Expression of catenins and E-cadherin during epithelial restitution in inflammatory bowel disease

Catenins are cytoplasmic proteins associated with E-cadherin, the prime mediator of cell–cell adhesion. Perturbation in any of these molecules results in altered intercellular adhesion, cell differentiation, and increased migration. In this study, the expression and cellular localization of catenins and E-cadherin in inflammatory bowel disease were examined. The expression of E-cadherin; α-, β-, and γ-catenin; and p120 was evaluated immunohistochemically in 31 paraffin-embedded colonic specimens from 21 patients with ulcerative colitis and Crohn's disease. Loss of normal membranous E-cadherin and α-catenin staining was detected at the mucosal edges around epithelial ulcerations in all cases of active ulcerative colitis and in 50 per cent of cases with active Crohn's disease. Reduced expression of p120 protein was also found at the margins of ulcerated mucosa in all cases of active ulcerative colitis and in 75 per cent of those with active Crohn's disease. There was a statistically significant correlation between the expression of E-cadherin, α-catenin and p120 and disease activity. There were no changes in β- and γ-catenin expression in either ulcerative colitis on Crohn's disease. These findings indicate that altered expression of E-cadherin, α-catenin, and p120 occurs during mucosal ulceration in inflammatory bowel disease. These changes may be involved in promoting cell migration during epithelial restitution of the gastrointestinal mucosa. © 1998 John Wiley & Sons, Ltd.     

Human neutrophil defensins induce lung epithelial cell proliferation in vitro

Repair of injured airway epithelium is often accompanied by an influx of leukocytes, and these cells have been suggested to contribute to the repair process. The aim of the present study was to investigate the effect of neutrophil defensins--antimicrobial peptides present in large amounts in the neutrophil--on proliferation of cultured lung epithelial cells. Neutrophil defensins at 4-10 microg/ml enhanced proliferation of the A549 lung epithelial cell line as assessed using cell counting, BrdU incorporation, and the tetrazolium salt MTT assay. Higher, cytotoxic concentrations of defensins decreased cell proliferation. Whereas defensin-induced cell proliferation was not inhibited by the EGF receptor tyrosine kinase inhibitor AG1478, it was completely inhibited by the mitogen-activated protein (MAP) kinase kinase (MEK) inhibitor U0126, suggesting that defensins mediate cell proliferation via an EGF receptor-independent, MAP kinase signaling pathway. Although the cytotoxic effect of defensins was inhibited by alpha1-proteinase inhibitor, the defensin-induced cell proliferation was not affected. These data suggest that neutrophil defensins may possibly be involved in epithelial repair in the airways by inducing lung epithelial cell proliferation.     

Transforming growth factor-alpha and epidermal growth factor receptor in colonic mucosa in active and inactive inflammatory bowel disease

Transforming growth factor-alpha (TGF-alpha) is overexpressed in colonic carcinomas and promotes mucosal wound healing. It may be implicated in chronic inflammatory bowel disease (IBD). We analyzed the expression of TGF-alpha and its receptor, epidermal growth factor receptor (EGF-r), in the colonic mucosa of patients with Crohn's disease (CD) or ulcerative colitis (UC), in active or inactive stages, as compared with controls. Proteins and mRNA were detected in biopsies from the right and left colon and in surgical colonic specimens. Immunoblot analysis revealed TGF-alpha protein as a 29 kDa band. This band was normally expressed in uninvolved colonic mucosa of patients with CD or UC whether in active or inactive stages, but decreased or absent in involved mucosa of active IBD, even when TGF-alpha mRNA and EGF-r protein were detected. In the unaffected mucosa of CD, the intensity of TGF-alpha immunoreactivity was similar to that of controls in the right colon but stronger (P = 0.05) in the left colon. There was no TGF-alpha overexpression in dysplastic regions. In conclusion, in active IBD disease, the decreased TGF-alpha protein amount seems not only related to epithelial cell loss but reflects a down-regulation at least at the protein level. We speculate that TGF-alpha does not play a role within the active stage but may be implicated later in the repair process.     

Changes in neuropeptide-containing nerves in human colonic mucosa with inflammatory bowel disease

The distribution abnormality of vasoactive intestinal polypeptide-containing nerves (VIP-nerves) and substance P-containing nerves (SP-nerves) was immunohistochemically investigated in the colonic mucosa with inflammatory bowel disease (IBD) in relation to colonic glands and blood vessels In the lamina propria. In active ulcerative colitis (UC), VIP- and SP-nerves decreased in severe inflammatory lesions. VIP-nerves were almost absent particularly around crypt abscesses. Even In resolving and quiescent UC, VIP-nerves still decreased, depending on the decrease of glands and blood vessels. On the other hand, both nerves Increased in some hypervascular lesions. In the uninvolved mucosa of UC, they did not change their distribution. In Crohn's disease, the distribution abnormality of both nerves resembled that of UC. These results suggest that the changes in VIP-and SP-nerve distributions in the mucosa with IBD are subsequent to mucosal inflammation and damage. However, these peptides are known to be immunoregulators, and their distribution abnormalities may induce the disorder of immunoregulation in the IBD mucosa and cause the mucosal damage and/or chronicity.     

Mucosal mast cells in irritable bowel syndrome and inflammatory bowel disease

Even though exciting progresses have been until now, further studies are necessary to clearly understand the significance of MMC. Mast cells are thought to participate in the pathogenesis of inflammatory bowel disease and irritable bowel syndrome. However, their role in the pathogenesis remains unsettled. The specific aims of this study were to (1) examine mucosal mast cell counts in the cecum in patient with IBS, and IBD (2) compare MMC between the disease groups. We showed increased MMC count in IBS.     

Expression of 5-lipoxygenase mRNA is unchanged in the colon of patients with active inflammatory bowel disease

BACKGROUND: In inflammatory bowel disease (IBD) the disease activity correlates with colonic concentrations of leukotrienes (LTs). The enzyme 5-lipoxygenase (5-LO) is responsible for the enzymatic production of LTs. It has previously been demonstrated in experimental models of inflammation, that 5-LO is activated through intracellular translocation of the pre-formed enzyme, and increased constitutive activation of 5-LO has been demonstrated in idiopathic pulmonary fibrosis. The objective of the present study was to investigate whether de novo synthesis of 5-LO is increased in patients with quiescent IBD, or is induced during acute exacerbations of IBD. METHODS: Sixty-one individuals were included in the study. Twenty-eight had ulcerative colitis (UC), 21 had Crohn's disease (CD), and 12 were healthy controls. A standard rigid rectoscopy was performed in all individuals. The degree of inflammation was assessed using a semi-quantitative scale. A mucosal biopsy was taken from the most inflamed area as judged macroscopically. mRNA for 5-LO was detected using a RT-PCR technique, and the assay applied was evaluated by control experiments. RESULTS: The expression of mRNA for 5-LO in colonic biopsies was similar in IBD patients with quiescent disease and healthy controls. When grouped according to endoscopically assessed disease activity the fraction of patients demonstrating 5-LO mRNA in colonic biopsies showed no significant change (p > 0,6; chi2 -test for trend). CONCLUSIONS: This study demonstrates no significant relationship between endoscopically assessed disease activity and relative presence of mRNA for 5-LO in colonic biopsies. Thus, there is no evidence of increased expression of 5-LO mRNA in either quiescent or active stages of IBD.     

Innate antimicrobial immunity in inflammatory bowel diseases

Inflammatory bowel diseases are characterized by chronic intestinal inflammation at different sites. Data from animal models as well as human patients including gene-association studies suggest that different components of the innate barrier function are primarily defective. These recent advances support the evolving hypothesis that intestinal bacteria induce inflammation predominantly as a result of a weakened innate mucosal barrier in genetically predisposed individuals. This article discusses our current understanding of the primary events of disease. Together, these findings should result in new therapeutic avenues aimed at restoring antimicrobial barrier function to prevent a bacterial-triggered inflammatory response.     

Isolation, antimicrobial activities, and primary structures of hamster neutrophil defensins.

Hamster (Mesocricetus auratus) neutrophil granules contain at least four microbicidal peptides belonging to the defensin family. These compounds were purified from granule acid extracts by reverse-phase chromatography and termed HaNP-1 to -4 (hamster neutrophil peptide). HaNP-1 and HaNP-3 revealed the most bactericidal activity, with a 50% inhibitory concentration of 0.3 to 0.8 microg/ml for Staphylococcus aureus and Streptococcus pyogenes strains. The HaNP-4 was always isolated in concentrations exceeding about 10 times the concentrations of other hamster peptides, but its antibacterial activity as well as that of HaNP-2 was relatively lower, probably as a result of conserved Arg residue substitutions. Other microorganisms were also tested, and generally, hamster defensins exhibited less potency against gram-negative bacteria. The amino acid sequence of hamster defensins showed a high percentage of identity to the sequence of mouse enteric defensins, reaching about 60% identical residues in the case of HaNP-3 and cryptdin 3.     

Eicosanoid production by the mucosa in inflammatory bowel disease after 5-ASA treatment

Eicosanoids were measured in biopsies of colonic mucosa from five patients with active ulcerative colitis before and after a four weeks of treatment with 5-amino-salicylic acid (5-ASA). Eicosanoid formation was determined after the addition of¹⁴C-arachidonic acid and stimulation with calcium ionophore A23187. 5-ASA given intra-rectally caused a non-selective suppression of prostanoids, leukotrienes and hydroxyeicosatetraenoic acids. Changes in arachidonic acid metabolism after 5-ASA treatment were not always reflected in changes in inflammation score.

     

Regulatory T cells and inflammatory bowel disease.

Recent studies have identified interleukin 10 as a differentiation factor for a novel subset of immune suppressive regulatory T cells. Here, Hervé Groux and Fiona Powrie discuss the role that these cells play in the regulation of immune responses to enteric antigens and suggest that a deficiency in these cells might be involved in the pathogenesis of inflammatory bowel disease.     

Veiled cells in chronic idiopathic inflammatory bowel disease.

The mononuclear cell system in the human gut wall of patients with Crohn's disease (CD), ulcerative colitis (UC) and normal controls was studied, with special reference to the so called antigen presenting veiled cells. These cells have already extensively been studied in the skin and are known as Langerhans' cells in the epidermis and dermis, veiled cells in the skin lymph and interdigitating cells in lymph nodes. Recently they were also found in gut associated lymphoid tissue, i.e. Peyer's patches of the rat. Here we describe the presence of similar cells in chronic idiopathic inflammatory bowel disease (CIBD). They resemble veiled cells in moving pattern, strong Ia positivity, no or only weak acid phosphatase activity, and ultrastructure. However, many of the described cells combine these characteristics with those of phagocytic macrophages. In the gut wall of controls veiled cells were virtually absent and phagocytic macrophages were almost exclusively recognized. These findings suggest that more intensive antigen handling takes place in the gut wall of CIBD patients than in normal gut. Clear cut associations with sex, age, duration or activity of disease were not observed in this limited study, and the exact significance of the presence of such cells needs further clarification.     

Expression of HLA-DR antigens by colonic epithelium in inflammatory bowel disease

The expression of HLA-DR and HLA-A,B,C antigens by human colonic epithelium has been examined in tissue sections of patients with inflammatory bowel disease using an immunohistological technique. Colonic epithelial cells from all 21 control subjects with histologically normal colonic mucosa were HLA-DR-. In contrast, in nine of 13 patients with active ulcerative colitis and 11 of 12 with active Crohn's disease the epithelium of involved colonic mucosa was HLA-DR+. HLA-DR antigens were found on the epithelium of only one of six patients with ulcerative colitis in remission and one of three with inactive Crohn's disease. Moreover, these antigens were not present on the epithelium of non-inflamed colonic mucosa in two patients with Crohn's disease in whom adjacent involved mucosa showed strong epithelial reactivity. This difference between patients with active and those with inactive disease is highly significant (P less than 0.005). These findings provide further evidence of the importance of cell-mediated immune mechanisms in the pathogenesis of inflammatory bowel disease.     

Expression of interleukin-8 gene in inflammatory bowel disease is related to the histological grade of active inflammation.

Interleukin-8 (IL-8) is a potent cytokine for recruitment and activation of neutrophils. To visualize its distribution in the intestinal mucosa and to understand better its possible role in the induction and promotion of inflammatory bowel disease, expression of the IL-8 gene was analyzed in resected bowel segments of 14 patients with active Crohn's disease or ulcerative colitis. In situ hybridization with IL-8 anti-sense RNA probes revealed strong and specific signals in the histologically affected mucosa. The number of cells expressing IL-8 gene correlated with the histological grade of active inflammation. In accordance with the characteristic histological signs of active disease, IL-8-expressing cells were diffusely distributed over the entire affected mucosa in patients with ulcerative colitis, whereas in patients with Crohn's disease, IL-8-expressing cells showed a focal distribution pattern. Cells expressing IL-8 were mainly located at the base of ulcers, in inflammatory exudates on mucosal surfaces, in crypt abscesses, and at the border of fistulae. Analysis of semi-serial sections pointed to macrophages, neutrophils, and epithelial cells as possible sources of this cytokine in active inflammatory bowel disease. We consistently failed to detect IL-8 messenger RNA in the mucosa of uninvolved bowel segments and in normal-appearing control mucosa of patients with colon cancer. In contrast, tissue specimens from two patients with acute appendicitis displayed IL-8-expressing cells in the mucosa. These results support the notion that IL-8 plays and important but nonspecific role in the pathogenesis of inflammatory bowel disease and that the production of IL-8 messenger RNA is restricted to areas with histological signs of inflammatory activity and mucosal destruction.     

Neuroinflammation in inflammatory bowel disease

Inflammatory bowel disease is a chronic intestinal inflammatory condition, the pathology of which is incompletely understood. Gut inflammation causes significant changes in neurally controlled gut functions including cramping, abdominal pain, fecal urgency, and explosive diarrhea. These symptoms are caused, at least in part, by prolonged hyperexcitability of enteric neurons that can occur following the resolution of colitis. Mast, enterochromaffin and other immune cells are increased in the colonic mucosa in inflammatory bowel disease and signal the presence of inflammation to the enteric nervous system. Inflammatory mediators include 5-hydroxytryptamine and cytokines, as well as reactive oxygen species and the production of oxidative stress. This review will discuss the effects of inflammation on enteric neural activity and potential therapeutic strategies that target neuroinflammation in the enteric nervous system.     

Activated CD4+ and CD8+ cytotoxic cells are present in increased numbers in the intestinal mucosa from patients with active inflammatory bowel disease.

The contribution of cell-mediated cytotoxicity to the pathogenesis of inflammatory bowel disease (IBD) is controversial, and results of in vitro assays vary according to experimental procedures. Therefore, we compared the frequency of cytotoxic effector cells in situ. On tissue sections of controls (n = 11), low frequencies of granzyme A and perforin mRNA-expressing cells are found in the lamina propria (1.77 +/- 0.15% and 1.46 +/- 0.12%, respectively) and in the epithelial cell layer (0.76 +/- 0.12% and 0.66 +/- 0.10%, respectively). In patients with IBD (n = 33), corresponding values were significantly (P < 0.02) higher, 6.1 +/- 0.40% and 5.92 +/- 0.57% for granzyme A and perforin expression in the lamina propria and 2.50 +/- 0.19% and 2.59 +/- 0.28%, respectively, in the epithelial compartment. Differences between ulcerative colitis and Crohn's disease are statistically not significant (P > 0.33). Activated cytotoxic cells are preferentially found at sites facing the intestinal lumen. Perforin mRNA-expressing cells are mainly CD8+ T cells. CD4+ T cells expressing perforin mRNA are mainly isolated from affected areas of patients with Crohn's disease. Immunostaining for perforin protein generally coincides with perforin mRNA in situ. These data demonstrate that cytotoxic cells are vigorously activated in situ in the intestinal mucosa of patients with active IBD.     

Environmental influences on T regulatory cells in inflammatory bowel disease

Inflammatory bowel disease (IBD) is characterized by chronic, idiopathic inflammation of the intestine. The disease is thought to result from a combination of genetic and environmental factors which ultimately leads to a mucosal immune system that overreacts to normal constituents of the mucosal microbiota. The inflammation in IBD is primarily mediated by inappropriate production of proinflammatory cytokines by CD4(+) T effector cells, effects that are suppressed by CD4(+) T regulatory cells. Defects in both the function of T regulatory cells, and the ability of T effector cells to be suppressed, have been implicated in IBD. In this review we will discuss environmental factors, including cytokines, vitamins A and D, and commensal bacteria, which influence the phenotype and function of regulatory T cells and thereby alter the course of IBD. We will also discuss how these environmental signals can be manipulated therapeutically in order to improve the function of regulatory T cells and ultimately restore mucosal homeostasis in patients with IBD.