CD4(+) T lymphocytes mediate colitis in HLA-B27 transgenic rats monoassociated with nonpathogenic Bacteroides vulgatus

Environmental and Microbial Factors in Inflammatory Bowel Disease Model Establishment: A Review Partly through Mendelian Randomization

Inflammatory bowel disease (IBD) is a complex condition resulting from environmental, microbial, immunologic, and genetic factors. With the advancement of Mendelian randomization research in IBD, we have gained new insights into the relationship between these factors and IBD. Many animal models of IBD have been developed using different methods, but few studies have attempted to model IBD by combining environmental factors and microbial factors. In this review, we examine how environmental factors and microbial factors affect the development and progression of IBD, and how they interact with each other and with the intestinal microbiota. We also summarize the current methods for creating animal models of IBD and compare their advantages and disadvantages. Based on the latest findings from Mendelian randomization studies on the role of environmental factors in IBD, we discuss which environmental and microbial factors could be used to construct a more realistic and reliable IBD experimental model. We propose that animal models of IBD should consider both environmental and microbial factors to better mimic human IBD pathogenesis and to reveal the underlying mechanisms of IBD at the immune and genetic levels. We highlight the importance of environmental and microbial factors in IBD pathogenesis and offer new perspectives and suggestions for improving experimental animal modeling. Our goal is to create a model that closely resembles the clinical picture of IBD.

The gut microbiome and HLA-B27-associated anterior uveitis: a case-control study

BACKGROUND

The human gut microbiome (GM) is involved in inflammation and immune response regulation. Dysbiosis, an imbalance in this ecosystem, facilitates pathogenic invasion, disrupts immune equilibrium, and potentially triggers diseases including various human leucocyte antigen (HLA)-B27-associated autoinflammatory and autoimmune diseases such as inflammatory bowel disease (IBD) and spondyloarthropathy (SpA). This study assesses compositional and functional alterations of the GM in patients with HLA-B27-associated non-infectious anterior uveitis (AU) compared to healthy controls.

METHODS

The gut metagenomes of 20 patients with HLA-B27-associated non-infectious AU, 21 age- and sex-matched HLA-B27-negative controls, and 6 HLA-B27-positive healthy controls without a history of AU were sequenced using the Illumina NovaSeq 6000 platform for whole metagenome shotgun sequencing. To identify taxonomic and functional features with significantly different relative abundances between groups and to identify associations with clinical metadata, the multivariate association by linear models (MaAsLin) R package was applied.

RESULTS

Significantly higher levels of the Eubacterium ramulus species were found in HLA-B27-negative controls (p = 0.0085, Mann-Whitney U-test). No significant differences in microbial composition were observed at all other taxonomic levels. Functionally, the lipid IVA biosynthesis pathway was upregulated in patients (p < 0.0001, Mann-Whitney U-test). A subgroup analysis comparing patients with an active non-infectious AU to their age- and sex-matched HLA-B27-negative controls, showed an increase of the species Phocaeicola vulgatus in active AU (p = 0.0530, Mann-Whitney U-test). An additional analysis comparing AU patients to age- and sex-matched HLA-B27-positive controls, showed an increase of the species Bacteroides caccae in controls (p = 0.0022, Mann-Whitney U-test).

CONCLUSION

In our cohort, non-infectious AU development is associated with compositional and functional alterations of the GM. Further research is needed to assess the causality of these associations, offering potentially novel therapeutic strategies.

In vitro triple coculture with gut microbiota from spondyloarthritis patients is characterized by inter-individual differences in inflammatory responses

Spondyloarthritis is a group of chronic inflammatory diseases that primarily affects axial or peripheral joints and is frequently associated with inflammation at non-articular sites. The disease is multifactorial, involving genetics, immunity and environmental factors, including the gut microbiota. In vivo, microbiome contributions are difficult to assess due to the multifactorial disease complexity. In a proof-of-concept approach, we therefore used a triple coculture model of immune-like, goblet and epithelial cells to investigate whether we could detect a differential impact from spondyloarthritis- vs. healthy-derived gut microbiota on host cell response. Despite their phylogenetic resemblance, flow cytometry-based phenotypic clustering revealed human-derived gut microbiota from healthy origin to cluster together and apart from spondyloarthritis donors. At host level, mucus production was higher upon exposure to healthy microbiota. Pro-inflammatory cytokine responses displayed more inter-individual variability in spondyloarthritis than in healthy donors. Interestingly, the high dominance in the initial sample of one patient of Prevotella, a genus previously linked to spondyloarthritis, resulted in the most differential host response upon 16 h host-microbe coincubation. While future research should further focus on inter-individual variability by using gut microbiota from a large cohort of patients, this study underscores the importance of the gut microbiota during the SpA disease course.

Novel Potassium-Competitive Acid Blocker, Tegoprazan, Protects Against Colitis by Improving Gut Barrier Function

Inflammatory bowel disease (IBD) is a chronic immune-mediated disorder characterized by prolonged inflammation of the gastrointestinal tract. IBD can result from gut barrier dysfunction, altered gut microbiota, and abnormal intestinal immunity induced by environmental factors in genetically susceptible individuals. Proton pump inhibitors (PPIs) such as rabeprazole are frequently employed for gastric acid inhibition. However, long-term PPI administration can alter the intestinal microbiome composition, possibly worsening IBD severity. The present study revealed that tegoprazan, a potassium-competitive acid blocker, significantly improved colitis in mice and enhanced the intestinal epithelial barrier function. Tegoprazan alleviated gut microbiota dysbiosis and enhanced the growth of Bacteroides vulgatus. In turn, B. vulgatus alleviated intestinal inflammation by inhibiting epithelial adhesion of pathogenic bacteria. Unlike rabeprazole, tegoprazan did not induce gut dysbiosis. Our findings provide novel insights into the potential role of tegoprazan as an intestinal protectant for IBD and as a therapeutic agent for gastric acid-related diseases.

Putative Pathobionts in HLA-B27-Associated Spondyloarthropathy

Spondyloarthritis (SpA) is a group of immune mediated inflammatory diseases with a strong association to the major histocompatibility (MHC) class I molecule, HLA-B27. Although the association between HLA-B27 and AS has been known for almost 50 years, the mechanisms underlying disease pathogenesis are elusive. Over the years, three hypotheses have been proposed to explain HLA-B27 and disease association: 1) HLA B27 presents arthritogenic peptides and thus creates a pathological immune response; 2) HLA-B27 misfolding causes endoplasmic reticulum (ER) stress which activates the unfolded protein response (UPR); 3) HLA-B27 dimerizes on the cell surface and acts as a target for natural killer (NK) cells. None of these hypotheses explains SpA pathogenesis completely. Evidence supports the hypothesis that HLA-B27-related diseases have a microbial pathogenesis. In animal models of various SpAs, a germ-free environment abrogates disease development and colonizing these animals with gut commensal microbes can restore disease manifestations. The depth of microbial influence on SpA development has been realized due to our ability to characterize microbial communities in the gut using next-generation sequencing approaches. In this review, we will discuss various putative pathobionts in the pathogenesis of HLA-B27-associated diseases. We pursue whether a single pathobiont or a disruption of microbial community and function is associated with HLA-B27-related diseases. Furthermore, rather than a specific pathobiont, metabolic functions of various disease-associated microbes might be key. While the use of germ-free models of SpA have facilitated understanding the role of microbes in disease development, future studies with animal models that mimic diverse microbial communities instead of mono-colonization are indispensable. We discuss the causal mechanisms underlying disease pathogenesis including the role of these pathobionts on mucin degradation, mucosal adherence, and gut epithelial barrier disruption and inflammation. Finally, we review the various uses of microbes as therapeutic modalities including pre/probiotics, diet, microbial metabolites and fecal microbiota transplant. Unravelling these complex host-microbe interactions will lead to the development of new targets/therapies for alleviation of SpA and other HLA-B27 associated diseases.

Effects of Smoking on Inflammatory Markers in a Healthy Population as Analyzed via the Gut Microbiota

The number of people who smoke has increased in recent years, and the incidence of smoking-related diseases increases annually. This study was conducted to explore whether smoking affects diseases via changes in the gut microbiota. We enrolled 33 smokers and 121 non-smokers. We collected fecal samples from all participants and performed whole-genome sequencing. Smoking significantly affected the gut microbiota. At the phylum through genus levels, the smokers' microbiotas showed slight changes compared with those of the non-smokers. The α- and β-diversities differed significantly between the smokers and non-smokers, and the smokers' gut microbiota compositions differed significantly from those of the non-smokers. At the species level, the relative abundances of Ruminococcus gnavus (P=0.00197) and Bacteroides vulgatus (P=0.0468) were significantly greater in the smokers than in the non-smokers, while the relative abundances of Faecalibacterium prausnitzii (P=0.0000052) and Akkermansia muciniphila (P=0.0057) were significantly lower in the smokers. Smoking increases inflammation in the body by inducing an increased abundance of proinflammatory bacteria. Non-smokers had higher abundances of anti-inflammatory microorganisms than did smokers; these microorganisms can produce short-chain fatty acids, which inhibit inflammation.

Bacteroides vulgatus diminishes colonic microbiota dysbiosis ameliorating lumbar bone loss in ovariectomized mice

There is a need to discover additional kinds of intestinal microbiota to supplement the probiotic-treatment of postmenopausal osteoporosis. Increasing evidence has indicated that Bacteroides vulgatus has potential as a probiotic for ameliorating postmenopausal bone loss. In this study, ovariectomized female C57/BL6 mice were treated with B. vulgatus ATCC 8482 gavage to investigate the differences in colonic microbiota composition, inflammation signal pathways, inflammatory cytokines, bone turnover markers, and lumbar vertebrae microstructure compared with the control group. Our results show that B. vulgatus ATCC 8482 diminished microbiota dysbiosis and subsequently down-regulated the colonic lipopolysaccharide/TLR-4/p-NF-κB pathway leading to decreased serum TNF-α. This reduced TNF-α/RANKL expression and induced ALP and Runx-2 expression in the 5th lumbar vertebra, leading to amelioration of bone loss and microstructure destruction in the lumbar vertebra of ovariectomized mice. Taken together, these results indicate that B. vulgatus could be a probiotic for treatment of postmenopausal lumbar osteoporosis.

The Association of Fecal Microbiota in Ankylosing Spondylitis Cases with C-Reactive Protein and Erythrocyte Sedimentation Rate

The purpose of this work was to identify the features of the gut microbiome in cases of ankylosing spondylitis (AS) testing positive for human leukocyte antigen- (HLA-) B27 and healthy controls (HCs) as well as to determine how bacterial populations were correlated with C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). Fecal DNA extracted from fecal samples from 10 AS cases and 12 HCs was subjected to 16S rRNA gene sequencing. The two research groups did not differ significantly regarding alpha diversity. By comparison to HCs, AS cases displayed a lower relative level of Bacteroidetes (P < 0.05), but a higher level of Firmicutes and Verrucomicrobia (P < 0.05). Furthermore, the correlation between the specific gut bacteria and ESR or CRP was investigated. At the phylum level, Firmicutes and Verrucomicrobia had a positive association with ESR and CRP, while Bacteroidetes exhibited an inverse correlation with ESR and CRP. Meanwhile, in terms of genus, Bacteroides had a positive association with ESR and CRP, whereas Ruminococcus and Parasutterella had an inverse correlation with ESR and CRP, and Helicobacter also displayed an inverse correlation with CRP. Such findings indicated dissimilarities between AS cases and HCs regarding the gut microbiome, as well as the existence of correlations between bacterial populations and both ESR and CRP.

Role of Human Leukocyte Antigens (HLA) in Autoimmune Diseases

Since the discovery of HLA 60 years ago, it has contributed to the understanding of the immune system as well as of the pathogenesis of several diseases. Aside from its essential role in determining donor-recipient immune compatibility in organ transplantation, HLA genotyping is meanwhile performed routinely as part of the diagnostic work-up of certain autoimmune diseases. Considering the ability of HLA to influence thymic selection as well as peripheral anergy of T cells, its role in the pathogenesis of autoimmunity is understandable. The aim of this paper is to provide a brief overview of the role and current clinical relevance of HLA-B27 in spondyloarthritis and HLA-B51 in Behçet's disease as well as HLA-DQ2/DQ8 in celiac disease and HLA-DRB1 in rheumatoid arthritis and to discuss possible future implications.

Role of Human Leukocyte Antigens (HLA) in Autoimmune Diseases

The aim of this review is to provide a brief overview of the role and current clinical relevance of HLA-B27 in spondyloarthritis and HLA-B51 in Behcet's disease as well as HLA-DQ2/DQ8 in celiac disease and HLA-DRB1 in rheumatoid arthritis and to discuss possible future implications.

HLA-B27 and human β2-microglobulin affect the gut microbiota of transgenic rats

The HLA-B27 gene is a major risk factor for clinical diseases including ankylosing spondylitis, acute anterior uveitis, reactive arthritis, and psoriatic arthritis, but its mechanism of risk enhancement is not completely understood. The gut microbiome has recently been shown to influence several HLA-linked diseases. However, the role of HLA-B27 in shaping the gut microbiome has not been previously investigated. In this study, we characterize the differences in the gut microbiota mediated by the presence of the HLA-B27 gene. We identified differences in the cecal microbiota of Lewis rats transgenic for HLA-B27 and human β2-microglobulin (hβ2m), compared with wild-type Lewis rats, using biome representational in situ karyotyping (BRISK) and 16S rRNA gene sequencing. 16S sequencing revealed significant differences between transgenic animals and wild type animals by principal coordinates analysis. Further analysis of the data set revealed an increase in Prevotella spp. and a decrease in Rikenellaceae relative abundance in the transgenic animals compared to the wild type animals. By BRISK analysis, species-specific differences included an increase in Bacteroides vulgatus abundance in HLA-B27/hβ2m and hβ2m compared to wild type rats. The finding that HLA-B27 is associated with altered cecal microbiota has not been shown before and can potentially provide a better understanding of the clinical diseases associated with this gene.

Smoking in inflammatory bowel disease: impact on disease course and insights into the aetiology of its effect

The chronic intestinal inflammation that characterises Crohn's disease and ulcerative colitis arises from a complex interplay between host genotype, the immune system, and the intestinal microbiota. In addition, environmental factors such as smoking impact on disease onset and progression. Individuals who smoke are more likely to develop Crohn's disease, and smoking is associated with recurrence after surgery and a poor response to medical therapy. Conversely, smoking appears protective against ulcerative colitis and smokers are less likely to require colectomy. The mechanism by which smoking exerts its impact on disease and the rational for the dichotomous effect in patients with Crohn's disease and ulcerative colitis is not clear. Recent evidence suggests that smoking induces alterations to both the innate and acquired immune system. In addition, smoking is associated with a distinct alteration in the intestinal microbiota both in patients with active Crohn's disease and healthy subjects.

Review article: Ulcerative colitis, smoking and nicotine therapy

BACKGROUND

Smoking is the best-characterised environmental association of ulcerative colitis (UC). Smoking has been observed to exert protective effects on both the development and progression of UC.

AIMS

To examine the association between UC and smoking, possible pathogenic mechanisms and the potential of nicotine as a therapeutic agent in the treatment of UC.

METHODS

A literature search was conducted through MEDLINE, using the MeSH search terms 'ulcerative colitis' and 'smoking' or 'nicotine'. Relevant articles were identified through manual review. The reference lists of these articles were reviewed to include further appropriate articles.

RESULTS

Ulcerative colitis is less prevalent in smokers. Current smokers with a prior diagnosis of UC are more likely to exhibit milder disease than ex-smokers and nonsmokers. There is conflicting evidence for smokers having reduced rates of hospitalisation, colectomy and need for oral corticosteroids and immunosuppressants to manage their disease. Multiple potential active mediators in smoke may be responsible for these clinical effects, including nicotine and carbon monoxide, but the precise mechanism remains unknown. Nicotine has demonstrated variable efficacy in the induction of remission in UC when compared to placebo and conventional medicines. Despite this, the high frequency of adverse events limits its clinical significance.

CONCLUSIONS

Nicotine's application as a therapeutic treatment in ulcerative colitis is limited. Presently, it may be an option considered only in selected cases of acute ulcerative colitis refractory to conventional treatment options. This review also questions whether nicotine is the active component of smoking that modifies risk and inflammation in ulcerative colitis.

Smokers with active Crohn's disease have a clinically relevant dysbiosis of the gastrointestinal microbiota

BACKGROUND

Patients with Crohn's disease (CD) have an intestinal dysbiosis with components of the microbiota exerting differential immune effects. Smoking is associated with an increased incidence of CD, more frequent relapse, and greater burden of surgery. This study aimed to investigate the association between smoking and the intestinal microbiota in patients with active CD.

METHODS

Patients with active CD (n = 103) and healthy controls (n = 66) were recruited and demographic and clinical data recorded including current smoking behavior. Fecal samples were collected and analyzed by fluorescent in situ hybridization using probes targeting 16S rRNA of bacteria previously shown to be altered in active CD (bifidobacteria, bacteroides, Clostridium coccoides-Eubacterium rectale, Escherichia coli, and Faecalibacterium prausnitzii).

RESULTS

In total, 29/101 (29%) patients with CD and 8/58 (14%) controls were current smokers (P = 0.032). Following multivariate analysis, smoking was found to have a significant and independent effect on the microbiota of patients with CD, with higher Bacteroides-Prevotella in smokers (38.4%) compared with nonsmokers (28.1%) (F((1,93)) = 12.6, P = 0.001). Healthy controls who smoked also had higher Bacteroides-Prevotella (34.8%) than nonsmokers (24.1%) (F((1,55)) = 4.5, P = 0.038). In the pooled multivariate analysis, patients with CD had higher bifidobacteria (F((1,156)) = 30.5, P < 0.001), higher Bacteroides-Prevotella (F((1,156)) = 6.5, P = 0.012), and lower F. prausnitzii (F((1,156)) = 3.8, P = 0.052) compared with healthy controls.

CONCLUSIONS

Smokers have luminal microbiota that consist of significantly higher bacteroides. Investigation of whether this is one mechanism through which the negative effects of smoking on CD are mediated is warranted.

Commensal Bacteroides species induce colitis in host-genotype-specific fashion in a mouse model of inflammatory bowel disease

The intestinal microbiota is important for induction of inflammatory bowel disease (IBD). IBD is associated with complex shifts in microbiota composition, but it is unclear whether specific bacterial subsets induce IBD and, if so, whether their proportions in the microbiota are altered during disease. Here, we fulfilled Koch's postulates in host-genotype-specific fashion using a mouse model of IBD with human-relevant disease-susceptibility mutations. From screening experiments we isolated common commensal Bacteroides species, introduced them into antibiotic-pretreated mice, and quantitatively reisolated them in culture. The bacteria colonized IBD-susceptible and -nonsusceptible mice equivalently, but induced disease exclusively in susceptible animals. Conversely, commensal Enterobacteriaceae were >100-fold enriched during spontaneous disease, but an Enterobacteriaceae isolate failed to induce disease in antibiotic-pretreated mice despite robust colonization. We thus demonstrate that IBD-associated microbiota alterations do not necessarily reflect underlying disease etiology. These findings establish important experimental criteria and a conceptual framework for understanding microbial contributions to IBD.

Commensal Bacteroides species induce colitis in host-genotype-specific fashion in a mouse model of inflammatory bowel disease

The intestinal microbiota is important for induction of inflammatory bowel disease (IBD). IBD is associated with complex shifts in microbiota composition, but it is unclear whether specific bacterial subsets induce IBD and, if so, whether their proportions in the microbiota are altered during disease. Here, we fulfilled Koch's postulates in host-genotype-specific fashion using a mouse model of IBD with human-relevant disease-susceptibility mutations. From screening experiments we isolated common commensal Bacteroides species, introduced them into antibiotic-pretreated mice, and quantitatively reisolated them in culture. The bacteria colonized IBD-susceptible and -nonsusceptible mice equivalently, but induced disease exclusively in susceptible animals. Conversely, commensal Enterobacteriaceae were >100-fold enriched during spontaneous disease, but an Enterobacteriaceae isolate failed to induce disease in antibiotic-pretreated mice despite robust colonization. We thus demonstrate that IBD-associated microbiota alterations do not necessarily reflect underlying disease etiology. These findings establish important experimental criteria and a conceptual framework for understanding microbial contributions to IBD.

The Role of HLA-B27 in Spondyloarthritis

This article summarizes the proceedings of a one-day international workshop held in July 2009 on the role of HLA-B27 in the pathogenesis of ankylosing spondylitis (AS) and related disorders. HLA-B27 is found in about 90% of patients with AS, with an odds ratio of about 100, but the mechanism underlying this association is not known. There are currently 3 major mechanistic hypotheses for this association: (1) T cell recognition of one or more B27 presented peptides; (2) B27 heavy-chain misfolding that induces an unfolded protein response; and (3) innate immune recognition of cell-surface expressed B27 heavy-chain dimers. None of these hypotheses accounts for the tissue specificity of the inflammation characteristic of AS. These hypotheses were discussed in the context of known epidemiologic, biochemical, structural, and immunologic differences among HLA-B27 subtypes; data from the HLA-B27 transgenic rat model of spondyloarthritis; the growing list of other genes that have been found to be associated with AS; and other data on the pathogenesis of spondyloarthritis. Proposed directions for future research include expanded efforts to define similarities and differences among the B27 subtypes; further development of animal models; identifying the interactions of B27 with the products of other genes associated with AS; and continued investigation into the pathogenesis of spondyloarthritis.

From HLA-B27 to spondyloarthritis: a journey through the ER

Almost four decades of research into the role of human leukocyte antigen-B27 (HLA-B27) in susceptibility to spondyloarthritis has yet to yield a convincing answer. New results from an HLA-B27 transgenic rat model now demonstrate quite convincingly that CD8(+) T cells are not required for the inflammatory phenotype. Discoveries that the HLA-B27 heavy chain has a tendency to misfold during the assembly of class I complexes in the endoplasmic reticulum (ER) and to form aberrant disulfide-linked dimers after transport to the cell surface have forced the generation of new ideas about its role in disease pathogenesis. In transgenic rats, HLA-B27 misfolding generates ER stress and leads to activation of the unfolded protein response, which dramatically enhances the production of interleukin-23 (IL-23) in response to pattern recognition receptor agonists. These findings have led to the discovery of striking T-helper 17 cell activation and expansion in this animal model, consistent with results emerging from humans with spondyloarthritis and the discovery of IL23R as an additional susceptibility gene for ankylosing spondylitis. Together, these results suggest a novel link between HLA-B27 and the T-helper 17 axis through the consequences of protein misfolding and open new avenues of investigation as well as identifying new targets for therapeutic intervention in this group of diseases.

Oxazolone-induced enterocolitis in zebrafish depends on the composition of the intestinal microbiota

BACKGROUND & AIMS

The pathogenesis of inflammatory bowel disease involves dysfunctional mucosal immune responses to commensal bacteria in genetically predisposed hosts. Interactions between host cells and bacteria are complicated, making it a challenge to assess their relative contribution to intestinal pathology. We developed a zebrafish model of enterocolitis to study these interactions.

METHODS

Enterocolitis was induced by intrarectal administration of the hapten oxazolone in adult wild-type and myeloperoxidase-reporter transgenic zebrafish in the presence or absence of antibiotics. Intestinal inflammation was evaluated by histological and flow cytometry analyses and cytokine profiling with quantitative real-time polymerase chain reaction. Changes in the composition of the intestinal microbiota following antibiotic administration were assessed by 16SrRNA sequencing and bacterial load was quantified by culture on nonselective media (colony-forming units).

RESULTS

In zebrafish, the infiltrate and severity of oxazolone-induced enterocolitis are influenced by the composition of the microbiota. Inflammation is characterized by granulocyte influx; epithelial damage; goblet cell depletion; and increased expression of interleukin-1beta, tumor necrosis factor-alpha, and interleukin-10. Zebrafish given vancomycin had bacterial populations dominated by Fusobacteria and reduced enterocolitis scores, intestinal damage, and percentages of infiltrating neutrophils and eosinophils. In contrast, zebrafish given colistin sulphate had a predominance of proteobacteria and reduced eosinophil and lymphocyte infiltration, but enterocolitis scores were not reduced.

CONCLUSIONS

In zebrafish with oxazolone-induced enterocolitis, components of the intestinal microbiota affect the severity and composition of the intestinal infiltrate.

Reduction of colonic inflammation in HLA-B27 transgenic rats by feeding Marie Ménard apples, rich in polyphenols

Inflammatory bowel diseases (IBD) are immunomediated ailments affecting millions of individuals. Although diet is regarded as an important factor influencing IBD, there are no accepted dietary recommendations presently available. We administered 7.6 % lyophilised apples obtained from two cultivars (Golden Delicious and Marie Ménard, low and high in polyphenols, respectively) to HLA-B27 transgenic rats which develop spontaneous IBD. After 3 months feeding, rats fed Marie Ménard apples had reduced myeloperoxidase activity (3.6 (sem 0.3) v. 2.2 (sem 0.2) U/g tissue; P < 0.05) and reduced cyclo-oxygenase-2 (P < 0.05) and inducible NO synthase gene expression (P < 0.01) in the colon mucosa and significantly less diarrhoea (P < 0.05), compared with control rats. Cell proliferation in the colon mucosa was reduced significantly by feeding Golden Delicious apples, with a borderline effect of Marie Ménard apples. Gene expression profiling of the colon mucosa, analysed using the Whole Rat Genome 4 x 44 K Agilent Arrays, revealed a down-regulation of the pathways of PG synthesis, mitogen-activated protein kinase (MAPK) signalling and TNFalpha-NF-kappaB in Marie Ménard-fed rats. In the stools of the animals of this group we also measured a significant reduction of bacteria of the Bacteriodes fragilis group. In conclusion, the administration of Marie Ménard apples, rich in polyphenols and used at present only in the manufacturing of cider, ameliorates colon inflammation in transgenic rats developing spontaneous intestinal inflammation, suggesting the possible use of these and other apple varieties to control inflammation in IBD patients.