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PubMed2001

Ischemic colitis during pregnancy and contraceptive medication.

Ischemic bowel disease is generally considered a disease of the elderly and usually consists of reversible colopathy. Nonocclusive causes of ischemic colitis include low-flow states due to cardiac dysfunction and hypovolemia and use of certain medications including progestational medication. We report 2 cases of ischemic colitis in young women. The first one occurred in a young patient who developed three consecutive episodes of ischemic colitis during her pregnancy, whereas the second woman presented with ischemic colitis in relation with the estrogen use. Each episode had a favorable outcome. Having ruled out an infectious cause, or a low blood flow state and in the absence of known thrombogenic disease, we hypothesized the etiology of these ischemic episodes to a high level of circulating estrogens due to pregnancy in the first case and oral contraceptive medication in the second. Physicians treating hemorrhagic colitis in young women should consider the use of contraceptive medication containing estrogens or pregnancy as possible causes.

Adult↗
PubMed2001

Beneficial effects of Batimastat (BB-94), a matrix metalloproteinase inhibitor, in rat experimental colitis.

BACKGROUND AND AIMS: Matrix metalloproteinases (MMPs) represent a group of enzymes that regulate cell-matrix composition playing a major role in the inflammatory response. In the present study we evaluated the ability of the MMP inhibitor Batimastat (BB-94) to modify the course of experimental colitis induced in the rat by trinitrobenzensulfonic acid (TNB). METHODS: Colitis was induced in 40 rats by intracolonic administration of TNB. Animals were divided into four groups of ten rats each: group 1 received only intracolonic TNB, group 2 received TNB+5 mg/kg intraperitoneal BB-94, group 3 TNB+10 mg/kg BB-94 and group 4 TNB+20 mg/kg BB-94. The MMP inhibitor was administered 30 min before induction of colitis and twice daily until death. Ten rats receiving only intracolonic 0.9% saline served as controls. Animals were killed after seven days; segments of colon were removed and used for histological score of inflammation and myeloperoxidase (MPO) activity. RESULTS: Rats receiving only intracolonic 0.9% saline showed no evidence of colitis. The inflammation score was 0.9, MPO activity 0.235 U/mg. Group 1 (TNB-treated rats) exhibited a high inflammation score (12.4) and MPO activity (0.715 U/mg). Conversely, BB-94-treated rats showed, compared to the TNB group, a significantly lower inflammation score and MPO activity in a dose-dependent fashion. Group 2: inflammatory score 10.1, MPO activity 0.474 (p < 0.05 vs. TNB); group 3: inflammatory score 8.3, MPO activity 0.287 (p < 0.01 vs. TNB); group 4: inflammatory score 5.0, MPO activity 0.256 (p < 0.01 vs. TNB). CONCLUSIONS: Treatment with BB-94 has dose-dependent beneficial effects on the inflammatory alterations in rat experimental colitis. Thus, the inhibition of MMPs may represent a novel therapeutic approach for treatment of intestinal inflammation.

Animals↗
PubMed2002

Studies on the expression and function of beta-3-adrenoceptors in the colon of rats with acetic acid-induced colitis.

Ulcerative colitis is characterized by dysfunctional motility. Our main objective in this investigation was to study the effect of an acetic acid-induced ulcerative colitis on the expression and function of beta(3)-adrenoceptors in the rat colon. Inflammation was induced by administering acetic acid intrarectally into rats. Levels of myeloperoxidase activity and beta(3)-adrenoceptor mRNA were measured in colon samples taken following acetic acid administration. Relaxation responses to beta(3)-adrenoceptor agonists were also studied. Ulcerative colitis was associated with significantly elevated levels of myeloperoxidase activity in the colon segments. Levels of beta(3)-adrenoceptor mRNA as well as the relaxation responses to isoprenaline and BRL 37344 were however not significantly different between inflamed and control tissue. Acetic acid-induced ulcerative colitis in rats was not associated with changes in the expression and/or function of beta(3)-adrenoceptors in the rat colon. Therefore, the dysfunctional motility that is characteristic of ulcerative colitis, is not likely to be due to changes in beta(3)-adrenergic mechanisms in this model.

Acetic Acid↗
PubMed2002

Could honey have a place in colitis therapy? Effects of honey, prednisolone, and disulfiram on inflammation, nitric oxide, and free radical formation.

BACKGROUND/AIMS: The purpose of this study was to investigate the potential therapeutic roles of honey, prednisolone and disulfiram in an experimental model of inflammatory bowel disease. Another aspect of the study was to find out whether these substances have any effect on nitric oxide (NO) and free radical production. METHODS: After the induction of colitis with trinitrobenzene sulfonic acid in 64 male rats, physiological saline, honey, prednisolone and disulfiram enemas were applied to the rats once daily for 3 days (acute treatment groups) or 7 days (chronic treatment groups). Control groups received only saline enemas. Rats were killed on the 4th or 8th days and their colonic mucosal damage was quantitated using a scoring system. Acute and chronic inflammatory responses were determined by a mucosal injury score, histological examination and measurement of the myeloperoxidase (MPO) activity of tissues. The content of malonylaldehyde (MDA) and NO metabolites in colon homogenates was also measured to assess the effects of these substances on NO and free oxygen radical production. RESULTS: Estimation of colonic damage by mucosal injury scoring was found to be strongly correlated with the histologic evaluation of colon specimens. On the other hand, mucosal injury scores were not correlated with MPO, MDA or NO values. There were significant differences between the MPO results of chronic-control and chronic-honey groups, as well as chronic-control and chronic-prednisolone groups (p = 0.03 and p = 0.0007). The acute honey, prednisolone, and disulfiram groups had significantly lower MDA results compared to the acute control group (p = 0.04, p = 0.02, and p = 0.04). In terms of NO, there was no significant difference between the treatment and control groups. NO was found to have a strong relationship with MDA (p = 0.03) and MPO values (p = 0.001). On the other hand, MPO results were not found to be correlated with MDA values (p > 0.05). CONCLUSIONS: MPO activity is not directly proportional to the severity of the inflammation, but it may only determine the amount of neutrophil in the tissues. Inflammatory cells are not the sole intensifying factor in colitis. Therefore, mucosal injury scores may not correlate well with MPO activities. In an inflammatory state NO and MPO levels have a strong relationship, since NO is released from the neutrophils. In an inflammatory model of colitis, intrarectal honey administration is as effective as prednisolone treatment. Honey may have some features in the treatment of colitis, but this issue requires further investigation. Honey, prednisolone and even disulfiram also have some value in preventing the formation of free radicals released from the inflamed tissues. Prednisolone may also have some possible benefits in the inhibition of NO production in colitis therapy.

Animals↗
PubMedDate not supplied

A new model of chronic colitis in SCID mice induced by adoptive transfer of CD62L+ CD4+ T cells: insights into the regulatory role of interleukin-6 on apoptosis.

OBJECTIVE: The proinflammatory cytokine interleukin (IL)-6 is involved in various chronic inflammatory processes. IL-6 is a predominant cytokine produced by lamina propria T cells in Crohn's disease and experimental colitis. This study was designed to examine the effect of a neutralizing IL-6-receptor (IL-6R) antibody on the programmed cell death of mucosal T cells in the CD62L+ CD4+ SCID transfer model of chronic experimental colitis in mice and to gain more insight into the pathogenesis of this transfer colitis model. METHODS: For adoptive transfer, we isolated CD62L+ CD4+ double-positive T cells from wild-type BALB/c mice followed by intraperitoneal application of 1 million cells in CB17 SCID mice. The purity of the transferred T-cell population was tested by FACS analysis. Cytokine secretion was measured by ELISA. Western blot analysis was performed to detect phospho-STAT-3 in protein extracts of splenic cells. Cryo- and paraffin colon cross-sections were used to perform immunochemical or fluorescence TUNEL stainings. RESULTS: We isolated CD62L+ CD4+ and CD62L- CD4+ T cells. In vitro studies showed an increased production of IL-4 by CD62L- CD4+ T cells compared to CD62L+ T cells. 8-10 weeks after transfer of CD62L+ CD4+ T cells in SCID mice, reconstituted mice developed wasting disease, anal prolapse and diarrhea, whereas mice reconstituted with CD62L- CD4+ did not, similar to anti-IL-6R-treated CD62L+ CD4+-reconstituted SCID mice. Anti-IL-6R-treated reconstituted SCID mice showed decreased levels of activated STAT-3. The previously described efficacy of anti-IL-6R antibody treatment on colitis activity appeared to be due to the induction of apoptosis, as many TUNEL-positive cells were detected in the lamina propria. CONCLUSIONS: These results suggest that the activation of the IL-6/STAT-3-signaling pathway plays a pivotal role in the pathogenesis of CD62L+ CD4+ transfer colitis. Moreover, the application of a neutralizing antibody to IL-6R induces apoptosis in transferred T cells. These data implicate the importance of anti-apoptotic pathways in chronic disease and might contribute to future therapies.

Adoptive Transfer↗
PubMed2003

Inhibitory effects of Bifidobacterium longum on experimental ulcerative colitis induced in mice by synthetic dextran sulfate sodium.

BACKGROUND/AIMS: The relationship between alterations in intestinal microflora and ulcerative colitis is still not clear. Whether improvement in bacterial populations might be a new strategy for prevention or treatment needs to be tested. METHODS: Ulcerative colitis was induced in mice by oral administration of synthetic dextran sulfate sodium (molecular weight 54,000). Inhibitory effects of concomitant treatment with Bifidobacterium longum were assessed in terms of total colon length and severity of histological changes. In addition, changes of microflora and short-chain fatty acids were tested in fecal samples and compared before and after treatment. RESULTS: Administration of B. longum significantly inhibited both shortening of total colon length and the severity of ulcerative colitis compared to controls. It was confirmed that the administered B. longum resided in the gut and blocked the decrease of lactobacilli in fecal samples in mice with dextran sulfate sodium-induced colitis. CONCLUSIONS: Oral administration of B. longum exerts marked inhibitory effects on ulcerative colitis in mice.

Animals↗
PubMed2006

Interleukin-6 genetic ablation protects from trinitrobenzene sulfonic acid-induced colitis in mice. Putative effect of antiinflammatory cytokines.

BACKGROUND: Interleukin (IL)-6 is a proinflammatory cytokine implicated in the pathogenesis of inflammatory bowel disease. IL-6 is locally upregulated in inflammatory bowel disease patients and in murine models of experimental colitis. Treatment with anti-IL-6 receptor antibody ameliorates intestinal inflammation. OBJECTIVE: It was the aim of this study to investigate the role of genetic IL-6 deficiency in trinitrobenzene sulfonic acid (TNBS)-mediated colitis, an experimental model inflammation that shares several features with Crohn's disease in humans. METHODS: Acute colitis was induced in wild-type and IL-6-deficient (Il-6(-/-)) mice by intracolonic administration of TNBS. Forty-eight hours after treatment, the local and systemic features of inflammation, i.e. food intake, weight loss, histological markers of colitis, cytokine expression by real-time PCR, food intake and body weight changes, were assessed. RESULTS: In wild-type mice, TNBS administration increased both IL-6 serum levels and local expression of IL-6 by 36 and 9 fold, respectively, compared with control, vehicle-injected mice. Compared with the wild-type mice, the Il-6(-/-) mice had significantly reduced intestinal inflammation as evidenced by epithelial damage, neutrophil infiltration, colon thickness and proinflammatory cytokine expression, following treatment with TNBS. Moreover, baseline levels of the antiinflammatory cytokines IL-10 and tumor growth factor-beta were significantly elevated in Il-6(-/-)compared with the wild-type mice. CONCLUSIONS: Our results demonstrate that Il-6(-/-)are partially protected from the development of TNBS-induced acute experimental colitis, most likely via their significantly elevated baseline levels of antiinflammatory cytokines.

Animals↗
PubMed1987

Time relationships between cessation of smoking and onset of ulcerative colitis.

From 5 centres 154 patients with ulcerative colitis and a history of smoking completed a questionnaire about the temporal relationship between diagnosis of colitis and cessation of smoking. One hundred and thirty-eight of these were ex-smokers and 107 (69.5%) had stopped smoking before the diagnosis of colitis was made. Fifty-six patients (52%) developed colitis within 3 years of stopping smoking. The findings suggest that smoking exerts protective effect against the development of ulcerative colitis.

Adolescent↗
PubMed1987

Differences in the immunoglobulin synthesis by peripheral blood lymphocytes in Crohn's disease and ulcerative colitis.

To determine whether patients with Crohn's disease and ulcerative colitis differ in their capacity to produce immunoglobulins, we have studied the in vitro immunoglobulin synthesis by peripheral blood lymphocytes of such patients and compared the results with those of healthy controls. The spontaneous immunoglobulin production by peripheral blood lymphocytes from Crohn's disease patients was significantly increased for both IgA and IgG, whereas for IgM the increase did not reach statistical significance. In ulcerative colitis, however, the spontaneous IgA and IgG production was almost identical to that of the healthy controls and thus lower than in Crohn's disease. Pokeweed mitogen stimulation resulted in a significantly enhanced immunoglobulin production in Crohn's disease and in controls, whereas peripheral blood lymphocytes from ulcerative colitis patients were found to be rather insensitive to pokeweed mitogen stimulation. Suppression of the stimulated immunoglobulin production by concanavalin A revealed considerable reduction in all groups studied. In general, the highest suppression was found in patients with Crohn's disease. In patients with Crohn's disease or ulcerative colitis there was no relation between the changes in the in vitro immunoglobulin synthesis and the population of B or T lymphocytes and monocytes present in the peripheral blood. The differences in the spontaneous and stimulated immunoglobulin synthesis by peripheral blood lymphocytes, as found in this study, point to major changes in the regulation of the immunoglobulin synthesis in Crohn's disease and ulcerative colitis.

Adult↗
PubMed1992

Low incidence of ulcerative colitis and proctitis in Bangladeshi migrants in Britain.

To assess the incidence of ulcerative colitis and proctitis in a defined migrant population, a retrospective, epidemiological community study was performed in the London Borough of Tower Hamlets from 1972 to 1989. The population of 164,000 includes 28,000 Bangladeshis. Potential cases were identified from hospital departments of pathology and medical records. There were 107 cases of ulcerative colitis in Europeans and 5 in Bangladeshis. There were 74 and 2 cases of proctitis in these communities, respectively. The mean standardised incidence of ulcerative colitis in Bangladeshis (1.8 cases/10(5)/year) was marginally lower than in Europeans (6.2 cases/10(5)/year, Z = 0.7, n.s.). The mean standardised incidence of proctitis in Bangladeshis was 0.6 cases/10(5)/year and in Europeans 3.2 cases/10(5)/year (Z = 0.6 n.s.). Anatomical extent of colitis was similar in all ethnic communities, although complications were less likely in minority groups. These findings suggest that the incidence of ulcerative colitis and proctitis in Bangladeshis, in Britain, is amongst the lowest in the world.

Age Factors↗
PubMed1994

Effect of experimental colitis on bone metabolism in the rat.

The influence of experimental colitis, induced by trinitrobenzenesulphonic acid with ethanol, on bone mineralisation and mineral metabolism was investigated in male rats. Three days after colitis induction, there was a significant rise (p < 0.01) in urinary calcium excretion, which was still present 20 days later (p < 0.05). Three weeks after colitis induction, urinary hydroxyproline excretion was significantly increased (p < 0.01), while urinary cyclic AMP and phosphorus decreased. Colitis was associated with reduced bone density (p < 0.025), ash weight (p < 0.05) and calcium/volume ratio (p < 0.05), whereas no change was found for bone volume and the phosphorus/volume and magnesium/volume ratios. Serum minerals remained unchanged. We conclude that chronic experimental colitis in the rat leads to resorptive hypercalciuria, increased urinary hydroxyproline and osteopenia. Considering site of inflammation, diet, sex, and absence of therapy, inflammatory mediators, e.g. cytokines, with known catabolic effects on bone, might be involved in the pathogenesis of osteopenia.

Animals↗
PubMed1996

Bacterial peptides enhance inflammatory activity in a rat model of colitis.

Bacterial products released within the gut lumen may alter the course of inflammatory bowel lesions. The effect of intraluminal N-formyl methionyl-leucyl-phenylalanine on mucosal release of inflammatory mediators was investigated in normal and colitis rats (at 1 and 7 days after induction of colitis by trinitrobenzenesulfonic acid). Under anesthesia, the distal colon was perfused using an isosmotic solution with or without synthetic N-formyl methionyl-leucyl-phenylalanine (100 nmol/ml). Effluents were assayed for eicosanoid (PGE2, TXB2 and LTB4) concentration. Myeloperoxidase activity was measured in colonic wall homogenates. In normal rats, peptide perfusion did not change mucosal release of PGE2, TXB2 and LTB4. Colitic rats showed high baseline release of eicosanoids. The peptide did not further increase PGE2 and TXB2 release, but significantly stimulated LTB4 both on days 1 and 7 after induction of colitis. Rats with high myeloperoxidase activity in the colonic wall showed a marked LTB4 response to the peptide. Finally, peptide perfusion increased tissue myeloperoxidase activity in colitis at day 7 but not in colitis at day 1 or in normal rats. In conclusion, bacterial products may activate inflammation. This mechanism of lumen-wall interaction might be involved in the perpetuation of inflammatory lesions of the colonic mucosa.

Animals↗
PubMed1990

Interleukin 1 suppresses inflammation in rabbit colitis. Mediation by endogenous prostaglandins.

Pretreatment with low-dose IL-1 has protective effects in animal models of inflammation or tissue injury, but the mechanisms of these protective effects are not established. To determine if prostaglandins are involved, we administered human recombinant IL-1 beta and measured rectal PGE2 production in rabbits with formalin-immune complex colitis. IL-1 beta (0.3 micrograms/kg) administered 24 h before induction of colitis increased PGE2 (231 +/- 36 to 1,299 +/- 572 pg/ml, P less than 0.01) and reduced subsequent inflammatory cell infiltration index (from 2.8 +/- 0.3 to 1.4 +/- 0.3, P less than 0.02) and edema (from 2.5 +/- 0.3 to 1.3 +/- 0.3, P less than 0.01) compared with vehicle-matched animals. Administration of ibuprofen (10 mg/kg i.v.) together with IL-1 beta prevented the stimulation of PGE2 and the reduction in inflammation. Colonic PGE2 production correlated inversely with subsequent severity of inflammation (P less than 0.02, r = -0.39) and edema (P less than 0.04, r = -0.35). IL-1-administration 30 min before induction of colitis did not affect the severity of inflammation. Similarly, pretreatment with a noninflammatory synthetic peptide (fragment 163-171) of human IL-1 beta, either 30 min or 24 h before colitis induction, did not reduce inflammation or increase prostaglandin synthesis. These data demonstrate that pretreatment with IL-1 beta 24 h before the induction of colitis reduces inflammation by a mechanism that requires prostaglandin synthesis.

Animals↗
PubMed1990

Interleukin 1 (IL-1) gene expression, synthesis, and effect of specific IL-1 receptor blockade in rabbit immune complex colitis.

Interleukin 1 (IL-1) may be a key mediator of inflammation and tissue damage in inflammatory bowel disease (IBD). In rabbits with immune complex-induced colitis, IL-1 alpha and beta mRNA levels were detectable at 4 h, peaked at 12 but were absent at 96 h after the induction of colitis. Colonic IL-1 tissue levels were measured by specific radioimmunoassays. IL-1 alpha was significantly elevated at 4 h (9.4 +/- 1.5 ng/g colon), progressively increased at 48 h (31 +/- 5.8 ng/g) and then decreased by 96 h (11.5 +/- 3.4 ng/g). IL-1 beta levels were 2.0 +/- 0.5 ng/g colon at 4 h, 5.0 +/- 1.6 ng/g at 48 h and undetectable by 96 h. By comparison, colonic levels of PGE2 and LTB4 were unchanged during the first 12 h and did not become elevated until 24 h. IL-1 alpha levels were highly correlated with inflammation (r = 0.885, P less than 0.0001), edema (r = 0.789, P less than 0.0001) and necrosis (r = 0.752, P less than 0.0005). Treatment with a specific IL-1 receptor antagonist (IL-1 ra) before and during the first 33 h after the administration of immune complexes markedly reduced inflammatory cell infiltration index (from 3.2 +/- 0.4 to 1.4 +/- 0.3, P less than 0.02), edema (from 2.2 +/- 0.4 to 0.6 +/- 0.3, P less than 0.01) and necrosis (from 43 +/- 10% to 6.6 +/- 3.2%, P less than 0.03) compared to vehicle-matched colitis animals. These studies demonstrate that (a) IL-1 gene expression and synthesis occur early in the course of immune complex-induced colitis; (b) are significantly elevated for 12 h before the appearance of PGE2 and LTB4; (c) tissue levels of IL-1 correlate with the degree of tissue inflammation and; (d) specific blockade of IL-1 receptors reduces the inflammatory responses associated with experimental colitis.

Antigen-Antibody Complex↗
PubMed2005

Toll-like receptor 9-induced type I IFN protects mice from experimental colitis.

Experimental colitis is mediated by inflammatory or dysregulated immune responses to microbial factors of the gastrointestinal tract. In this study we observed that administration of Toll-like receptor 9 (TLR9) agonists suppressed the severity of experimental colitis in RAG1-/- but not in SCID mice. This differential responsiveness between phenotypically similar but genetically distinct animals was related to a partial blockade in TLR9 signaling and defective production of type I IFN (i.e., IFN-alpha/beta) in SCID mice upon TLR9 stimulation. The addition of neutralization antibodies against type I IFN abolished the antiinflammatory effects induced by TLR9 agonists, whereas the administration of recombinant IFN-beta mimicked the antiinflammatory effects induced by TLR9 agonists in this model. Furthermore, mice deficient in the IFN-alpha/beta receptor exhibited more severe colitis than wild-type mice did upon induction of experimental colitis. These results indicate that TLR9-triggered type I IFN has antiinflammatory functions in colitis. They also underscore the important protective role of type I IFN in intestinal homeostasis and suggest that strategies to modulate innate immunity may be of therapeutic value for the treatment of intestinal inflammatory conditions.

Adaptor Proteins, Signal Transducing↗
PubMed2005

L-selectin and beta7 integrin on donor CD4 T cells are required for the early migration to host mesenteric lymph nodes and acute colitis of graft-versus-host disease.

The homing receptors L-selectin and alpha4beta7 integrin facilitate entry of T cells into the gut-associated organized lymphoid tissues such as the mesenteric lymph nodes and Peyer patches. We studied the impact of inactivation of genes encoding these receptors on the ability of purified donor CD4+ T cells to induce acute lethal graft-versus-host disease (GVHD) associated with severe colitis in irradiated major histocompatibility complex (MHC)-mismatched mice. Whereas lack of expression of a single receptor had no significant impact on the severity of colitis and GVHD, the lack of expression of both receptors markedly ameliorated colitis and early deaths observed with wild-type (WT) T cells. The changes in colitis and GVHD were reflected in a marked reduction in the early accumulation of donor T cells in the mesenteric lymph nodes and subsequently in the colon. The purified WT donor CD4+ T cells did not accumulate early in the Peyer patches and failed to induce acute injury to the small intestine. In conclusion, the combination of CD62L and beta7 integrin is required to induce acute colitis and facilitate entry of CD4+ donor T cells in the mesenteric nodes associated with lethal GVHD in allogeneic hosts.

Animals↗
PubMed2006

Matrix metalloproteinase-9 modulates intestinal injury in rats with transmural colitis.

Proteolysis and degradation of extracellular matrix by metalloproteinases (MMPs) may contribute to intestinal injury in inflammatory bowel disease. In the present study, we investigated the pathogenic role of gelatinases (MMP-9 and MMP-2) on transmural colonic injury in a rat model of chronic colitis, which was induced by intracolonic instillation of trinitrobenzene sulfonic acid (TNBS). The activity and expression of MMP-2 and MMP-9 were measured in colonic tissue and peripheral neutrophils by fluorescence, zymography, Western blot, or immunohistochemistry at different time-points. Furthermore, myeloperoxidase content in colonic homogenates was analyzed to evaluate inflammation. Finally, morphological changes were assessed following early or delayed administration of CGS-27023-A, a synthetic inhibitor of MMPs. We found that the induction of colitis led to a significant up-regulation in tissue gelatinase concentration, whereas no changes in collagenase activity were observed. In addition, up-regulation of pro-MMP-9, but not of pro-MMP-2, was found on Days 7 and 10 following the induction of colitis. Furthermore, transmural MMP-9 was detected by immunofluorescent staining in the inflamed tissue. Consistent with tissue samples, neutrophils from colitic rats showed a significantly increased activity of pro-MMP-9. Finally, early but not delayed treatment with CGS-27023-A attenuated colonic mucosal injury in rats with TNBS-induced colitis. In conclusion, up-regulation of MMP-9 in peripheral and colonic neutrophils modulates transmural colonic injury in rats with TNBS-induced colitis.

Animals↗
PubMed2006

Suppression of experimental colitis by intestinal mononuclear phagocytes.

The contribution of innate immunity to inflammatory bowel disease (IBD) remains an area of intense interest. Macrophages (MØ) and dendritic cells (DC) are considered important factors in regulating the onset of IBD. The goal of this study was to determine if intestinal mononuclear phagocytes (iMNP) serve a pathological or protective role in dextran sulfate sodium (DSS)-induced colitis in mice. Using a conditional MØ/DC depletion transgenic mouse line--MØ Fas-induced apoptosis--to systemically deplete iMNP, DSS colitis histopathology was shown to be more severe in MØ/DC-depleted compared with MØ/DC-intact mice. Similarly, localized iMNP depletion by clodronate-encapsulated liposomes into C57BL/6, BALB/c, and CB.17/SCID mice also increased DSS colitis severity, as indicated by increased histopathology, weight loss, rectal bleeding, decreased stool consistency, and colon length compared with MØ/DC-intact, DSS-treated mice. Histology revealed that iMNP depletion during DSS treatment led to increased neutrophilic inflammation, increased epithelial injury, and enhanced mucin depletion from Goblet cells. iMNP depletion did not further elevate DSS-induced expression of TNF-alpha and IFN-gamma mRNA but significantly increased expression of CXCL1 chemokine mRNA. Myeloperoxidase activity was increased in colons of MØ/DC-depleted, DSS-treated mice, compared with DSS alone, coincident with increased neutrophil infiltration in diseased colons. Neutrophil depletion combined with MØ/DC depletion prevented the increase in DSS colitis severity compared with MØ/DC depletion alone. This study demonstrates that iMNP can serve a protective role during development of acute colitis and that protection is associated with MØ/DC-mediated down-regulation of neutrophil infiltration.

Administration, Oral↗