Indomethacin inhibits cell proliferation and increases cell losses in rat gastrointestinal epithelium

Morphometric analysis of the porcine gastrointestinal tract in a 10-day high-dose indomethacin administration with or without probiotic bacteria Escherichia coli Nissle 1917

BACKGROUND

Nonsteroidal anti-inflammatory drugs may cause severe injury to all parts of the gastrointestinal tract. It has been hypothesised that probiotic bacteria might reduce this adverse effect. The aim of this study was to perform a morphometric evaluation of the gastrointestinal tract in experimental pigs treated using a 10-day high-dose of indomethacin with or without Escherichia coli Nissle 1917 (EcN).

METHODS

Twenty-four healthy mature pigs were included: Group A (controls; 6 animals), Group B (EcN; n = 6), Group C (indomethacin; n = 6) and Group D (EcN & indomethacin; n = 6). EcN (3.5 × 10(10) live bacteria/day for 14 days) and/or indomethacin (15 mg/kg/day for 10 days) were administered. Specimens of the stomach, small and large bowel were routinely processed for microscopic examination. The height of glandular mucosa, height and width of interfoveolar spaces and villi and basement size of epithelial cells were evaluated.

RESULTS

Different effects of indomethacin and EcN on particular parts of the gastrointestinal tract were shown. The indomethacin and probiotics group demonstrated a significantly lower height of cryptal mucosa and colonocytes and widening of the basement size of colonocytes compared to controls (p = 0.004; p < 0.001; p = 0.025). The height of cryptal mucosa was significantly higher in the EcN group compared to controls (p = 0.001).

CONCLUSIONS

Indomethacin alone induced marked adaptation of the gastric mucosa. EcN alone provided a significant favourable trophic effect on the colonic mucosa. However, indomethacin and probiotics administered together comprise the worst impact on all porcine stomach, small and large bowel.

Nimesulide inhibits crypt epithelial cell proliferation at 6 hours in the small intestine in CD-1 mice

To determine whether the gut-sparing selectivity of cyclooxygenase-2 inhibitors is related to early crypt kinetic mechanisms, this study compared the primary effects on small intestinal mucosal epithelial cell proliferation and morphometry of a nonselective dual cyclooxygenase inhibitor, indomethacin, with a cyclooxygenase-2 selective inhibitor, nimesulide. Indomethacin downregulated the crypt cell production rate in the proximal small intestine, and nimesulide reduced cell proliferation in the proximal and distal small intestine. Compared to controls, there were smaller proliferating compartments in the crypts in midintestinal segments in both indomethacin- and nimesulide-treated groups, but more dividing cells in the distal intestine in indomethacin-treated group. Crypt cellularity, numbers, and width were unchanged from control values in both treated groups, suggesting a reduction in crypt cell emigration. Despite its selectivity for inhibiting cyclooxygenase-2, nimesulide induces similar but widespread initial effects on intestinal cell kinetics when compared to indomethacin.

Nimesulide alters cell recruitment into mitosis in murine intestinal crypts without influencing the cell production rate

The use of nonsteroidal anti-inflammatory drugs (NSAIDs) that exhibit COX-2 selectivity is associated with fewer gastrointestinal side effects than seen with more traditional NSAIDs. To determine whether the early effects on cell kinetics in the intestinal mucosal epithelium described after COX-2 selective inhibition are sustained following continuous therapy with these inhibitors, assessments of morphometry and cryptal cell proliferation in the murine small intestinal mucosa were made at 24 hr after treatment with indomethacin, a dual COX inhibitor (10 mg/kg body weight intraperitoneally), nimesulide, a selective COX-2 inhibitor (15 mg/kg body weight intraperitoneally), or vehicle. Nimesulide-treated intestine was elongated beyond control values, in contrast to the shorter indomethacin-treated intestine, but anomalous villous forms were present in both treated groups. Both treatments induced expansion and contraction of proliferating compartments in the crypts in different regions of the intestine but nimesulide did not alter crypt cell production rates, in contrast to the down-regulation induced by indomethacin. These findings may provide some of the fundamental basis for the gut-sparing properties seen in patients treated with COX-2 selective inhibitors.

Cell cycle time and rate of entry of cells into mitosis in the small intestine of young rats

Cell cycle time (T(C)) and the rate of entry of cells into mitosis (r(M)) in the jejunum and duodenum of young rats were investigated using the stathmokinetic method. The cell cycle times in the jejunum were 24.3 and 28.3 h in light and dark periods, respectively. Cell cycle times in the duodenum were 17.1 and 21.5 h in light and dark periods, respectively. Rates of entry of cells into mitosis in the jejunum were 1.2 and 1.1 cells/cell/h in light and dark periods and rates of entry of cells into mitosis in the duodenum were 1.4 and 1.8 cells/cell/h in light and dark periods, respectively. Although these changes to cell cycle time values are not statistically significant, the variation between the two periods should be considered in relation to its possible biological effects.

Heat shock preconditioning modulates proliferation and apoptosis after superficial injury in isolated guinea pig gastric mucosa via an eicosanoid and protein synthesis-dependent mechanism

AIM

In restitution after superficial injury of the gastric mucosa, the epithelial continuity is restored by cellular migration. We have shown that heat shock preconditioning inhibits restitution after superficial injury. This study investigates the effect of heat shock preconditioning on tissue proliferation and apoptosis.

EXPERIMENTAL DESIGN

Paired guinea pig gastric mucosae were mounted and perfused in Ussing chambers (37 degrees C). After heat shock preconditioning (42 degrees C) (30 min) and normothermic recovery (37 degrees C) (150 min) or normothermic perfusion, a superficial injury was induced by luminal exposure to 1.25 mol/L NaCl (5 min) followed by a 3 h restitution. During perfusion, the mucosa was exposed to 30 micromol/L arachidonic acid (AA) to enhance heat shock response, to 50 micromol/L quercetin (Q) to inhibit the metabolism of arachidonic acid via lipoxygenases, to 50 micromol/L indomethacin (In) to inhibit the metabolism of arachidonic acid via cyclo-oxygenases, or to 150 micromol/L cycloheximide (CHX) to inhibit de novo protein synthesis. After the experiment the mucosa was prepared for immunohistochemical analysis of the expression of Mib-1 proliferation antigen and pro-apoptotic protein Bax.

RESULTS

Heat shock decreased Mib-1/Bax ratio and this effect was maintained after superficial injury and exposure to Q, to AA+CHX or to In+CHX. Exposure to CHX, to AA, to In+Q, to In+AA, In+AA+Q or to In+AA+CHX, however, blocked the effect of heat shock preconditioning. The decreasing effect of heat shock preconditioning on Mib-1/Bax ratio could be reversed by exposure to AA+Q or to In.

CONCLUSION

The heat-preconditioning-induced effects on the mucosa are reversible and sensitive to exogenous pharmacological modulation. Heat shock preconditioning inhibits proliferation of superficially injured isolated gastric mucosa by a mechanism involving eicosanoid pathways and de novo protein synthesis.

Mitogenic action of tumour necrosis factor-alpha and interleukin-8 on explants of human duodenal mucosa

Our aim is to examine whether tumour necrosis factor-alpha (TNF-alpha) and interleukin affect the mitotic activity in explants of human duodenal mucosa and to estimate the release of cytokines from explants incubated with TNF-alpha. Biopsy specimens of normal duodenal mucosa were taken from 19 subjects that underwent upper endoscopy for investigation of dyspeptic symptoms or chronic gastrointestinal bleeding. The specimens were processed following guidelines for organ culture technique. Paired biopsy specimens from 12 subjects were cultured for 23 h to achieve steady state and thereafter the explants were incubated 25 h with 10(-13)-10(-9) M of TNF-alpha or IL-8. Mitoses were arrested in the metaphase by adding vincristine sulphate for the last three hours. The explants were then fixed and processed for microdissection. Fifteen crypts were microdissected and the total number of metaphases was determined using the whole crypt as reference volume. The number of metaphases per crypt was also estimated in explants incubated with 10(-10) M TNF-alpha in the presence of anti-IL-8 antibodies. Additional duodenal explants from seven subjects were incubated with 10(-10) M TNF-alpha for 25 h. Thereafter the release of IL-1-beta, IL-6, IL-8 and interferon gamma (IFN-gamma) into the culture medium was measured by enzyme immunoassay and expressed as pg/mg protein. TNF-alpha and IL-8 significantly increased the number of metaphases/crypts (P<0.0001). The addition of anti-IL-8 slightly reduced the number of metaphases/crypt compared to the values observed in the explants incubated with 10(-10) M TNF-alpha alone (P<0.0001). The number of metaphases/crypt in the explants incubated with 10(-10) M TNF-alpha in the presence of anti-IL-8 antibodies was, however, markedly and significantly higher than that of the controls (P<0.000). TNF-alpha induced the release of IL-8 (P<0.01) and IL-6 (P<0.05) from the duodenal explants. TNF-alpha and IL-8 are potent mitogens to human small intestinal crypts. The mitogenic action of TNF-alpha is primarily a direct effect of the cytokine and only to a minor extent mediated by a secondary production of IL-8 in the duodenal explant. Our findings indicate that TNF-alpha and IL-8 may participate in the regulation of cell proliferation in the human small intestinal epithelium.

Keratinocyte growth factor-2 (FGF-10) promotes healing of experimental small intestinal ulceration in rats

Keratinocyte growth factor-2 (KGF-2, repifermin) is a homolog of KGF-1 with epithelial mitogenic activities. We investigated the therapeutic role of KGF-2 in intestinal ulceration and its mechanisms of protection. KGF-2 (0.3-5 mg/kg) was administered before or after induction of small intestinal ulceration by indomethacin (Indo) in prevention and treatment protocols. In acute studies, KGF-2 was injected for up to 7 days before or daily for 5 days after Indo. In a 15-day chronic study, KGF-2 was injected intravenously daily beginning before or 7 days after Indo. Injury was evaluated by blinded macroscopic and microscopic inflammatory scores, epithelial BrdU staining, tissue IL-1beta, PGE(2), and hydroxyproline concentrations, and collagen type I RNA expression. In vitro effects of KGF-2 were evaluated by epithelial cellular proliferation, restitution of wounded monolayers, PGE(2) secretion, and expression of COX-2 and collagen mRNA. Intravenous KGF-2 significantly decreased acute intestinal injury by all parameters and significantly decreased chronic ulceration. Pretreatment, daily infusion, and delayed treatment were effective. KGF-2 promoted in vitro epithelial restitution with only modest effects on epithelial cell proliferation, stimulated COX-2 expression in cultured epithelial cells, and upregulated in vitro and in vivo PGE(2) production. KGF-2 did not affect in vivo fibrosis, although it induced collagen expression in cultured intestinal myofibroblasts. These results suggest that KGF-2 inhibits intestinal inflammation by stimulating epithelial restitution and protective PGs.

Prostaglandins prevent decreased epithelial cell proliferation associated with dextran sodium sulfate injury in mice

BACKGROUND & AIMS

Although dextran sodium sulfate (DSS)-induced colitis is a commonly used model of colonic injury, the mechanism of this model is not understood. The aim of this study was to determine the contribution of prostaglandins to the mechanism of DSS-induced epithelial injury.

METHODS

Mice were treated with 3% DSS in the drinking water for 5 days followed by water only (recovery). Tissue prostaglandin E2 (PGE2) levels were measured, proliferating cells per cecal crypt were determined by bromodeoxyuridine labeling, and the cellular localization of cyclooxygenase (COX)-1 and COX-2 was determined by immunohistochemistry.

RESULTS

DSS decreased the number of proliferating epithelial cells per crypt by approximately 90% and decreased the height of cecal crypts by 40%. Administration of dimethyl PGE2 with DSS reversed the effect of DSS on proliferation but not its effect on crypt shortening. COX-1 was expressed in the crypt epithelium and lamina propria mononuclear cells; DSS treatment down-regulated COX-1 expression only in the epithelium. Dimethyl PGE2 reversed the effect of DSS on COX-1 expression. Recovery was associated with a return to normal COX-1 expression in the epithelium. COX-2 was expressed in lamina propria mononuclear cells.

CONCLUSIONS

Epithelial cell proliferation in the presence of DSS contains a PGE2-sensitive component.

Cyclooxygenase 2 is induced in colonic epithelial cells in inflammatory bowel disease

BACKGROUND & AIMS

Prostaglandins are synthesized by cyclooxygenases (COX)-1 and -2. The expression and cellular localization of COX-1 and COX-2 in normal human colon and inflammatory bowel disease (IBD) surgical resections were studied.

METHODS

COX-1 and COX-2 protein expression and cellular localization were assessed by Western blotting and immunohistochemistry.

RESULTS

COX-1 protein was expressed at equal levels in normal, Crohn's disease, and ulcerative colitis colonic epithelial cells. COX-2 protein was not detected in normal epithelial cells but was detected in Crohn's disease and ulcerative colitis epithelial cells. Immunohistochemistry of normal, Crohn's colitis, and ulcerative colitis tissue showed equivalent COX-1 expression in epithelial cells in the lower half of the colonic crypts. COX-2 expression was absent from normal colon, whereas in Crohn's colitis and ulcerative colitis, COX-2 was observed in apical epithelial cells and in lamina propria mononuclear cells. In Crohn's ileitis, COX-2 was present in the villus epithelial cells. In ulcerative colitis, colonic epithelial cells expressing COX-2 also expressed inducible nitric oxide synthase.

CONCLUSIONS

COX-1 was localized in the crypt epithelium of the normal ileum and colon, and its expression was unchanged in IBD. COX-2 was undetectable in normal ileum or colon, but it was induced in apical epithelial cells of inflamed foci in IBD.

Sulphasalazine, olsalazine and sulphapyridine induce mitogenic actions in the rat intestinal epithelium

Our aim was to study the influence of sulphasalazine (SASP), olsalazine (ADS) and sulphapyridine (SP) on the cell kinetics of the intestinal epithelium in conventional rats. Groups of rats were treated with SASP, ADS or SP for 9 days. After an intraperitoneal injection of a metaphase blocker, the rats were killed and the jejunum, ileum and colon were examined in histological sections by means of the cumulative mitotic index (MI), growth fraction and number of cells in crypts and villi. SP increased both the MI in the jejunum, ileum and colon and the number of crypt cells (p < 0.05 vs controls). In contrast, SASP and ADS increased the MI only in the colonic epithelium (p < 0.05 vs controls). The growth fraction was essentially unaffected. Our results suggest that SASP, SP and ADS have a selective compartment-dependent proliferative action on the epithelium of the intestinal tract.