The role of the tumor necrosis factor receptor in 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis in mice

Fn14 and TNFR2 as regulators of cytotoxic TNFR1 signaling

Tumor necrosis factor (TNF) receptor 1 (TNFR1), TNFR2 and fibroblast growth factor-inducible 14 (Fn14) belong to the TNF receptor superfamily (TNFRSF). From a structural point of view, TNFR1 is a prototypic death domain (DD)-containing receptor. In contrast to other prominent death receptors, such as CD95/Fas and the two TRAIL death receptors DR4 and DR5, however, liganded TNFR1 does not instruct the formation of a plasma membrane-associated death inducing signaling complex converting procaspase-8 into highly active mature heterotetrameric caspase-8 molecules. Instead, liganded TNFR1 recruits the DD-containing cytoplasmic signaling proteins TRADD and RIPK1 and empowers these proteins to trigger cell death signaling by cytosolic complexes after their release from the TNFR1 signaling complex. The activity and quality (apoptosis versus necroptosis) of TNF-induced cell death signaling is controlled by caspase-8, the caspase-8 regulatory FLIP proteins, TRAF2, RIPK1 and the RIPK1-ubiquitinating E3 ligases cIAP1 and cIAP2. TNFR2 and Fn14 efficiently recruit TRAF2 along with the TRAF2 binding partners cIAP1 and cIAP2 and can thereby limit the availability of these molecules for other TRAF2/cIAP1/2-utilizing proteins including TNFR1. Accordingly, at the cellular level engagement of TNFR2 or Fn14 inhibits TNFR1-induced RIPK1-mediated effects reaching from activation of the classical NFκB pathway to induction of apoptosis and necroptosis. In this review, we summarize the effects of TNFR2- and Fn14-mediated depletion of TRAF2 and the cIAP1/2 on TNFR1 signaling at the molecular level and discuss the consequences this has in vivo.

The Proteolytic Fraction From Vasconcellea cundinamarcensis Latex Displays Anti-Inflammatory Effect in A Mouse Model of Acute TNBS-Induced Colitis

The proteolytic fraction (P1G10) from Vasconcellea cundinamarcensis, displays gastric protective and healing activities in different skin lesions in mice and human. In an excisional model, this fraction accelerates resolution of lesions and modulates inflammatory mediators. Based on these data, we assessed its anti-inflammatory activity in murine colitis model, induced by 2,4,6-trinitrobenzenesulfonic acid (TNBS) adopted by its physiopathological similarity with human colitis. Twenty four hours after colitis induction followed by three days of treatment, P1G10 at 0.3 and 3.0 mg/Kg induced 30% increase in body weight (p < 0.0001) and ~80% reduction in colon macroscopic damage score (p < 0.05) compared to the untreated TNBS-induced colitis group. Histological analyses showed that 0.3 mg/Kg P1G10 reduced the inflammatory profile and tissue damage (47%, p < 0.05) when it was proteolytically active. Compared to TNBS group, 0.3 mg/Kg P1G10 reduced MPO activity (80%, p < 0.01), MCP-1 (47%, p < 0.05) and TNF-α (50%, no significant) and increased IL-10 (330%, p < 0.001) levels in the supernatant of colonic tissue homogenate. P1G10 treatment also reduced COX-2 expression (60%, p < 0.05) and metalloprotease-2 activity (39%, p < 0.05) while increased globet cell density (140%, p < 0.01), that contributes to mucus layer protection in colonic tissue. Taken together, these findings suggest that low doses of active P1G10 promotes lesion resolution, at least in part by its anti-inflammatory activity, in TNBS-colitis model.

Inactive Rhomboid Protein 2 Mediates Intestinal Inflammation by Releasing Tumor Necrosis Factor-α

BACKGROUND

Tumor necrosis factor (TNF)-α is a major proinflammatory cytokine that plays a key role in inflammatory bowel disease (IBD). Inactive rhomboid protein 2 (iRhom2) is essential for activating TNF-α-converting enzyme (TACE) in immune cells, which regulates TNF-α release. The aim of the study was to investigate the role of iRhom2 in intestinal inflammation in IBD.

METHODS

The expression of iRhom2 and TACE in lipopolysaccharide (LPS)-stimulated COLO 205 and RAW 264.7 cells was assessed by reverse transcription polymerase chain reaction (RT-PCR) and Western blot analysis. The expression of iRhom2 and TACE in the colonic tissue of IBD patients and 2,4,6-trinitrobenzenesulfonic acid solution (TNBS)-treated mice was determined by RT-PCR and immunohistochemistry. To assess the role of iRhom2 in intestinal inflammation, colitis was induced in wild-type and iRhom2-/- mice by the administration of TNBS enema.

RESULTS

In LPS-stimulated COLO 205 and RAW 264.7 cells, the mRNA and protein levels of TACE and iRhom2 were upregulated. The expression of TACE and iRhom2 in the colon of the IBD patients and TNBS-treated mice was significantly enhanced. The inflammatory cells that expressed high levels of iRhom2 in the colon were identified as macrophages. Finally, iRhom2 deficiency ameliorated TNBS-induced colitis by inhibiting TNF-α release.

CONCLUSIONS

iRhom2 has an important role in intestinal inflammation through TNF-α secretion in immune cells, which suggests that iRhom2 could be a novel therapeutic target for IBD.

TNFR2 expression by CD4 effector T cells is required to induce full-fledged experimental colitis

There is now compelling evidence that TNFR2 is constitutively expressed on CD4(+) Foxp3(+) regulatory T cells (Tregs) and TNF-TNFR2 interaction is critical for the activation, expansion and functional stability of Tregs. However, we showed that the expression of TNFR2 was also up-regulated on CD4(+) Foxp3(-) effector T cells (Teffs) upon TCR stimulation. In order to define the role of TNFR2 in the pathogenic CD4 T cells, we compared the effect of transferred naïve CD4 cells from WT mice and TNFR2(-/-) mice into Rag 1(-/-) recipients. Transfer of TNFR2-deficient Teff cells failed to induce full-fledged colitis, unlike WT Teffs. This was due to defective proliferative expansion of TNFR2-deficient Teff cells in the lymphopenic mice, as well as their reduced capacity to express proinflammatory Th1 cytokine on a per cell basis. In vitro, the proliferative response of TNFR2 deficient naïve CD4 cells to anti-CD3 stimulation was markedly decreased as compared with that of WT naïve CD4 cells. The hypoproliferative response of TNFR2-deficient Teff cells to TCR stimulation was associated with an increased ratio of p100/p52, providing a mechanistic basis for our findings. Therefore, this study clearly indicates that TNFR2 is important for the proliferative expansion of pathogenic Teff cells.

Tumor Necrosis Factor Receptor 2 Restricts the Pathogenicity of CD8(+) T Cells in Mice With Colitis

BACKGROUND & AIMS

Tumor necrosis factor receptor 2 (TNFR2, Tnfrsf1b) regulates multiple aspects of immune function, but little is known about its role in the immunopathogenesis of inflammatory bowel disease (IBD). We investigated whether TNFR2 restricts the activity of specific immune cell subtypes to protect against the development of colitis in mice.

METHODS

Tnfr2(-/-) mice were crossed with interleukin (Il) 10(-/-) mice, which spontaneously develop colitis, to generate Il10(-/-)Tnfr2(-/-) mice. Colonic tissues were collected from Il10(-/-)Tnfr2(-/-) mice along with Il10(-/-) mice (controls) and analyzed by flow cytometry and histology. Bone marrow was transplanted into Il10(-/-) and Il10(-/-)Tnfr2(-/-) mice from Il10(-/-) or Il10(-/-)Tnfr2(-/-) donors by intravenous injection. CD8(+) T cells were neutralized in Il10(-/-)Tnfr2(-/-) mice by intraperitoneal injection of anti-CD8 or isotype control antibodies. Colitis was induced in Rag2(-/-) mice by intravenous injections of naïve CD8(+) T cells isolated from C57BL/6 or Tnfr2(-/-) mice.

RESULTS

Il10(-/-)Tnfr2(-/-) mice spontaneously developed more severe colitis compared with Il10(-/-) controls, characterized by selective expansion of colonic CD8(+) T cells. Transplantation of TNFR2-deficient bone marrow resulted in significantly increased incidence and severity of colitis. Transcriptome analyses showed that the expression of genes regulated by TNFR2 were specific to CD8(+) T cells and included genes associated with risk for IBD. Depletion of CD8(+) T cells from Il10(-/-)Tnfr2(-/-) mice prevented colonic inflammation. Adoptive transfer of TNFR2-null naïve CD8(+) T cells compared with CD8(+) T cells from control mice increased the severity of colitis that developed in Rag2(-/-) mice.

CONCLUSIONS

TNFR2 protects mice from colitis by inhibiting the expansion of colonic CD8(+) T cells. TNFR2 regulates expression of genes that regulate CD8(+) T cells and have been associated with susceptibility to IBD. Disruption in TNFR2 signaling might therefore be associated with pathogenesis. Strategies to increase levels or activity of TNFR2 and thereby reduce the activity of CD8(+) T cells might be developed to treat IBD patients with CD8(+) T cell dysfunction.

Lack of TNFRI signaling enhances annexin A1 biological activity in intestinal inflammation

We evaluated whether the lack of TNF-α signaling increases mucosal levels of annexin A1 (AnxA1); the hypothesis stems from previous findings showing that TNF-α neutralization in Crohn's disease patients up-regulates systemic AnxA1 expression. Biopsies from healthy volunteers and patients under anti-TNF-α therapy with remittent ulcerative colitis (UC) showed higher AnxA1 expression than those with active disease. We also evaluated dextran sulfate sodium (DSS)-acute colitis in TNF-α receptor 1 KO (TNFR1-/-) strain with impaired TNF-α signaling and C57BL/6 (WT) mice. Although both strains developed colitis, TNFR1-/- mice showed early clinical recovery, lower myeloperoxidase (MPO) activity and milder histopathological alterations. Colonic epithelium from control and DSS-treated TNFR1-/- mice showed intense AnxA1 expression and AnxA1+ CD4+ and CD8+ T cells were more frequent in TNFR1-/- animals, suggesting an extra supply of AnxA1. The pan antagonist of AnxA1 receptors exacerbated the colitis outcome in TNFR1-/- mice, supporting the pivotal role of AnxA1 in the early recovery. Our findings demonstrate that the TNF-α signaling reduction favors the expression and biological activity of AnxA1 in inflamed intestinal mucosa.

Targeting tumour necrosis factor receptor 1 assembly reverses Th17-mediated colitis through boosting a Th2 response

OBJECTIVE

The soluble preligand assembly domain (PLAD) of tumour necrosis factor receptor 1 (TNFR1) interferes with receptor trimerisation to block downstream signalling, and mediates Th17 suppression. We explored the therapeutic potential of recombinant PLAD.Fc protein on a spontaneous experimental colitis.

DESIGN

A T-cell-specific BLIMP-1 knockout mouse model with mixed Th1/Th17 responses, resembling human Crohn's disease (CD) was established, and its colitogenic phenotype was characterised. Mice, 9 weeks old, were treated with PLAD.Fc protein at 5 mg/kg of body weight twice per week for 16 weeks, and presence of colitis was monitored by the appearance of diarrhoea, weight loss, and by histological colonic scoring. Activation status, cytokine profiles, and transcription factors in T cells were further analysed.

RESULTS

The colitogenic phenotype in BLIMP-1 knockout mice was alleviated when an interleukin (IL)-23 knockdown transgene was introduced, indicating a therapeutic potential by downregulating IL-23-Th17 axis in these knockout mice. In PLAD.Fc-treated group, the mouse body weight remained stable and only mild disease scores were revealed. The percentage of naive CD4 T cells was increased and that of effector/memory CD4 T cells was decreased after PLAD.Fc-treatment. Moreover, the levels of IFN-γ, IL-17, IL-21, IL-22, IL-23R, granulocyte-macrophage colony-stimulating factor (GM-CSF) and TNF-α were diminished. Strikingly, Th2-associated cytokines (IL-4, IL-13 and IL-10) in sera, as well as percentages of Th2 cells, were increased in PLAD.Fc-treated mice. However, PLAD.Fc-mediated suppression of effector phenotypes in Th1/Th17 was abrogated after neutralising IL-10.

CONCLUSIONS

The Th2 cytokine milieu induced by PLAD.Fc rebalanced T-helper cell subsets and conferred a protection against colitis in BLIMP-1 knockout mice.

Protective effect of pioglitazone on sepsis-induced intestinal injury in a rodent model

BACKGROUND

Pathogenesis and treatment of inflammatory gut barrier failure is an important problem in critical care. In this study, we examined the role of pioglitazone, an agonist of peroxisome proliferator-activated receptor gamma, in gut barrier failure during experimental peritonitis in rats.

MATERIALS AND METHODS

Male rats were randomly divided into three groups as follows: sham, sepsis, and sepsis + pioglitazone. Sepsis was achieved by means of the cecal ligation and puncture (CLP). Pioglitazone was administered intraperitoneally (10 mg/kg/d) for 7 d before the experiment. Animals were killed at 24 h or followed 72 h for survival. The tissue level of tumor necrosis factor-α, interleukin-6, superoxide dismutase, malondialdehyde, and myeloperoxidase was measured. Intestinal mucosa injury was assessed histologically. The plasma fluorescein isothiocyanate-dextran, D-lactic acid, and intestinal diamine oxidase were determined to evaluate the permeability and integrity of intestinal mucosal epithelium. Vena cava blood and tissue samples were used to monitor bacterial translocation.

RESULTS

Intestinal inflammation, oxidize stress, neutrophil infiltration, morphology injury, and impaired permeability of the small intestine in the CLP group were found more severe than those in the sham group. Application of pioglitazone not only minimized all the indicators of intestinal injury and barrier failure but also improved the survival of septic rats induced by CLP.

CONCLUSIONS

Our novel findings suggest that pioglitazone could protect against intestinal injury and maintain intestinal barrier integrity and might be a useful strategy to ameliorate intestinal failure in polymicrobial sepsis.

Redeeming an old foe: protective as well as pathophysiological roles for tumor necrosis factor in inflammatory bowel disease

Tumor necrosis factor (TNF) and its receptors TNFR1 and TNFR2 are major therapeutic targets for inflammatory bowel disease. Research advances have demonstrated that TNF produces pleiotropic responses in the gastrointestinal (GI) tract. Although in excess TNF can contribute to GI pathology, TNF is also a critical protective factor to promote GI homeostasis following injury and inflammation. Genetic studies using candidate and genome-wide association study approaches have identified variants in TNF or its receptors that are associated with Crohn's disease or ulcerative colitis in multiple populations, although the basis for these associations remains unclear. This review considers the efficacy and mechanism of anti-TNF therapies for inflammatory bowel disease to reconcile the many disparate aspects of TNF research and to consider the potential protective effects of TNF signaling in GI health.

An important role of tumor necrosis factor receptor-2 on natural killer T cells on the development of dsRNA-enhanced Th2 cell response to inhaled allergens

BACKGROUND

Recent evidence indicates that TNF-α is a key mediator of the development of dsRNA-enhanced Th2 cell response to inhaled allergens. Natural killer T (NKT) cells may be a candidate source of Th2-polarizing cytokines.

OBJECTIVE

The objective of this study was to evaluate the role of lung NKT cells on the development of TNF-α-mediated Th2 cell response.

METHODS

A virus-associated asthma mouse model was generated by the administration of ovalbumin (OVA, 75 μg) and poly[I:C] (0.1 μg). Role of NKT and type I NKT cells was evaluated using CD1d- and Jα18-deficient mice. TNF-α receptors (TNFRs) were antagonized by using TNFR blocking peptides.

RESULTS

The number of infiltrated NKT cells was increased in a virus-associated asthma mouse model. Increase in Th2 and Th17 cytokine levels in wild-type mice were abolished in both CD1d- and Jα18-deficient mice. In vitro co-culture experiments with alveolar macrophages and NKT cells showed that TNF-α produced by macrophages in the presence of poly[I:C] acts on NKT cells, inducing production of Th2-polarizing cytokines. Moreover, the induction of Th2-polarizing cytokines by poly[I:C] or recombinant TNF-α was impaired in both CD1d- and Jα18-deficient mice and that the above effect was reversed by a TNF-α receptor-2 (TNFR2) blocking peptide, but not by a TNFR1 blocker.

CONCLUSIONS

These findings suggest that NKT cells play a key role in the development of Th2 cell response to inhaled allergens and that TNF-α produced by alveolar macrophages induces Th2 cell response, via TNFR2 on NKT cells.

The Role of Tumour Necrosis Factor in the Pathogenesis of Immune-Mediated Diseases

Immune-mediated inflammatory diseases (IMIDs), such as rheumatoid arthritis, psoriatic arthritis, psoriasis, axial spondyloarthropathies, Crohn's disease, ulcerative colitis and juvenile idiopathic arthritis, comprise a group of chronic disorders characterized by an immune-mediated pathogenesis. Although at clinical presentation these diseases appear unrelated, they have been recognized to share similar pathogenic mechanisms. Data from epidemiological and genetic studies further support the concept that IMIDs are interrelated, as they can co-occur in the same patient and share a similar genetic susceptibility. The specific aetiologies of IMIDs remain unknown, but all are known to involve dysregulation of the immune system, including an over-expression of the pro-inflammatory cytokine tumour necrosis factor (TNF). The pivotal role played by TNF in the pathogenesis and pathophysiology of IMIDs has been documented by extensive preclinical and clinical investigations, and confirmed by the efficacy of anti-TNF biotechnological drugs, such as etanercept, infliximab and adalimumab, in the therapeutic management of these disorders. In this narrative review, we discuss the available data on the TNF-dependent pathogenesis of IMIDs and associations among the different disorders. Although much remains to be discovered about the pathogenesis and aetiology of IMIDs, their common inflammatory pathological features may explain why they can be successfully targeted by anti-TNF drugs. Among these, adalimumab, a fully human monoclonal antibody, has been approved for treatment ofnine distinct IMID indications and it is likely to become a valuable therapeutic tool for this complex cluster of chronic inflammatory disorders.

Protective role of tumor necrosis factor (TNF) receptors in chronic intestinal inflammation: TNFR1 ablation boosts systemic inflammatory response

Tumor necrosis factor-α (TNF-α) acts as a key factor for the development of inflammatory bowel diseases (IBDs), whose function is known to be mediated by TNF receptor 1 (TNFR1) or TNFR2. However, the precise role of the two receptors in IBD remains poorly understood. Herein, chronic colitis was established by oral administration of dextran sulfate sodium (DSS) in TNFR1 or TNFR2-/- mice. Unexpectedly, TNFR1 or TNFR2 deficiency led to exacerbation of signs of colitis compared with wild-type (WT) counterparts. Of note, TNFR1 ablation rendered significantly increased mortality compared with TNFR2 and WT mice after DSS. Aggravated pathology of colitis in TNFR1-/- or TNFR2-/- mice correlated with elevated colonic expression of proinflammatory cytokines and chemokines. Importantly, ablation of TNFR1 or TNFR2 increased apoptosis of colonic epithelial cells, which might be due to the heightened ratio of Bax/Bcl-2 and increased expression of caspase-8. Intriguingly, despite comparable intensity of intestinal inflammation in TNFR-deficient mice after DSS, systemic inflammatory response (including splenomegaly and myeloid expansion) was augmented dramatically in TNFR1-/- mice, instead of TNFR2-/- mice. Granulocyte-macrophage colony-stimulating factor (GMCSF) was identified as a key mediator in this process, as neutralization of GMCSF dampened peripheral inflammatory reaction and reduced mortality in TNFR1-/- mice. These data suggest that signaling via TNFR1 or TNFR2 has a protective role in chronic intestinal inflammation, and that lacking TNFR1 augments systemic inflammatory response in GMCSF-dependent manner.

Opposite role of tumor necrosis factor receptors in dextran sulfate sodium-induced colitis in mice

Tumor necrosis factor-α (TNF-α) is a key factor for the pathogenesis of inflammatory bowel diseases (IBD), whose function is known to be mediated by TNF receptor 1 (TNFR1) or 2. However, the precise role of the two receptors in IBD remains poorly understood. Herein, acute colitis was induced by dextran sulfate sodium (DSS) instillation in TNFR1 or 2−/− mice. TNFR1 ablation led to exacerbation of signs of colitis, including more weight loss, increased mortality, colon shortening and oedema, severe intestinal damage, and higher levels of myeloperoxidase compared to wild-type counterparts. While, TNFR2 deficiency had opposite effects. This discrepancy was reflected by alteration of proinflammatory cytokine and chemokine production in the colons. Importantly, TNFR1 ablation rendered enhanced apoptosis of colonic epithelial cells and TNFR2 deficiency conferred pro-apoptotic effects of lamina propria (LP)-immune cells, as shown by the decreased ratio of Bcl-2/Bax and enhanced nuclear factor (NF)-κB activity.

Moxibustion inhibits apoptosis and tumor necrosis factor-alpha/tumor necrosis factor receptor 1 in the colonic epithelium of Crohn's disease model rats

BACKGROUND

Previous studies have shown that moxibustion on Tianshu (ST25) and Qihai (CV6) is effective for treating Crohn's disease. However, the mechanism of moxibustion has not been clearly elucidated.

AIM

The purpose of this study was to investigate the effect of moxibustion on the inhibition of colonic epithelial cell apoptosis and on tumor necrosis factor alpha (TNF-alpha) and tumor necrosis factor receptor TNF receptor-1 (TNFR1) and TNFR2 and to determine the mechanism of its protective effect using Crohn's disease (CD) model rats.

METHODS AND RESULTS

The experimental CD rat models were established by the administration of trinitrobenzene sulfonic acid. In the herbs-partitioned moxibustion (HPM) and mild-warm moxibustion (MWM) groups, moxibustion was administered to Tianshu (ST25) and Qihai (CV6) acupoints once daily for 14 days. In the salicylazosulfapyridine (SASP) group, SASP was administered twice daily for 14 days. A normal control (NC) group and a model control (MC) group were also studied. The levels of TNF-alpha and its mRNA, TNFR1 as well as the rate of colonic epithelial cell apoptosis were significantly decreased in the HPM, MWM and SASP groups compared with the MC group. The HPM and MWM groups had lower mRNA expression and lower protein levels of TNF-alpha compared to the SASP group. The HPM and MWM groups exhibited less apoptosis than the SASP group.

CONCLUSIONS

Moxibustion may inhibit colonic epithelial cell apoptosis by reducing the high expression of TNF-alpha and TNFR1 to protect the defective colonic epithelial barrier in CD model rats.

Colitogenic role of tumour necrosis factor (TNF) receptors in trinitrobenzene sulphonic acid colitis: TNF-R1 ablation does not affect systemic inflammatory response

Tumour necrosis factor (TNF)-α plays a critical role in the pathogenesis of T helper type 1-mediated colitis such as Crohn's disease. However, the roles of its two receptors in mediating pathology remain largely unknown. In this study, trinitrobenzene sulphonic acid (TNBS) was used to induce colitis in TNF-receptor single or double knock-out (DKO) BALB/c mice and in wild-type counterparts. TNF-R1(-/-) mice had significantly less weight loss, reduced mortality, colon shortening and oedema, colon histological damage and lower levels of colon myeloperoxidase compared with wild-type (WT) BALB/c mice. A similar manifestation was also observed in TNF-R2(-/-) and TNF-R1(-/-) TNF-R2(-/-) (TNF-R DKO) mice. Strikingly, systemic inflammatory response (including splenomegaly and monocyte expansion) was found in WT and TNF-R1(-/-) mice after TNBS, instead of TNF-R2(-/-) and TNF-R DKO mice. Attenuated pathology of colitis in TNF-R1(-/-) or TNF-R2(-/-) mice correlated with lower amounts of interleukin (IL)-6, IL-1β, monocyte chemotactic protein (MCP)-1, IL-12p70 and interferon (IFN)-γ production in the colons. Importantly, ablation of TNF-R1 or TNF-R2 reduced the number of terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labelling (TUNEL)-positive apoptotic epithelial cells in the affected colons compared with WT TNBS-instilled controls, which might be due to the heightened ratio of Bcl-2/Bax and reduced activity of nuclear factor (NF)-κB. These findings suggest that either TNF-R1 or TNF-R2 plays a pathogenic role in the pathology of colitis and TNF signalling via TNF-R1 or TNF-R2 alone is not sufficient for inducing mucosal damage.

Resveratrol suppresses colitis and colon cancer associated with colitis

Resveratrol is a naturally occurring polyphenol that exhibits pleiotropic health beneficial effects, including anti-inflammatory, cardio-protective, and cancer-protective activities. It is recognized as one of the more promising natural molecules in the prevention and treatment of chronic inflammatory and autoimmune disorders. Ulcerative colitis is an idiopathic, chronic inflammatory disease of the colon associated with a high colon cancer risk. Here, we used a dextran sulfate sodium (DSS) mouse model of colitis, which resembles human ulcerative colitis pathology. Resveratrol mixed in food ameliorates DSS-induced colitis in mice in a dose-dependent manner. Resveratrol significantly improves inflammation score, downregulates the percentage of neutrophils in the mesenteric lymph nodes and lamina propria, and modulates CD3(+) T cells that express tumor necrosis factor-alpha and IFN-gamma. Markers of inflammation and inflammatory stress (p53 and p53-phospho-Ser(15)) are also downregulated by resveratrol. Because chronic colitis drives colon cancer risk, we carried out experiments to determine the chemopreventive properties of resveratrol. Tumor incidence is reduced from 80% in mice treated with azoxymethane (AOM) + DSS to 20% in mice treated with AOM + DSS + resveratrol (300 ppm). Tumor multiplicity also decreased with resveratrol treatment. AOM + DSS-treated mice had 2.4 +/- 0.7 tumors per animal compared with AOM + DSS + 300 ppm resveratrol, which had 0.2 +/- 0.13 tumors per animal. The current study indicates that resveratrol is a useful, nontoxic complementary and alternative strategy to abate colitis and potentially colon cancer associated with colitis.

Role of TNF receptors, TNFR1 and TNFR2, in dextran sodium sulfate-induced colitis

BACKGROUND

In this study we determined the consequence of the absence of each TNF receptor, TNFR1 or TNFR2, in the dextran sulfate sodium (DSS) model of colitis.

METHODS

Wildtype (WT), TNFR1(-/-) and TNFR2(-/-) mice were fed 3% w/v DSS in drinking water for 5 days followed by 2 (day 7) or 7 (day 12) days of tap water.

RESULTS

The colons from untreated TNFR1(-/-) and TNFR2(-/-) mice were histologically normal. Following DSS, all strains became inflamed. TNFR1(-/-) mice had a more severe clinical score at days 8 and 9 compared to WT and TNFR2(-/-) mice despite similar histopathological damage in their colons. The more severe clinical score was associated with a reduced macrophage infiltration into the colonic mucosa. TNFR2(-/-) mice showed increased indicators of disease including increased colon weight, a shrunken cecum, and an increased number of ulcers compared to TNFR1(-/-) and WT strains at day 7. Mucosal levels of TNFR2 were elevated in colitic mice compared to uninflamed controls, with no difference between strains on day 7 but on day 12, unlike WT mice, levels were reduced in TNFR1(-/-) mice. There was no difference in the number of TUNEL-positive apoptotic colonic epithelial cells between strains, nor in total cleaved caspase 3 levels between strains, measured by Western blot of colon homogenates.

CONCLUSIONS

While deficiency of either receptor contributes to some measures of DSS colitis, the histopathological scores are similar, indicating that TNF receptors either do not play a major role or are redundant in the pathology associated with DSS colitis.

Microglial activation and TNFalpha production mediate altered CNS excitability following peripheral inflammation

Peripheral inflammation leads to a number of centrally mediated physiological and behavioral changes. The underlying mechanisms and the signaling pathways involved in these phenomena are not yet well understood. We hypothesized that peripheral inflammation leads to increased neuronal excitability arising from a CNS immune response. We induced inflammation in the gut by intracolonic administration of 2,4,6-trinitrobenzene sulfonic acid (TNBS) to adult male rats. To examine the excitability of the brain in vivo, we administered pentylenetetrazole (PTZ; a GABAergic antagonist) intravenously to evoke clonic seizures. Rats treated with TNBS showed increased susceptibility to PTZ seizures that was strongly correlated with the severity and progression of intestinal inflammation. In vitro hippocampal slices from inflamed, TNBS-treated rats showed increased spontaneous interictal burst firing following application of 4-aminopyridine, indicating increased intrinsic excitability. The TNBS-treated rats exhibited a marked, reversible inflammatory response within the hippocampus, characterized by microglial activation and increases in tumor necrosis factor alpha (TNFalpha) levels. Central antagonism of TNFalpha using a monoclonal antibody or inhibition of microglial activation by i.c.v. injection of minocycline prevented the increase in seizure susceptibility. Moreover, i.c.v. infusion of TNFalpha in untreated rats for 4 days also increased seizure susceptibility and thus mimicked the changes in seizure threshold observed with intestinal inflammation. Our finding of a microglia-dependent TNFalpha-mediated increase in CNS excitability provides insight into potential mechanisms underlying the disparate neurological and behavioral changes associated with chronic inflammation.

Mode of function of biological anti-TNF agents in the treatment of inflammatory bowel diseases

TNF-alpha has been identified as a major mediator in the pathophysiology of inflammation. Anti-TNF agents, either as a neutralising antibody or a soluble TNF receptor, have markedly influenced the clinical management of several chronic inflammatory disorders. Whereas it seems likely that neutralisation of soluble and membrane-bound TNF might be a key mechanism of any anti-TNF agent, the potential of the anti-TNF antibody infliximab to induce lymphocyte/monocyte apoptosis in Crohn's disease has been considered an additional important mechanism. Other potential mode of actions include induction of the anti-inflammatory cytokines IL-10 or TGF-beta via retrograde signalling or induction of a certain subset of regulatory T cells. Certolizumab, a pegylated fully human anti-TNF monoclonal antibody also effective in Crohn's disease, lacks the capacity to induce apoptosis. Therefore, the capacity to induce apoptosis and neutralisation of TNF alone are insufficient to explain clinical efficacy of anti-TNF agents in human inflammatory bowel diseases.

Critical appraisal of the current practice in murine TNBS-induced colitis

There is no standard practice in the induction of colitis by 2,4,6-trinitrobenzene sulfonic acid. In this review the current practice in 2,4,6-trinitrobenzene sulfonic acid colitis is studied using 20 recently published articles. We compare the different protocols, discuss the mechanism of disease and give recommendations for the future use of the model.