Inflammatory bowel disease: immunodiagnostics, immunotherapeutics, and ecotherapeutics

[PPARgamma-gene therapy using an adenovirus vector for inflammatory bowel disease]

Peroxisome proliferator-activated receptor gamma (PPARgamma) is one of the nuclear receptors that plays a central role in adipocyte differentiation and insulin sensitivity. Recently, PPARgamma has also been recognized as a suppressive regulator of inflammation in the gastrointestinal tract. We summarize here the therapeutic benefits of PPARgamma-gene therapy using a replication-deficient adenovirus vector expressing PPARgamma (AdRGD-PPARgamma). We demonstrate that PPARgamma- protein levels are decreased in dextran sodium sulfate-induced colitis and restored in this model by intraperitoneal administration of the AdRGD-PPARgamma. Treatment with AdRGD-PPARgamma and PPARgamma-specific ligands resulted in a marked amelioration of tissue inflammation associated with the colitis, including reduction in intercellular adhesion molecule-1, cyclooxygenase-2, and tumor necrosis factor-alpha expression. Our results suggest that gene delivery of PPARgamma may open up a novel therapeutic approach for inflammatory bowel diseases such as Crohn's disease and ulcerative colitis.

Epidemiologic and clinical characteristics of children with newly diagnosed inflammatory bowel disease in Wisconsin: a statewide population-based study

OBJECTIVE

To define epidemiologic and clinical characteristics of newly diagnosed pediatric inflammatory bowel disease (IBD) in a large population-based model.

STUDY DESIGN

All pediatric gastroenterologists providing care for Wisconsin children voluntarily identified all new cases of IBD during a 2-year period. Demographic and clinical data were sent to a central registry prospectively for analysis.

RESULTS

The incidence of IBD in Wisconsin children was 7.05 per 100,000, whereas the incidence for Crohn's disease was 4.56, more than twice the rate of ulcerative colitis (2.14). An equal IBD incidence occurred among all ethnic groups, and children from sparsely and densely populated counties were equally affected. The majority (89%) of new IBD diagnoses were nonfamilial.

CONCLUSIONS

This study provides novel, prospective, and comprehensive information on pediatric IBD incidence within the United States. The surprisingly high incidence of pediatric IBD, the predominance of Crohn's disease over ulcerative colitis, the low frequency of patients with a family history, the equal distribution of IBD among all racial and ethnic groups, and the lack of a modulatory effect of urbanization on IBD incidence collectively suggest that the clinical spectrum of IBD is still evolving and point to environmental factors contributing to the pathogenesis.

Probiotics in inflammatory bowel disease: a critical review

Intestinal bacteria play a key role in inflammatory bowel disease. Probiotics attempt to modify disease by favourably altering bacterial composition, immune status, and inflammation. Until recently, probiotic therapy was considered 'folk' medicine, but there now is emerging interest on the part of the general public and scientific communities in the use of probiotics in human disease. This practical, evidence-based review examines probiotics as therapy for inflammatory bowel disease in humans. There are very few such published randomized clinical trials, but some data exist that possibly show an efficacy of probiotics as maintenance therapy in chronic relapsing pouchitis. Obstacles to providing probiotic therapy include selection of appropriate strains, poorly regulated probiotic quality standardization, processing and human biologic factors which impair probiotic viability, difficulty in maintaining new bacterial populations in the gut, and local product unavailability. Studies have focused on specific inflammatory bowel disease subgroups, limiting general applicability for the practitioner. Basic research highlights the importance of bacteria in these conditions, and the possibility that probiotics will modify physiological parameters. Well-designed, randomized clinical studies are still required to define the role of probiotics as therapeutic agents in inflammatory bowel disease.

Role of bacteria in experimental colitis

Epidemiology suggests some relationship between the establishment of the gut flora and the risk of developing inflammatory bowel disease. Unrestrained activation of the immune system against commensal bacteria appears to be responsible for the chronicity of these diseases. In animal models, broad-spectrum antibiotics reduce the bacterial load and militate against intestinal inflammation. Several bacterial species found in of the common microflora, including anaerobes, are able to invade the colonic wall when there is dysfunction of the colonic mucosal barrier. Most aerobes provoke focal areas of acute inflammation, but some anaerobes in the predominant flora induce diffuse a fibrogenic transmural response. Current research aims to identify the probiotics that might act against these bacteria. Colonization with specific probiotic strains, including a bacterium genetically engineered to secrete interleukin-10, prevents spontaneous colitis in susceptible mice. Certain lactobacilli exhibit anti-inflammatory properties naturally, i.e. without previous genetic manipulation. Prebiotics may increase colonization by lactobacilli and can prevent mucosal inflammation. Modulation of the gut flora with probiotics may prove useful in the prevention and control of inflammatory bowel diseases.

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.

Probiotics: a perspective on problems and pitfalls

Therapeutic manipulation of gut flora with probiotics promises to be a useful strategy for several disorders, including infectious, inflammatory and neoplastic conditions. However, there are large gaps in the knowledge of the normal flora and of the optimal use of probiotic products. At present, there is no reliable in vitro predictor of in vivo efficacy of putative probiotics. Indeed, probiotic performance should be defined in the context of the disease indication for which it is intended. This will require rigorous prospective clinical trials. In addition, guidelines for routine clinical use of probiotics are confounded by insufficient data on optimum strain selection, dose, delivery vehicle and monitoring. Before the promise can be fulfilled, problems and potential pitfalls with probiotic therapy need resolution.

In vivo mucosal delivery of bioactive human interleukin 1 receptor antagonist produced by Streptococcus gordonii

BACKGROUND

Interleukin-1 (IL-1) is a cytokine involved in the initiation and amplification of the defence response in infectious and inflammatory diseases. IL-1 receptor antagonist (IL-1ra) is an inactive member of the IL-1 family and represents one of the most potent mechanisms for controlling IL-1-dependent inflammation. IL-1ra has proven effective in the therapy of acute and chronic inflammatory diseases in experimental animal models and also in preliminary clinical trials. However, optimisation of therapeutic schedules is still needed. For instance, the use of drug delivery systems targeting specific mucosal sites may be useful to improve topical bioavailability and avoid side effects associated with systemic administration.

RESULTS

In order to develop systems for the delivery of IL-1ra to mucosal target sites, a Streptococcus gordonii strain secreting human IL-1ra was constructed. The recombinant IL-1ra produced by S. gordonii was composed of the four amino acid residues RVFP of the fusion partner at the N-terminus, followed by the mature human IL-1ra protein. RFVP/IL-1ra displayed full biological activity in vitro in assays of inhibition of IL-1beta-induced lymphocyte proliferation and was released by recombinant S. gordonii in vivo both at the vaginal and the gastrointestinal mucosa of mice. RFVP/IL-1ra appeared beneficial in the model of ulcerative colitis represented by IL-2-/- mice (knock-out for the interleukin-2 gene), as shown by the body weight increase of IL-2-/- mice locally treated with S. gordonii producing RFVP/IL-1ra.

CONCLUSIONS

These results indicate that recombinant S. gordonii can be successfully used as a delivery system for the selective targeting of mucosal surfaces with therapeutic proteins.

Indeterminate colitis

A diagnosis of Crohn's disease (CD) and ulcerative colitis (UC) is based on a combination of clinical, histologic, endoscopic, and radiologic data. The distinction between UC and CD can be difficult because of the lack of a differentiating single gold standard. Indeterminate colitis (IC) was introduced by pathologists for the diagnosis of surgical colectomy specimens showing an overlap between the features of UC and CD. The diagnosis of IC was based on macroscopic and microscopic features. The term indeterminate colitis is in recent years more widely applied to include all cases with endoscopic, radiographic, and histologic evidence of chronic inflammatory bowel disease confined to the colon, but without fulfilment of diagnostic criteria for UC and CD. As for UC and CD, the diagnosis of IC has therefore become a clinicopathologic diagnosis. IC is generally considered to be a temporary diagnosis. The clinical characteristics of patients with IC are, however, somewhat different from the characteristics of those with UC. Furthermore, serologic markers such as perinuclear antineutrophil cytoplasmic antibody and anti-Saccharomyces cerevisiae, which are strongly linked with UC and CD, are both negative in a subset of patients with IC. Therefore, the possibility that IC could be a separate entity must be investigated.

Dietary glycine prevents chemical-induced experimental colitis in the rat

BACKGROUND & AIMS

In this study, the effect of dietary glycine on experimental colitis induced by 2,4,6-trinitrobenzene sulphonic acid (TNBS) and dextran sulfate sodium (DSS) in the rat was evaluated.

METHODS

Male Wistar rats were fed a diet containing 5% glycine or casein as controls starting 3 days before experiments, and were given a single intracolonic injection of TNBS (50 mg/rat, dissolved in 50% ethanol). Similarly, some rats were given 3% DSS orally in drinking water for 5 days to induce colitis as a second model. The severity of colitis was evaluated pathologically, and tissue myeloperoxidase (MPO) activity was measured. Further, mRNA and protein levels for interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha, cytokine-induced neutrophil chemoattractant (CINC), and macrophage inflammatory protein (MIP)-2 were detected by reverse-transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA), respectively.

RESULTS

A diet containing glycine ameliorated diarrhea and body weight loss caused by TNBS, and improved both macroscopic and histologic scores of colitis significantly. TNBS-induced increases in MPO activities in the colonic tissue were blunted significantly in glycine-fed animals. Further, dietary glycine largely prevented increases in IL-1beta and TNF-alpha in the colon 2 days after TNBS, and TNBS induction of CINC and MIP-2 in the colonic tissue also was abrogated by glycine. Importantly, the protective effect of glycine was significant even when TNBS colitis was once established. Moreover, dietary glycine also was preventive in a second, DSS-induced colitis model.

CONCLUSIONS

Dietary glycine prevents chemical-induced colitis by inhibiting induction of inflammatory cytokines and chemokines. It is postulated that glycine may be useful for the treatment of inflammatory bowel diseases as an immunomodulating nutrient.

Inhibitory effect of probiotic Escherichia coli strain Nissle 1917 on adhesion to and invasion of intestinal epithelial cells by adherent-invasive E. coli strains isolated from patients with Crohn's disease

BACKGROUND

Pathogenic adherent-invasive Escherichia coli have been isolated from ileal lesions of Crohn's disease.

AIM

: To investigate the non-pathogenic E. coli strain Nissle 1917 (Mutaflor) as possible maintenance therapy in inflammatory bowel disease by testing its ability to prevent adherent-invasive E. coli strains from adhering to and invading human intestinal epithelial cells in vitro.

METHODS

Bacterial adhesion to and invasion of intestinal epithelial cells (Intestine-407) were assessed by counting the colony-forming units. The inhibitory effect of E. coli Nissle 1917 was determined after co-incubation with adherent-invasive E. coli strains or after pre-incubation of the intestinal epithelial cells with this probiotic strain prior to infection with adherent-invasive E. coli strains.

RESULTS

Strain Nissle 1917 exhibited dose- and time-dependent adherence to intestinal epithelial cells and inhibited the adhesion and invasion of various adherent-invasive E. coli strains. In co-infection experiments, the inhibitory effect on adherent-invasive E. coli adhesion reached 78-99.9%. Pre-incubation of intestinal epithelial cells with strain Nissle 1917 reduced adherent-invasive E. coli adhesion by 97.2-99.9%. The inhibitory effect on adherent-invasive E. coli invasion paralleled that on adhesion.

CONCLUSION

As strong and significant inhibitory effects on adherent-invasive E. coli adhesion and invasion were observed in co-infection and pre-infection experiments, E. coli Nissle 1917 could be efficient for preventive or curative probiotic therapy in patients with Crohn's disease.

Is nutrition an aetiological factor for inflammatory bowel disease?

Inflammatory bowel disease (IBD) is a chronic inflammatory process, the aetiology of which is complex and probably multi-factorial. Nutrition has been proposed to be an important aetiological factor for IBD. The present review critically examines the relationship between components of the diet (such as sugar, fat, fibre, fruit and vegetables, and protein) and IBD, including ulcerative colitis and Crohn's disease. In addition, it investigates the possible role of infant feeding practices in the development of IBD.

A novel PPAR gamma gene therapy to control inflammation associated with inflammatory bowel disease in a murine model

BACKGROUND & AIMS

Peroxisome proliferator-activated receptor gamma (PPAR gamma) is one of the nuclear receptors that plays a central role in adipocyte differentiation and insulin sensitivity. PPAR gamma has also recently been recognized as an endogenous regulator of intestinal inflammation. However, its levels are decreased during chronic inflammation in human and mice, thus limiting PPAR gamma ligand therapy during established disease. We sought to determine whether this decrease in PPAR gamma could be counteracted by a gene therapy approach.

METHODS

We characterized PPAR gamma levels in experimental colitis associated with dextran sodium sulfate administration to mice. In this model, the therapeutic benefits of PPAR gamma gene therapy using a replication-deficient adenovirus vector expressing PPAR gamma (Ad-PPAR gamma) was assessed.

RESULTS

PPAR gamma protein levels were decreased in whole colonic tissue, lamina propria lymphocytes, and peritoneal exudate cells during the course of colitis. PPAR gamma gene delivery using Ad-PPAR gamma restored responsiveness to a PPAR gamma ligand, resulting in marked amelioration of tissue inflammation associated with the colitis, which included attenuation of intercellular adhesion molecule-1, cyclooxygenase-2 and tumor necrosis factor-alpha expression.

CONCLUSIONS

Our results suggest that gene delivery of PPAR gamma can be used to restore and/or enhance endogenous anti-inflammatory processes that are normally operative in mammalian tissues such as in the colon.

Lipoxins: pro-resolution lipid mediators in intestinal inflammation

Many inflammatory processes are self-limiting, suggesting the existence of endogenous anti-inflammatory mechanisms. Among the lipid mediators generated during cell-cell interactions are the lipoxins (LX, including LXA(4) and B(4)), a distinct class of lipoxygenase-derived eicosanoids. Aspirin acetylation of cyclooxygenase 2 also promotes the generation of a series of 15-epimers of LXA(4), known as aspirin-triggered lipoxins (ATL), that may account for some of the bioactivity profile of aspirin and possibly of nonsteroidal anti-inflammatory drugs. Native LX are rapidly inactivated in vivo, and stable analogs of LXA(4), LXB(4), and ATL have been synthesized that possess enhanced bioavailability and potency as anti-inflammatory eicosanoids. Here, we review current in vitro, ex vivo, and in vivo evidence supporting cytoprotective and proresolution roles for LX in intestinal inflammation. LXA(4), LXA(4) analogs, and ATL analogs inhibit neutrophil chemotaxis, adhesion to epithelium, and epithelial cell chemokine release. In addition, LX blunt TNF-alpha-stimulated inflammatory responses, cyclooxygenase product generation, and epithelial cell apoptosis and are cytoprotective for cytokine-activated colonic mucosa ex vivo. LX, ATL, and synthetic LX analogs have already been demonstrated to possess impressive antiinflammatory and proresolution efficacy in a range of experimental models of inflammation in vivo. Further elucidation of the role of LX in intestinal epithelial cell biology and immune function may yield novel therapeutic approaches in inflammatory bowel disease and possibly gastrointestinal cancer.

Adenoviral transfer of the murine oncostatin M gene suppresses dextran-sodium sulfate-induced colitis

The use of biologics has promising potential in the treatment of inflammation. Studies with cultured cells and mouse models of disease have ascribed proinflammatory and anti-inflammatory functions to oncostatin M (OSM) and the related cytokine, interleukin-6 (IL-6). Here, we examined the effect of systemic administration of adenoviral (Ad) vectors encoding either murine OSM (AdMuOSM) or murine IL-6 (AdMuIL-6) in a mouse model of colitis. BALB/c mice were treated with a 5-day course of 4% dextran-sodium sulfate (DSS) water with or without administration of adenoviral vectors (i.p. or i.m. at 10(7) plaque-forming units [pfu]) given as a cotreatment or therapy. The deletion variant of the adenovirus served as a control for adenoviral infection. Colitis was assessed by (1) morphology (damage score, macrophage infiltration, apoptosis) and (2) function (myeloperoxidase activity and Ussing chamber analysis of epithelial ion transport). Infection with adenovirus alone did not affect colonic form or function. AdMuOSM (either i.p. or i.m.) significantly reduced the severity of the DSS-induced colitis. There was less damage, reduced macrophage infiltration, fewer apoptotic bodies, and a significant improvement in stimulated ion transport in colonic tissues from the treated mice. No benefit of AdMuIL-6 treatment was observed in this model system. Thus, systemic administration of AdMuOSM given as a cotreatment and to a lesser extent as a therapy was found to be of benefit in DSS-induced colitis, a murine model of inflammatory bowel disease (IBD).

The effect of non-pathogenic Escherichia coli in symptomatic uncomplicated diverticular disease of the colon

BACKGROUND

The effect of probiotics in symptomatic uncomplicated diverticular disease of the colon has not been followed.

DESIGN

Treatment (T1) with an intestinal antimicrobial (dichlorchinolinol) and absorbent (active coal tablets) was compared with the same set-up supplemented with non-pathogenic Escherichia coli(T2) in a prospective open trial.

SETTING

The study was performed at the outpatient department of a tertiary centre.

PARTICIPANTS

Fifteen subjects (5 males, 10 females) aged 68-91 years (average 74.8 years) presented with abdominal pain, irregular defecation, bloating and excessive flatulence. Diagnosis was established with colonoscopy, double-contrast barium enema, or both.

INTERVENTIONS

The T1 regimen was administered for 1 week. In the T2 regimen, the application of E. coli strain Nissle (Mutaflor capsules, 2.5 x 10(10) viable bacteria/capsule) followed immediately after T1 for an average of 5.2 weeks.

MAIN OUTCOME MEASURES

The lengths of two successive remissions with the T1 set-up were compared with the length of remission after T2. The intensity of symptoms before and after administration of the probiotic was also evaluated. RESULTS The lengths of two successive remissions after T1 amounted to 2.66 and 2.20 months (average 2.43 months). The average length of remission after T2 was 14.1 months (P < 0.001). All symptoms after T2 decreased significantly (P < 0.001).

CONCLUSIONS

Non-pathogenic strain Nissle significantly prolonged the remission period and improved the abdominal syndrome in symptomatic uncomplicated diverticular disease. A randomized, placebo-controlled study is recommended.

Gut flora in health and disease

The human gut is the natural habitat for a large and dynamic bacterial community, but a substantial part of these bacterial populations are still to be described. However, the relevance and effect of resident bacteria on a host's physiology and pathology has been well documented. Major functions of the gut microflora include metabolic activities that result in salvage of energy and absorbable nutrients, important trophic effects on intestinal epithelia and on immune structure and function, and protection of the colonised host against invasion by alien microbes. Gut flora might also be an essential factor in certain pathological disorders, including multisystem organ failure, colon cancer, and inflammatory bowel diseases. Nevertheless, bacteria are also useful in promotion of human health. Probiotics and prebiotics are known to have a role in prevention or treatment of some diseases.

Alterations of the dominant faecal bacterial groups in patients with Crohn's disease of the colon

BACKGROUND AND AIMS

The colonic microflora is involved in the pathogenesis of Crohn's disease (CD) but less than 30% of the microflora can be cultured. We investigated potential differences in the faecal microflora between patients with colonic CD in remission (n=9), patients with active colonic CD (n=8), and healthy volunteers (n=16) using culture independent techniques.

METHODS

Quantitative dot blot hybridisation with six radiolabelled 16S ribosomal ribonucleic acid (rRNA) targeting oligonucleotide probes was used to measure the proportions of rRNA corresponding to each phylogenetic group. Temporal temperature gradient gel electrophoresis (TTGE) of 16S rDNA was used to evaluate dominant species diversity.

RESULTS

Enterobacteria were significantly increased in active and quiescent CD. Probe additivity was significantly lower in patients (65 (11)% and 69 (6)% in active CD and quiescent CD) than in healthy controls (99 (7)%). TTGE profiles varied markedly between active and quiescent CD but were stable in healthy conditions.

CONCLUSION

The biodiversity of the microflora remains high in patients with CD. Enterobacteria were observed significantly more frequently in CD than in health, and more than 30% of the dominant flora belonged to yet undefined phylogenetic groups.

Role of enteric glial cells in inflammatory bowel disease

Enteric glial cells (EGCs) represent an extensive but relatively poorly described cell population within the gastrointestinal tract. Accumulating data suggest that EGCs represent the morphological and functional equivalent of CNS astrocytes within the enteric nervous system (ENS). The EGC network has trophic and protective functions toward enteric neurons and is fully implicated in the integration and the modulation of neuronal activities. Moreover, EGCs seem to be active elements of the ENS during intestinal inflammatory and immune responses, sharing with astrocytes the ability to act as antigen-presenting cells and interacting with the mucosal immune system via the expression of cytokines and cytokine receptors. Transgenic mouse systems have demonstrated that specific ablation of EGC by chemical ablation or autoimmune T-cell targeting induces an intestinal pathology that shows similarities to the early intestinal immunopathology of Crohn's disease. EGCs may also share with astrocytes the ability to regulate tissue integrity, thereby postulating that similar interactions to those observed for the blood-brain barrier may also be partly responsible for regulating mucosal and vascular permeability in the gastrointestinal tract. Disruption of the EGC network in Crohn's disease patients may represent one possible cause for the enhanced mucosal permeability state and vascular dysfunction that are thought to favor mucosal inflammation.

Leukocyte adsorptive apheresis for the treatment of active ulcerative colitis: a prospective, uncontrolled, pilot study

BACKGROUND AND AIMS

Active ulcerative colitis (UC) is characterized by infiltration of activated granulocytes and monocytes/macrophages (GM) within the large bowel mucosa. GM are major sources of inflammatory cytokines, and in UC they are elevated with increased survival time. We investigated the possibility that reducing the level of these cells might promote remission of active UC.

METHODS

Thirty-one patients with active corticosteroid refractory (refractory) UC, mean age of 42 years, duration of UC 6 years, clinical activity index (CAI) of 15, disease activity index (DAI) of 10, and 8 corticosteroid naive patients (naive), mean age of 36 years, duration of UC 2 years, CAI of 11, DAI of 8 were recruited. Each patient was treated with up to 11 cycles of granulocyte and monocyte adsorptive apheresis over 11 weeks by using a 335-mL capacity column filled with cellulose acetate beads that adsorb GM.

RESULTS

At week 12, 81% of refractory (CAI, 3; P < 0.001 and DAI, 4; P < 0.001) and 88% of naive (CAI, 1; P = 0.012 and DAI, 3; P = 0.011) patients achieved remission. Early relapse was not a feature, and at 12 months, 26 of 33 patients had maintained their remission. The treatment was well tolerated, and no severe side effects were observed.

CONCLUSIONS

The outcome of this study suggests that reduction of circulating granulocytes and monocytes results in alleviation of inflammation and promotes clinical remission in patients with severe active UC that has not responded to intensive corticosteroid treatment. These data suggest that formal controlled studies are warranted.

The host-microbe interface within the gut

Colonization with bacteria is critical for the normal structural and functional development and optimal function of the mucosal immune system. Unrestrained mucosal immune activation in response to bacterial signals from the lumen is, however, a risk factor for inflammatory bowel disease. Therefore, mucosal immune responses to indigenous flora require precise control and an immunosensory capacity for distinguishing commensals from pathogens. The use of germ-free animal models with selective colonization strategies combined with modern molecular techniques promises to clarify the molecular signals responsible for host-flora interactions in health and disease. At least half of the resident flora cannot be cultured by conventional techniques but are identifiable by molecular methods. Collectively, the resident flora represent a virtual organ with a metabolic activity in excess of the liver and a microbiome in excess of the human genome. An improved understanding of this hidden organ holds secrets relevant to several infectious, inflammatory and neoplastic disease mechanisms.

Inflammatory bowel disease: new insights into pathogenesis and treatment

Despite all the advances in our understanding of the pathophysiology of inflammatory bowel disease (IBD), we do not know the cause. Some of the most recently available data have been discussed here and yet it is now becoming increasingly accepted that immunogenetics play an important role in the predisposition, modulation, and perpetuation of IBD. The mucosal immune system is the central effector of intestinal inflammation and injury, with cytokines playing a central role in modulating inflammation. The role of intestinal milium, and enteric flora in particular, appears to be of greater significance than previously held. A review is made of the main areas of research exploring the mechanisms more intimately associated with the development of IBD, providing advances in the agents currently used, and identifying a host of new therapeutic agents potentially interacting with or interrupting specific targets in the genesis of IBD.

Variable response to probiotics in two models of experimental colitis in rats

BACKGROUND AND AIM

Clinical and experimental data suggest an important role for intestinal microflora in the pathogenesis of inflammatory bowel disease, and probiotics have been shown to ameliorate pouchitis. We evaluated the effect of different preparations of probiotic bacteria on experimental colitis in rats.

METHODS

Rats were treated daily intragastrically with two probiotic preparations, VSL#3 or strain GG (LGG), 7 days before induction of colitis and for another week thereafter. Colitis was induced by intracolonic administration of either dinitrobenzene sulfonic acid (DNBS) or iodoacetamide. Rats were killed 7 days after induction of colitis, the colon isolated, washed, weighed, lesion area measured, and mucosa processed for determination of myeloperoxidase (MPO) and nitric oxide synthase (NOS) activities and prostaglandin E2 (PGE2) generation.

RESULTS

In rats cotreated with VSL#3 or LGG and iodoacetamide, there was a significant decrease in the lesion area, 98 +/- 37 mm and 142 +/- 43 mm, respectively, as compared with 342 +/- 66 mm in the control group. Colonic wet weight significantly decreased to 1.3 +/- 0.1 g/10 cm and 1.4 +/- 0.1 g/10 cm, respectively, as compared with 1.7 +/- 0.1 g/10 cm. There was also a significant decrease in PGE2 generation, MPO, and NOS activities in the VSL#3 and LGG treatment groups. Presence of VSL#3 bacteria in the rat's colon was confirmed by culture and polymerase chain reaction (PCR) amplification. Neither probiotic preparation had an effect on the extent of colonic damage in DNBS-induced colitis.

CONCLUSION

Both VSL#3 and LGG significantly ameliorated colitis induced by the sulfhydryl-blocker iodoacetamide, but had no effect on the immune-mediated DNBS-induced colitis. The results suggest a possible role for sulfhydryl compounds in the protective effect of probiotic bacteria, and support their use in patients with inflammatory bowel disease.

The place of probiotics in human intestinal infections

A number of studies have been carried out on the effect of several probiotic species on treatment and prevention of intestinal infections. The most commonly used microorganisms are lactic-acid producing bacteria such as lactobacilli and bifidobacteria belonging to the human normal microflora. In vitro and animal studies have shown that probiotic microorganisms interfere with the colonisation of Helicobacter pylori and of enteropathogenic microorganisms. In humans the significance is more uncertain. Clinically significant benefits of probiotics have been demonstrated in the treatment of rotavirus induced diarrhoea and of Saccharomyces boulardii in the prevention of antibiotic-associated diarrhoea (AAD). In patients suffering from inflammatory bowel disease, several probiotic strains have been shown to be as effective as traditional medication in preventing relapses. Standardised and well performed studies are needed to elucidate further the mechanisms of action and the clinical significance of probiotics.

Antitumour necrosis factor therapy in Crohn's disease

The key role and contribution of various pro-inflammatory cytokines in common chronic inflammatory disorders such as inflammatory bowel disease (IBD) has been thoroughly investigated in recent years. Besides IL-1, TNF-alpha has been identified as one of the central immune mediators controlling inflammatory processes. Not surprisingly, neutralisation of these cytokines has been introduced into clinical research. Crohn's disease (CD) is one of the chronic inflammatory disorders where TNF-alpha seems to have a particularly important role. Neutralisation of this cytokine by specific antibodies, for example infliximab, has been shown recently to affect the clinical phenotype of this disorder. Other TNF-neutralising approaches such as etanercept have also been studied in patients with CD but with less successful outcomes. These new cytokine-targeting approaches have changed clinical medicine in the field of inflammatory disorders.

Probiotics and inflammatory bowel disease: from fads and fantasy to facts and future

Probiotic therapy is attracting the renewed interest of clinicians and basic investigators from a variety of traditional research disciplines. While the theoretical rationale for modifying the commensal flora of the gastrointestinal tract in specific circumstances appears sound and requires scientific pursuit, the field of probiotics has been clouded by exaggerated claims from some quarters. In general, many of the claims for therapeutic efficacy have not been well substantiated, but the field is now poised for evaluation within the realm of evidence-based medicine. Alterations in commensal bacterial flora within the gastrointestinal tract are associated with susceptibility to pathogens such as Clostridium difficile and there is persuasive evidence that the normal flora may participate in the pathogenesis of inflammatory bowel disease and other chronic diseases in genetically susceptible individuals. This has prompted various strategies to fortify or otherwise modify the enteric flora by dietary supplements containing probiotic formulations. Detailed comparisons of probiotic performance amongst different bacterial strains have not been performed in vivo in man or under clinical trial conditions, and the level of scientific characterisation of individual organisms has been variable. In addition, it cannot be assumed that the same probiotic is equally suitable for all individuals. Moreover, the heterogeneity of clinical disorders such as Crohn's disease and ulcerative colitis implies that strain-specific properties may be required for subset-specific categories of patients. While cocktails of probiotics offer convenience, therapeutic progress may require clarification of the mechanism of probiotic action and may be delayed until individual bacterial components have been rigorously studied. More importantly, the full potential of therapeutic manipulation of the enteric flora with probiotics or other strategies may not be optimally realised until the composition and metabolic activities of the normal flora are better understood.

Advances in the medical therapy of inflammatory bowel disease

The medical therapy of inflammatory bowel disease (IBD) has advanced significantly over the past year. Serologic markers of IBD have been further investigated and better defined, showing some discriminatory power with potential therapeutic implications. Studies of azathioprine and 6-mercaptopurine metabolites will make it easier and safer to use these effective drugs. Clinical data using other immunomodulators, including 6-thioguanine, mycophenolate mofetil, cyclosporine, and tacrolimus, continue to accrue with positive results. Infliximab has become even more firmly established as a reliable and effective therapy for active and fistulizing Crohn disease and may even be helpful in some patients with resistant ulcerative colitis. However, the recognition of potential complications of infliximab therapy has increased with the accumulated clinical experience. Results from trials of other biologic therapies directed at tumor necrosis factor alpha have been disappointing so far, although preliminary studies with biologics directed at adhesion molecules are encouraging. Growing appreciation of the importance of the enteric microflora in IBD has led to a considerable interest in manipulating intestinal bacteria for therapeutic benefit, and trials of both probiotics and prebiotics show promise.

Probiotics in clinical conditions

Probiotics are nonpathogenic microorganisms which, when ingested, exert a positive influence on the health or physiology of the host. Their mechanisms of action and effects are now studied using the same pharmacological approach as for drugs. This article summarizes and comments on evidence for the positive effects of probiotics in various clinical situations. Substantial evidence can be achieved when randomized controlled trials or meta-analyses show positive results. The clinical situations studied include prevention or treatment of antibiotic-associated disorders, gastroenteritis, and diarrhea, lactose intolerance, intestinal infections and colonization by pathogenic bacteria (including Helicobacter pylori and Clostridium difficile), traveler's diarrhea, irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), colonic cancer, urogenital infections and tumors, allergy (especially atopic eczema), vaccination, and cholesterol lowering. Current probiotics have an excellent safety record--another topic discussed in this article.

The transcription factor T-bet regulates mucosal T cell activation in experimental colitis and Crohn's disease

The balance between pro and antiinflammatory cytokines secreted by T cells regulates both the initiation and perpetuation of inflammatory bowel diseases (IBD). In particular, the balance between interferon (IFN)-gamma/interleukin (IL)-4 and transforming growth factor (TGF)-beta activity controls chronic intestinal inflammation. However, the molecular pathways that evoke these responses are not well understood. Here, we describe a critical role for the transcription factor T-bet in controlling the mucosal cytokine balance and clinical disease. We studied the expression and function of T-bet in patients with IBD and in mucosal T cells in various T helper (Th)1- and Th2-mediated animal models of chronic intestinal inflammation by taking advantage of mice that lack T-bet and retroviral transduction techniques, respectively. Whereas retroviral transduction of T-bet in CD62L(+) CD4(+) T cells exacerbated colitis in reconstituted SCID mice, T-bet-deficient T cells failed to induce colitis in adoptive transfer experiments suggesting that overexpression of T-bet is essential and sufficient to promote Th1-mediated colitis in vivo. Furthermore, T-bet-deficient CD62L(-) CD4(+) T cells showed enhanced protective functions in Th1-mediated colitis and exhibited increased TGF-beta signaling suggesting that a T-bet driven pathway of T cell activation controls the intestinal balance between IFN-gamma/IL-4 and TGF-beta responses and the development of chronic intestinal inflammation in T cell-mediated colitis. Furthermore, TGF-beta was found to suppress T-bet expression suggesting a reciprocal relationship between TGF-beta and T-bet in mucosal T cells. In summary, our data suggest a key regulatory role of T-bet in the pathogenesis of T cell-mediated colitis. Specific targeting of this pathway may be a promising novel approach for the treatment of patients with Crohn's disease and other autoimmune diseases mediated by Th1 T lymphocytes.

Regulation of alpha1-proteinase inhibitor release by proinflammatory cytokines in human intestinal epithelial cells

alpha1-Proteinase inhibitor (alpha1-PI) is the main serine proteinase inhibitor in human plasma. Apart from its synthesis in the liver, this anti-inflammatory protein is also synthesized by and excreted from human intestinal epithelial cells. Antiinflammatory actions of alpha1-PI are thought to be of relevance in the pathogenesis of inflammatory bowel disease. To investigate the role of macrophage-derived cytokines on alpha1-PI secretion from intestinal epithelial cells, we cultured Caco-2 cells until differentiation (14 days in culture) on permeable filter supports. Monolayers of differentiated Caco-2 cells were then co-cultured with human peritoneal macrophages, grown on plastic in the basolateral chamber. Under these conditions, alpha1-PI secretion from Caco-2 cells was enhanced by 45%, probably by a direct action of macrophage-derived cytokines on Caco-2 cells. To extend this observation further, we treated differentiated Caco-2 cells with macrophage-derived proinflammatory cytokines (IL-1beta, IL-8, TNF-alpha), as well as with lymphocyte-derived cytokines IL-2, IL-6 and IFN-gamma. As early as after 24h treatment, IL-2 and IL-8 induced a significant and dose-dependent increase of alpha-1-PI secretion into cell culture medium; this effect was completely reversed after immunoneutralization by the antibodies against IL-2 and IL-8 alpha1-PI secretion was only slightly decreased after treatment with IFN-gamma, while IL-1beta, IL-6 and TNF-alpha had no effect. alpha1-PI secretion correlated well with the expression of this protein in differentiated Caco-2 cells after cytokine treatment, as confirmed by Western blot. Our data imply that, in vitro, alpha1-PI secretion in enterocyte-like Caco-2 cells is up-regulated by IL-2 and IL-8. Our results suggest that both lymphocyte- and macrophage-derived cytokines regulate secretion of the anti-inflammatory protein alpha1-PI in intestinal epithelial cells.

Medical treatment of Crohn's disease

Crohn's disease is not medically (and is rarely surgically) curable. Patients do, however, live a normal life span. The goal of therapy is to optimize the quality of life, minimize disease activity and disease-related complications, and avoid therapeutic toxicity.

New developments in the treatment of inflammatory bowel disease

Therapy of inflammatory bowel disease (IBD) is rapidly changing with the advent of new discoveries in disease pathogenesis. The need for targeted therapies against the uncontrolled immuno-inflammatory reaction in IBD together with a prerequisite for minimal side effects is driving improvement in old medicines and is leading to the development of new drugs. This review introduces emerging changes in IBD treatment, such as improvements in conventional IBD medications or their use. Balsalazide, budesonide and changes in the use of 5-aminosalicylate (5-ASA) products and purine analogues, such as azathioprine, are discussed. Additionally, studies examining the role of drugs newly introduced into IBD therapy, such as mycophenolate mofetil (MMF), thalidomide and heparin, are stated. Emerging biological therapies, such as therapies against TNF, therapies to enhance anti-inflammatory cytokines, therapeutic manoeuvres to disrupt immune cell trafficking, anti-oxidant therapies, as well as non-conventional treatments, such as diet therapies, prebiotics and probiotics, and helminth therapies are discussed.

Crohn's disease

Crohn's disease is a disorder mediated by T lymphocytes which arises in genetically susceptible individuals as a result of a breakdown in the regulatory constraints on mucosal immune responses to enteric bacteria. Regulation of immune reactivity to enteric antigens has improved understanding of the pathophysiological mechanisms of Crohn's disease, and has expanded therapeutic options for patients with this disorder. Disease heterogeneity is probable, with various underlying defects associated with a similar pathophysiological outcome. Although most conventional drug treatments are directed at modification of host response, therapeutic manipulation of the enteric flora is becoming a realistic option.

Inflammation and colorectal cancer: IBD-associated and sporadic cancer compared

Ulcerative colitis and colonic Crohn's disease (together known as inflammatory bowel disease or IBD) are both associated with increased risk for colorectal cancer. Although it is customary to emphasize differences in the biology of IBD-associated and sporadic colon cancer, we believe these are far outweighed by the similarities. These similarities suggest that they might have similar pathogenic mechanisms. Because the normal colon is arguably in a continual state of low-grade inflammation in response to its microbial flora, it is reasonable to speculate that both IBD-associated and sporadic colon cancer might be the consequence of bacteria-induced inflammation.

Altered glycosylation in inflammatory bowel disease: a possible role in cancer development

Ulcerative colitis and Crohn's disease (together known as Inflammatory Bowel Disease or IBD) are both associated with increased risk for colorectal cancer. Although it is conventional to emphasise differences between IBD-associated and sporadic colon cancer, such as a lower rate of Adenomatosis Polyposis Coli mutations and earlier p53 mutations, IBD-associated cancer has a similar dysplasia-cancer sequence to sporadic colon cancer, similar frequencies of major chromosomal abnormalities and of microsatellite instability and similar glycosylation changes. This suggests that IBD-associated colon cancer and sporadic colon cancer might have similar pathogenic mechanisms. Because the normal colon is arguably in a continual state of low-grade inflammation in response to its microbial flora, it is reasonable to suggest that both IBD-associated and sporadic colon cancer may be the consequence of bacteria-induced inflammation. We have speculated that the glycosylation changes might result in recruitment to the mucosa of bacterial and dietary lectins that might otherwise pass harmlessly though the gut lumen. These could then lead to increased inflammation and/or proliferation and thence to ulceration or cancer. The glycosylation changes include increased expression of onco-fetal carbohydrates, such as the galactose-terminated Thomsen-Friedenreich antigen (Gal beta1,3GalNAc alpha-), increased sialylation of terminal structures and reduced sulphation. These changes cannot readily be explained by alterations in glycosyltransferase activity but similar changes can be induced in vitro by alkalinisation of the Golgi lumen. Consequences of these changes may be relevant not only for cell-surface glycoconjugates but also for intracellular glycoconjugates.

PPARgamma and inflammatory bowel disease: a new therapeutic target for ulcerative colitis and Crohn's disease

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a nuclear receptor that is known to play a central role in adipocyte differentiation and insulin sensitivity. Through work in several animal models of intestinal inflammation, it is now recognized that PPARgamma also inhibits tissue injury associated with immune activation. These studies point to PPARgamma as a novel anti-inflammatory mediator with broad therapeutic potential.