An animal model of longitudinal ulcers in the small intestine induced by intracolonically administered indomethacin in rats

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.

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.

Preventive effect of immunosuppressive agents against indomethacin-induced small intestinal ulcers in rats

The mechanism of nonsteroidal antiinflammatory drug-induced intestinal ulcers is not clearly understood. To evaluate whether immunosuppressants have a preventive effect against indomethacin-induced gastrointestinal damage, we investigated the effects of prednisolone, cyclosporin, and the newly developed immunosuppressant FK-506 in intracolonically indomethacin-treated rats: 24 mg/kg of indomethacin, administered intracolonically for two days, caused gastric ulcers and two types of small intestinal ulcers (longitudinal ulcers and scattered small ulcers). Pretreatment with intraperitoneal immunosuppressants reduced the size of gastric ulcers. Both cyclosporin (10 mg/kg) and FK-506 (1 mg/kg, 2 mg/kg) treatments significantly reduced the incidence and the length of the longitudinal ulcers of the small intestine when compared to the vehicle-treated controls, whereas prednisolone (20 mg/kg) did not show any preventive effect. Furthermore, the number of small scattered ulcers of the small intestine was significantly reduced by the high dose of FK-506 (2 mg/kg), but not by cyclosporin or prednisolone. These findings indicate that immunosuppressants have protective and antiinflammatory effects in indomethacin-induced gastroenteropathy, suggesting that cytokines may be important mediators in the pathogenesis of enteropathy induced by nonsteroidal antiinflammatory drugs.