Effects of diet on experimentally induced intestinal ulcers in rats: morphology and tissue leukotrienes

Elemental Diet Regulates Intestinal Permeability and Antibody Production in Indomethacin-Induced Intestinal Injury Rats

Crohn's disease is a type of inflammatory bowel disease of unknown etiology. Administration of indomethacin (Indo) to rats induces acute mucosal lesions similar to those observed in Crohn's disease patients, but the damage can be prevented by feeding the animals an elemental diet (ED). In this study, we examined changes in intestinal macroscopic appearance, permeability, and immunoglobulin production after administration of Indo to male Sprague-Dawley rats fed normal lab chow or an ED. Intestinal damage was induced by subcutaneous injection of Indo on two successive days. Mucosal permeability, as measured by urinary excretion of phenolsulfonphthalein, peaked on day 2 after Indo injection, whereas the most severe intestinal damage, as scored by macroscopic inflammatory changes, was observed on day 3. Flow cytometric analysis of mesenteric lymph node cells revealed that the proportion of CD45RA⁺ cells was increased after Indo treatment. Furthermore, in vitro-cultured mesenteric lymph node and spleen lymphocytes from Indo-treated rats produced higher levels of IgA and IgG than did cells from vehicle-treated rats. In contrast, IgG and albumin concentrations in plasma were significantly decreased by Indo administration. Notably, none of the Indo-induced changes was observed in ED-fed rats. These findings suggest that an ED may prevent the appearance of Indo-induced mucosal lesions, at least in part, by modulating intestinal permeability and antibody production.

Effects of Mesalazine on Morphological and Functional Changes in the Indomethacin-Induced Inflammatory Bowel Disease (Rat Model of Crohn's Disease)

Morphological and functional changes have been investigated in the rat model of Crohn's disease. The inflammatory bowel disease was induced by indomethacin (1 × 10 mg/kg s.c. for 3 days). Morphological alterations were evaluated by macroscopic scoring system and on the base of histological changes in the small intestine. Functional activities were studied by determination of the intestinal and hepatic elimination of p-Nitrophenol (PNP) and its metabolites (PNP-glucuronide: PNP-G and PNP-sulfate: PNP-S) during the luminal perfusion of PNP. It was found that the indomethacin induced severe macroscopic changes (hyperaemia, petechia, bleeding, erosions, ulcerations) and significant histological alterations in the small intestine of rats which were definitely inhibited by mesalazine (1000 mg/kg by gastric tube for 3 days). Disappearance of PNP from the luminal perfusion solution was diminished by indomethacin which was corrected by administration of mesalazine. Significant depression was found in the luminal appearance of PNP metabolites by giving of indomethacin and these alterations could not be compensated by mesalazine.Hepatic elimination of PNP (biliary excretion of PNP and its metabolites) was decreased definitely by indomethacin which was - at least partly - compensated by mesalazine.The findings of the present study suggest that the indomethacin-induced inflammation in the small intestine represents a useful rat model of Crohn's disease. Morphological and functional alterations caused by indomethacin can be compensated by mesalazine.

Histomorphometric changes of small intestine in pregnant rat

Food intake of rats increases during pregnancy. This requires changes in the structure of the small intestine to absorb additional food. The aim of the present study was to investigate the morphological changes in the layers of small intestine in rats during pregnancy. Duodenum, jejunum and ileum of 18 pregnant Sprague-Dawley rats (day 7, 14 and 21 of pregnancy) were collected. Villous height and width and thickness of lamina propria, tunica muscularis entirely and separately (circular and longitudinal layers) were measured on transverse sections. During pregnancy increasing villi length and muscular layer thickness was observed in duodenum. Furthermore, along with the progress of gestation greatest histomorphometric change in small intestine was observed in the jejunum. The reduction in the ileum histomorphologic indices was observed during pregnancy. In conclusion, increase in histomorphologic indices of duodenum and jejunum supplies more capacity of duodenum to digest food intake during pregnancy and decrease in these indices in ileum controls the absorption of excess produced amino acids and glucose by hyperphagia.

Small bowel injury induced by selective cyclooxygenase-2 inhibitors: a prospective, double-blind, randomized clinical trial comparing celecoxib and meloxicam

BACKGROUND

Selective cyclooxygenase (COX)-2 inhibitors are less harmful to the small bowel mucosa than non-selective anti-inflammatory drugs. We aimed to compare the severity of small bowel mucosal injury in healthy volunteers induced by two selective COX-2 inhibitors, celecoxib and meloxicam, in a randomized, double-blind trial, using capsule endoscopy (CE).

METHODS

Twenty-nine healthy subjects were randomized to take either celecoxib (200 mg twice daily) or meloxicam (10 mg once daily) for 2 weeks. The incidence and the number of small bowel mucosal injuries (bleeding, ulcers, and erosions) observed by CE were compared between the two groups.

RESULTS

The overall incidence of small bowel mucosal injury was not different between the celecoxib group (6 of 14 subjects, 42.9%) and the meloxicam group (4 of 15 subjects, 26.7%, P = 0.45). In subjects with positive CE findings, the number of ulcers was greater in the meloxicam group than in the celecoxib group (P = 0.02), while such a trend was not found with regard to erosions (P = 0.52). The distribution of mucosal lesions within the small bowel was similar in the two groups.

CONCLUSIONS

Selective COX-2 inhibitors are not completely safe for the small bowel. The mucosal lesions may be less severe with celecoxib than with meloxicam.

Microcirculatory changes in experimental mesenteric longitudinal ulcers of the small intestine in rats

Rats receiving intracolonic administration of indomethacin develop longitudinal ulcers on the mesenteric side of the small intestine that are similar to those seen in the acute phase of Crohn's disease. To investigate the causative role of microcirculatory disturbances and to elucidate the therapeutic effect of antioxidants on this enteropathy in rats, we serially evaluated changes in regional blood flow of the small intestine using laser Doppler perfusion imaging and the colored microsphere injection method. Both methods disclosed stepwise hyperperfusion limited to the mesenteric side of the small intestine following transient ischemia during the initial 30-60 minutes. In addition, both a radical scavenger and a radical production inhibitor significantly ameliorated the mesenteric longitudinal ulcers. We concluded that ischemia-reperfusion on the mesenteric side accompanying excessive production of radicals might be strongly involved in indomethacin-induced longitudinal ulcers of the small intestine in rats.

Blockade of tumor necrosis factor-alpha-converting enzyme improves experimental small intestinal damage by decreasing matrix metalloproteinase-3 production in rats

OBJECTIVE

Tumor necrosis factor (TNF)-alpha-converting enzyme (TACE), which has been purified, regulates maturity of TNF-alpha. Matrix metalloproteinases (MMPs) play a key role in various inflammatory conditions. The incidence of intestinal damage has increased, but the mechanism and treatment have not been well understood. The purpose of this study was to investigate the roles of TACE and MMP in indomethacin (Indo)-induced intestinal damage as well as the therapeutic effects of TACE inhibitor and selective MMP inhibitor (sMMPi) on this intestinal damage in rats.

MATERIAL AND METHODS

In the first experiment, serial changes in intestinal ulcers and the production of MMP were investigated. In the second experiment, we assessed the effect of three TACE and/or MMP inhibitors and the production of TNF-alpha, TACE, MMP-3, -9 and tissue inhibitor of MMP (TIMP)-1. The rats were divided into five groups: a control group, and four groups that received Indo alone, Indo plus TACE inhibitor (GM6001), Indo plus a selective MMP-3 inhibitor and Indo plus an MMP-9/13 inhibitor, respectively.

RESULTS

MMP-3 was overexpressed at 24 h after Indo administration, when intestinal injury was most prominent macroscopically and microscopically. GM6001 significantly decreased ulcer severity and suppressed MMP-3 in a dose-dependent fashion. The selective MMP-3 inhibitor dose-dependently ameliorated intestinal damage to the same degree as GM6001, but the MMP-9 inhibitor had no effect on the injury.

CONCLUSIONS

MMP-3 inhibition ameliorates intestinal damage without apparently affecting either TNF-alpha or TACE production and the dose-response curve suggests that the beneficial effect of the so-called TACE inhibitor is actually mainly mediated via MMP-3 inhibition rather than TNF-alpha inhibition.

Medical management of diverticular disease

Diverticular disease is a common disorder affecting 30-55% of the population in the developed world. It has been described as "a deficiency disease of Western civilization", a theory that has been proposed since it was observed that diverticular disease was uncommon in African and other developing countries where dietary fibre consumption was high. At the turn of the century the medical treatment of colonic diverticulosis involved the avoidance of "roughage", which was felt to exacerbate the problem. However, the use of high fibre diets in the prevention and treatment of the symptoms of diverticular disease has now become commonplace, and the development of this practice is discussed in this chapter.

Effects of anti-tumour necrosis factor, interleukin-10 and antibiotic therapy in the indometacin-induced bowel inflammation rat model

BACKGROUND

The administration of indometacin to rats increases intestinal permeability and induces inflammatory pathology of the small bowel. This represents a potential model for Crohn's disease.

AIMS

To analyse the pathogenic role of T cells, tumour necrosis factor and bacterial flora in indometacin-induced changes in small bowel permeability and inflammation.

METHODS

Rats were given indometacin, 13 mg/kg, on day 1 and day 2. The effects of antibiotic (metronidazole, aztreonam and amoxicillin/clavulanic acid), anti- tumour necrosis factor and interleukin-10 therapy were evaluated. The parameters used were weight change, serum haemoglobin, chromium-51 ethylenediaminetetra-acetate permeability and macro-and microscopic score on day 5. Results in conventionally harboured rats were compared with those in T-cell-free rats. Additional in vitro experiments were carried out to test the effect of metronidazole on tumour necrosis factor production.

RESULTS

Indometacin administration resulted in small bowel ulcers and inflammation, independently of T cells. Metronidazole was more potent than amoxicillin/clavulanic acid and anti-tumour necrosis factor in improving the indometacin-induced small bowel inflammation. Only part of the efficacy was through improvement of increased intestinal permeability. Aztreonam and interleukin-10 had no effect. Metronidazole also suppressed in vitro lipopolysaccharide-induced tumour necrosis factor production, suggesting a therapeutic effect of this drug through the inhibition of tumour necrosis factor.

CONCLUSIONS

These data implicate anaerobic bacteria and tumour necrosis factor production, but not T cells, as essential elements of the pathogenesis of indometacin-induced small bowel inflammation. Tumour necrosis factor is also involved in the change in intestinal permeability. Metronidazole was the most efficacious drug in this model, probably because it suppressed anaerobic bacteria and directly inhibited tumour necrosis factor production.

Effect of diet on changes in small intestinal blood flow following intracolonic administration of indomethacin to rats

Liquid diet (LD) is known to be protective against indomethacin-induced enteropathy, which is thought to be associated with ischemic change. We tested the hypothesis that the solid component of diet modulates small intestinal blood flow (SIBF) following indomethacin administration. In the first experiment, male Wistar rats were divided into 18-hr-fasted and normal diet groups. Indomethacin (20 mg/kg) or vehicle was administered intracolonically. SIBF was measured on both the mesenteric and antimesenteric sides of the intestine, using the hydrogen gas clearance method. In the second experiment, rats were given LD alone or LD with increasing concentration of soluble/insoluble fiber for seven days. The baseline SIBF was significantly higher in the groups with normal diet and LD with fiber than in the fasting and LD groups. Following indomethacin administration, SIBF gradually decreased in the groups with normal diet and LD with insoluble fiber, while neither liquid diet nor fasting reduced SIBF. There was no difference in SIBF between the mesenteric and antimesenteric sides of the intestine in any group. Our findings suggest that solid components of diet increase basal SIBF and decrease SIBF following indomethacin administration.

Experimental enteropathy in athymic and euthymic rats: synergistic role of lipopolysaccharide and indomethacin

The aim of this study was to investigate the immunologic and microbiological bases of indomethacin enteropathy. Athymic nude and euthymic specific pathogen-free (SPF) rats were reared under conventional or SPF conditions. In each group, indomethacin was given intrarectally for 2 days. Indomethacin enteropathy was evaluated using a previously described ulcer index and tissue myeloperoxidase activity. Both euthymic and athymic nude rats developed intestinal ulcers to the same degree under conventional conditions but no or minimal ulcer under SPF conditions. Pretreatment of conventional rats with intragastric kanamycin sulfate, an aminoglycoside antibiotic, attenuated indomethacin enteropathy in a dose-dependent fashion. Interestingly, when lipopolysaccharide was injected intraperitoneally in kanamycin-pretreated rats, it fully restored enteropathy in these rats in a dose-dependent manner. We confirmed that kanamycin decreased the number of gram-negative bacteria and endotoxin concentration of the small intestine in a dose-dependent fashion. These results indicate that indomethacin enteropathy is bacteria dependent and does not require a T cell function. Synergy between indomethacin and bacterial lipopolysaccharide may play a major role in this enteropathy.

Protective effect of lactosucrose on intracolonic indomethacin-induced small-intestinal ulcers in rats

BACKGROUND

Little is known about the role of intestinal microflora in the development of indomethacin-induced enteropathy. The aim of this study was to evaluate the effects of lactosucrose, an indigestible oligosaccharide, on intestinal microflora and on indomethacin-induced enteropathy in rats.

METHODS

Male Wistar rats were fed either sucrose (SC) or lactosucrose (LS) for 2 weeks. Indomethacin (24 mg/kg/ day) was administered into the colon twice, 24 h apart, and intestinal ulcers in SC and LS groups were compared macroscopically. In another experiment the bacterial composition in the mid-small-intestinal segment was determined in both groups before and after treatment with indomethacin.

RESULTS

After indomethacin treatment small-intestinal ulcers were less severe in the LS than in the SC group (ulcer index: median, 0.13 (range, 0.05-0.19) versus 0.23 (0.13-0.34); P < 0.05). Total bacterial count did not differ significantly between the two groups. Indomethacin increased the number of Enterobacteriaceae in both groups, but the increase was less in the LS group. The number of streptococci was also significantly increased in the SC group but not in the LS group.

CONCLUSION

These results suggest that LS has some protective effects on indomethacin-induced enteropathy and that this protective effect is in part due to the maintenance of intestinal microflora.

Leucocyte endothelial cell adhesion in indomethacin induced intestinal inflammation is correlated with faecal pH

BACKGROUND

Recent studies indicate that faecal pH is acidified in patients with inflammatory bowel disease compared with healthy controls. In healthy volunteers, stool pH, faecal flora, and bile acid concentration could be affected by means of elemental diets.

AIMS

To assess the role of variations of faecal pH on leucocyte endothelial cell adhesion in indomethacin induced long lasting ileitis in rats.

METHODS

Indomethacin (7.5 mg/kg subcutaneously) was injected twice, 24 hours apart. Rats were either fed with the identical diet before and 10 days after the induction of inflammation until the experiment, or the diet was changed at the time of induction. Ten postcapillary mesenteric venules (30 microns diameter) per animal were observed using intravital microscopy. Macroscopic visible intestinal ulceration was scored and faecal pH of different sections of the small bowel was determined.

RESULTS

Small intestinal faecal pH was 8.5 in controls and 8.0 in indomethacin treated animals. Indomethacin significantly changed microcirculatory parameters: there was a 2.3-fold increase in leucocyte adherence, a 3.2-fold increase in leucocyte emigration, and a 20% reduction in shear rate. Application of various diets or diet combinations resulted in variations in faecal pH ranging from 7.8 to 8.8 which were inversely correlated with macroscopic ulcerations (r = -0.67). Leucocyte adherence was attenuated with increased pH and augmented with decreased pH (r = -0.55). Venular wall shear rate was positively correlated with faecal pH (r = 0.48) while leucocyte emigration showed no correlation. Leucocyte rolling velocity was not significantly altered. Normalisation of faecal pH by different alkalising drugs induced a significant decrease in leucocyte adherence in standard fed, indomethacin treated rats.

CONCLUSIONS

Faecal pH is lowered in the indomethacin model of long lasting ileitis in rats, which is similar to human inflammatory bowel disease. Alkalisation of faecal pH due to different diets or alkalising drugs reduces indomethacin induced leucocyte endothelial cell adhesion and macroscopic intestinal damage. These results may provide a rationale for the therapeutic effect of enteral diets in Crohn's disease.