Indomethacin inhibits cell proliferation in the oxyntic epithelium of the rat

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.

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.

PGE(2) receptors and synthesis in human gastric mucosa: perturbation in cancer

Recent evidence suggests that prostanoids are an important participant in the pathobiology of gastric adenocarcinoma, but the location and identity of cells in tumor-adjacent gastric mucosa able to synthesize and/or bind specific prostanoids is not clear. Using probes for cyclooxygenase 1 and 2 mRNA and protein as well as for the EP family of PGE(2) receptors, we sought to define the biology of prostanoids in adjacent human gastric mucosa at the site of tumor invasion. In mucosa adjacent to an invasive gastric adenocarcinoma, expression of cyclooxygenase was prominent, with COX 1 primarily in mucosal T lymphocytes surrounding nests of tumor cells. Densitometry showed these tumor-adjacent cells had substantial levels of COX 1 immunoreactive protein (relative intensity, 3.2). Cyclooxygenase 2 was newly expressed among these cells as well, but was limited in number (<25% of cyclooxygenase-positive T lymphocytes) in tumor-adjacent mucosa. Further, CD3(+) mononuclear cells, adjacent to tumor, strongly expressed prostanoid receptor EP(4) (relative intensity, 8.0), but cells with this receptor were not evident in the tumor itself. In contrast, normal gastric mucosa showed a consistent and structured expression of cyclooxygenase and PGE(2) receptor immunoreactive protein among mucosal cells. Cyclooxygenase 1 and PGE(2) receptor EP(4) were expressed on mucosal CD3(+) T lymphocytes in the lumenal (upper) third of gastric mucosa; and prostanoid receptors EP(2), EP(3) and EP(4), on gastric epithelia lining gastric pits. In situ hybridization with COX cDNAs confirmed these findings, and neither COX 2-specific mRNA nor protein was detected in normal gastric tissue. Our studies suggest that synthetic machinery and receptors for PGE(2), prominently expressed by T lymphocytes in gastric mucosa at the boundary of normal mucosa with tumor cells, may play a central role in prostanoid-driven tumorigenesis of this tissue.

Eicosanoids and the large intestine

During the past three decades, many studies have been conducted to determine the precise role of eicosanoids in colorectal physiology and pathophysiology. This research has increased our understanding of bioactive lipid signaling, and may contribute to the development of more effective therapeutic modalities for digestive diseases in the future. The purpose of this report is to provide a brief overview of the role of eicosanoids in the colon and rectum. This information has been organized according to both functional and disease-related categories. The role of eicosanoids in colonic secretion, motility, inflammatory bowel disease, and colorectal neoplasia will be discussed.

Involvement of cyclooxygenase-2 in proliferation and morphogenesis induced by transforming growth factor alpha in gastric epithelial cells

Transforming growth factor alpha is one of the most potent growth factors for gastrointestinal epithelium. In this study, we examined the roles of cyclooxygenase-2 on proliferation and morphogenesis of RGM1 rat gastric epithelial cells after stimulation with transforming growth factor alpha in vitro, RGM1 cells increased expression of cyclooxygenase-2 messenger RNA 20-60 min after stimulation with transforming growth factor alpha. Transforming growth factor alpha stimulated [3H]thymidine incorporation and tubulogenesis of RGM1 cells in collagen matrix, both of which were significantly suppressed by treatment with a cyclooxygenase-2 specific inhibitor, NS-398 or cyclooxygenase-2 antisense oligonucleotide. Both of the treatment lowered prostanoid production by enzyme immunoassay. The transforming growth factor alpha-induced expression of cyclooxygenase-2 is followed by cell proliferation and development of tubular morphology of RGM1 gastric epithelial cells. Treatment with cyclooxygenase-2 inhibitor and cyclooxygenase-2 antisense oligonucleotide suppressed these responses induced by transforming growth factor alpha suggesting the involvement of cyclooxygenase-2 in proliferation and morphogenesis in gastric mucosal epithelium.

Endogenous prostaglandins and microflora modulate DNA synthesis and neuroendocrine peptides in the rat gastrointestinal tract

BACKGROUND

Previous studies suggest that E2 prostaglandins and the microflora may participate in the regulation of endocrine cells and of gastrointestinal cell kinetics. Our aim is to examine the actions of endogenous prostaglandins and of the microflora on gastrointestinal cell proliferation and tissue levels of neuroendocrine peptides.

METHODS

Germfree and ex-germfree rats were treated with subcutaneous placebo or 1.5 mg/kg indomethacin for 3 days. All rats were labeled with 3H-methyl-thymidine, and biopsy specimens from different parts of the gastrointestinal tract were processed for autoradiography. DNA synthesis was estimated by the labeling index, except in the oxyntic mucosa, where the total number of labeled cells present in 7.5 mm mucosa was used. The concentration of neuroendocrine peptides was determined by radioimmunoassay.

RESULTS

In the germfree rat, indomethacin reduced DNA synthesis in the fundus, duodenum, and proximal jejunum (P < 0.05) and the number of villous cells throughout the small intestine (P < 0.05). Exposure to microflora increased DNA synthesis in the proximal and distal jejunum, ileum, and colon (P < 0.05 versus germfree controls) and the number of crypt cells in the distal small intestine and colon (P < 0.05) and reduced the number of villous cells in the small intestine (P < 0.05) but did not affect tissue concentrations of neuroendocrine peptides. Indomethacin increased the concentration of somatostatin in the stomach, duodenum, and colon of germfree rats (P < 0.001), the concentration of calcitonin gene-related peptide (CGRP) and enteroglucagon in the proximal and distal jejunum and ileum (P < 0.001), and the concentration of glucagon in the colon (P < 0.05). The concentrations of somatostatin, CGRP, and glucagon were lower in indomethacin-treated ex-germfree rats than in indomethacin-treated germfree rats (P < 0.01).

CONCLUSIONS

Indomethacin selectively reduced DNA synthesis in the upper gastrointestinal tract of germfree rats, indicating a basal stimulatory role for endogenous prostaglandins on cell proliferation. Endogenous prostaglandins modulate synthesis or release of gastrointestinal neuroendocrine peptides. Somatostatin may mediate indomethacin-induced reduction of DNA synthesis. The microflora stimulates cell proliferation and influences tissue levels of neuroendocrine peptides in a manner opposite to that of indomethacin.

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

Gastrointestinal cell proliferation was estimated in histological sections of rats treated with low and high doses of parenteral indomethacin for 3 to 60 days. Mitoses were arrested with vincristine and cells in S phase were labeled with tritiated thymidine. Short-term, low-dose treatments reduced the mitotic activity in the oxyntic and small intestinal epithelium, whereas moderate doses restored the mitotic index and high doses increased the proliferative activity and produced epithelial hyperplasia. Long-term, low-dose treatments increased cell proliferation in the small intestine and reduced the number of villous cells. Indomethacin did not affect the proliferative response elicited by refeeding in the oxyntic mucosa, but the simultaneous administration of prostaglandin E2 analog increased the number of arrested mitoses. The turnover of labeled cells was accelerated by indomethacin, particularly in the small intestine. These findings indicate that prostaglandins are regulators of the cell kinetics of the gastrointestinal epithelium but, at the same time, they disclose the presence of trophic mechanisms that are independent of the synthesis of endogenous prostaglandins.

Eicosanoids and the gastrointestinal tract

Determining the role of eicosanoids in gastrointestinal physiology and pathophysiology has been an active area of investigation over the past 20 years. The landmark discovery of prostaglandin endoperoxide synthase and other enzymes involved in the production of arachidonic acid products (lipoxygenases and epoxygenases) ushered in a new era of research. The goal of this review is to distill a large body of work pertaining to studies of eicosanoids in the gastrointestinal tract. This review has been organized according both to functional (secretion and motility) and disease-related (inflammation, mucosal injury, and neoplasia) effects. The aim of this article is to present a clear summary of this area of gastroenterology so that future research can be directed in a logical and productive manner.

Effects of diclofenac sodium and indomethacin on proliferation and collagen synthesis of lens epithelial cells in vitro

We investigated the effects of diclofenac sodium and indomethacin on the proliferation of and collagen synthesis by lens epithelial cells (LECs) of human cataracts in culture. The anterior capsule with attached LECs, obtained by anterior capsulotomy during cataract surgery, was cultured directly without cell dispersion. When the culture became almost confluent, diclofenac sodium or indomethacin at various concentrations was added to the incubation medium. The incorporation of 3H-thymidine and 3H-proline into the LECs was measured after the cells were labeled with these radioactive materials. Both drugs greatly suppressed the incorporation of 3H-thymidine and of 3H-proline, indicating that they inhibit cell division and collagen synthesis by LECs. Both drugs may help prevent posterior capsule opacification.

Influence of indomethacin and difluoromethylornithine on human tumour growth in nude mice

Biopsy material from six human colorectal carcinomas was transplanted to 114 nude mice. A treatment protocol was established which included no treatment (control, C), indomethacin (I), difluoromethylornithine (D) or a combination of both (ID). The influence of the various drugs on tumour weight and protein kinase CK2 activity was monitored. CK2 activity was measured because in all tumours examined so far the enzyme activity was found to be enhanced several-fold when compared to the non-neoplastic tissue of the same patient. More than half of the investigated tumours showed a conspicuous reduction in weight after drug treatment, and I and the combination of D/I were significantly effective using the mixed model analysis. Furthermore, we have tried to discover whether there is a change in the subcellular localisation of protein kinase CK2 subunits associated with drug treatment. We analysed the tumours and the non-neoplastic control tissues by immunohistochemistry using antibodies directed against the CK2 subunits and against the proliferation marker Mib. In addition, we have also investigated the behaviour of the nucleolar protein B23 which has also been shown to be enhanced several-fold in rapidly proliferating tissue and which is also a substrate for CK2. The immunohistochemical data suggest that, irrespective of the drug treatment and the observed reduction in CK2 activity, the CK2 subunits remain localised in the nucleus.

Nonsteroidal anti-inflammatory drug use and sporadic colorectal adenomas

First, and most importantly, the standard of care for treating adenomatous polyps is polypectomy and not therapy with NSAIDs. The initial clinical observation by Waddell and Loughry in 1983 that sulindac treatment influenced rectal polyps in patients with FAP has led to a considerable amount of research, commentary, and discussion during the past decade. These original observations have been validated by controlled clinical trials. Work presented in this issue by Ladenheim et al. indicates that sulindac may not be effective therapy for sporadic polyps that are present before initiation of treatment (secondary prevention). Even though their study may have failed to show a small effect of NSAIDs on polyps, further investigation of the ability of NSAIDs to cause regression of established polyps is probably not warranted. A more clinically relevant question, whether or not these agents can be used in a primary prevention strategy to prevent the development of adenomas in a colon devoid of these lesions, is currently being addressed in a large trial with sufficient statistical power to render firm conclusions (personal communication, January 1995). The multiple reports that sulindac treatment causes regression of adenomas in patients with FAP has stimulated research directed at understanding the molecular basis for these effects. If we are able to understand the molecular mechanism by which NSAIDs decrease the risk of colorectal cancer, we might be able to design more effective drugs or other approaches that would be clinically useful in humans for colorectal cancer chemoprevention.

Up-regulation of cyclooxygenase 2 gene expression in human colorectal adenomas and adenocarcinomas

BACKGROUND/AIMS

Several clinical, epidemiological, and animal studies indicate that nonsteroidal anti-inflammatory drugs (NSAIDs) may alter the incidence of colorectal cancer. A likely target for NSAIDs is cyclooxygenase, a key enzyme in arachidonic acid metabolism. Two isoforms of this enzyme have been identified; cyclooxygenase (COX) 1 and COX-2. The present study was undertaken to determine if there is differential expression of these isoforms in colorectal neoplasia, and, if so, at what stage in malignant transformation this occurs.

METHODS

COX-1 and COX-2 messenger RNA (mRNA) levels were determined by Northern blot analysis of poly(A)+ RNA isolated from human colorectal cancers, adenomas, and accompanying normal mucosa.

RESULTS

There was a marked increase in COX-2 mRNA levels in 12 of 14 carcinomas (86%) compared with paired normal mucosa. In contrast, there was equivalent intensity of the COX-1 mRNA transcript between the normal mucosa and cancer in all 14 cases. In six pairs of colorectal adenomas and normal mucosa, three showed up-regulation of COX-2 in the adenoma compared with the normal mucosa. Because COX-2 expression is low to undetectable in normal colorectal mucosa, 14 unpaired adenomas were examined for COX-2 expression; a clearly detectable transcript was identified in six (43%).

CONCLUSIONS

COX-2, but not COX-1, gene expression is markedly elevated in most human colorectal cancers compared with accompanying normal mucosa. Furthermore, COX-2 expression seems to be increased in a subset of adenomas. COX-2 may provide an attractive therapeutic target in colorectal neoplasia.