Intestinal microflora in human and experimental inflammatory bowel disease

Diet and Inflammatory Bowel Disease: What Quality Standards Should Be Applied in Clinical and Laboratory Studies?

Many patients suffering from inflammatory bowel disease (IBD) follow restrictive diets, as many respective recommendations circulate. Efforts are made to evaluate and summarize the published information, for example, in a recent consensus manuscript by the International Organization for the Study of IBD (IOIBD). However, the standards that should be applied to make claims about dietary effects are poorly defined. In this manuscript, the scientific basis of recommendations for nutritional interventions in IBD is analyzed. Epidemiological evidence on diet in IBD is always biased by numerous factors, and the number of robust dietary intervention studies is limited due to methodological difficulties. Therefore, animal models are used to test hypotheses with respect to dietary factors and intestinal inflammation. Naturally, animal models have limitations, and knowledge of key characteristics of colitis animal models is crucial to understand their advantages and disadvantages. In recent years the important role of the microbiota for IBD and dietary factors has been discovered. Microbiota data are added to many publications on IBD and nutrition. The quality of those data varies largely. Subsequently, quality standards for microbiota analyses also are discussed. Finally, quality requirements to be applied on recommendations for dietary changes in patients with IBD are suggested.

Elucidation of Proteus mirabilis as a Key Bacterium in Crohn's Disease Inflammation

BACKGROUND & AIMS

Proteus spp, Gram-negative facultative anaerobic bacilli, have recently been associated with Crohn's disease (CD) recurrence after intestinal resection. We investigated the genomic and functional role of Proteus as a gut pathogen in CD.

METHODS

Proteus spp abundance was assessed by ure gene-specific polymerase chain in 54 pairs of fecal samples and 101 intestinal biopsies from patients with CD and healthy controls. The adherence, invasion, and intracellular presence of 2 distinct isolates of Proteus mirabilis in epithelial cells were evaluated using immunofluorescence and electron microscopy. Intracellular gene expression profiles and regulated pathways were analyzed by RNA sequencing and KEGG pathway analysis. Biologic functions of 2 isolates of P mirabilis were determined by in vitro cell culture, and in vivo using conventional mice and germ-free mice.

RESULTS

Proteus spp were significantly more prevalent and abundant in fecal samples and colonic tissue of patients with CD than controls. A greater abundance of the genus Fusobacterium and a lesser abundance of the genus Faecalibacterium were seen in patients with CD with a high Proteus spp abundance. All 24 Proteus monoclones isolated from patients with CD belonged to members of P mirabilis lineages and 2 isolates, recovered from stool or mucosa, were used in further studies. Mice gavaged with either P mirabilis strain had more severe colonic inflammation. Co-culture of the isolates with epithelial cell lines showed bacterial adherence, invasion, increased production of pro-inflammatory cytokines IL-18 and IL-1α, and cell necrosis. Both isolates induced key pro-inflammatory pathways, including NOD-like receptor signaling, Jak-STAT signaling, and MAPK signaling, and induced pro-inflammatory genes and activated inflammation-related pathways in gnotobiotic mice.

CONCLUSIONS

P mirabilis in the gut is associated with CD and can induce inflammation in cells and animal models of colitis. P mirabilis can act as a pathobiont and play a crucial role in the pathogenesis of CD.

Biological pathways involved in the development of inflammatory bowel disease

Apoptosis, autophagy and necrosis are three distinct functional types of the mammalian cell death network. All of them are characterized by a number of cell's morphological changes. The inappropriate induction of cell death is involved in the pathogenesis of a number of diseases.Pathogenesis of inflammatory bowel diseases (ulcerative colitis, Crohn's disease) includes an abnormal immunological response to disturbed intestinal microflora. One of the most important reason in pathogenesis of chronic inflammatory disease and subsequent multiple organ pathology is a barrier function of the gut, regulating cellular viability. Recent findings have begun to explain the mechanisms by which intestinal epithelial cells are able to survive in such an environment and how loss of normal regulatory processes may lead to inflammatory bowel disease (IBD).This review focuses on the regulation of biological pathways in development and homeostasis in IBD. Better understanding of the physiological functions of biological pathways and their influence on inflammation, immunity, and barrier function will simplify our expertice of homeostasis in the gastrointestinal tract and in upgrading diagnosis and treatment.

Long-term alteration of intestinal microbiota in patients with ulcerative colitis by antibiotic combination therapy

Previous work has demonstrated that intestinal bacteria, such as Fusobacterium varium (F. varium), contribute to the clinical activity in ulcerative colitis (UC); thus, an antibiotic combination therapy (amoxicillin, tetracycline, and metronidazole (ATM)) against F. varium can induce and maintain UC remission. Therefore, we investigated whether ATM therapy induces a long-term alteration of intestinal microbiota in patients with UC. Patients with UC were enrolled in a multicenter, randomized, double-blind, placebo-controlled study. Biopsy samples at the beginning of the trial and again at 3 months after treatment completion were randomly obtained from 20 patients. The terminal restriction fragment length polymorphism (T-RFLP) in mucosa-associated bacterial components was examined to assess the alteration of the intestinal microbiota. Profile changes of T-RFLP in mucosa-associated bacterial components were found in 10 of 12 patients in the treatment group and in none of 8 in the placebo group. Dice similarity coefficients using the unweighted pair group method with arithmetic averages (Dice-UPGMA) confirmed that the similarity of mucosal microbiota from the descending colon was significantly decreased after the ATM therapy, and this change was maintained for at least 3 months. Moreover, at 3 months after treatment completion, the F. varium/β-actin ratio, examined by real-time PCR using nested PCR products from biopsy samples, was reduced less than 40% in 8 of 12 treated patients, which was higher, but not significantly, than in 4 of 8 patients in the placebo group. Together, these results suggest that ATM therapy induces long-term alterations in the intestinal microbiota of patients with UC, which may be associated, at least in part, with clinical effects of the therapy.

Profiling of ABC transporters during active ulcerative colitis and in vitro effect of inflammatory modulators

BACKGROUND AND AIM

Inflammatory bowel disease is characterized by chronic inflammation of the gastro intestinal tract that manifests as ulcerative colitis and Crohn's disease. Comparative expression profiles of selected ABC transporter genes during active ulcerative colitis and intestinal tuberculosis were studied, and we also investigated the effect of inflammatory modulators on the expression of the transporters in HT-29 cells.

METHODS

Using the GEO database, we selected ABC transporter genes that are differentially regulated during active UC and validated the altered expression in biopsies samples by RT-PCR. We also analyzed the effect of inflammatory modulators like TNF-α, lipopolysaccharides (LPS) and drugs (5-ASA, prednisolone and hydrocortisone) on the expression of ABCA1, ABCB8, ABCF2 and ABCC4 using HT-29 cells.

RESULTS

We observed significant up-regulation of ABCA1 and ABCA3 while ABCF2, ABCC6, ABCB8 and ABCC4 were down-regulated during UC. ABCC4 was up-regulated in ITB but down-regulated in UC, whereas others showed similar patterns both in UC and ITB. Upon stimulation of HT29 cells by TNF-α, up-regulation of ABCA1, ABCB8, ABCF2 and ABCC4 was seen, and further using inhibitors we found that it was mediated through reactive oxygen species or NF-kB or both. LPS caused a dose dependent and significant down-regulation of ABCB8, ABCF2 and ABCC4 without any effect on ABCA1. The cells treated with drugs 5-ASA, prednisolone and hydrocortisone, exhibited up-regulation of transporters only at a higher dose.

CONCLUSION

Altered expression of the above transporters may be associated with the disease. The study also hints at possible mechanisms of differential expression.

Does our food (environment) change our gut microbiome ('in-vironment'): a potential role for inflammatory bowel disease?

Human biology can only be fully assessed by combining an analysis of both the host and its surrounding environment. As a part of the environment, the human gastrointestinal tract hosts more than 100 trillion bacteria making up the gut microbiota. The human host provides a nutrient-rich environment while the microbiota provides indispensable functions that humans cannot exert themselves. Shifts in the bacterial makeup of the human gut microbiota have been associated with disorders such as inflammatory bowel disease (IBD), irritable bowel syndrome and obesity. However, since most bacteria inhabiting our gut are not cultivable to date, until recently little was known about their individual functions. Metagenomics, i.e. the analysis of the collective genomes present in a defined ecosystem, gives insight into these specific functions. The first extensive catalogue of the intestinal metagenome outnumbers the size of the human genome by a factor of 150. Recently, 3 distinct 'types' of gut composition within the human population have been highlighted. These so-called 'enterotypes' are characterized by the dominant genera (Bacteroides, Prevotella and Ruminococcus) and their co-occurring phylogenetic groups. In accordance with the previously described impact of nutritional behavior (diet, probiotics and prebiotics) on specific bacterial populations, an association has been observed between long-term dietary habits and enterotypes. This recent discovery, i.e. that belonging to one or the other enterotype might be modulated by the diet opens up new perspectives in the fields of IBD, nutrition and therapeutic strategies.

Association of a functional variant in the Wnt co-receptor LRP6 with early onset ileal Crohn's disease

Ileal Crohn's Disease (CD), a chronic small intestinal inflammatory disorder, is characterized by reduced levels of the antimicrobial peptides DEFA5 (HD-5) and DEFA6 (HD-6). Both of these α-defensins are exclusively produced in Paneth cells (PCs) at small intestinal crypt bases. Different ileal CD-associated genes including NOD2, ATG16L1, and recently the β-catenin-dependant Wnt transcription factor TCF7L2 have been linked to impaired PC antimicrobial function. The Wnt pathway influences gut mucosal homeostasis and PC maturation, besides directly controlling HD-5/6 gene expression. The herein reported candidate gene study focuses on another crucial Wnt factor, the co-receptor low density lipoprotein receptor-related protein 6 (LRP6). We analysed exonic single nucleotide polymorphisms (SNPs) in a large cohort (Oxford: n = 1,893) and prospectively tested 2 additional European sample sets (Leuven: n = 688, Vienna: n = 1,628). We revealed an association of a non-synonymous SNP (rs2302685; Ile1062Val) with early onset ileal CD (OR 1.8; p = 0.00034; for homozygous carriers: OR 4.1; p = 0.00004) and additionally with penetrating ileal CD behaviour (OR 1.3; p = 0.00917). In contrast, it was not linked to adult onset ileal CD, colonic CD, or ulcerative colitis. Since the rare variant is known to impair LRP6 activity, we investigated its role in patient mucosa. Overall, LRP6 mRNA was diminished in patients independently from the genotype. Analysing the mRNA levels of PC product in biopsies from genotyped individuals (15 controls, 32 ileal, and 12 exclusively colonic CD), we found particularly low defensin levels in ileal CD patients who were carrying the variant. In addition, we confirmed a direct relationship between LRP6 activity and the transcriptional expression of HD-5 using transient transfection. Taken together, we identified LRP6 as a new candidate gene in ileal CD. Impairments in Wnt signalling and Paneth cell biology seem to represent pathophysiological hallmarks in small intestinal inflammation and should therefore be considered as interesting targets for new therapeutic approaches.

Relationship between human intestinal dendritic cells, gut microbiota, and disease activity in Crohn's disease

BACKGROUND

Altered intestinal dendritic cell (DC) function underlies dysregulated T-cell responses to bacteria in Crohn's disease (CD) but it is unclear whether composition of the intestinal microbiota impacts local DC function. We assessed the relationship between DC function with disease activity and intestinal microbiota in patients with CD.

METHODS

Surface expression of Toll-like receptor (TLR)-2, TLR-4, and spontaneous intracellular interleukin (IL)-10, IL-12p40, IL-6 production by freshly isolated DC were analyzed by multicolor flow cytometry of cells extracted from rectal tissue of 10 controls and 28 CD patients. Myeloid DC were identified as CD11c(+) HLA-DR(+lin-/dim) cells (lin = anti-CD3, CD14, CD16, CD19, CD34). Intestinal microbiota were analyzed by fluorescent in situ hybridization of fecal samples with oligonucleotide probes targeting 16S rRNA of bifidobacteria, bacteroides-prevotella, C. coccoides-E. rectale, and Faecalibacterium prausnitzii.

RESULTS

DC from CD produced higher amounts of IL-12p40 and IL-6 than control DC. IL-6(+) DC were associated with the CD Activity Index (r = 0.425; P = 0.024) and serum C-reactive protein (CRP) (r = 0.643; P = 0.004). DC expression of TLR-4 correlated with disease activity. IL-12p40(+) DC correlated with ratio of bacteroides: bifidobacteria (r = 0.535, P = 0.003). IL-10(+) DC correlated with bifidobacteria, and IL-6(+) DC correlated negatively with F. prausnitzii (r = -0.50; P = 0.008). The amount of TLR-4 on DC correlated negatively with the concentration of F. prausnitzii.

CONCLUSIONS

IL-6 production by intestinal DC is increased in CD and correlates with disease activity and CRP. Bacterially driven local IL-6 production by intestinal DC may overcome regulatory activity, resulting in unopposed effector function and tissue damage. Intestinal DC function may be influenced by the composition of the commensal microbiota.

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.

Nutrition modulation of gastrointestinal toxicity related to cancer chemotherapy: from preclinical findings to clinical strategy

Chemotherapy-induced gut toxicity is a major dose-limiting toxicity for many anticancer drugs. Gastrointestinal (GI) complications compromise the efficacy of chemotherapy, promote overall malnutrition, aggravate cancer cachexia, and may contribute to worsened prognosis. The GI tract is an attractive target for nutrition modulation, owing to its direct exposure to the diet, participation in uptake and metabolism of nutrients, high rate of cell turnover, and plasticity to nutrition stimuli. Glutamine, ω-3 polyunsaturated fatty acids, and probiotics/prebiotics are therapeutic factors that potentially modulate GI toxicity related to cancer treatments. Preclinical and clinical evidence are reviewed to critically define plausible benefits of these factors and their potential development into adjuncts to cancer chemotherapy. Mechanisms underlying the action of these nutrients are being unraveled in the laboratory. Optimal strategies to translate these findings into clinical care still remain to be elucidated. Key questions that remain to be answered include the following: which nutrient or combination of nutrients is selected for which patient and chemotherapy regimen? What mechanisms are responsible for modulation, and how are nutrient(s) administered in a clinically optimal manner? Research exploring interactions between different nutrients in GI protection is ongoing and demands further understanding. How nutrition preparations given to chemotherapy-treated patients are formulated in terms of component selection and dose optimization should be carefully studied and justified.

Dietary polydextrose prevents inflammatory bowel disease in trinitrobenzenesulfonic acid model of rat colitis

Inflammatory bowel disease (IBD) is a multifactorial intestinal disorder that involves interactions among the immune system, genetic susceptibility, and environmental factors, especially the bacterial flora. Polydextrose, a polysaccharide constituted by 90% nondigestible and nonabsorbable soluble fibers, has several physiological effects consistent with those of dietary fibers, including proliferation of colon microflora. Because sulfasalazine presents serious side effects through long-term use at high doses, the aim of the present study was to evaluate the preventative effect of polydextrose on trinitrobenzenesulfonic acid-induced intestinal inflammation and its effects on the intestinal anti-inflammatory activity of sulfasalazine. Results indicated that polydextrose and its association with sulfasalazine present an anti-inflammatory effect that reduces myeloperoxidase activity, counteracts glutathione content, and promotes reductions in lesion extension and colonic weight/length ratio.

Could Helicobacter organisms cause inflammatory bowel disease?

The discovery of Helicobacter pylori sparked a revolution in the understanding and management of peptic ulcer disease and gastric cancer. Other Helicobacter species are recognized as important pathogenic agents in colitic diseases of rodents and primates, in particular Helicobacter bilis, Helicobacter fennelliae, Helicobacter hepaticus and Helicobacter trogontum. Helicobacter bilis and H. hepaticus are now routinely used to initiate rodent models of inflammatory bowel disease (IBD), particularly in immunocompromised hosts. Molecular evidence exists linking various non-pylori Helicobacter spp. with human IBD; however, attempts to culture organisms in this disease cohort have proved unsuccessful to date. Attributing causation has therefore proved elusive. Seven enterohepatic, non-pylori Helicobacter organisms have been successfully cultured from humans, namely Helicobacter canadensis, Helicobacter canis, Helicobacter cinaedi, H. fennelliae, Helicobacter pullorum, Helicobacter winghamensis and Helicobacter sp. flexispira taxon 8 (now classified as H. bilis). Of these, H. cinaedi and H. fennelliae are the closest to fulfilling Koch's postulates as causative agents in homosexual proctitis. The possibility that novel Helicobacter organisms have a role in the initiation of human IBD warrants further consideration and targeted investigations.

Pathogenic and protective roles of MyD88 in leukocytes and epithelial cells in mouse models of inflammatory bowel disease

BACKGROUND & AIMS

Toll-like receptors (TLR) are innate immune receptors involved in recognition of the intestinal microflora; they are expressed by numerous cell types in the intestine, including epithelial cells, myeloid cells, and lymphocytes. Little is known about the relative contributions of TLR signaling in distinct cellular compartments to intestinal homeostasis. We aimed to define the roles of TLR signals in distinct cell types in the induction and regulation of chronic intestinal inflammation.

METHODS

We assessed the roles of the shared TLR signaling adaptor protein, MyD88, in several complementary mouse models of inflammatory bowel disease, mediated by either innate or adaptive immune activation. MyD88-deficient mice and bone marrow chimeras were used to disrupt TLR signals selectively in distinct cellular compartments in the intestine.

RESULTS

MyD88-dependent activation of myeloid cells was required for the development of chronic intestinal inflammation. By contrast, although epithelial cell MyD88 signals were required for host survival, they were insufficient to induce intestinal inflammation in the absence of an MyD88-competent myeloid compartment. MyD88 expression by T cells was not required for their pathogenic and regulatory functions in the intestine.

CONCLUSIONS

Cellular compartmentalization of MyD88 signals in the intestine allow the maintenance of host defense and prevent deleterious inflammatory responses.

Newly developed antibiotic combination therapy for ulcerative colitis: a double-blind placebo-controlled multicenter trial

OBJECTIVES

Fusobacterium varium may contribute to ulcerative colitis (UC). We conducted a double-blind placebo-controlled multicenter trial to determine whether antibiotic combination therapy induces and/or maintains remission of active UC.

METHODS

Patients with chronic mild-to-severe relapsing UC were randomly assigned to oral amoxicillin 1500 mg/day, tetracycline 1500 mg/day, and metronidazole 750 mg/day, vs. placebo, for 2 weeks, and then followed up. The primary study end point was clinical response (Mayo score at 3 months after treatment completion) and secondary end points were clinical and endoscopic score improvements at 12 months. Anti-F. varium antibodies were measured by enzyme-linked immunosorbent assay.

RESULTS

Treatment and placebo groups each had 105 subjects. At the primary end point, response rates were significantly greater with antibiotics than with placebo (44.8 vs. 22.8%, P=0.0011). Endoscopic scores significantly improved at 3 months (P=0.002 vs. placebo). Remission rates were 19.0% (antibiotics) vs. 15.8% (placebo) at 3 months (P=0.59). At the secondary end point, response rates were significantly greater with antibiotics than with placebo (49.5 vs. 21.8%, respectively, P<0.0001). Endoscopic scores were significantly improved at 12 months after antibiotic treatment (P=0.002 vs. placebo). Remission rates had improved to 26.7% with antibiotics vs. 14.9% for placebo, at 12 months (P=0.041). F. varium antibody titers decreased in responders but not in nonresponders, and more in the antibiotic than in the placebo group. More pretreatment steroid-dependent UC patients discontinued corticosteroids after treatment completion (6 months: 28.6 vs. 11.8%, respectively, P=0.046; 9 months: 34.7 vs. 13.7%, respectively, P=0.019; and 12 months: 34.7 vs. 13.7%, respectively, P=0.019). These effects were greater in the subanalysis of the active group (Mayo scores of 6-12) than in that of total cases (0-12). No serious drug-related toxicities occurred.

CONCLUSIONS

The 2-week triple antibiotic therapy produced improvement, remission, and steroid withdrawal in active UC more effectively than a placebo.

The role of infection in the aetiology of inflammatory bowel disease

We have greatly increased our understanding of the genetics of inflammatory bowel disease (IBD) in the last decade; however, migrant studies highlight the importance of environment in disease risk. The possibility that IBD is an infection has been debated since the first description of Crohn's disease. Mycobacterium avium paratuberculosis was the first organism to be suggested as an IBD pathogen, and it has been argued that it fulfils Koch's postulates and could be designated the cause of Crohn's disease. Other organisms have been postulated as possible IBD pathogens, including various Helicobacter species, one of which has been identified in primate colitis;others are widely used in animal models of IBD. Adherent invasive Escherichia coli appear specific to ileal Crohn's disease and have been shown to induce the release of TNF-alpha, a key cytokine in IBD inflammation. The aim of this article is to give a concise overview of the infections postulated as being relevant to the onset of IBD. We will also briefly cover the immunology underpinning IBD, in addition to reviewing current knowledge regarding other microorganisms that are associated with modifying the risk of developing IBD. It may be that infectious organisms have an orchestrator role in the development of dysbiosis and subsequently IBD.

Mucosal bacterial microflora and mucus layer thickness in adolescents with inflammatory bowel disease

AIM: To assess the mucosa-associated bacterial microflora and mucus layer in adolescents with inflammatory bowel disease (IBD).

METHODS: Sixty-one adolescents (mean age 15 years, SD ± 4.13) were included in the study. Intestinal biopsies from inflamed and non-inflamed mucosa of IBD patients and from controls with functional abdominal pain were cultured under aerobic and anaerobic conditions. The number of microbes belonging to the same group was calculated per weight of collected tissue. The mucus thickness in frozen samples was measured under a fluorescent microscope.

RESULTS: The ratios of different bacterial groups in inflamed and non-inflamed mucosa of IBD patients and controls were specific for particular diseases. Streptococcus spp. were predominant in the inflamed mucosa of Crohn’s disease (CD) patients (80% of all bacteria), and Lactobacillus spp. were predominant in ulcerative colitis patients (90%). The differences were statistically significant (P = 0.01-0.001). Lower number of bifidobacteria was observed in the whole IBD group. A relation was also found between clinical and endoscopic severity and decreased numbers of Lactobacillus and, to a lesser extent, of Streptococcus in biopsies from CD patients. The mucus layer in the inflamed sites was significantly thinner as compared to controls (P = 0.0033) and to non-inflamed areas in IBD patients (P = 0.031).

CONCLUSION: The significantly thinner mucosa of IBD patients showed a predominance of some aerobes specific for particular diseases, their numbers decreased in relation to higher clinical and endoscopic activity of the disease.

The probiotic preparation, VSL#3 induces remission in patients with mild-to-moderately active ulcerative colitis

BACKGROUND & AIMS

Probiotics can maintain ulcerative colitis (UC) in remission effectively, but little is known of their ability to induce remission. We conducted a multicenter, randomized, double-blind, placebo-controlled trial of a high-potency probiotic, VSL#3, for the treatment of mild-to-moderately active UC.

METHODS

Adult patients with mild-to-moderate UC were assigned randomly to groups that were given 3.6 x 10(12) CFU VSL#3 (n = 77) or placebo (n = 70), twice daily for 12 weeks. The primary end point was a 50% decrease in the Ulcerative Colitis Disease Activity Index (UCDAI) at 6 weeks. The secondary end points included remission by 12 weeks and reduction in total individual UCDAI parameters from baseline at 12 weeks. Intention-to-treat analysis was performed.

RESULTS

At week 6, the percentage of patients with an improvement in UCDAI score that was greater than 50% was significantly higher in the group given VSL#3 (25; 32.5%) than the group given placebo (7; 10%) (P = .001). At week 12, there were 33 patients given VSL#3 (42.9%) who achieved remission, compared with 11 patients given placebo (15.7%) (P < .001). Furthermore, significantly more patients given VSL#3 (40; 51.9%) achieved a decrease in their UCDAI that was greater than 3 points, compared with those given placebo (13; 18.6%) (P < .001). The VSL#3 group had significantly greater decreases in UCDAI scores and individual symptoms at weeks 6 and 12, compared with the placebo group.

CONCLUSIONS

VSL#3 is safe and effective in achieving clinical responses and remissions in patients with mild-to-moderately active UC.

Phylogenetic analysis of inflammatory bowel disease associated Escherichia coli and the fimH virulence determinant

BACKGROUND

Evidence supports the role of adherent invasive Escherichia coli (AIEC) in the pathogenesis of inflammatory bowel disease (IBD). However, little is known about the phylogenetic structure and origin of this group of bacteria. Multi-locus sequence typing (MLST), and fimH sequence analysis were performed to elucidate the phylogenetic relationships between E. coli strains isolated from IBD tissue.

METHODS

Thirty-six E. coli isolated from IBD patients and healthy individuals were used. MLST analysis of the adk, fumC, gyrB, icd, mdh, purA, and recA housekeeping genes was performed. The fimH gene was also sequenced and phylogenetically analyzed. Biochemical profiling of strains were performed using the API 20 E system.

RESULTS

MLST analysis distinguished 9 new alleles and 11 new sequence types, nearly all of which belonged to IBD isolates. E. coli isolated from IBD patients were more likely to be grouped into separate clonal clusters by eBURST analysis of allelic profiles (P = 0.02). Sequencing of fimH placed putative AIEC strains into the same cluster with the uro-pathogenic E. coli CFT073 and the avian-pathogenic E. coli O1:K1:H7.

CONCLUSIONS

MLST analysis suggested that E. coli isolated from IBD patients did not evolve from a unique ancestral background. Together with the fimH sequence we conclude that AIEC represent a group of bacteria that have been able to take advantage of an "IBD microenvironment" and likely shares common genes with extraintestinal pathogens like uro-pathogenic CFT073 and avian-pathogenic O1:K1:H7 E. coli. Future research should focus on genes that are unique to AIEC.

Innate antimicrobial host defense in small intestinal Crohn's disease

Paneth cells (PCs) are specialized epithelial cells predominantly found in the small intestinal crypts of Lieberkuehn. They produce different broad spectrum antimicrobial peptides most abundantly the alpha-defensins HD-5 and -6 (DEFA5 und DEFA6). Both these PC products show a specific reduction in small intestinal Crohn's disease (CD) - a form of inflammatory bowel disease (IBD). Their decrease is independent of current inflammation and an association with a NOD2 frameshift mutation has been demonstrated. More recently, another independent and even more frequent mechanism has been found which is linked to diminished levels of the Wnt pathway transcription factor TCF7L2 (also known as TCF4). Besides regulating the expression of HD-5 and HD-6 as TCF4 target genes, the Wnt pathway also orchestrates Paneth cell differentiation and maturation and controls stem cell maintenance in the small intestine. Besides NOD2 (which is predominantly expressed in PC) and ATG16L1 (inter alia important in the exocytosis of PC products), TCF4 is the third gene which is associated with small intestinal CD and Paneth cell antimicrobial function. Thus, Paneth cells seem to be key player emphazising a paramount importance of antimicrobial host defense in small intestinal CD pathogenesis.

Influence of standard treatment on ileal and colonic antimicrobial defensin expression in active Crohn's disease

BACKGROUND

Crohn's Disease (CD), a chronic intestinal inflammation, is currently treated primarily by therapeutics which are directed against inflammatory responses. Recent findings though suggest a central role of the innate immune barrier in the pathophysiology. Important factors providing this barrier are antimicrobial peptides like the alpha- and beta-defensins. Little is known about in vivo effects of common drugs on their expression.

AIM

To analyse the influence of corticosteroids, azathioprine and aminosalicylate treatment on ileal and colonic antimicrobial peptides in active CD and also assess the role of inflammation.

METHODS

We measured the expression of antimicrobial peptides and pro-inflammatory cytokines in 75 patients with active CD.

RESULTS

Ileal and colonic alpha- and beta-defensins as well as LL37 remained unaffected by corticosteroids, azathioprine or aminosalicylate treatment. Additionally, we did not observe a negative coherency between Paneth cell alpha-defensins and any measured cytokines. HBD2 and LL37 unlike HBD1 levels were linked to inflammatory cytokines and increased in highly inflamed samples.

CONCLUSIONS

Current oral drug treatment seems to have no major effect on the expression of antimicrobial peptides. In contrast to HBD2 and LL37, ileal levels of HD5 and HD6 and colonic HBD1 level are independent of current inflammation. Innovative drugs should aim to strengthen protective innate immunity.

Negative interactions with the microbiota: IBD

Mucosal surfaces are colonized by a complex microbiota that provides beneficial functions under normal physiological conditions, but is capable of contributing to chronic inflammatory disease in susceptible individuals. Of the mucosal tissues, the mammalian intestine harbors an especially high number of microbes with a remarkable diversity. Inflammatory bowel disease (IBD) is a group of chronic relapsinginflammatory disorders of the intestinal mucosa. Evidence from human studies and animal models provides compelling support that intestinal microbes play a key role in disease pathogenesis. While the existence a specific causative pathogen is possible, it appears more likely that intestinal microbes normally present as commensal microbiota may trigger inflammation and perpetuate disease in genetically susceptible individuals. There may be also a shift in the makeup of the commensal flora to a nonphysiologic composition that is more prone to disease (termed dysbiosis). Evidence supports that genetic susceptibility stems from one or more defects in mucosal immune functions, including microbe recognition, barrier function, intercellular communication and antimicrobial effector mechanisms. It is quite plausible to imagine that the chronic inflammation of IBD may in some cases be a normal immune response to an abnormal adherent invasive microbiota and in other cases an over exuberant immune response to an otherwise normal commensal microbiota.

Probiotic E. coli treatment mediates antimicrobial human beta-defensin synthesis and fecal excretion in humans

Inducible epithelial human beta-defensins (hBD) play an important role in intestinal barrier function. In vitro studies showed that clinically effective probiotics induce antimicrobial hBD-2. Here, we aimed to assess the in vivo effect in healthy volunteers and also addressed how defensins affect probiotic survival. Symbioflor 2 containing one strain of several viable genotypes of Escherichia coli was administered to 23 healthy individuals. After 3 weeks, fecal hBD-2 peptide was increased in 78% (mean 3.7-fold; P<0.0001). Interestingly, the fecal hBD-2 peptide was still elevated 9 weeks after treatment (P=0.008). In vitro studies revealed that this effect was mediated by only one out of three tested E. coli genotypes and comparable to probiotic E. coli Nissle 1917 (10- to 15-fold). Functional assays showed that all tested bacteria were similarly killed by defensins allowing to speculate about a suicidal character of this effect. Defensin induction seems to be a common and important mechanism of probiotic treatment.

Crohn's disease-associated Escherichia coli LF82 aggravates colitis in injured mouse colon via signaling by flagellin

BACKGROUND

Ileal lesions in Crohn's disease patients are colonized by pathogenic adherent-invasive Escherichia coli (AIEC) that harbor various virulence factors involved in adhesion to and invasion of intestinal epithelial cultured cells. We investigated in a mouse model of colonic inflammation the behavior of virulent AIEC reference bacteria LF82 compared to that of nonflagellated LF82 mutants.

METHODS

BALBc/J mice with intact or dextran sulfate sodium (DSS)-injured colon were orally challenged daily with 10(8) bacteria. The severity of colitis was assessed by determining disease activity index, colonic histological score, and myeoloperoxidase activity. Flagellin receptor and cytokine expression was measured by reverse-transcriptase polymerase chain reaction (RT-PCR) in colonic tissue.

RESULTS

In contrast to nonpathogenic E. coli, virulent LF82 bacteria exacerbated colitis in DSS-treated mice, substantially reducing survival rate, greatly lowering stool consistency, inducing marked weight loss and increased rectal bleeding, and significantly increasing erosive lesions and mucosal inflammation. Nonflagellated LF82 mutants behaved like nonpathogenic E. coli K-12. Interestingly, oral infection with LF82 virulent bacteria, but not with a nonvirulent LF82 mutant, induced a 7.0-fold increase in the levels of TLR5 and a 3.1-fold increase in those of ipaf mRNA, which encode respectively membrane and cytosolic receptors involved in the recognition of flagellin. Hence, a 5.6-fold increase in IL-1beta and a 5.3-fold increase in mRNA of IL-6 were observed in mice challenged with AIEC LF82 bacteria.

CONCLUSIONS

Crohn's disease-associated virulent AIEC LF82 bacteria, via expression of flagella, are able to potentiate an inflammatory mucosal immune response involving increased expression of TLR5 and IPAF flagellin receptors.

Regulatory CD4+ CD25+ T cells prevent thymic dysfunction in experimental chronic colitis

Chronic colitis in T-cell deficient Tg epsilon26 mice develops due to a dysfunction of the thymus which generates colitogenic T cells after bone marrow (BM) transplantation. Regulatory CD4+ CD25+ T cells have been shown to prevent colitis in this model by normalizing the peripheral T-cell pool. We tested the hypothesis that T-cell normalization takes place in the thymus. Tg epsilon26 mice were transplanted with BM (BM-->Tg epsilon26 mice) and consequently received either CD4+ CD25+ or CD4+ CD25- cells from syngenic wild type mice. Furthermore, untransplanted Tg epsilon26 mice received CD4+ CD25+ or CD4+ CD25- cells or complete mesenteric lymph node cells. Transfer of regulatory. CD4+ CD25+ cells normalized the total number of thymocytes and the percentage and number of double positive CD4+ CD8+ cells in transplanted mice while percentage of single positive CD4+ and CD8+ thymocytes in BM-->Tg epsilon26 mice was reduced upon CD4+ CD25+ transfer. Timing of CD4+ CD25+ cell injection was important as transfer later than 7 days after BM transplantation failed to prevent abnormal thymic T-cell distribution in BM-->Tg epsilon26 mice. Isolated CD4+ CD25+ cell transfer without preceding BM transplantation failed to reconstitute thymic architecture. Differences of thymic cell composition could not be exclusively explained by presence or absence of colitis, respectively, because 19 days after BM transplantation when both groups showed no histological signs of colitis, animals transferred with CD4+ CD25+ T cells had a significantly higher percentage and number of CD4+ CD25+ thymocytes and CD4+ Foxp3+ cells than BM-->Tg epsilon26 mice. In conclusion, early CD4+ CD25+ cotransfer prevents thymic dysfunction which underlies immune-mediated bowel inflammation in BM-->Tg epsilon26 mice.

Role of bacteria in the etiopathogenesis of inflammatory bowel disease

Increased numbers of mucosa-associated Escherichia coli are observed in both of the major inflammatory bowel diseases, Crohn's disease (CD) and ulcerative colitis (UC). A potential pathophysiological link between the presence of pathogenic invasive bacteria and genetic host susceptibility of patients with ileal CD is suspected. In CD patients, with increased ileal expression of the CEACAM6 molecule acting as a receptor recognized by type 1 pilus bacterial adhesin, and with the identification of mutations in the NOD2-encoding gene, the presence of pathogenic invasive bacteria could be the link between abnormal ileal bacterial colonization and innate immune responses to invasive bacteria. In a susceptible host, the sequential etiological steps of the disease induced by adherent-invasive E. coli (AIEC) are: (1) abnormal colonization via binding to the CEACAM6 receptor, which is overexpressed in the ileal mucosa of CD patients; (2) ability to adhere to and to invade intestinal epithelial cells, which allows bacteria to cross the mucosal barrier; (3) survival and replication within infected macrophages in the lamina propria; and (4) induction of tumor necrosis factor-α secretion and granuloma formation.

Adherent-invasive Escherichia coli in inflammatory bowel disease

Increased numbers of mucosa-associated Escherichia coli are observed in both major inflammatory bowel diseases, Crohn's disease (CD) and ulcerative colitis (UC). With the identification of mutations in the NOD2-encoding gene in patients with CD and given the intracellular location of NOD2, the presence of pathogenic invasive bacteria could be the link between innate immune response to invasive bacteria and the development of the inflammation. Adherent-invasive E. coli (AIEC) are isolated from ileal biopsies of 36.4% of patients with ileal involvement of CD. These pathogenic E. coli colonize the intestinal mucosa by adhering to intestinal epithelial cells and are also true invasive pathogens, able to invade intestinal epithelial cells and to replicate intracellularly. AIEC strains also survive and replicate extensively within macrophages without inducing host cell death, and their high replication rates induce the secretion of large amounts of tumor necrosis factor alpha (TNF-alpha). There is also evidence suggesting that AIEC is involved in the formation of granulomas. The presence of AIEC is restricted to CD patients. Mucosa-associated E. coli in patients with UC can adhere to intestinal epithelial cells and induce the secretion of IL-8, but there is no evidence that these E. coli strains are invasive.

Role of mammalian chitinases in inflammatory conditions

It has been hypothesized that dysregulated host/microbial interactions play a pivotal role in the pathogenesis of inflammatory bowel disease. However, the exact mechanisms underlying the induction and perpetuation of the intestinal disorder are unclear. Recently, we unexpectedly discovered significantly upregulated gene expression of chitinase 3-like-1 in inflamed colon of the dextran sulfate sodium-induced colitis model by employing the DNA-microarray analysis. Chitinase 3-like-1 has a chitin binding ability, but lacks the enzymatic activity of lysing microbial cell wall. Chitinase 3-like-1 protein is mainly expressed in colonic epithelial cells and macrophages in the inflamed colon of dextran sulfate sodium-induced colitis. Chitinase 3-like-1, which can be upregulated after pro-inflammatory cytokine stimulation, possesses an ability to enhance the adhesion and internalization of intracellular bacteria into colonic epithelial cells. Most importantly, in vivo neutralization of chitinase 3-like-1 significantly suppressed the development of dextran sulfate sodium-induced colitis by dramatically decreasing the bacterial adhesion and invasion into colonic epithelial cells. Furthermore, anti-chitinase 3-like-1 antibody-treated mice exhibited a significantly lower load of Salmonella typhimurium in peripheral organs as compared to control rabbit IgG-treated mice. Recently, it has been reported that acidic mammalian chitinase is expressed in the setting of T helper-2-associated inflammation and subsequently induces airway hyperresponsiveness in allergic asthma patients. In addition, pan-chitinase inhibitor significantly ameliorates T helper-2-mediated inflammation and airway hypersensitivity. These studies provide to be a novel insight into the physiological role of mammalian chitinases in host/microbial interactions, and inhibition of chitinase activity would be considered a novel therapeutic strategy of allergic and inflammatory disorders.

Paneth cells, defensins, and the commensal microbiota: A hypothesis on intimate interplay at the intestinal mucosa

Mucosal surfaces are colonized by a diverse and dynamic microbiota. Much investigation has focused on bacterial colonization of the intestine, home to the vast majority of this microbiota. Experimental evidence has highlighted that these colonizing microbes are essential to host development and homeostasis, but less is known about host factors that may regulate the composition of this ecosystem. While evidence shows that IgA has a role in shaping this microbiota, it is likely that effector molecules of the innate immune system are also involved. One hypothesis is that gene-encoded antimicrobial peptides, key elements of innate immunity throughout nature, have an essential role in this regulation. These effector molecules characteristically have activity against a broad spectrum of bacteria and other microbes. At mucosal surfaces, antimicrobial peptides may affect the numbers and/or composition of the colonizing microbiota. In humans and other mammals, defensins are a predominant class of antimicrobial peptides. In the small intestine, Paneth cells (specialized secretory epithelial cells) produce high quantities of defensins and several other antibiotic peptides and proteins. Data from murine models indicate that Paneth cell defensins play a pivotal role in defense from food and water-borne pathogens in the intestinal lumen. Recent studies in humans provide evidence that reduced Paneth cell defensin expression may be a key pathogenic factor in ileal Crohn's disease, a subgroup of inflammatory bowel disease (IBD), and changes in the colonizing microbiota may mediate this pathogenic mechanism. It is also possible that low levels of Paneth cell defensins, characteristic of normal intestinal development, may predispose premature neonates to necrotizing enterocolitis (NEC) through similar close links with the composition of the intestinal microbiota. Future studies to further define mechanisms by which defensins and other host factors regulate the composition of the intestinal microbiota will likely provide new insights into intestinal homeostasis and new therapeutic strategies for inflammatory and infectious diseases of the bowel.

What is the origin of ulcerative colitis? Still more questions than answers

Despite more than a century of existence as a clinical entity, the true origin of ulcerative colitis still remains elusive. Several factors probably contribute to the development of this condition. Recently discovered technologies have clarified the role of bacterial species, which may account for intestinal dysbiosis, as a factor triggering ulcerative colitis. Genetic susceptibility together with abnormal innate immunoreactivity probably comprise the essential prerequisites for the initiation and perpetuation of ulcerative colitis. Although the genetic background has been more clearly recognised in patients with Crohn's disease than in those with ulcerative colitis, some candidate loci associated with ulcerative colitis have also been intensively studied. Additionally, environmental factors may interfere with inherent predispositions to ulcerative colitis, and either suppress or reinforce them. Whatever the origin, the search for the aetiology of ulcerative colitis must have the same goal: the improvement of treatment and the quality of life in patients with ulcerative colitis.

Differences between tissue-associated intestinal microfloras of patients with Crohn's disease and ulcerative colitis

A leading hypothesis for the role of bacteria in inflammatory bowel diseases is that an imbalance in normal gut flora is a prerequisite for inflammation. Testing this hypothesis requires comparisons between the microbiota compositions of ulcerative colitis and Crohn's disease patients and those of healthy individuals. In this study, we obtained biopsy samples from patients with Crohn's disease and ulcerative colitis and from healthy controls. Bacterial DNA was extracted from the tissue samples, amplified using universal bacterial 16S rRNA gene primers, and cloned into a plasmid vector. Insert-containing colonies were picked for high-throughput sequencing, and sequence data were analyzed, yielding species-level phylogenetic data. The clone libraries yielded 3,305 sequenced clones, representing 151 operational taxonomical units. There was no significant difference between floras from inflamed and healthy tissues from within the same individual. Proteobacteria were significantly (P = 0.0007) increased in Crohn's disease patients, as were Bacteroidetes (P < 0.0001), while Clostridia were decreased in that group (P < 0.0001) in comparison with the healthy and ulcerative colitis groups, which displayed no significant differences. Thus, the bacterial flora composition of Crohn's patients appears to be significantly altered from that of healthy controls, unlike that of ulcerative colitis patients. Imbalance in flora in Crohn's disease is probably not sufficient to cause inflammation, since microbiotas from inflamed and noninflamed tissues were of similar compositions within the same individual.

Culture-independent analyses of temporal variation of the dominant fecal microbiota and targeted bacterial subgroups in Crohn's disease

Gut microbiota shows host-specific diversity and temporal stability and significantly contributes to maintenance of a healthy gut. However, in inflammatory bowel disease, this microbiota has been implicated as a contributory factor to the illness. This study compared bacterial dynamics in Crohn's disease patients to those in a control group using a culture-independent method to assess the temporal stability, relative diversity, and similarity of the dominant fecal microbiota, Clostridium spp., Bacteroides spp., Bifidobacterium spp., and lactic acid bacteria spp. (LAB) for all individuals. Fecal samples were collected over several time points from individuals with Crohn's disease who were in remission (n = 11), from Crohn's disease patients who relapsed into an active Crohn's disease state (n = 5), and from a control group (n = 18). Denaturing gradient gel electrophoresis profiles were generated for the different microbial groups by specifically targeting different regions of the 16S rRNA gene and were compared on the basis of similarity and diversity. The temporal stability of dominant species for all Crohn's disease patients was significantly lower (P < 0.005) than that for the control group. Analysis of group-specific profiles for Bifidobacterium spp. found that they were similar in all samples, while the diversity of the LAB varied significantly between the groups, but temporal stability was not significantly altered. We observed significant changes in two functionally important mutualistic groups of bacteria, viz., Clostridium and Bacteroides spp., which may have implications for the host's gut health, since some genera are involved in production of short-chain fatty acid, e.g., butyrate.

Use of antibiotics in the treatment of inflammatory bowel disease

An increasing amount of evidence suggests that enteric flora may have a role in the pathogenesis of inflammatory bowel disease (IBD). Patients with IBD appear to have an altered composition of luminal bacteria that may provide the stimulus for the chronic inflammation characterizing IBD. The suspected role of bacteria in the pathogenesis of IBD provides the rationale for using agents, such as antibiotics, that alter the intestinal flora. However, there remains much uncertainty about the optimal use of antibiotics in the treatment of Crohn's disease, ulcerative colitis, and pouchitis. This article reviews the literature and presents a clinical model for the use of antibiotics in IBD.

Paneth cell defensins: key effector molecules of innate immunity

Antimicrobial peptides are fundamental effector molecules of innate immunity, utilized in host defence by virtually all organisms studied. These gene-encoded peptides have direct antibiotic activity against a wide range of bacteria and other microbes. In humans and other mammals, defensins are a predominant class of such peptides. In the mammalian small intestine, Paneth cells, specialized secretory epithelial cells located at the base of the crypt invaginations lining the intestinal wall, produce defensins and other antibiotic proteins. Recent investigations in murine models provide compelling support for the hypothesis that enteric defensins play a pivotal role in defence from food- and water-borne pathogens in the intestinal lumen. Investigations by others indicate that intestinal commensal bacteria are key factors in the pathogenesis of IBD (inflammatory bowel disease) in genetically susceptible humans. Recent studies provide evidence that reduced expression of Paneth cell defensins may be a key factor in the pathogenesis of ileal Crohn's disease, a subgroup of IBD. Future studies to further define the function and regulation of Paneth cell defensins will enhance our understanding of normal small bowel physiology, and probably contribute to a better understanding of the pathogenesis of inflammatory and infectious diseases of the bowel. Such knowledge may provide new therapeutic targets and strategies.

Reduced Paneth cell alpha-defensins in ileal Crohn's disease

The pathogenesis of Crohn's disease (CD), an idiopathic inflammatory bowel disease, is attributed, in part, to intestinal bacteria that may initiate and perpetuate mucosal inflammation in genetically susceptible individuals. Paneth cells (PC) are the major source of antimicrobial peptides in the small intestine, including human alpha-defensins HD5 and HD6. We tested the hypothesis that reduced expression of PC alpha-defensins compromises mucosal host defenses and predisposes patients to CD of the ileum. We report that patients with CD of the ileum have reduced antibacterial activity in their intestinal mucosal extracts. These specimens also showed decreased expression of PC alpha-defensins, whereas the expression of eight other PC products either remained unchanged or increased when compared with controls. The specific decrease of alpha-defensins was independent of the degree of inflammation in the specimens and was not observed in either CD of the colon, ulcerative colitis, or pouchitis. The functional consequence of alpha-defensin expression levels was examined by using a transgenic mouse model, where we found changes in HD5 expression levels, comparable to those observed in CD, had a pronounced impact on the luminal microbiota. Thus, the specific deficiency of PC defensins that characterizes ileal CD may compromise innate immune defenses of the ileal mucosa and initiate and/or perpetuate this disease.

Effectiveness of antibiotic combination therapy in patients with active ulcerative colitis: a randomized, controlled pilot trial with long-term follow-up

OBJECTIVE

It is proposed that Fusobacterium varium might be one of the elusive pathogenic factors in ulcerative colitis (UC). Our goal was to assess whether an antibiotic combination therapy against F. varium is effective for induction and maintenance of remission of UC.

MATERIAL AND METHODS

Twenty chronic, active UC patients with F. varium infection were enrolled consecutively and were randomly assigned to receive amoxicillin, tetracycline or metronidazole per os for 2 weeks (treatment group; n=10), or no antibiotics (control group; n=10). F. varium was sensitive to the antibiotics. Symptom assessment, endoscopic and histological evaluations were performed blind before enrollment at 3-5 months and 12-14 months after the treatment. Serum immunoglobulins to F. varium were measured using an enzyme-linked immunosorbent assay (ELISA). Immunohistochemical detection of F. varium in biopsy specimens was carried out using the avidin-biotin complex method.

RESULTS

The clinical activity, endoscopic and histological scores in the treatment group decreased significantly at 3-5 and 12-14 months after the end of treatment compared with those in the control group (p=0.001-0.036). The remission rate in the treatment group was higher than that in the control group (p=0.037). In addition, the titers of antibody to F. varium and the F. varium density in the mucosa decreased at both the short- and long-term follow-ups in the treatment group (p=0.0002-0.049). No serious drug-related toxicity was observed during the trial.

CONCLUSIONS

The 2-week antibiotic combination therapy against F. varium was effective and safe in patients with chronic, active ulcerative colitis in this long-term follow-up study.

Partially hydrolyzed guar gum down-regulates colonic inflammatory response in dextran sulfate sodium-induced colitis in mice

Partially hydrolyzed guar gum (PHGG), a water-soluble dietary fiber produced by a controlled partial enzymatic hydrolysis of guar gum beans, has various physiological actions. The aim of the present study was to elucidate the beneficial effects of PHGG on colonic mucosal damage and on the inflammatory response in a dextran sulfate sodium (DSS) colitis model. After 2 weeks of prefeeding of PHGG, acute colitis was induced with 8% DSS in female BALB/c mice. Colonic mucosal inflammation was evaluated clinically, biochemically and histologically. Mucosal protein contents and mRNA levels of tumor necrosis factor-alpha (TNF-alpha) were determined by immunoassay and reverse transcription polymerase chain reaction. Disease activity scores determined by weight loss, stool consistency and blood in stool in DSS-treated mice were significantly lower in the PHGG-treated mice compared with the control mice. Shortening of the colon was significantly reversed by PHGG. Histological study also showed a reduced infiltration of inflammatory cells, especially neutrophils, and mucosal cell disruption in PHGG-treated mice compared with the control mice. The increases in tissue-associated myeloperoxidase activity and thiobarbituric acid-reactive substances after DSS administration were both significantly inhibited by pretreatment with PHGG. Partially hydrolyzed guar gum also inhibited increases in intestinal TNF-alpha protein and mRNA expression after DSS administration, respectively. These results suggest that chronic ingestion of PHGG prevents the development of DSS-induced colitis in mice via the inhibition of mucosal inflammatory response.

Therapeutic effects of rectal administration of basic fibroblast growth factor on experimental murine colitis

BACKGROUND & AIMS

Basic fibroblast growth factor (bFGF) is a promising therapeutic agent for various diseases. It remains unclear, however, whether bFGF is effective for the treatment of inflammatory bowel disease. The aim of this study was to examine the efficacy of bFGF on 2 experimental murine colitis models and to investigate its molecular mechanisms.

METHODS

We evaluated the effects of human recombinant bFGF (hrbFGF) on mice with dextran sulfate sodium (DSS)-induced colitis and mice with trinitrobenzene sulfonic acid (TNBS)-induced colitis as well as normal mice. Body weight, survival rate, and histologic findings of the colonic tissues were examined. Gene expression of tumor necrosis factor (TNF)-alpha, cyclooxygenase (COX)-2, transforming growth factor (TGF)-beta, mucin 2 (MUC2), intestinal trefoil factor (ITF), and vascular endothelial growth factor (VEGF) in the colonic tissues was determined. The proliferation activity of hrbFGF on the colonic epithelium was evaluated by immunohistochemistry.

RESULTS

Rectal administration of hrbFGF ameliorated DSS-induced colitis in a dose-dependent manner. Gene expression of TNF-alpha was significantly reduced in the colonic tissues of mice with DSS-induced colitis treated with hrbFGF, whereas MUC2 and ITF messenger RNA expression was up-regulated. Rectal administration of hrbFGF significantly improved the survival rate of mice with TNBS-induced colitis and partially ameliorated colitis. hrbFGF significantly increased the number of Ki-67-positive cells in the colonic epithelium of normal mice, and up-regulated the gene expression of COX-2, TGF-beta, MUC2, ITF, and VEGF in the colonic tissues.

CONCLUSIONS

Rectal administration of bFGF might be a promising option for the treatment of inflammatory bowel disease.

Antibacterial and antimycobacterial treatment for inflammatory bowel disease

A variety of medicines have been used for the treatment of inflammatory bowel disease. Antibacterial therapy has demonstrated promise by both improving symptoms and causing disease remission. The mechanism is unknown, but may be related to either eliminating a key pathogen, decreasing the number of bacterial secretory products or defective particles, a direct immunomodulating effect, or reducing secondary bacterial invasion. Historically, a large number of bacterial species have been suspected as being major contributors to the etiology of inflammatory bowel disease, including ulcerative colitis and Crohn's disease. Many trials of antibacterial agents have been carried out in inflammatory bowel disease. Recently, treatments have focused on Gram-negative anaerobes and mycobacteria. The present paper briefly reviews antimicrobial and antimycobacterial treatments in inflammatory bowel disease.

Modern therapy for inflammatory bowel disease

Modern therapy for inflammatory bowel disease implies that therapy should be disease modifying rather than merely symptomatic. To achieve this goal, induction and maintenance of bowel healing are mandatory. Long-term bowel healing results in fewer hospitalizations and less surgery. Only immunosuppression therapy and biological approaches, or a combination of both, result in long-term healing of the bowel mucosa. Unsolved issues are when these drugs should be initiated and whether we should aim at eradicating the bowel inflammation from the onset of therapeutic intervention immediately following diagnosis. Identification of genetic and serologic parameters which allow prediction of the course of the disease would be useful for identifying patients who need aggressive treatment early in the disease. Once total control of the disease is achieved, long-term maintenance of a healed bowel is important. We hypothesize that changing the gut flora, e.g. using probiotics, may allow maintenance of bowel healing after induction with biologicals and immunosuppression.

Lactobacillus plantarum 299V in the treatment and prevention of spontaneous colitis in interleukin-10-deficient mice

Interleukin (IL)-10-deficient (IL-10-/-) mice develop colitis under specific pathogen-free (SPF) conditions and remain disease free if kept sterile (germ free [GF]). We used four different protocols that varied the time-points of oral administration of Lactobacillus plantarum 299v (L. plantarum) relative to colonization with SPF bacteria to determine whether L. plantarum could prevent and treat colitis induced by SPF bacteria in IL-10-/- mice and evaluated the effect of this probiotic organism on mucosal immune activation. Assessment of colitis included blinded histologic scores, measurements of secreted colonic immunoglobulin isotypes, IL-12 (p40 subunit), and interferon (IFN)-gamma production by anti-CD3-stimulated mesenteric lymph node cells. Treating SPF IL-10-/- mice with L. plantarum attenuated previously established colonic inflammation as manifested by decreased mucosal IL-12, IFN-gamma, and immunoglobulin G2a levels. Colonizing GF animals with L. plantarum and SPF flora simultaneously had no protective effects. Gnotobiotic IL-10-/- mice monoassociated with L. plantarum exhibited mild immune system activation but no colitis. Pretreatment of GF mice by colonization with L. plantarum, then exposure to SPF flora and continued probiotic therapy significantly decreased histologic colitis scores. These results demonstrate that L. plantarum can attenuate immune-mediated colitis and suggest a potential therapeutic role for this agent in clinical inflammatory bowel diseases.

Induction of mucosal immune responses by bacteria and bacterial components

Bacteria have well documented abilities to induce protective as well as pathogenic mucosal immune responses, with the type of response dependent on the genetically programmed balance of pro- and anti-inflammatory cytokines and T-lymphocyte subsets. Inflammatory bowel disease, especially Crohn disease and periodontal disease, appear to be overly aggressive cellular immune responses to some, but not all, normal resident bacteria. Recent evidence suggests that the balance of protective (probiotic) and aggressive commensal luminal bacterial species is an additional determinant of mucosal homeostasis (tolerance) versus pathogenic immune responses (loss of tolerance) and that this balance can be therapeutically manipulated. Mucosal pathogens elicit a characteristic profile of cytokines from epithelial cells, including chemokines that recruit effector cells to the site of invasion to clear the invading organism. The molecular mechanisms of epithelial attachment and invasion of bacterial pathogens (eg, Salmonella, Shigella, pathogenic Escherichia coli, and Yersinia) and the mechanisms of injury induced by Clostridium difficile toxins and Helicobacter pylori are beginning to be understood, as are the innate and cognate host immune responses to these organisms, leading to novel means to effectively block bacterial injury and induce protective immune responses through immunization.