitis, 20 biopsies from 16 patients with irritable bowel syndrome, 8 biopsies from 5 patients with parasitic infections, and 9 biopsies from 7 patients with eosinophilic gastroenteritis were immunostained for mast cell tryptase, c-kit (CD117), and CD25. Mucosal mast cells were quantitated, and the presence or absence of CD25 expression on mast cells was determined. In SM patients, mast cells in the small intestine and colon numbered >100/high-power field (HPF) in nearly all cases (mean 196/HPF; range 74 to 339). This was significantly higher than in GI biopsies from UP patients (mean 17/HPF; range 8 to 32, P<0.0001) and all inflammatory diseases (P<0.01). Mast cell density in other disorders ranged from a mean of 12/HPF in H. pylori gastritis to 47/HPF in parasitic infections. Interestingly, all SM biopsies (and none of the other cases) contained aggregates or confluent sheets of mast cells. In addition, mast cells in all SM cases were positive for CD25, whereas GI mucosal mast cells in UP and all other control cases were negative. In conclusion, quantitation of mast cells can be helpful to diagnose SM in GI mucosal biopsies, although mast cells are also markedly increased in parasitic infections. Aggregates or sheets of mast cells are only seen in SM. Immunoreactivity for CD25 in GI mucosal mast cells is specific for SM and can be used to confirm the diagnosis.

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.

Synovial mast cells: role in acute and chronic arthritis

Mast cells reside in the normal synovium and increase strikingly in number in rheumatoid arthritis and other joint diseases. Given the broad spectrum of activity of this lineage, it has for decades been considered probable that mast cells are involved in the pathophysiology of synovitis. Recent work in murine arthritis has substantiated this suspicion, showing that mast cells can contribute importantly to the initiation of inflammatory arthritis. However, the role of the greatly expanded population of synovial mast cells in established arthritis remains unknown. Here we review the current understanding of mast cell function in acute arthritis and consider the potentially important influence of this cell on key processes within the chronically inflamed synovium, including leukocyte recruitment and activation, fibroblast proliferation, angiogenesis, matrix remodeling, and injury to collagen and bone. We also consider recent evidence supporting an immunomodulatory or anti-inflammatory role for mast cells as well as pharmacologic approaches to the mast cell as a therapeutic target in inflammatory arthritis.

The histamine H4 receptor in autoimmune disease

Histamine exerts its actions through four known receptors. The recently cloned histamine receptor, H4R, has been shown to have a role in chemotaxis and mediator release in various types of immune cells including mast cells, eosinophils, dendritic cells and T cells. H4R antagonists have been shown to have anti-inflammatory properties and efficacy in a number of disease models, such as those for asthma and colitis in vivo. Recently, H4R antagonists have been developed with high receptor affinity and specificity, which make them good tools for further characterisation of the receptor in animal models and, eventually, in humans. Histamine and the cells that produce it, such as mast cells and basophils, have long been thought to be involved in allergic conditions but there has recently been recognition that they may also play a role in various autoimmune diseases. Given this and the fact that the H4R has function in mast cells, dendritic cells and T cells, antagonists for the receptor may be useful in treating autoimmune diseases in addition to allergy.

The role of mast cells in common gastrointestinal diseases

The gastrointestinal tract is a rich source of mast cells with an enormous surface area that permits a high degree of interaction between the mast cell and the intestinal contents. The active metabolic products of the mast cell influence gastrointestinal secretion, absorption, and motility through paracrine effects of local mast cell activation and also cause systemic effects through the release of cellular products into the bloodstream. Recent advances in our knowledge of the immune system and the recognition that the gastrointestinal immune function might be partially mediated through gastrointestinal mucosal mast cells has opened mast cell research to the field of gastroenterology. Local gastrointestinal proliferation of mast cells in response to recognized or obscure stimuli can alter gastrointestinal function and induce systemic symptoms. Symptoms can arise from the increased number of mast cells, overproduction of specific mast cell mediators, and hyperactivity of the enteric nervous system that induces mast cell activation. The diseases mentioned in this review represent a small proportion of areas where mast cell function might play an important role in the response to disease and generation of symptoms.

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.

Low mast cell density in the human duodenal mucosa from chronic inflammatory duodenal bowel disorders is associated with defective villous architecture

BACKGROUND

Mast cells (MC) have recently been implicated in the processes of tissue homeostasis, remodeling and repair.

DESIGN

In this study, the total and tryptase-reactive mast cell populations were quantified in the duodenal mucosa of 27 subjects suffering from chronic inflammatory bowel disorders. Mast cell density was both related to the general villous architecture (normal or defective) and to the microvascular density in the duodenal mucosa.

RESULTS

Total mast cell and tryptase-positive mast cell subpopulation densities were found to be significantly reduced in the samples with defective villous architecture in comparison with those exhibiting a normal villous profile. In these last samples, a relevant proportion of mucosal mast cells exhibited ultrastructural features of secretory activity, in particular piecemeal degranulation. Finally, no correlation was established between microvascular density and tryptase activity, as it has been previously demonstrated in other pathological conditions.

CONCLUSIONS

Overall, these findings indicate a significant correlation between mast cell density and the duodenal mucosal architecture.

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.

Differentiation between ulcerative colitis and Crohn's disease by a quantitative immunohistochemical evaluation of T lymphocytes, neutrophils, histiocytes and mast cells

Mucosal biopsy criteria has limited validity in terms of discrimination between ulcerative colitis (UC) and Crohn's disease (CD). The aim of this study was to set up quantitative immunohistochemical criteria, with a special focus on inflammatory cell distribution within individual specimens and throughout the large bowel. Quantitative evaluation was performed for the density of CD8+, CD45RO+, neutrophil elastase+, CD68+ and mast cell tryptase+ cells in affected and unaffected mucosa taken from 41 patients with UC and 61 patients with CD. Each slide was examined at the highest and lowest density fields, which were further divided into the upper and deeper half of mucosa. Multiple logistic regression analysis using 51 features as independent variables constructed a predictive equation finding the probability of UC (PUC), and the diagnostic categories were subsequently defined based on a receiver-operating characteristic curve. The analysis disclosed five significant features suggesting UC; these implied intense infiltration of CD8+ and mast cell tryptase+ cells, diffuse infiltration of neutrophil elastase+ and CD68+ cells, and continuous infiltration of CD45RO+ cells. The criteria consisted of three diagnostic categories, 'suggestive of UC (PUC > or = 0.7)', 'indeterminate (0.3 < PUC < 0.7)', and 'suggestive of CD (PUC < or = 0.3)'; the criteria had values for sensitivity and specificity exceeding 95%. The immunohistochemical criteria distinguishing UC from CD may help to confirm the diagnosis in patients with ambiguous endoscopic and histological diagnosis.

Mast cell and neuroendocrine cytoplasmic autoantigen(s) detected by monoclonal pANCA antibodies

pANCA is a marker antibody expressed in most patients with ulcerative colitis, and its cognate antigen is potentially an immunologic target in this disease. This study evaluates whether pANCA detects an autoantigen that is expressed in the colonic mucosa. Immunohistochemistry of colon specimens with human pANCA monoclonal antibodies (Fab 5-2 and 5-3) revealed a minor population of immunoreactive mucosal cells bearing a cytoplasmic vesicle antigen. By distribution, morphology, and tryptase expression, these were identified as mast cells. Immunofluorescent analysis revealed similar immunoreactivity of mouse mast cell lines and human KU812. Western analysis of mouse mast cell lines revealed immunoreactive proteins, and these were distinct from previously proposed pANCA antigens (histone H1, HMG 1 and 2, and neutrophil vesicle antigens). Cognate antigen for Fab 5-2 and 5-3 was also expressed in other tissue mast cells, cerebellar neurons, and pancreatic islet cells. These findings identify a novel cytoplasmic autoantigen(s) associated with UC by its presence in colonic mucosa and recognition by a disease-associated marker antibody.

Necrotizing enterocolitis and C-KIT

BACKGROUND/PURPOSE

In the gut, C-KIT is important for immune system homeostasis, and C-KIT+ cells are known to increase during inflammation. Recently the authors identified that spontaneous intestinal mucosal erosion develops in C-KIT-depleted W/Wv mice after day 14 of life at a high frequency, whereas genotypically normal litter mates do not. The authors hypothesized that a lack of C-KIT may be implicated in the development of necrotizing enterocolitis (NEC).

METHODS

Bowel specimens were taken during surgery or postmortem from nine cases of NEC (mean gestational age, 32.0 weeks), six age-matched cases of enteritis, and 10 age-matched controls. Specimens were formalin fixed, paraffin embedded, and labeled with antibody to C-KIT. The number of C-KIT+ cells from five random fields per specimen were compared under light microscopy (200x). Results were expressed as the mean +/- SD and compared using the analysis of variance (ANOVA) test.

RESULTS

In enteritis, the number of C-KIT+ cells in the lamina propria and submucosa was significantly higher than in controls (P<.01) indicative of their involvement in inflammation. However, in NEC, the number of C-KIT+ cells in the lamina propria and submucosa was significantly lower than in controls (P<.05) despite histological evidence of inflammation.

CONCLUSION

A lack of C-KIT+ cells may exert a causal influence on the development of NEC.

Ultrastructural effects of intravascularly injected polyethylene glycol-hemoglobin in intestinal mucosa

Polyethylene glycol (PEG)-conjugated Hb (PEG-Hb) is being considered as a blood substitute. Previously, we showed that PEG-Hb extravasates rapidly from the intestinal mucosa and causes transient epithelial sloughing, resulting in temporary unimpeded passage of material between the intestinal lumen and the microcirculation. The present study quantifies the time course of factors related to this disturbance. Anesthetized Sprague-Dawley rats (350-450 g) were injected with a bolus of PEG-Hb (10 mg/ml) in saline. Control animals received saline, alone or with Dextran 70 (5 mg/ml). After 2, 8, 15, 60, or 90 min, the small intestine was perfusion fixed for microscopy (4 animals for each time point). Epithelial cell detachment and mucosal mast cell degranulation peaked at 2 and 8-15 min, respectively, but by 90 min were back to normal. Goblet cell secretion increased with time up to 8-15 min, after which it leveled off. Mean interstitial width was significantly greater 8 min after injection than for controls and continued to increase with time. In capillaries, endothelial fenestral diaphragms were replaced by thick, amorphous structures. Mesenteric mast cell degranulation was significantly greater 60-90 min after injection compared with controls. We propose that these results are consistent with intravascular injection of PEG-Hb invoking a transient inflammatory response in the intestine.

A quantitative immunohistochemical evaluation of inflammatory cells at the affected and unaffected sites of inflammatory bowel disease

Levels of T lymphocytes, histiocytes and mast cells have been reported to be increased in the affected mucosa of Crohn's disease (CD) and ulcerative colitis (UC), but the colorectal distribution of these cells is not fully understood. We hypothesized that differences in cell densities between CD and UC would be characteristic, not only in the affected, but also in the unaffected mucosa. The aims of the present study were to clarify whether there were any differences in cell densities in CD, UC and infectious colitis (IC) in the affected mucosa and between CD and UC in the unaffected mucosa. Using mouse monoclonal antibodies recognizing memory T cells (OPD4), cytotoxic/suppressor T cells (C8/144B), histiocytes (PG-M1) and mast cells (AA1), we evaluated mucosal cell densities in biopsy specimens from both endoscopically affected and unaffected sites of CD (n = 12) and UC (n = 15) and from affected sites of IC (n = 10). Ten normal controls were also examined. At affected sites, all cells were significantly more abundant in UC than in the other conditions, except that the density of PG-M1+ in CD was similar to that seen in UC. Although the densities of OPD4+ and C8/144B+ cells at unaffected sites were slightly higher in both CD and UC and in UC, respectively, there was no significant difference in cell densities between CD and UC. The ratio of OPD4+ cell density at affected sites to that at unaffected sites was appreciably higher in UC than in CD. The results suggest that a common feature of UC and CD is an increase in PG-M1+ cells at the affected mucosa but that the other inflammatory cells studied are more abundant, particularly in UC, and that the difference between UC and CD is conspicuous when comparing the OPD4+ cell density of the affected mucosa with that of the unaffected mucosa.

Evaluation of the role of mast cells in the progression of acetic acid-induced colitis in mice

BACKGROUND

Mast cells are widely distributed in the gastrointestinal mucosa. However, their role in the pathogenesis of inflammatory bowel disease remains unsettled. The aim of the present study is to clarify the relative importance of mast cells in the progression of acetic acid-induced colitis in mice.

METHODS

Mast cell-deficient W/Wv and their normal littermate +/+ mice were given intrarectal administration of 5% acetic acid. The severity of colonic damage, the number of mast cells, and myeloperoxidase (MPO) activities in the colonic tissues were examined.

RESULTS

The severity of colonic damage was comparable between W/Wv and +/+ mice. In both groups of animals kinetic changes of the severity of the mucosal damage agreed well with that of MPO activities in the colonic mucosa. Pretreatment with a mast cell stabilizer, ketotifen, did not affect the severity of colitis in +/+ mice.

CONCLUSIONS

These results discount, but do not disprove, the role of mast cells in the progression of acetic acid-induced colitis in mice.

Role of histamine in a rat model of colitis

We examined the possible involvement of mast cells in a rat model of colitis, by monitoring levels of histamine at various times after inducing inflammation with intrarectal trinitrobenzene sulfonic acid in 50% ethanol. The ability of a histamine H1 antagonist, diphenhydramine, to modify colitis was also assessed. As expected, trinitrobenzene sulfonic acid in 50% ethanol induced a sustained colitis. Myeloperoxidase levels in macroscopically damaged tissue peaked at one week, and declined thereafter. In contrast, tissue histamine levels were normal at one week, then increased in damaged tissue to approximately four times normal levels at four weeks. Indices of inflammation were markedly suppressed at one week by diphenhydramine, while tissue histamine levels were unaffected. Chronic colitis in rats is thus apparently accompanied by a local mast cell hyperplasia or influx. Moreover, antagonism of a major mast cell mediator, histamine, significantly reduces the severity of inflammation in this model.

Evidence for mast cell, leukotriene and nitric oxide involvement in the regulation of the adrenoceptor number of inflamed small intestine in guinea pigs

Changes in the populations of neurotransmitter receptors involved in the control of intestinal smooth muscle function have been associated with the altered motility of the inflamed gut. Thus, trinitrobenzenesulphonic acid (TNBS)-induced gut inflammation is accompanied by an increase in alpha- and a decrease in beta-adrenoceptor numbers in guinea pig small intestine. In the present study, we investigated the effects of anti-inflammatory compounds (cyclooxygenase inhibitor indomethacin, lipooxygenase inhibitor MK-886, nitric oxide synthase inhibitor NG-nitro-L-arginine methylester (L-NAME), mast cell stabilizer doxantrazole) on TNBS-induced adrenoceptor changes. Smooth muscle adrenoceptor populations, labelled by subtype-specific radioligands 6 days after TNBS, were significantly different from those of sham-treated controls: alpha 1- and alpha 2-adrenoceptor numbers increased by more than 50%, while beta-adrenoceptor numbers decreased by more than 50%. These changes, associated with severe inflammation as assessed histologically and by myeloperoxidase assay, were prevented by doxantrazole or L-NAME, and only partly by MK-886. In contrast, indomethacin did not prevent these changes. It appears then that: (a) mast cell mediators, nitric oxide and leukotrienes are likely to contribute to TNBS-induced changes in adrenoceptor populations in the guinea pig inflamed intestine; (b) there is no evidence for prostanoid involvement in this process. It was suggested that changes in smooth muscle adrenoceptor populations may be an important mechanism by which gut inflammation alters intestinal motility.

Immune regulation of human colonic electrolyte transport in vitro

The role of lamina propria cells in regulating human colonic ion transport was investigated in vitro. Normal human colonic mucosae were mounted in Ussing chambers, and short circuit current changes (delta SCC) were monitored in response to immune cell activation. Anti-human immunoglobulin E (anti-IgE) and formyl-Methionyl-Leucyl-Phenylalanine (fMLP) were used to stimulate mast cells and phagocytes respectively. Anti-IgE (100 micrograms/ml) and fMLP (100 microM) evoked rapid onset, inward delta SCC (mean (SEM) max delta SCC 19.3 (2.8) and 29.4 (4.7) microA/0.63 cm2 respectively). A pharmacological approach was used to identify the charge carrying ion species and to characterise mediators involved in the SCC response. Responses to each secretagogue were significantly attenuated by bumetanide, indicating that the delta SCC was at least partly due to electrogenic chloride secretion. Piroxicam reduced the delta SCC to mast cell and phagocyte activation by 91.1 (3.4)% and 48.2 (25.2)% respectively, implicating eicosanoids as mediators of the responses. Mepyramine (100 microM) reduced the SCC responses to anti-IgE by 79.6 (12.0)% but did not significantly alter delta SCC responses to fMLP. Desensitisation to repeated anti-IgE or fMLP stimulation, and cross desensitisation between each of the stimuli, were features of immune cell activation. In summary, we have shown that activation of immune cells can stimulate electrogenic chloride secretion. Such events in vivo will result in gradient driven secretory diarrhoea, which may occur as a protective response to enteric-dwelling parasites, or as a feature of local bowel inflammation.

Gastrointestinal food hypersensitivity: basic mechanisms of pathophysiology

Gastrointestinal symptoms occur in a large number of patients with food allergies. Immediate hypersensitivity mechanisms may give rise to the nausea, vomiting, abdominal pain, and diarrhea experienced by these patients. However, there are limited human data about the pathophysiological basis for these symptoms. Most of the available information comes from a variety of animal models. This article reviews the literature using models of intestinal food hypersensitivity, as well as human studies, that have contributed to our understanding of the pathophysiological mechanisms in gastrointestinal food hypersensitivity.

Colonic mucosal mast cell distribution at line of demarcation of active ulcerative colitis

We examined the distribution of colonic mucosal mast cells in 25 patients with active ulcerative colitis, with a clear line of demarcation separating active inflammation from normal mucosa. Biopsies, at least one adjacent to the line of demarcation, one in inflamed mucosa, and one above were obtained during colonoscopy. Eight patients had elevated mast cells throughout the colon, and 12 had increased numbers at the line of demarcation of disease. Mean numbers of mast cells from these patients were 6.3 (+/- 2.1 SD) in active inflammation, 19.5 (+/- 7.1 SD) at the line of demarcation, and 15.8 (+/- 8.4 SD) in normal mucosa. Histologic inflammation decreased as mast cells increased. The accumulation of mast cells at the visible line of demarcation between normal and abnormal mucosa suggests mast cells play a critical role in either accelerating the process of inflammation or in suppressing continued extension of the disease.

The Role of the Mast Cell in Clinical Gastrointestinal Disease with Special Reference to Systemic Mastocytosis

The gastrointestinal tract is a rich source of mast cells with an enormous surface area that permits a high degree of interaction between the mast cell and intestinal luminal contents. The active metabolic products of the mast cell influence gastrointestinal secretion, absorption, and motility through paracrine effects of local mast cell degranulation and also cause systemic effects through the release of cellular products into the blood stream. Systemic mastocytosis influences physiologic function through the systemic effects of mast cell products released from focal (e.g., bone marrow) or wide spread increases in mast cell number. Local gastrointestinal proliferation of mast cells in response to recognized (e.g., gluten in celiac sprue) or obscure stimuli can alter gastrointestinal function and induce systemic symptoms. Celiac sprue, inflammatory bowel disease, and non-ulcer dyspepsia are three examples of gastrointestinal diseases in which mast cells can be implicated in the pathophysiology of the symptoms.