Immunoregulatory properties of IL-13 in patients with inflammatory bowel disease; comparison with IL-4 and IL-10

IL-33 Drives Expansion of Type 2 Innate Lymphoid Cells and Regulatory T Cells and Protects Mice From Severe, Acute Colitis

The hallmarks of inflammatory bowel disease are mucosal damage and ulceration, which are known to be high-risk conditions for the development of colorectal cancer. Recently, interleukin (IL)-33 and its receptor ST2 have emerged as critical modulators in inflammatory disorders. Even though several studies highlight the IL-33/ST2 pathway as a key factor in colitis, a detailed mode of action remains elusive. Therefore, we investigated the role of IL-33 during intestinal inflammation and its potential as a novel therapeutic target in colitis. Interestingly, the expression of IL-33, but not its receptor ST2, was significantly increased in biopsies from the inflamed colon of IBD patients compared to non-inflamed colonic tissue. Accordingly, in a mouse model of Dextran Sulfate Sodium (DSS) induced colitis, the secretion of IL-33 significantly accelerated in the colon. Induction of DSS colitis in ST2-/- mice displayed an aggravated colon pathology, which suggested a favorable role of the IL 33/ST2 pathway during colitis. Indeed, injecting rmIL-33 into mice suffering from acute DSS colitis, strongly abrogated epithelial damage, pro-inflammatory cytokine secretion, and loss of barrier integrity, while it induced a strong increase of Th2 associated cytokines (IL-13/IL-5) in the colon. This effect was accompanied by the accumulation of regulatory T cells (Tregs) and type 2 innate lymphoid cells (ILC2s) in the colon. Depletion of Foxp3+ Tregs during IL-33 treatment in DSS colitis ameliorated the positive effect on the intestinal pathology. Finally, IL-33 expanded ILC2s, which were adoptively transferred to DSS treated mice, significantly reduced colonic inflammation compared to DSS control mice. In summary, our results emphasize that the IL-33/ST2 pathway plays a crucial protective role in colitis by modulating ILC2 and Treg numbers.

Interleukin-13 and interleukin-33 mRNA are underexpressed in the duodenal mucosa of German Shepherd dogs with chronic enteropathy

BACKGROUND

A recent genome-wide association study in German Shepherd dogs (GSDs) with chronic enteropathy (CE) has identified polymorphisms in the Th2 cytokine genes.

HYPOTHESIS/OBJECTIVE

To determine if the expression of the Th2 cytokines, interleukin-13 (IL-13) and interleukin-33 (IL-33), is altered in the duodenal mucosa of GSDs with CE compared to non-GSDs with CE and healthy dogs.

ANIMALS

Twenty client-owned dogs diagnosed with CE (10 GSDs and 10 non-GSDs) at the Bristol Veterinary School and 8 healthy Beagle dogs from the Iowa State University Service Colony.

METHODS

Retrospective study using archived paraffin-embedded duodenal biopsy samples. A novel RNA in situ hybridization technology (RNAscope) was used to hybridize IL-13 and IL-33 mRNA probes onto at least 10 sections from duodenal biopsy samples for each dog. RNAscope signals were visualized using a microscope and semi-quantitative assessment was performed by a single operator.

RESULTS

Based on duodenal villus, subvillus, epithelial, and lamina propria average expression scores, GSDs with CE had significantly lower IL-13 and IL-33 mRNA expression compared to non-GSDs with CE (IL-13, P < .04; IL-33, P < .02) and healthy Beagle dogs (IL-13, P < .02; IL-33, P < .004).

CONCLUSIONS AND CLINICAL IMPORTANCE

Similar to human patients with ulcerative colitis, a subtype of human inflammatory bowel disease, these data indicate that Th2 cytokines may be involved in the pathogenesis of CE in GSDs.

Marine microalgae bioengineered Schizochytrium sp. meal hydrolysates inhibits acute inflammation

Bioengineered marine microalgae Schizochytrium sp. is currently used to produce docosahexaenoic acid (DHA). However, following DHA extraction, the remaining protein-rich materials are not well utilized. In this study, we report that marine microalgae bioengineered Schizochytrium sp. hydrolysate (MESH), which exhibits a unique peptide profile as identified by Ultra Performance Liquid Chromatography coupled with Q-TOF mass spectrometry(UPLC/Q-TOF-MS), ameliorated bowel inflammation in mice. In a mouse model of experimentalcolitis induced by dextran sulfate sodium, compared with the control mice, the mice treated with MESH were highly resistant to colitis, as demonstrated by marked reductions in body weight loss, clinical colitis scores, colonic histological damage, and colonic inflammation. Mechanistically, MESH attenuated the induction of pro-inflammatory cytokines and increased the induction of anti-inflammatory cytokines. MESH also promoted the proliferation of colonic crypt stem cells and progenitor cells required for crypt repair. Collectively, these results reveal a previously unrecognized role of MESH as a potential anti-inflammatory treatment for colitis.

Orally administered Taenia solium Calreticulin prevents experimental intestinal inflammation and is associated with a type 2 immune response

Intestinal helminth antigens are inducers of type 2 responses and can elicit regulatory immune responses, resulting in dampened inflammation. Several platyhelminth proteins with anti-inflammatory activity have been reported. We have identified, cloned and expressed the Taenia solium calreticulin (rTsCRT) and shown that it predominantly induces a type 2 response characterized by IgG1, IL-4 and IL-5 production in mice. Here, we report the rTsCRT anti-inflammatory activity in a well-known experimental colitis murine model. Mice were orally immunized with purified rTsCRT and colitis was induced with trinitrobenzene sulfonic acid (TNBS). Clinical signs of disease, macroscopic and microscopic tissue inflammation, cytokine production and micronuclei formation, as a marker of genotoxicity, were measured in order to assess the effect of rTsCRT immunization on experimentally induced colitis. rTsCRT administration prior to TNBS instillation significantly reduced the inflammatory parameters, including the acute phase cytokines TNF-α, IL-1β and IL-6. Dampened inflammation was associated with increased local expression of IL-13 and systemic IL-10 and TGF-β production. Genotoxic damage produced by the inflammatory response was also precluded. Our results show that oral treatment with rTsCRT prevents excessive TNBS-induced inflammation in mice and suggest that rTsCRT has immunomodulatory properties associated with the expression of type 2 and regulatory cytokines commonly observed in other helminths.

Frequency of CD4+CD161+ T Cell and Interleukin-10 Expression in Inflammatory Bowel Diseases

Mucosal immune dysregulation associated with T cells plays a critical role in the development of inflammatory bowel diseases (IBD). However, the definite significances of these cells in IBD still remain unclear. Therefore, we investigated the population and expression of CD4⁺CD161⁺ T cells in the colonic lamina propria mononuclear cells (LPMCs) in patients with IBD by analyses using flow cytometry and immunohistochemistry. Interleukin-10 (IL-10) mRNA levels in both LPMCs and CD4⁺ T cells in lamina propria (LP-CD4⁺ T cells) were measured using a real-time quantitative reverse transcription-polymerase chain reaction. IL-10 production was investigated with immunohistochemistry. The results revealed that the population of CD4⁺CD161⁺ T cells was significantly decreased in active ulcerative colitis (UC) compared with inactive UC (P < 0.05). The CD4⁺CD161⁺ T cell population was inversely correlated with disease activity in patients with UC (r = −0.6326, P = 0.0055), but there was no significant correlation in those with Crohn’s disease. Over-expression of IL-10 mRNA in both LPMCs and LP-CD4⁺ T cells were detected in active UC. Immunohistochemistry revealed decreased frequency of CD161⁺ cells and increased IL-10 positive cells in active UC. The frequency of CD4⁺CD161⁺ T cells and IL-10 expression was supposed to be associated with the pathological status of mucosal immunoregulation in IBD.

Potential role for ET-2 acting through ETA receptors in experimental colitis in mice

OBJECTIVE AND DESIGN

This study attempted to clarify the roles of endothelins and mechanisms associated with ET_A/ET_B receptors in mouse models of colitis.

MATERIALS AND METHODS

Colitis was induced by intracolonic administration of 2,4,6-trinitrobenzene sulfonic acid (TNBS, 1.5 mg/animal) or dextran sulfate sodium (DSS, 3%). After colitis establishment, mice received Atrasentan (ET_A receptor antagonist, 10 mg/kg), A-192621 (ET_B receptor antagonist, 20 mg/kg) or Dexamethasone (1 mg/kg) and several inflammatory parameters were assessed, as well as mRNA levels for ET-1, ET-2 and ET receptors.

RESULTS

Atrasentan treatment ameliorates TNBS- and DSS-induced colitis. In the TNBS model was observed reduction in macroscopic and microscopic score, colon weight, neutrophil influx, IL-1β, MIP-2 and keratinocyte chemoattractant (KC) levels, inhibition of adhesion molecules expression and restoration of IL-10 levels. However, A192621 treatment did not modify any parameter. ET-1 and ET-2 mRNA was decreased 24 h, but ET-2 mRNA was markedly increased at 48 h after TNBS. ET-2 was able to potentiate LPS-induced KC production in vitro. ET_A and ET_B receptors mRNA were increased at 24, 48 and 72 h after colitis induction.

CONCLUSIONS

Atrasentan treatment was effective in reducing the severity of colitis in DSS- and TNBS-treated mice, suggesting that ET_A receptors might be a potential target for inflammatory bowel diseases.

Distinct immune signatures in the colon of Crohn's disease and ankylosing spondylitis patients in the absence of inflammation

Crohn's disease (CD) is an inflammatory bowel disease characterized by patchy inflammation of the gastrointestinal tract. Ankylosing spondylitis (AS) is primarily characterized by inflammation of the lower vertebral column, and many patients with AS present with inflammatory gut symptoms. Genome-wide association studies have highlighted significant overlap in short nucleotide polymorphisms for both diseases. We hypothesized that patients with CD and AS have a common intestinal immune signature, characterized by inflammatory T cells, compared with healthy people. We designed a pilot study to determine both the feasibility of defining complex immune signatures from primary tissue, and differences in the local immune signature of people with inflammatory diseases compared with healthy people. Intestinal biopsies were obtained by colonoscopy from healthy patients, non-inflamed regions of CD patients and AS patients with inflammatory gut symptoms. A flow cytometry platform was developed measuring polyfunctional T-cell populations based on cytokines, surface molecules and transcription factors. There was overlap in the immune signature of people with CD or AS, characterized by changes in the frequency of regulatory T cells, compared with healthy people. There were significant differences in frequencies of other polyfunctional T-cell populations-CD patients had an increased frequency of T cells producing interleukin-22 (IL-22) and interferon-γ, whereas AS patients had an increased frequency of T cells producing IL-2; compared with healthy people. These data indicate that the local immune signature could be described in these patients and that distinct immune mechanisms may underlie disease progression.

Substance P mediates pro-inflammatory cytokine release form mesenteric adipocytes in Inflammatory Bowel Disease patients

BACKGROUND & AIMS

Substance P (SP), neurokinin-1 receptors (NK-1Rs) are expressed in mesenteric preadipocytes and SP binding activates proinflammatory signalling in these cells. We evaluated the expression levels of SP (Tac-1), NK-1R (Tacr-1), and NK-2R (Tacr-2) mRNA in preadipocytes isolated from patients with Inflammatory Bowel Disease (IBD) and examined their responsiveness to SP compared to control human mesenteric preadipocytes. The Aim of our study is to investigate the effects of the neuropeptide SP on cytokine expression in preadipocytes of IBD vs control patients and evaluate the potential effects of these cells on IBD pathophysiology via SP-NK-R interactions.

METHODS

Mesenteric fat was collected from control, Ulcerative colitis (UC) and Crohn's disease (CD) patients (n=10-11 per group). Preadipocytes were isolated, expanded in culture and exposed to substance P. Colon biopsies were obtained from control and IBD patients.

RESULTS

Tacr-1 and -2 mRNA were increased in IBD preadipocytes compared to controls, while Tac-1 mRNA was increased only in UC preadipocytes. SP differentially regulated the expression of inflammatory mediators in IBD preadipocytes compared to controls. Disease-dependent responses to SP were also observed between UC and CD preadipocytes. IL-17A mRNA expression and release increased after SP treatment in both CD and UC preadipocytes, while IL-17RA mRNA increased in colon biopsies from IBD patients.

CONCLUSIONS

Preadipocyte SP-NK-1R interactions during IBD may participate in IBD pathophysiology. The ability of human preadipocytes to release IL-17A in response to SP together with increased IL-17A receptor in IBD colon opens the possibility of a fat-colonic mucosa inflammatory loop that may be active during IBD.

Activated Syndecan-1 shedding contributes to mice colitis induced by dextran sulfate sodium

BACKGROUND

Syndecan-1(Sdc1) plays important roles in many steps of inflammatory responses. In ulcerative colitis patients, decreased Sdc1 expression was observed and Sdc1 analogue heparin could improve the disease course. A better understanding of how Sdc1 functions in colitis will benefit the disease intervention.

AIMS

To evaluate the role of Sdc1 in dextran sulfate sodium (DSS)-induced colitis.

METHODS

BALB/c mice were grouped randomly into control, DSS, and heparin+DSS. The DSS group was given 4% DSS orally and heparin+DSS group was given 4% DSS with heparin (enoxaparin) subcutaneously, while the control was given distilled water orally. All mice were killed at day 7. Disease activities, histopathological changes, membrane-bound and free Sdc1 level and mRNA expression of Sdc1, IL-1, and IL-10 in colon mucosa were detected.

RESULTS

Significant colitis was observed in the DSS group, but disease activity index and histological score showed significant lower in the heparin+DSS group than those in the DSS group. Compared to the control group, decreased Sdc1 protein expression was detected in colon mucosa of DSS-induced colitis while Sdc1 ectodomain level in serum was much higher. Inhibited Sdc1 ectodomain shedding was detected in the heparin+DSS group compared to the DSS group. RT-PCR demonstrated that both IL-1 and IL-10 expression were up-regulated in DSS-induced colitis while heparin lessened the up-regulation extent.

CONCLUSIONS

Sdc1 shedding is activated in DSS-induced colitis and heparin, which mimics Sdc1 functions, relieves colitis severity by inhibiting Sdc1 shedding and down-regulating cytokines expression.

Colitis and intestinal inflammation in IL10-/- mice results from IL-13Rα2-mediated attenuation of IL-13 activity

BACKGROUND & AIMS

The cytokine interleukin (IL)-10 is required to maintain immune homeostasis in the gastrointestinal tract. IL-10 null mice spontaneously develop colitis or are more susceptible to induction of colitis by infections, drugs, and autoimmune reactions. IL-13 regulates inflammatory conditions; its activity might be compromised by the IL-13 decoy receptor (IL-13Rα2).

METHODS

We examined the roles of IL-13 and IL-13Rα2 in intestinal inflammation in mice. To study the function of IL-13Rα2, il10(-/-) mice were crossed with il13rα2(-/-) to generate il10(-/-)il13rα2(-/-) double knockout (dKO) mice. Colitis was induced with the gastrointestinal toxin piroxicam or Trichuris muris infection.

RESULTS

Induction of colitis by interferon (IFN)-γ or IL-17 in IL-10 null mice requires IL-13Rα2. Following exposure of il10(-/-) mice to piroxicam or infection with T muris, production of IL-13Rα2 increased, resulting in decreased IL-13 bioactivity and increased inflammation in response to IFN-γ or IL-17A. In contrast to il10(-/-) mice, dKO mice were resistant to piroxicam-induced colitis; they also developed less severe colitis during chronic infection with T muris infection. In both models, resistance to IFN-γ and IL-17-mediated intestinal inflammation was associated with increased IL-13 activity. Susceptibility to colitis was restored when the dKO mice were injected with monoclonal antibodies against IL-13, confirming its protective role.

CONCLUSIONS

Colitis and intestinal inflammation in IL10(-/-) mice results from IL-13Rα2-mediated attenuation of IL-13 activity. In the absence of IL-13Rα2, IL-13 suppresses proinflammatory Th1 and Th17 responses. Reagents that block the IL-13 decoy receptor IL-13Rα2 might be developed for inflammatory bowel disease associated with increased levels of IFN-γ and IL-17.

Identification of immunological parameters associated with the alveolar bone level in periodontal patients

Purpose

The present study was performed to clarify the relationship between periodontal disease severity and selected immunological parameters consisting of serum IgG titer against periodontopathogenic bacteria, the expression of the helper T-cell cytokine by gingival mononuclear cells, and patients' immunoreactivity to cross-reactive heat shock protein (HSP) epitope peptide from P. gingivalis HSP60.

Methods

Twenty-five patients with moderate periodontitis had their gingival connective tissue harvested of gingival mononuclear cells during an open flap debridement procedure and peripheral blood was drawn by venipuncture to collect serum. The mean level of interproximal alveolar bone was calculated to be used as an index for periodontal disease severity for a given patient. Each of selected immunologic parameters was subject to statistical management to seek their correlations with the severity of periodontal disease.

Results

A significant correlation could not be identified between serum IgG titers against specific bacteria (Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum, Actinobacillus actinomycetemcomitans, and Streptococcus mutans) and the severity of periodontal disease. Expression of interleukin (IL)-10 by gingival mononuclear cells was statistically significant in the group of patients who had higher levels of alveolar bone height. However, a similar correlation could not be demonstrated in cases for IL-4 or interferon-γ. Patients' serum reactivity to cross-reactive epitope peptide showed a significant correlation with the amount of alveolar bone.

Conclusions

It was concluded that expression of IL-10 by gingival mononuclear cells and patients' sero-reactivity to the cross-reactive HSP peptide of P. gingivalis HSP60 were significantly correlated with alveolar bone height.

Therapeutic effects of four strains of probiotics on experimental colitis in mice

AIM: To investigate the therapeutic effects of four strains of probiotics (E. feacalis, L. acidophilus, C. butyricum and B. adolescentis) on dextran sulphate sodium (DSS)-induced experimental colitis in Balb/c mice.

METHODS: Eighty Balb/c mice were randomly divided into 8 groups. Weight-loss, fecal character, fecal occult blood and hematochezia were recorded daily. Disease activity index (DAI) scores were also evaluated everyday. Length of colon was measured and histological scores were evaluated on the 13th day. Myeloperoxidase (MPO) activity was detected. Interleukin-1 (IL-1) and IL-4 expression was detected by ELISA and RT-PCR.

RESULTS: The four strains of probiotics relieved the inflammatory condition of DSS-induced experimental colitis in mice. Weight loss was slowed down in all probiotics-treated mice. Even weight gain was observed by the end of probiotics treatment. The DAI and histological scores of probiotics-treated mice were lower than those of mice in the control group (1.9 ± 0.2 vs 8.6 ± 0.4, P < 0.05 for E. faecalis). The length of colon of probiotics-treated mice was longer than that of mice in the control group (10.3 ± 0.34 vs 8.65 ± 0.77, P < 0.05 for E. faecalis). The four strains of probiotics decreased the MP activity and the IL-1 expression, but increased the IL-4 expression. E. faecalis had a better effect on DSS-induced experimental colitis in mice than the other three strains.

CONCLUSION: The four strains of probiotics have beneficial effects on experimental colitis in mice. E. faecalis has a better effect on DSS-induced experimental colitis in mice than the other three strains. Supplement of probiotics provides a new therapy for UC.

Aberrant activation of nuclear factor of activated T cell 2 in lamina propria mononuclear cells in ulcerative colitis

AIM: To investigate the role of nuclear factor of activated T cell 2 (NFAT2), the major NFAT protein in peripheral T cells, in sustained T cell activation and intractable inflammation in human ulcerative colitis (UC).

METHODS: We used two-dimensional gel-electrophoresis, immunohistochemistry, double immunohistochemical staining, and confocal microscopy to inspect the expression of NFAT2 in 107, 15, 48 and 5 cases of UC, Crohn’s disease (CD), non-specific colitis, and 5 healthy individuals, respectively.

RESULTS: Up-regulation with profound nucleo-translocation/activation of NFAT2 of lamina propria mononuclear cells (LPMC) of colonic mucosa was found specifically in the affected colonic mucosa from patients with UC, as compared to CD or NC (P < 0.001, Kruskal-Wallis test). Nucleo-translocation/activation of NFAT2 primarily occurred in CD8+T, but was less prominent in CD4+ T cells or CD20+B cells. It was strongly associated with the disease activity, including endoscopic stage (τ = 0.2145, P = 0.0281) and histologic grade (τ = 0.4167, P < 0.001).

CONCLUSION: We disclose for the first time the nucleo-translocation/activatin of NFAT2 in lamina propria mononuclear cells in ulcerative colitis. Activation of NFAT2 was specific for ulcerative colitis and highly associated with disease activity. Since activation of NFAT2 is implicated in an auto-regulatory positive feedback loop of sustained T-cell activation and NFAT proteins play key roles in the calcium/calcineurin signaling pathways, our results not only provide new insights into the mechanism for sustained intractable inflammation, but also suggest the calcium-calcineurin/NFAT pathway as a new therapeutic target for ulcerative colitis.

Distinctive pattern of cytokine production and adhesion molecule expression in peripheral blood memory CD4+ T cells from patients with active Crohn's disease

An expansion of both circulating and intestinal lamina propria CD4+ CD45RO+ T cells has been described in patients with Crohn's disease. We studied both the cytokine profile and the expression of adhesion molecules on this T-cell subset. Peripheral blood CD4+ CD45RO+ T cells from patients with Crohn's disease (n=45) were assessed by flow cytometry and RT-PCR methods. The cytokine profile was also measured in intestinal lamina propria from seven patients. They were classified according to the CDAI and the results were compared with those of patients with ulcerative colitis (n=21) and noninflammatory intestinal conditions (n=15), and healthy controls (n=39). The mean percentage of circulating CD4+ CD45RO+ T cells producing intracellular TNF was higher in active than in inactive Crohn's disease patients (p < 0.001), active (p = 0.49) and inactive ulcerative colitis (p = 0.019), and healthy controls (p =0. 017). TNF expression correlated with CDAI (p < 0.001). An increased expression of intracellular IL-2, IL-6, and IL-10 in active Crohn's disease patients was also found. CD62L was downregulated in active Crohn's disease patients while no differences were observed in CD49d and CD11a expression. Lamina propria CD4+ CD45RO+ T cells from active Crohn's disease lesions showed an increased intracellular staining of TNF, IFN-gamma, and IL-10. Both peripheral and intestinal mucosa CD4+ CD45RO+ T cells from active Crohn's disease patients show an increased production of TNF. In addition, the circulating CD4+ CD45RO+ T-cell subset expresses a pattern of adhesion molecules that promotes homing to extranodal lymphoid tissues. This T-cell subset may play a relevant role in the immunopathogenesis of Crohn's disease.

Johne's disease, inflammatory bowel disease, and Mycobacterium paratuberculosis

Johne's disease is a chronic diarrhea affecting all ruminants. Mycobacterium avium subsp. paratuberculosis (MAP), a slowly growing mycobacteria, is the etiologic agent. There is also a concern that MAP might be a causative agent of some cases of inflammatory bowel disease in humans, especially Crohn's disease. Food products including pasteurized bovine milk have been suggested as potential sources of human infection. This review addresses microbial factors that may contribute to its pathogenicity. In addition, the experimental evidence defining MAP as the cause of Johne's disease and the issues and controversies surrounding its potential pathogenic role in humans are discussed.

Intestinal interleukin-13 in pediatric inflammatory bowel disease patients

BACKGROUND

Interleukin-13 (IL-13) is a multifunctional cytokine whose net principle action is to diminish inflammatory responses. Dysregulation of IL-13 production has been proposed to contribute to intestinal inflammation in inflammatory bowel disease (IBD) patients. Previous studies implicate IL-13 in IBD pathogenesis; however, they fail to accurately reflect in vivo intestinal IL-13 production. We evaluate IL-13, IL-6, and IL-1beta elaborations from colonic organ cultures of pediatric IBD patients

METHODS

Endoscopic lamina propria biopsies or surgical specimens from pediatric patients with IBD were organ cultured and supernatants evaluated by enzyme-linked immunosorbent assay for IL-1beta, IL-6, and IL-13.

RESULTS

IL-13 concentrations were significantly reduced in ulcerative colitis (UC) patients when compared with normal controls (P = 0.002) and Crohn disease (CD) patients (P = 0.001). End-stage UC patients at colectomy had lower intestinal IL-13 production than all other UC patients (P = 0.002). No significant correlation was found between IL-13 concentration and histologic disease severity (P = 0.134).

CONCLUSIONS

Diminished intestinal IL-13 production is present in UC patients and wanes further with clinical disease progression. These findings suggest that UC patients may be differentiated from CD patients by intestinal IL-13 quantitation, and UC patients may benefit from IL-13 enhancing therapies.

Patients with inflammatory bowel disease (IBD) reveal increased induction capacity of intracellular interferon-gamma (IFN-gamma) in peripheral CD8+ lymphocytes co-cultured with intestinal epithelial cells

Intestinal epithelial cells seem to play a key role during IBD. The network of cellular interactions between epithelial cells and lamina propria mononuclear cells is still incompletely understood. In the following co-culture model we investigated the influence of intestinal epithelial cells on cytokine expression of T cytotoxic and T helper cells from patients with IBD and healthy controls. Peripheral blood mononuclear cells (PBMC) were purified by a Ficoll-Hypaque gradient followed by co-incubation with epithelial cells in multiwell cell culture insert plates in direct contact as well as separated by transwell filters. We used Caco-2 cells as well as freshly isolated colonic epithelia obtained from surgical specimens. Three-colour immunofluorescence flow cytometry was performed after collection, stimulation and staining of PBMC with anti-CD4, anti-CD8, anti-IFN-gamma and anti-IL-4. Patients with IBD (Crohn's disease (CD), n = 12; ulcerative colitis (UC), n = 16) and healthy controls (n = 10) were included in the study. After 24 h of co-incubation with Caco-2 cells we found a significant increase of IFN-gamma-producing CD8+ lymphocytes in patients with IBD. In contrast, healthy controls did not respond to the epithelial stimulus. No significant differences could be found between CD and UC or active and inactive disease. A significant increase of IFN-gamma+/CD8+ lymphocytes in patients with UC was also seen after direct co-incubation with primary cultures of colonic crypt cells. The observed epithelial-lymphocyte interaction seems to be MHC I-restricted. No significant epithelial cell-mediated effects on cytokine expression were detected in the PBMC CD4+ subsets. Patients with IBD-even in an inactive state of disease-exert an increased capacity for IFN-gamma induction in CD8+ lymphocytes mediated by intestinal epithelial cells. This mechanism may be important during chronic intestinal inflammation, as in the case of altered mucosal barrier function epithelial cells may become targets for IFN-gamma-producing CD8+ lymphocytes.

Colonic expression and synthesis of interleukin 13 and interleukin 15 in inflammatory bowel disease

A dysregulated local immune reaction with unbalanced cytokine expression seems essential in inflammatory bowel disease (IBD), i.e. ulcerative colitis (UC) and Crohn's disease (CD). Since the roles of interleukin (IL-)13 and IL-15 remain unclear, this study aimed at studying intestinal expression of IL-13 and IL-15 in IBD.

METHODS

In colonic biopsies from 24 UC, 18 CD, and 12 controls IL-13 and IL-15 were measured using ELISA, and their gene expressions were assessed by RT-PCR. Leukocytes were visualised histochemically.

RESULTS

Concentrations of IL-13 were decreased in UC (median 56 pg/mg tissue; interquartile range 30-99 pg/mg) compared to CD (82 pg/mg tissue; 41-122;P=0.004) and controls (83 pg/mg tissue; 18-134;P>0.05), and lower in active UC (53 pg/mg tissue; 33-96) than in inactive UC (80 pg/mg tissue; 65-99;P=0.02). IL-15 concentrations were higher in CD patients (34 pg/mg tissue; 24-53) as compared to controls (20 pg/mg tissue; 15-21;P=0.001) whilst being 22 pg/mg tissue (15-32) in UC. IL-13 mRNA and IL-15 mRNA were detected in 20% and 15%, respectively. Infiltration of leukocytes correlated inversely with IL-13 levels (P=0.02).

CONCLUSION

Active UC is associated with decreased colonic IL-13 suggesting that IL-13 levels are diminished as a part of UC exacerbations, or that exacerbations follow active downregulation of IL-13.

IL-10, but not IL-4, suppresses infection-stimulated bone resorption in vivo

Periapical bone resorption occurs following infection of the dental pulp and is mediated mainly by IL-1alpha in the murine model. The production and activity of IL-1alpha is modulated by a network of regulatory cytokines, including those produced by Th1 (pro-inflammatory) and Th2 (anti-inflammatory) subset T cells. This study was designed to assess the functional role of the Th2-type cytokines IL-4 and IL-10 in infection-stimulated bone resorption in vivo. The dental pulps of the first molars were exposed and infected with a mixture of four common endodontic pathogens, and bone destruction was determined by micro-computed tomography at sacrifice on day 21. The results demonstrate that IL-10(-/-) mice had significantly greater infection-stimulated bone resorption in vivo compared with wild-type mice (p < 0.001), whereas IL-4(-/-) exhibited no increased resorption. IL-10(-/-) had markedly elevated IL-1alpha production within periapical inflammatory tissues (>10-fold) compared with wild type (p < 0.01), whereas IL-4(-/-) exhibited decreased IL-1alpha production (p < 0.05). IL-10 also suppressed IL-1alpha production by macrophages in a dose-dependent fashion in vitro, whereas IL-4 had weak and variable effects. We conclude that IL-10, but not IL-4, is an important endogenous suppressor of infection-stimulated bone resorption in vivo, likely acting via inhibition of IL-1alpha expression.

Chronic colitis in IL-10-/- mice: insufficient counter regulation of a Th1 response

IL-10-deficient (IL-10-/-) mice, generated by a gene-targeted mutation, develop abnormal immune responses as a result of uncontrolled interactions between antigen presenting cells and lymphocytes. The studies reviewed herein have focused on the enterocolitis that spontaneously develops in IL-10-/- mice. Not unexpectedly, heightened production of proinflammatory mediators accompanied pathologic changes in the gastrointestinal tract of young mutants. In a series of studies, the proinflammatory mediators responsible for initiating the pathogenic response were distinguished from those that were elicited as a consequence of persistent inflammation. We have also investigated the possibility that different mediators are involved in the inductive versus the maintenance phase of disease. The findings of these mechanistic studies as they relate to our understanding of progressive inflammatory disease and the role of IL-10 in controlling the acute and chronic stages are discussed.

In vitro interleukin-13 production by peripheral blood in patients with newly diagnosed insulin-dependent diabetes mellitus and their first degree relatives

It is generally accepted that proinflammatory cytokines secreted by macrophages/monocytes as well as cytotoxic T cells are responsible for pancreatic B-cell destruction in animal models of autoimmune diabetes and presumably in insulin-dependent diabetes mellitus (IDDM) in humans. The aim of the present study was to evaluate the production of interleukin (IL)-13-a Th2 cells derived anti-inflammatory cytokine, by peripheral blood of newly diagnosed IDDM patients and their first degree relatives with a low or high risk of IDDM development. The study was carried out in 20 patients with a recent onset of type 1 diabetes, their first degree relatives with high (with DRB1*03 and/or DRB1*04 HLA class II alleles and two or more autoantibodies directed against pancreatic B-cell antigens) (n = 20) or a low (with DQB1*0602 allele) risk of type 1 diabetes development (n = 10) and a control age matched group of healthy volunteers (n = 18). IL-13 concentrations in supernatant of 72 h cultures of peripheral blood after incubation with phytohemagglutinin (PHA) or PHA+ insulin were quantified by enzyme-linked immunosorbent assay (ELISA). The levels of IL-13 in the supernatants were significantly lower in at high risk of IDDM first degree relatives of diabetic patients (P < 0.02), higher in subjects with low genetic risk of diabetes type 1 (P < 0.02), and normal in IDDM patients in comparison to the control group. We have also observed that the adding of human insulin to the cultures resulted in a significant increase of in vitro IL-13 production in prediabetics, but not in the other studied groups. In conclusion our findings suggest that the IL-13 alterations could play an important role in the pathogenesis of type 1 diabetes. We would speculate that IL-13 as an anti-inflammatory cytokine and a mediator of the Th2 pathway could be the potential therapeutic approach in the prevention of type 1 diabetes.

Glucocorticoids Induce Apoptosis in Human Monocytes: Potential Role of IL-1β

Glucocorticoids (GC) are potent anti-inflammatory and immunosuppressive agents that act on a variety of immune cells, including monocytes and macrophages. However, the exact cellular mechanisms underlying this anti-inflammatory capacity are still unknown. In our study, we determined the induction of apoptosis by GC in human monocytes. Peripheral blood monocytes were isolated by density centrifugation methods with a purity of &gt;90% and were cultured in RPMI 1640 medium. Monocyte apoptosis was determined by four independent methods, including annexin-V staining, TUNEL, DNA-laddering, and typical morphology by means of transmission electron microscopy. TNF-α and IL-1β were measured by ELISA. GC receptor was blocked with mifepristone. Caspase 3 was inhibited with caspase-3 inhibitor (DEVD-CHO). Stimulation with different GC at therapeutic concentrations resulted in monocyte apoptosis in a time- and dose-dependent manner. Necrosis was excluded by propidium iodide staining. Proinflammatory cytokines such as IL-1β and TNF-α were down-regulated by GC treatment. Continuous treatment of monocytes with IL-1β, but not with TNF-α, could almost completely prevent GC-induced cell death. The addition of mifepristone or caspase-3 inhibitor could partially abrogate GC-induced apoptosis as well as GC-induced inhibition of IL-1β. This is the first study to demonstrate induction of apoptosis by GC in human monocytes. GC-induced monocyte apoptosis may be partially mediated through effects on IL-1β production. It is conceivable that GC exert their anti-inflammatory capacity in various diseases, at least in part, by the induction of apoptosis in monocytes.

High levels of IL-10 secreting cells are present in blood in cerebrovascular diseases

Ischemic stroke is associated with altered systemic immune responses both early after the onset and in the recovery phase. Interleukin (IL)-10, a Th2 related cytokine, has multiple effects on different cell types, including T and B lymphocytes, monocytes, neutrophils and mast cells. IL-4 is another Th2 cytokine that inhibits the synthesis of pro-inflammatory cytokines by Th1 clones. We used enzyme-linked immunospot assays to detect and enumerate blood mononuclear cells (MNC) secreting IL-10 and IL-4 spontaneously as well as after stimulation with myelin basic protein (MBP), considered to be an autoantigen of possible pathogenic importance in, for example, multiple sclerosis, to evaluate the involvement of anti-inflammatory cytokines in ischemic stroke. All patients with ischemic stroke and cerebral hemorrhage had strongly elevated numbers of IL-10 secreting blood MNC compared with healthy individuals. Numbers of MBP-reactive IL-10 secreting blood MNC were also elevated in a proportion of the patients with stroke and hemorrhage. Levels of IL-4 secreting blood MNC did not differ in ischemic stroke versus healthy individuals. The anti-inflammatory IL-10 could play a pivotal role in ischemic stroke as well as cerebral hemorrhage.

Diminished responses to IL-13 by human monocytes differentiated in vitro: role of the IL-13Ralpha1 chain and STAT6

The primary IL-13 receptor complex on human monocytes is believed to be a heterodimer comprised of the IL-4R alpha chain and the IL-2R gamma chain (gamma(c))-like molecule, IL-13R alpha1. mRNA levels for IL-13R alpha1, but not IL-4R alpha, were markedly decreased in in vitro monocyte-derived macrophages (MDMac), and with increasing time of monocytes in culture correlated with the loss of IL-13 regulation of lipopolysaccharide-induced TNF-alpha production. Analysis of cell lines Daudi and THP-1 that differentially express gamma(c) and IL-13R alpha1 showed that IL-13 can activate STAT6 in IL-13R alpha1-positive THP-1 cells but not in gamma(c)-positive, IL-13R alpha1-negative Daudi cells. IL-13 activation of STAT6 was reduced in MDMac which was associated with diminished IL-13-induced expression of CD23 and MHC class II. However, with reduced IL-13R alpha1 expression and low nuclear STAT6 activity, some IL-13-induced responses were unaltered in magnitude in MDMac. In the absence of functional IL-13R alpha1 and gamma(c), IL-13 must signal through an alternative receptor complex on MDMac. Experiments with a blocking antibody to IL-4R alpha showed that this chain remains an essential component of the IL-13 receptor complex on MDMac.

Interleukin (IL)-13 and IL-4 are potent inhibitors of IL-8 secretion by human intestinal epithelial cells

Intestinal epithelial cells are able to produce soluble mediators that initiate or amplify inflammatory events in the intestinal mucosa. Interleukin (IL) -8 is suggested to be a cytokine playing a major role during the acute and chronic processes in inflammatory bowel disease (IBD). TH-2 cytokines have been described as down-regulating the inflammatory response. We analyzed the effects of IL-10, IL-13, and IL-4 on IL-8 secretion in intestinal epithelial cells. The human colonic epithelial cell line Caco-2 and freshly isolated intestinal epithelial cells were used. Cells were stimulated with IL-1beta after treatment with TH-2 cytokines. Levels of IL-8 were determined by employing enzyme-linked immunosorbent assay (ELISA). Stimulation with IL-1beta results in a time-dependent IL-8 secretion. The addition of IL-4 and IL-13, but not IL-10, to activated epithelial cells resulted in a strong decrease in IL-8 secretion. Maximal inhibition required that TH-2 cytokines be added up to 60 min before or simultaneous with stimulatory agents. We present novel findings that IL-4 and IL-13 strongly down-regulate IL-8 secretion from intestinal epithelial cells. A microenvironment containing high concentrations of IL-4 and IL-13 may alter the recruitment of immune cells to enterocytes at least partly by inhibiting IL-8 production. This inhibition might diminish the severity of the intestinal inflammatory response and, thus reduce clinical disease activity.

C-X-C and C-C chemokine expression and secretion by the human colonic epithelial cell line, HT-29: differential effect of T lymphocyte-derived cytokines

Differential chemokine production by colonic epithelial cells is thought to contribute to the characteristic increased infiltration of selected population of leukocytes cells in inflammatory bowel disease. We have previously demonstrated that IL-13 enhances IL-1alpha-induced IL-8 secretion by the colonic epithelial cell line HT-29. We have now explored the C-C chemokine expression and modulation in this system. The combination of TNF-alpha and IFN-gamma was the minimal stimulation required for regulated on activation, normal T cell expressed and secreted (RANTES) and monocyte chemoattractant protein (MCP-1) mRNA expression and secretion by HT-29 cells. The same stimulation induced a stronger IL-8 mRNA expression and secretion. Pretreatment with IL-13 or IL-4, reduced significantly the RANTES, and MCP-1, but not IL-8 mRNA expression and secretion. In contrast, IL-10 had no effect on either MCP-1, or RANTES, or IL-8 generation. Pretreatment of HT-29 cells with wortmannin suggested that the IL-13-induced inhibition of C-C chemokine expression is via activation of a wortmannin-sensitive phosphatidylinositol 3-kinase. These data demonstrate that colonic epithelial cell chemokine production can be differentially regulated by T cell-derived cytokines and suggest an interplay between epithelial cells and T lymphocytes potentially important in the intestinal inflammation.

Interleukin-4 and interleukin-13: their similarities and discrepancies

Interleukin-4 (IL-4) and the closely related cytokine, interleukin-13 (IL-13) share many biological and immunoregulatory functions on B lymphocytes, monocytes, dendritic cells and fibroblasts. Both IL-4 and IL-13 genes are located in the same vicinity on chromosome 5 and display identical major regulatory sequences in their respective promoters, thus explaining their restricted secretion pattern to activated T cells and mast cells. The IL-4 and IL-13 receptors are multimeric and share at least one common chain called IL-4R alpha. Recent progress made in the description of IL-4 and IL-13 receptor complex have demonstrated the existence of two types of IL-4 receptors: one constituted by the IL-4R alpha and the gamma c chain, and a second constituted by the IL-4 R alpha and the IL-13R alpha 1 and able to transduce both IL-4 and IL-13 signals. Specific IL-13 receptors are results from the association between the IL-4R alpha and the IL-13R alpha 2 or between two IL-13R alpha. Furthermore, similarities in IL-4 and IL-13 signal transduction have been also described, thus explaining the striking overlapping of IL-4- and IL-13-induced biological activities such as regulation of antibody production and inflammation. However, the restricted expression of IL-4 to type 2 helper T lymphocytes as well as the inability of IL-13 to regulate T cell differentiation due to a lack of IL-13 receptors on T lymphocytes represent the major differences between these cytokines. This would indicate that although IL-4 and IL-13 share a large number of properties, precise mechanisms of regulation are also present to guarantee their distinct functions.

The role of IL-10 in inflammatory bowel disease: "of mice and men"

Inflammatory bowel disease (IBD) is a generic term typically used to describe a group of idiopathic inflammatory intestinal conditions in humans that are generally divided into Crohn's disease and ulcerative colitis. Although the etiology of these diseases remains unknown, a number of rodent models of IBD have recently been identified, all sharing the concept that the development of chronic intestinal inflammation occurs as a consequence of alterations in the immune system that lead to a failure of normal immunoregulation in the intestine. On the basis of these models, it has been hypothesized that the development of IBD in humans may be related to a dysregulated immune response to normal flora in the gut. Immunodeficient scid mice injected with CD4+ CD45RB(high) T cells and mice deficient in interleukin (IL)-10 (IL-10-/-) are among the rodent models of IBD. In both models, there is inflammation and evidence of a Th1-like response in the large intestine, characterized by CD4+ T-cell and macrophage infiltrates, and elevated levels of interferon-gamma. Because IL-10 is an immunomodulatory cytokine that is capable of controlling Th1-like responses, the role of IL-10 was investigated in these models. IL-10 was shown to be important in regulating the development of intestinal inflammation in both models. These results provided key data that supported initiation of clinical trials evaluating the efficacy of IL-10 in patients with IBD.

Expression of inducible nitric oxide synthase activity in human colon epithelial cells: modulation by T lymphocyte derived cytokines

BACKGROUND

Nitric oxide (NO) synthesis and inducible nitric oxide synthase (iNOS) expression are increased in colonic biopsy specimens from patients with ulcerative colitis, but the cellular source of NO production is not known.

AIMS

To examine the distribution of iNOS in human colonic mucosa and to explore the ability of T lymphocyte derived cytokines to regulate iNOS expression and activity in human colonic epithelial cells.

METHODS

iNOS expression was examined using immunohistochemistry in colonic biopsy samples from 12 patients with ulcerative colitis and three with infectious colitis and compared with 10 normal controls. In vitro iNOS expression and activity were determined in HT-29 cell cultures; nitrite levels were measured using a fluorescent substrate, iNOS mRNA expression by northern blot analysis, and iNOS protein expression by western blot analysis.

RESULTS

No iNOS expression was detected (10 of 10) in non-inflamed mucosa derived from normal controls. In 11 of 12 cases of newly diagnosed ulcerative colitis, iNOS protein was expressed in the epithelial cells, while no other positive cells were found in the lamina propria. Similar iNOS labelling was found in colonic biopsy samples from patients with infectious colitis in the acute phase, but when re-examined in samples from patients in total remission, no iNOS staining was observed. Both interleukin (IL)-13 and IL-4, but not IL-10, are potent inhibitors of iNOS expression and activity induced by an optimal combination of cytokines, namely IL-1 alpha, tumour necrosis factor alpha and interferon gamma.

CONCLUSIONS

The data suggest that the epithelium is the major source of iNOS activity in ulcerative colitis and that IL-13 and IL-4 may act as intrinsic regulators of NO generation in intestinal inflammation.

IL-10 synergizes with IL-4 and IL-13 in inhibiting lysosomal enzyme secretion by human monocytes and lamina propria mononuclear cells from patients with inflammatory bowel disease

Tissue injury and inflammation in inflammatory bowel disease (IBD) are associated with enhanced monocytic lysosomal enzyme release. In this study, peripheral monocytes and lamina propria mononuclear cells (LPMNC) were isolated from IBD patients and normal controls. Cells were stimulated with lipopolysaccharide after treatment with IL-13, IL-4, and IL-10, and enzyme secretion was assessed by using the corresponding p-nitrophenyl glycosides as substrates. Molecular forms of cathepsin D were examined to describe the mode of enzyme release. IL-10 and IL-4 strongly down-regulate enzyme secretion in IBD monocytes. IBD monocytes showed a diminished responsiveness to the inhibitory effect of IL-13. Impaired monocyte response was not found with combinations of IL-13 and IL-10 or IL-4 and IL-10. LPMNC from involved IBD mucosa showed significantly higher enzyme secretion compared with LPMNC from noninvolved IBD mucosa but responded inefficiently to either IL-4, IL-13, or IL-10 alone. However, combined treatment with IL-10 and IL-4 or IL-10 and IL-13 strongly suppressed enzyme release by these cells. Both the precursor and mature forms of cathepsin D were elevated in IBD patients. While IL-13 reduced mainly the precursor form, the effect of IL-4 and IL-10 concerns both the precursor and mature form of cathepsin D. Our results favor the potent clinical utility of combined treatment, thus improving chances of developing effective treatments for human IBD.

IL-4, IL-10 and IL-13 down-regulate monocyte-chemoattracting protein-1 (MCP-1) production in activated intestinal epithelial cells

Several studies have demonstrated that intestinal epithelial cells play a major role in the initiation and perpetuation of intestinal inflammation by secreting proinflammatory cytokines and chemokines. MCP-1 is suggested to be a chemokine that plays a major part during intestinal inflammation in inflammatory bowel disease (IBD). Immunoregulatory cytokines such as IL-4, IL-10 and IL-13 have been described to exert anti-inflammatory properties on various cell types. The aim of our study was to determine the effect of Th2 cytokines on the production of MCP-1 by activated intestinal epithelial cells. We examined Caco-2 cells as well as intestinal epithelial cells which were isolated from surgical specimens. Production of the chemokine MCP-1 was determined under stimulated and non-stimulated conditions. IL-4, IL-10 and IL-13 were added to stimulated epithelial cells under various culture conditions. Supernatants were analysed for cytokine concentrations using ELISAs. Under stimulation with physiological agents like IL-1beta or tumour necrosis factor-alpha (TNF-alpha), we observed markedly increased concentrations of MCP-1 in supernatants of Caco-2 cells and intestinal epithelial cells. IL-4, IL-10 and IL-13 all had the capacity to down-regulate the production of MCP-1 in Caco-2 cells as well as in freshly isolated epithelial cells. Caco-2 cells which were primed with Th2 cytokines 24 h before stimulation were subsequently decreased in their ability to be stimulated by IL-1beta or TNF-alpha for MCP-1 production. As MCP-1 has been shown to play a major role during intestinal inflammation, the in vitro suppression of MCP-1 in enterocytes suggests the in vivo use of regulatory cytokines in patients with active IBD.

Therapeutic effects of interleukin-4 gene transfer in experimental inflammatory bowel disease

Inflammatory bowel disease (IBD) is characterized by altered immunoregulation and augmented intestinal synthesis of nitric oxide. The purpose of this study was to determine the effects of exogenous IL-4, introduced by a recombinant human type 5 adenovirus (Ad5) vector, on the tissue injury associated with an experimental model of colonic immune activation and inflammation. Colitis was induced in rats by the intrarectal administration of trinitrobenzene sulfonic acid (TNB) dissolved in 50% ethanol, and control rats received saline via the same route. 1 h later, all rats were randomized into two groups. The first group was injected intraperitoneally (ip) with 3.0 x 10(6) plaque forming units (PFUs) of Ad5 transfected with murine interleukin-4 (Ad5IL-4) and the second group was injected ip with the same amount of Ad5 expressing the Escherichia coli Lac Z gene (Ad5LacZ). One-half of the colitic and control rats were injected again with 3.0 x 10(6) PFUs of Ad5IL-4 or Ad5LacZ on day 3 of the 6-d study. When introduced once or twice via the peritoneal route into control rats, Ad5LacZ was localized to the serosal lining of the peritoneal cavity, the diaphragm and the liver on day 6. One or two injections of Ad5IL-4 into rats also produced measurable levels of circulating IL-4. TNB-colitis in both Ad5LacZ-treated groups was associated with pronounced elevations in serum IFN-gamma, and mucosal ulceration of the distal colon. Myeloperoxidase and inducible nitric oxide synthase II (NOS II) synthetic activity were also increased by 30- and fivefold, respectively, above control levels in the distal colon. However, two injections of Ad5IL-4 into colitic rats caused the overexpression of IL-4, and significantly inhibited tissue damage, serum and colon IFN-gamma levels and myeloperoxidase activity in the distal colon. In addition, NOS II gene expression and NOS II nitric oxide synthesis was significantly inhibited. No therapeutic effect was observed in rats injected once with Ad5IL-4. Thus, IL-4, introduced by Ad5, is therapeutic during acute inflammation in the rat colon. The therapeutic effect of IL-4 was associated with an inhibition of inducible nitric oxide expression and a reduction in nitric oxide synthesis.

Colon carcinoma cell lines stimulate monocytes and lamina propria mononuclear cells to produce IL-10

Cytokines released from tumour cells may have function as signals to neighbouring immune and inflammatory cells. Several studies have shown that the immunoregulatory cytokines IL-10 and transforming growth factor-beta1 (TGF-beta1) as well as prostaglandin-E2 (PGE2) play an important role in tumour-induced immunosuppression. The aim of the study was to investigate the effect of colon carcinoma cell lines on IL-10 production in peripheral monocytes (PBMC) and lamina propria mononuclear cells (LPMC). We examined four colon carcinoma cell lines (HT-29, Caco-2, Colo-320 and HCT-116) and determined their production of TGF-beta1, IL-10 and PGE2. Peripheral monocytes were isolated by density gradient centrifugation and LPMC were isolated from surgical specimens using a collagenase digestion method. Monocytes and LPMC were cultured with colon carcinoma cell conditioned medium or in co-culture with colon carcinoma cells. Supernatants were then determined for the production of IL-10 by ELISA assays. All colon carcinoma cell lines stimulated peripheral monocytes as well as LPMC to produce markedly increased levels of IL-10. Colon cancer cells secreted negligible levels of IL-10, but high amounts of TGF-beta1 and PGE2. Neutralization of TGF-beta1 by administration of anti-TGF-beta as well as neutralization of PGE2 with anti-PGE2 antisera reduced the IL-10 production of monocytes markedly, indicating that tumour cell-derived TGF-beta1 and PGE2 are major factors for IL-10 stimulation. In vitro stimulation of monocytes with TGF-beta1 and PGE2 could confirm that TGF-beta1 as well as PGE2 at picogram concentrations were able to prime monocytes for enhanced IL-10 production. Our results demonstrate that colon carcinoma cell lines enhance the ability of monocytes and intestinal macrophages to produce IL-10. The stimulation of monocyte IL-10 by colon cancer cell-derived TGF-beta1 and PGE2 may act as a tumour-protecting mechanism by impairing the activation of anti-tumour cytokines.

Importance of combined treatment with IL-10 and IL-4, but not IL-13, for inhibition of monocyte release of the Ca(2+)-binding protein MRP8/14

Expression of the two myeloic related proteins MRP8 and MRP14 is restricted to distinct stages of monocytic differentiation. Heterodimeric MRP8/14 complexes (27E10 antigen) have been shown to represent their biologically active forms. In this study, we investigated the effects of Th2-cytokines on release of these proteins from freshly obtained blood monocytes and monocytes cultured for 7 days in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF). Monocytes were stimulated with pokeweed mitogen (PWM) in the presence or absence of interleukin-13 (IL-13), IL-4 and IL-10, and secretion of MRP8, MRP14 and MRP8/14 was assessed by using a sandwich enzyme-linked immunosorbent assay system. Peripheral monocytes secreted significantly increased amounts of MRP14 and MRP8/14 but not MRP8 under stimulation with PWM. IL-10 and IL-4, but not IL-13, down-regulated the PWM-stimulated MRP8/14 secretion in a dose-dependent manner. Maximal inhibition required that IL-10 and IL-4 be added up to 1 h before or simultaneous with PWM. A combination of IL-10 and IL-4 even at suboptimal concentrations significantly suppressed protein secretion much more than using IL-10 or IL-4 at a doubled concentration alone. Peripheral monocytes cultured for 7 days in the presence of GM-CSF showed two-to threefold higher protein levels compared with freshly obtained blood monocytes but responded inefficiently to either IL-4, IL-13, or IL-10 alone. However, treatment with IL-10 in combination with IL-4 but not IL-13 strongly suppressed MRP14 and MRP8/14 release by these cells. The unresponsiveness of 7-day-cultured blood macrophages suggests that more differentiated and activated cells may lose their ability to respond to anti-inflammatory cytokines. Combined cytokine treatment may therefore more effectively control the progression of chronic inflammatory processes.

Synergistic effect of immunoregulatory cytokines on peripheral blood monocytes from patients with inflammatory bowel disease

Active inflammatory bowel disease (IBD) is characterized by increased monocyte secretion of proinflammatory cytokines. Immunoregulatory cytokines such as Interleukin (IL)-4, IL-10, and IL-13 are capable of inhibiting the proinflammatory cytokine response of activated monocytes. The aim of our study was to determine the effect of different antiinflammatory cytokines under various culture conditions and to evaluate combinations of antiinflammatory cytokines in down-regulating monocyte response in IBD. Peripheral monocytes from patients with active IBD were isolated and stimulated with pokeweed mitogen (PWM). IL-4, IL-10, IL-13 and a combination of IL-4/IL-10 and IL-10/IL-13 were added at different concentrations and different times. Secretion of IL-1beta and TNF-alpha was assessed using sandwich ELISA systems. There was a diminished down-regulation of TNF-alpha by IL-4 and IL-13 in IBD when the cytokines were added at the time of stimulation, while there was a significantly higher down-regulation when monocytes were primed with these Th-2 cytokines 24 hr before activation. IL-10 plus IL-4 and IL-10 plus IL-13, respectively, inhibited the proinflammatory cytokine response of monocytes as well as matured macrophages much more than IL-4, IL-10, or IL-13 alone. Even at suboptimal concentrations for each cytokine alone, a combination of cytokines showed synergistic inhibitory effects. In summary, a combination of antiinflammatory cytokines is more effective in down-regulating the response of activated monocytes than using the cytokines alone and thus may have a potential therapeutic benefit for patients with IBD.