Induction and modulation of gastrointestinal inflammation

Neuropeptides as pleiotropic modulators of the immune response

Although necessary to eliminate pathogens, inflammation can lead to serious deleterious effects in the host if left unchecked. During the inflammatory response, further damage may arise from potential autoimmune responses occurring when the immune cells and molecules that respond to pathogen-derived antigens also react to self-antigens. In this sense, the identification of endogenous factors that control exacerbated immune responses is a key goal for the development of new therapeutic approaches for inflammatory and autoimmune diseases. Some neuropeptides that are produced during the ongoing inflammatory response have emerged as endogenous anti-inflammatory agents that could collaborate in tuning the balanced steady state of the immune system. These neuropeptides participate in maintaining immune tolerance through two distinct mechanisms: by regulating the balance between pro-inflammatory and anti-inflammatory factors, and by inducing the emergence of regulatory T cells with suppressive activity against autoreactive T cell effectors. Indeed, a functioning neuropeptide system contributes to general health, and alterations in the levels of these neuropeptides and/or their receptors lead to changes in susceptibility to inflammatory and autoimmune diseases. Recently, we found that some neuropeptides also have antimicrobial and antiparasitic actions, suggesting that they could act as primary mediators of innate defense, even in the most primitive organisms. In this review, we use the vasoactive intestinal peptide as example of an immunomodulatory neuropeptide to summarize the most relevant data found for other neuropeptides with similar characteristics, including adrenomedullin, urocortin, cortistatin and ghrelin.

Teupolioside, a phenylpropanoid glycosides of Ajuga reptans, biotechnologically produced by IRBN22 plant cell line, exerts beneficial effects on a rodent model of colitis

The aim of the present study was to examine the effects of phenylpropanoid glycoside, teupolioside, biotechnologically produced by IRBN22 Ajuga reptans cell line, in rats subjected to experimental colitis. Colitis was induced in rats by intracolonic instillation of dinitrobenzene sulfonic acid (DNBS). Teupolioside was administered daily orally (0.2 or 2mgkg(-1)). On Day 4, animals were sacrificed and tissues were taken for histological and biochemical analysis. Four days after DNBS administration, colon TNF-alpha and IL-1beta productions were increased, associated with colon damage. Neutrophil infiltration, by myeloperoxidase activity, in the mucosa was associated with up-regulation of ICAM-1 and P-selectin and high levels of malondialdehyde. Immunohistochemistry for nitrotyrosine and poly (ADP-ribose) polymerase (PARP) showed an intense staining in the inflamed colon. Biochemical methods and zymography were used to analyze MMP-9 and -2 activities in colon tissues from DNBS-injured rats. Treatment with teupolioside significantly reduced the appearance of diarrhoea and the loss of body weight. This was associated with a remarkable amelioration in the disruption of the colonic architecture and a significant reduction in colonic myeloperoxidase activity and malondialdehyde levels. Teupolioside also reduced the pro-inflammatory cytokines release, the appearance of nitrotyrosine and PARP immunoreactivity in the colon and reduced the up-regulation of ICAM-1 and the expression of P-selectin. Therefore, teupolioside also reduced proMMP-9 and -2 activity induced in the colon by DNBS administration. The results of this study suggested that administration of teupolioside may be beneficial for treatment of inflammatory bowel disease.

Current view of the immunopathogenesis in inflammatory bowel disease and its implications for therapy

Although the aetiology of inflammatory bowel disease (IBD) remains unknown, the pathogenesis is gradually being unravelled, seeming to be the result of a combination of environmental, genetic, and immunological factors in which an uncontrolled immune response within the intestinal lumen leads to inflammation in genetically predisposed individuals. Multifactorial evidence suggests that a defect of innate immune response to microbial agents is involved in IBD. This editorial outlines the immunopathogenesis of IBD and their current and future therapy. We present IBD as a result of dysregulated mucosal response in the intestinal wall facilitated by defects in epithelial barrier function and the mucosal immune system with excessive production of cytokines growth factors, adhesion molecules, and reactive oxygen metabolites, resulting in tissue injury. Established and evolving therapies are discussed in the second part of this editorial and at the end of this section we review new therapies to modulate the immune system in patients with IBD.

The role of HLA-G in gastrointestinal inflammatory disease and malignancy

Human leukocyte antigen (HLA)-G has been shown to act as an immune-inhibitory molecule and to interfere with the normal functions of natural killer (NK) cells and T-cells, conferring a potential route for HLA-G expressing cells to escape host immune surveillance. These findings have led to the rather intense study of HLA-G expression in several different arenas, including organ transplantation, inflammatory conditions, and in a wide variety of neoplasms including hematolymphoid neoplasms, visceral carcinomas, gliomas, and dermal-based neoplasms. This review will focus on the role of HLA-G in inflammatory conditions of the bowel, which can serve as an initiator of neoplastic alterations, as well as examine HLA-G expression and function in a variety of gastrointestinal malignancies. Although there are only a limited number of studies that have examined HLA-G in the gastrointestinal tract, the role of HLA-G has been controversial in this organ system with conflicting results reported even within the same tumor type.

Glutamine-enriched total parenteral nutrition in patients with inflammatory bowel disease

BACKGROUND

Studies in animal models of inflammatory bowel disease (IBD) suggest that supplementation of total parenteral nutrition with glutamine (gln), a conditionally essential amino acid in catabolic conditions, increases gln plasma concentrations, reduces intestinal damage, improves nitrogen balance and may improve the course of the disease. However, human data supporting this assumption are missing.

METHODS

A total of 24 consecutive patients with an acute exacerbation of IBD (19 Crohn's disease; five ulcerative colitis) and scheduled for total parenteral nutrition (TPN) (>7 days) were randomised. Parallel to a standardised anti-inflammatory therapy, the patients received either a TPN with 1.5 g/kg body weight of a standard amino acid or an isonitrogenic, isocaloric TPN with 1.2 g/kg body weight of a standard amino acid and 0.3 g/kg L-alanine-L-glutamine. Primary end points were gln plasma concentrations and intestinal permeability assessed by urinary lactulose and D-xylose ratio.

RESULTS

Gln plasma levels did not differ significantly in either group throughout the study. Intestinal permeability did not change within 7 days either with or without gln supplementation (Delta-lactulose/xylose ratio: 0.01+/-0.05 (gln+) vs 0.02+/-0.1 (gln-)). The observed changes in inflammatory and nutritional parameters, and also disease activity, length of TPN and hospital stay, were independent of glutamine substitution. Five (41%) patients in the gln+ group and three (25%) patients in the gln- group needed surgical intervention.

CONCLUSION

Although limited by the sample size, these results do not support the hypothesis that glutamine substitution has an obvious biochemical or clinical benefit in patients with active IBD scheduled for total parenteral nutrition.

Leukocytapheresis is effective in inducing but not in maintaining remission in ulcerative colitis

GOALS AND BACKGROUND

Ulcerative colitis (UC) is a chronic inflammatory bowel disease characterized by dense infiltration of lymphocytes, plasma cells, neutrophils, and monocyte-macrophages into the colonic mucosa. Leukocytapheresis is a procedure for selectively removing white blood cells from withdrawn blood. It is used for the treatment of several autoimmune diseases. This study was performed to evaluate the effectiveness of leukocytapheresis for inducing and maintaining remission in corticosteroid-resistant UC, as compared with corticosteroid-responsive UC.

STUDY

Forty-five patients with active UC who were treated with a dose of 1 mg/kg per day or more of prednisolone given systemically for at least 2 weeks were evaluated. Twenty patients (6 males, 14 females) in whom improvement was induced only by high doses of prednisolone were allocated as the corticosteroid-responsive group. The other 25 patients (11 males, 14 females) who did not respond to the above-mentioned dose of prednisolone therapy were allocated as the corticosteroid-resistant group and received leukocytapheresis therapy once a week for 5 weeks. Of patients who had a remission, the corticosteroid-responsive group continued to have the conventional therapy and the corticosteroid-resistant group were given leukocytapheresis once every 4 weeks for at least 2 years as maintenance therapy.

RESULTS

Remission was induced by 5 weeks of leukocytapheresis in 23 of the 25 (92%) patients with corticosteroid-resistant active UC. The number of days required to achieve remission of UC was fewer in patients who received leukocytapheresis than in those who did not. Follow-up study of the patients who had remission showed similar relapse rates at 2 years in the patients who received leukocytapheresis and those given high doses of prednisolone alone.

CONCLUSIONS

Leukocytapheresis is an effective treatment of acute corticosteroid-resistant UC but does not prevent the recurrence of UC.

L-Selectin, α4β1, and α4β7 Integrins Participate in CD4+ T Cell Recruitment to Chronically Inflamed Small Intestine

CD4+ T cells are essential for development and perpetuation of Crohn's disease, a chronic immune-mediated condition that affects primarily the small intestine. Using novel models of Crohn's disease-like ileitis (i.e., SAMP1/YitFc and CD4+ T cell transfer models), we have begun to understand the adhesive pathways that mediate lymphocyte trafficking to the chronically inflamed small bowel. Expansion of the CD4/beta7+ population and increased mucosal addressin cell adhesion molecule-1 (MAdCAM-1) expression were observed within the intestinal lamina propria with disease progression. However, Ab blockade of the beta7 integrin, the alpha4beta7 heterodimer, MAdCAM-1, or L-selectin did not attenuate inflammation. Blockade of two pathways (L-selectin and MAdCAM-1 or alpha4 integrins) was required to improve ileitis. Further analyses showed that 55 +/- 7% of the mesenteric lymph node alpha4beta7+CD4 expressed L-selectin. These L-selectin+ T cells were the main producers of TNF-alpha and the predominant ileitis-inducing subpopulation. Mechanistically, combined blockade of L-selectin and MAdCAM-1 depleted the intestinal lamina propria of CD4+ T cells that aberrantly coexpressed alpha4beta7 and alpha4beta1 integrins, markedly decreasing local production of TNF-alpha and IFN-gamma. Thus, pathogenic CD4+ T cells not only use the physiologic alpha4beta7/MAdCAM-1 pathway, but alternatively engage alpha4beta1 and L-selectin to recirculate to the chronically inflamed small intestine.

Colonic bacterial superantigens evoke an inflammatory response and exaggerate disease in mice recovering from colitis

BACKGROUND & AIMS

There is renewed interest in commensal bacteria as triggers of idiopathic disease, a concept that is prominent in inflammatory bowel disease (IBD). Here the effect of intracolonic instillation of Staphylococcus aureus enterotoxin B (SEB), a model superantigen (SAgs: potent T-cell stimuli), into mice was examined.

METHODS

Mice (Balb/c, severe combined immunodeficient [SCID], V beta 8(+) ovalbumin transgenic [OVA-Tg], interleukin 10 [IL-10] knockout [KO]) received a single intrarectal (IR) dose of SAg and colonic form (histology, myeloperoxidase [MPO] activity) and function (ion transport) were assessed 12-72 hours later. In subsequent studies the potential for SEB to reactivate disease in mice recovering from dextran sodium sulfate (DSS)-induced colitis (5 days at 4% [wt/vol] followed by 14 days normal water) was examined.

RESULTS

SEB-treated Balb/c mice displayed a time- and dose-dependent colonic inflammation (increased MPO, histologic damage score, and macrophage number). Similar events occurred in response to other SAgs, namely S. aureus enterotoxin A (SEA) and Yersinia pseudotuberculosis mitogen. Ion transport, the driving force for water movement, was unaffected by SEB treatment. SCID mice developed no inflammation after IR SEB delivery, whereas OVA Tg mice displayed enhanced responsiveness. Although SEB treatment of IL-10 KO mice did elicit a response, the inflammation was transitory and did not hasten the spontaneous colitis seen in these mice. Finally, mice recovering from DSS-induced colitis showed a worsening of the disease when challenged with SEB; IR SEB evoked significant increases in MPO, macrophage infiltration, T-cell activation (i.e., CD25 expression), and perturbed epithelial ion transport.

CONCLUSIONS

Lumen-derived bacterial SAgs can elicit a local inflammation and aggravate enteric inflammatory disorders in which they were not the causative agent.

PACAP in immunity and inflammation

The pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide belonging to the VIP/secretin/glucagon family of peptides, produced by the lymphoid cells, which exerts a wide spectrum of immunological functions controlling the homeostasis of immune system through different receptors expressed in various immunocompetent cells. In the last decade, PACAP has been clearly identified as a potent anti-inflammatory factor that exerts its function by regulating the production of both anti- and proinflammatory mediators. In this sense, PACAP prevents death by septic shock, an acute inflammatory disease with a high mortality. In addition, PACAP regulates the expression of costimulatory molecules, inasmuch as this related to the modulation in the shift from Th1 towards Th2 differentiation. We recently reported that PACAP prevents the deleterious effects of arthritis by downregulating both inflammatory and autoimmune components of the disease. Therefore, PACAP and analogs have been proposed as very promising candidates, alternative to other existing treatments, for treating acute and chronic inflammatory and autoimmune diseases, such as septic shock, arthritis, multiple sclerosis, Crohn's disease, or autoimmune diabetes.

Emergence of perianal fistulizing disease in the SAMP1/YitFc mouse, a spontaneous model of chronic ileitis

BACKGROUND & AIMS

SAMP1/Yit mice spontaneously develop chronic terminal ileitis, reminiscent of the human disease described by Crohn et al. in 1932. Several new phenotypic features have appeared in our colony after more than 20 generations of brother-sister mating. In this report, we describe the distinguishing features of the SAMP1/YitFc substrain at the University of Virginia, compared with the Japanese SAMP1/Yit parental strain.

METHODS

A colony of SAMP1/Yit mice was established at the University of Virginia in 1996, from 2 breeding pairs obtained from Japan. A systematic characterization of their phenotypic and immunologic characteristics was performed at 4, 10, 40, and more than 60 weeks of age.

RESULTS

The following differences were observed: (1) SAMP1/YitFc mice displayed established ileitis as early as 10 weeks of age, (2) the incidence of skin lesions inversely correlated with the occurrence of intestinal inflammation, (3) mice develop chronic ileitis with prominent muscular hypertrophy and focal collagen deposition in inflamed segments, (4) mesenteric lymph node lymphocytes acquired an activated phenotype coincident with disease progression, (5) high interferon-gamma production was detected by 4 weeks of age and preceded the onset of ileitis, and (6) a subgroup of mice (approximately 5%) developed perianal disease with ulceration and fistulae.

CONCLUSIONS

The SAMP1/YitFc substrain exhibits unique characteristics when compared with the original Japanese strain. Of particular interest is the emergence of perianal fistulizing disease, to our knowledge the first report of such occurrence in an animal model of inflammatory bowel disease.

Effect of laparoscopy on immune function

BACKGROUND

Laparoscopic surgery is believed to lessen surgical trauma and so cause less disturbance of immune function. This may contribute to the rapid recovery noted after many laparoscopic operations. Preservation of both systemic and intraperitoneal immunity is particularly important in surgery for sepsis or cancer and so an understanding of the impact of laparoscopy on immune function is relevant.

METHODS

Literature on immunological changes following laparoscopy and open surgery was identified from Medline, along with cross-referencing from the reference lists of major articles on the subject.

RESULTS AND DISCUSSION

Despite a few contradictory reports, systemic immunity appears to be better preserved after laparoscopic surgery than after open surgery. However, the local intraperitoneal immune system behaves in a particular way when exposed to carbon dioxide pneumoperitoneum; suppression of intraperitoneal cell-mediated immunity has been demonstrated in a number of studies. This feature may be clinically important and should be acknowledged when considering laparoscopic surgery in patients with malignancy or sepsis.

Probiotic impact on microbial flora, inflammation and tumour development in IL-10 knockout mice

BACKGROUND

The enteric bacterial flora has been implicated in the pathogenesis of enterocolitis and colon cancer in C57BL/6 IL-10 knockout mice. Probiotic Lactobacilli modify the enteric flora and are thought to have a beneficial effect on enterocolitis. We conducted a controlled feeding trial in IL-10 knockout mice using the probiotic Lactobacillus salivarius ssp. salivarius UCC118.

AIM

To determine the effect of probiotic consumption on the gastrointestinal microflora, tumour development and colitis in IL-10 knockout mice.

METHODS

Twenty IL-10 knockout mice were studied (10 consumed probiotic organisms in milk and 10 consumed unmodified milk) for 16 weeks. Faecal microbial analysis was performed weekly to enumerate excretion of the probiotic UCC118, total lactobacilli, Clostridium perfringens, bacteroides, coliforms, bifidobacteria and enterococci. At sacrifice, the small and large bowel were microbiologically and histologically assessed.

RESULTS

L. salivarius UCC118 was detected in faeces from all mice in the probiotic fed group, but not the control group. Faecal coliform and enterococci levels were significantly reduced in probiotic fed animals compared to the controls (P < 0.05). At sacrifice, a significant reduction in C. perfringens numbers was observed in the test mice (P < 0.05). There were no fatalities in the test group compared to two deaths from fulminant colitis in the control group. Only one test mouse developed colonic adenocarcinoma compared to five in the control group. Test animal mucosal inflammation consistently scored lower than that of the control mice.

CONCLUSION

In this placebo controlled trial, modification of enteric flora in IL-10 knockout mice by probiotic lactobacilli was associated with reduced prevalence of colon cancer and mucosal inflammatory activity.

Inflammatory bowel disease: immunodiagnostics, immunotherapeutics, and ecotherapeutics

Treatment options for inflammatory bowel disease (IBD) reflect a continuing shift from empiricism to strategies based on improved understanding of the pathophysiology of disease. In susceptible individuals, IBD appears to be the result of defective regulation of mucosal immune interactions with the enteric microflora. This has prompted research directed at the interface of the traditional disciplines of immunology, microbiology, and epithelial cell biology. Whereas immunodiagnostics have been of limited clinical value in IBD, assessments of mucosal rather than systemic immune function are promising. Therapeutically, there is an increasing trend toward more aggressive and earlier use of immunomodulatory agents, particularly for prevention of relapse, with cytokine manipulation as a bridge therapy to achieve remission in patients with acute severe disease. Although most drug treatments are directed toward altering the host response, the rationale for manipulating the enteric flora appears sound and will be the basis of additional future therapeutic strategies. Notwithstanding the widening range of options for drug therapy in IBD, other outcome modifiers and well-established principles of managing chronic disease are as important as ever.

Limited CD4 T-cell diversity associated with colitis in T-cell receptor alpha mutant mice requires a T helper 2 environment

BACKGROUND & AIMS

T-cell receptor alpha mutant (TCRalpha(-/-)) mice spontaneously develop chronic colitis mediated by CD4(+) TCRalpha(-)beta(+) T cells. The aim of this study was to analyze the mechanisms of expansion of these cells by characterization of the TCRbeta repertoire.

METHODS

TCRbeta repertoire was analyzed by reverse-transcription polymerase chain reaction/Southern blot and DNA sequencing. Clonality of T cells was examined in the lymphoid tissues and colons of TCRalpha(-/-) mice and interleukin 4-deficient TCRalpha(-/-) mice. In addition, an in vitro culture system using syngeneic colonic epithelial cells as antigens was used.

RESULTS

The clonal expansion of a restricted subset of Vbeta8.2(+) T cells was characterized by conservation of a single negatively charged amino acid residue in the second position of the complementarity-determining region 3 (CDR3). These T cells were observed in the diseased colon and appendix (cecal patch) of TCRalpha(-/-) mice, but not germfree TCRalpha(-/-) mice. Culture of polyclonal T cells from young TCRalpha(-/-) mice with colonic epithelial cells under T helper 2 conditions resulted in the survival of Vbeta8.2(+) T cells characterized by the same CDR3 pattern. In addition, the transfer of the cultivated T cells induced mild colitis in recombination-activating gene 1 mutant mice.

CONCLUSIONS

In the TCRalpha(-/-) mice, the development of colitis is associated with the presence of a restricted diversity of Vbeta8. 2(+) T-cell subsets characterized by a specific TCR motif. The limited diversity of lamina propria T cells that are derived from naive T cells expanded by reacting with luminal bacterial antigens is likely caused by the survival of these T cells after stimulation with self-antigens in the presence of a T helper 2 environment.

Probiotics and inflammatory bowel disease: is there a scientific rationale?

Most conventional forms of drug therapy suppress or modify the host immunoinflammatory response and neglect the other contributor to disease pathogenesis-the environmental microflora. Probiotics are live microbial food ingredients that alter the enteric microflora and have a beneficial effect on health. The rationale for using probiotics in IBD is mainly based on evidence from human studies and experimental animal models implicating intestinal bacteria in the pathogenesis of these disorders. The relationship between bacteria and intestinal inflammation is complex and does not appear to reflect a simple cause and effect. Similarly, the field of probiotics is complex and in need of rigorous research. Until the indigenous flora are better characterized and mechanisms of probiotic action defined, the promise of probiotics in IBD is unlikely to be fulfilled. Because of strain-specific variability and clinical and therapeutic heterogeneity within Crohn's disease and ulcerative colitis, it cannot be assumed that a given probiotic is equally suitable for all individuals. Although preliminary results of probiotic therapy in animal models and humans with ulcerative colitis and pouchitis have been encouraging, their efficacy in treatment or maintenance of remission of Crohn's disease remains to be clarified. However, the circumstantial evidence for some form of biotherapeutic modification of the enteric flora in Crohn's disease seems compelling. In the future, probiotics may offer a simple adjunct to conventional therapy with the emphasis on diet shifting from one of nutritional replenishment alone to a more functional role.

Mucosal immunity and inflammation. II. The yin and yang of T cells in intestinal inflammation: pathogenic and protective roles in a mouse colitis model

Inflammatory bowel disease (IBD) is a multifactorial immune disorder of uncertain etiology. The advent of several mouse models of mucosal inflammation that resemble IBD has provided insight into the mechanisms governing both normal and pathological mucosal immune function. In a widely used adoptive transfer model, the injection into immunodeficient mice of a subset of CD4(+) T lymphocytes, the CD4(+)CD45RBhigh cells, leads to inflammation of the intestine. Pathogenesis is due in part to the secretion of proinflammatory cytokines. The induction of colitis can be prevented by cotransfer of another CD4(+) subpopulation, the CD4(+)CD45RBlow T cells. This population behaves analogously to the CD4(+)CD45RBhigh population in terms of the acquisition of activation markers and homing to the host intestine. However, their lymphokine profile when activated is different, and anti-inflammatory cytokines secreted and/or induced by CD4(+)CD45RBlow T cells prevent colitis. In this themes article, a description of the adoptive transfer model is given, the factors that promote and prevent colitis pathogenesis are discussed, and some controversial aspects of the model are addressed.