Effects of nonsteroidal anti-inflammatory drugs and misoprostol on gastroduodenal epithelial proliferation in arthritis

Proton pump inhibitor co-therapy normalizes the increased cell turnover of the gastric mucosa both in NSAID and selective COX-2 users

Proton pump inhibitor (PPI) co-therapy is considered the best strategy in preventing gastrointestinal complications during non-steroidal anti-inflammatory drug (NSAID) treatment, but there is limited information available on its effect on gastric mucosal cell kinetics. To evaluate the effect of PPI co-therapy on gastric mucosa we investigated epithelial cell proliferation, apoptosis, epithelial growth factor receptor (EGFR) and p53 expression in patients on chronic non-selective NSAID or cyclooxygenase-2 selective inhibitor (COX-2) treatment. Gastric biopsies of the antrum were taken from 10-10 patients on chronic NSAID and COX-2, therapy prior and after 6 months PPI co-therapy, and 10 controls without any treatment. Cell proliferation, apoptosis, EGFR and p53 expression were measured by immunohistochemistry. At least 600 glandular epithel cells were encountered and results were expressed as % of total cells counted. We found increased cell proliferation in patients on chronic COX-2 but not on NSAID therapy. Patients on either NSAID or COX-2 therapy had an increased p53 and decreased EGFR expression. PPI therapy reversed not only the increased cell proliferation and p53 expression, but also the suppressed EGFR expression when administered as co-therapy. The fewer gastrointestinal side effects observed during chronic COX-2 therapy may partially be the result of the higher cell proliferation. This effect is not mediated by the EGFR pathway. PPI co-therapy normalizes the disturbed cell kinetics irrespective of NSAID treatment used.

Insights into the mechanisms of gastric adaptation to aspirin-induced injury: a role for regenerating protein but not trefoil peptides

The phenomenon of reduced gastric mucosal injury despite repeated doses of a damaging agent is termed adaptation. Adaptation to nonsteroidal anti-inflammatory drug-induced injury has been clearly demonstrated in both humans and experimental animals; however, the precise mechanisms remain unclear. We hypothesized that mediators of adaptation might be the regenerating protein (RegI) and the trefoil peptides TFF1 and TFF2, because these proteins play pivotal roles in gastric mucosal protection and repair. The gene expression and the protein levels of these proteins were measured and compared in normal, aspirin-injured, and aspirin-adapted rat stomachs. TFF gene and protein expression levels were similar in all three groups, whereas RegI gene expression and protein levels in adapted stomach were increased. A time course analysis of RegI expression during the onset and offset of adaptation showed that mucosal RegI increased during the development of adaptation, was maintained during subsequent aspirin dosing, and returned to baseline levels once dosing had ceased and adaptation was lost-indicative of a causal role in the adaptation process. Colocalization of increased RegI with gastric epithelial areas showing increased proliferation also suggests that RegI may be an important mediator of the resolution of mucosal injury that is characteristic of gastric adaptation to aspirin.

Effect of cyclooxygenase-2 inhibition on human Helicobacter pylori gastritis: mechanisms underlying gastrointestinal safety and implications for cancer chemoprevention

Cyclooxygenase (COX)-2 expression and prostaglandin production is increased by Helicobacter pylori infection. Non-selective COX inhibitors reduce prostaglandins and mucosal proliferation in infected mucosa and may reduce gastric cancer risk, but ulceration precludes their use. COX-2 inhibitors cause fewer ulcers and may be chemopreventive. Physiological studies of COX-2 inhibitors in humans with H. pylori infection have not been performed.

AIM

To study the impact of COX-2 specific inhibition on gastric prostaglandin levels, H. pylori gastritis and proliferation.

METHODS

Twenty infected (eight males, 12 females; age 38 +/- 1.8) and six uninfected (four males, two females; age 36 +/- 3.5) healthy volunteers received rofecoxib 25 mg daily for 14 days. Endoscopic biopsies were evaluated for prostaglandin E2 (PGE2) content, gastritis and proliferation.

RESULTS

Before drug therapy, compared to uninfected, H. pylori-infected subjects had significantly higher: (a) gastric mucosal PGE2 (pg/mg tissue) in the gastric body and antrum, (b) H. pylori score in body and antrum and (c) mid-gland proliferation index in antrum and body. The COX-2 inhibitor did not significantly affect PGE2 levels, gastritis scores or proliferation indices in the body or antrum in the H. pylori-positive or -negative subjects.

CONCLUSION

The predominant source of increased gastric PGE2 in H. pylori infection appears to be COX-1-derived. In non-ulcerated H. pylori gastritis, COX-2 inhibition does not affect cellular proliferation. Rofecoxib's lack of effect on gastric prostaglandin levels and proliferation in H. pylori-infected mucosa may explain the absence of an increased ulcer risk among COX-2 inhibitor users with H. pylori infection. The lack of significant effect on intermediate biomarkers raises uncertainty regarding the potential of specific COX-2 inhibitors for chemoprevention of gastric cancer.

Effects of nonsteroidal anti-inflammatory drugs on Helicobacter pylori-infected gastric mucosae of mice: apoptosis, cell proliferation, and inflammatory activity

Helicobacter pylori and nonsteroidal anti-inflammatory drugs (NSAIDs) are two well-known important causative factors of gastric damage. While H. pylori increases apoptosis and the proliferation of gastric epithelial cells and is an important factor in peptic ulcer and gastric cancer, NSAIDs induce cell apoptosis and have antineoplastic effects. We investigated the effects of NSAIDs (a nonselective cyclooxygenase [COX] inhibitor [indomethacin] and a selective COX-2 inhibitor [NS-398]) on the apoptosis and proliferation of gastric epithelial cells and gastric inflammation in H. pylori-infected mice. C57BL/6 mice were sacrificed 8 weeks after H. pylori SS1 inoculation. Indomethacin (2 mg/kg) or NS-398 (10 mg/kg) was administered subcutaneously once daily for 10 days before sacrifice. The following were assessed: gastric inflammatory activity, gastric COX protein expression by Western blotting; gastric prostaglandin E(2) levels by enzyme immunoassay, apoptosis by terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling, and cell proliferation by Ki67 immunostaining. Compared to the controls, H. pylori infection and/or NSAID treatment increased COX-1 and COX-2 protein expression. Gastric prostaglandin E(2) levels, apoptotic index, cell proliferation index, neutrophil activity, and the degree of chronic inflammation were all increased by H. pylori infection, and these effects were significantly decreased by indomethacin treatment. However, NS-398 treatment after H. pylori infection did not induce a significant reduction, although it did result in a tendency to decrease. These results show that NSAIDs can reverse the increased apoptosis and proliferation of epithelial cells and inflammatory activity in the stomachs of H. pylori-infected mice and that, like COX-2 activation, COX-1 induction contributes to the change of gastric mucosal cell turnover and inflammation induced by H. pylori infection.

Comparison of the effects of concanavalin-A and epidermal growth factor on epithelial cell proliferation in the rat intestine

BACKGROUND

Concanavalin-A, the lectin present in Jack beans, binds to mannose- and glucose-containing residues and can interact with the epidermal growth factor receptor and moderate cell proliferation in vitro.

AIM

To compare the actions of concanavalin-A and epidermal growth factor on the gastrointestinal tract in vivo.

METHODS

Rats maintained on total parenteral nutrition were given intragastric concanavalin-A, intravenous epidermal growth factor or concanavalin-A and epidermal growth factor. Cell proliferation and crypt fission were assayed in 'micro-dissected' crypts.

RESULTS

Concanavalin-A and epidermal growth factor both significantly elevated proliferation in the small intestine and colon. No significant interaction between the effects of these two agents was seen, except in the mid small intestine where there was a synergistic interaction. Concanavalin-A had no effect on crypt branching. Epidermal growth factor significantly reduced branching in the distal small intestine and mid colon.

CONCLUSION

The effects of the two agents appeared to be separate, except in the mid small intestine where they were additive. This is in marked contrast with the actions reported in vitro, where concanavalin-A is a powerful inhibitor of epidermal growth factor-induced cell proliferation. Concanavalin-A thus has potential for enhancing the functions of the small intestine.

Resistance to apoptosis is a mechanism of adaptation of rat stomach to aspirin

Adaptation of the gastric mucosa to nonsteroidal anti-inflammatory drug-induced injury is a well-documented phenomenon, but the mechanisms are not known. We investigated whether changes in stress protein expression and apoptosis play roles in adaptation of rat stomach to aspirin. RT-PCR and Western blotting techniques were used to analyze mRNA and protein expression of HSP72 and HSP90 and cleavage of caspase 3 protein. Apoptosis was detected by the TUNEL method and quantified. HSP72 mRNA and protein expression was unchanged in adapted mucosa, whereas HSP90 mRNA and protein levels decreased. Caspase 3 protein was activated, and the number of apoptotic cells increased in mucosa after one aspirin dose. However, in adapted mucosa after aspirin, activated caspase 3 and the number of apoptotic cells had returned to basal levels. Induction of the stress response was found not to be a mechanism of mucosal adaptation against multiple doses of aspirin. Our results lead us to propose instead that resistance to aspirin-induced apoptosis plays a role in the protective phenomenon of adaptation.

Does the response of the intestinal epithelium to keratinocyte growth factor vary according to the method of administration?

BACKGROUND

Keratinocyte growth factor (KGF) is a potent mitogen and may be of value for the treatment of conditions such as short bowel syndrome and chemotherapy-induced mucositis. However the most efficacious route and method of administration is unclear.

METHODS

Rats maintained by total parenteral nutrition (TPN) were given KGF (1 mg/kg/rat/day, i.v.) infused continuously or as a once-daily injection. The same dose was also given s.c. to chow-fed rats. Changes in gut growth were assessed by measurement of wet weight, proliferation (vincristine induced metaphase arrest) and crypt branching index. Changes in gut hormone profile were also determined to examine if any trophic effects were mediated via this mechanism.

RESULTS

KGF caused a 70-100% increase in wet weight of the stomach, small and large intestine of TPN-fed rats (P < 0.01) with no significant differences seen between the two methods of administration. The increase in metaphase counts was greatest in the stomach (about seven-fold P < 0.01), but was less pronounced in the distal small intestine and colon (about 50% increase). The trophic effect of KGF was much less prominent in orally-fed rats. Crypt branching index was significantly reduced by KGF in the proximal small intestine of TPN, but not orally-fed rats. Plasma gastrin, PYY, total glucagon, enteroglucagon and GLP-1 all increased by two-three-fold (all P < 0.01) in response to KGF whereas insulin levels fell by about 25% in the TPN group.

CONCLUSIONS

The mitogenic action of KGF occurred predominantly in the stomach and proximal small intestine. Its efficacy was less pronounced in orally-fed animals, suggesting KGF may be of greatest benefit in conditions associated with lowered intestinal proliferation. Clinical trials of KGF can probably use single daily i.v. injections without reduction in efficacy.

Effect of naproxen on the hamster gastric antrum: ulceration, adaptation and efficacy of anti-ulcer drugs

BACKGROUND

Various animal models of non-steroidal anti-inflammatory drug (NSAID)-induced gastric ulceration exist. These models have limitations, which make them less relevant to the human situation.

AIM

: To develop a more simple and more relevant model of NSAID-induced gastric ulceration and adaptation.

METHODS

Gastric ulceration was evaluated following the orogastric administration of naproxen (80 mg/kg b.d.) to hamsters. The effects of misoprostol and famotidine on gastric acid secretion and ulceration were also determined. Gastric adaptation was evaluated by proliferating cell nuclear antigen (PCNA) immunohistochemistry, in hamsters given naproxen for 3 weeks. Antral resistance to acute injury by NSAIDs and ethanol was also determined in these animals.

RESULTS

Naproxen caused primarily gastric antral ulceration, which decreased from day 3 to day 21. This gastric adaptation was accompanied by an increase in PCNA positive cells, particularly on days 7 and 14. The adapted gastric antral mucosa was resistant to acute damage by various agents. Misoprostol (1 or 100 microg/kg) prevented antral ulceration, without affecting gastric acid secretion. Despite decreasing acid output by> 90%, famotidine (30 mg/kg) failed to prevent ulceration.

CONCLUSION

The administration of naproxen (80 mg/kg b.d.) to hamsters is a simple, reliable and relevant method for evaluating NSAID-induced gastric antral ulceration and adaptation.

Growth markers in the human gastric mucosa during adaptation to continued aspirin administration

The mechanism of gastric mucosal adaptation to continued aspirin (ASA) administration is unknown. We have investigated growth and proliferation markers in healthy subjects under prolonged ASA treatment. In eight healthy volunteers, ASA treatment (2 g/day) was continued for 14 days. Endoscopy was performed before medication; at days 3, 7, and 14 of ASA treatment; and at days 16 and 18 (2 and 4 days, respectively, after medication was ceased). Gastric biopsies from oxyntic and antral mucosa were studied by histology and by histochemistry for proliferating cell nuclear antigen (PCNA), epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha), and epidermal growth factor receptor (EGFr). ASA treatment did not change the expression of EGF and EGFr significantly. The PCNA index showed local inconsistent variations. However, increased TGF-alpha expression after ASA was noted, particularly in hyperplastic surface epithelium. Edema and teleangiectases were common in gastric mucosa after ASA. An increasing incidence of foveolar hyperplasia was also noted in the antral mucosa. Healthy subjects on prolonged ASA treatment gradually develop parameters of chronic reactive gastritis accompanied by increased TGF-alpha expression in gastric surface epithelial cells, especially in hyperplastic areas.

Gastric adaptation to aspirin and stress enhances gastric mucosal resistance against the damage by strong irritants

BACKGROUND

Gastric mucosal adaptation to injury induced by repeated application of aspirin (ASA) or stress is a well-documented phenomenon, but it is known whether such adaptation affects the mucosal tolerance to other strong irritants.

METHODS

In this study gastric adaptation was induced by repeated daily administration of acidified ASA for 4 consecutive days (Series A) or by 3.5H of water immersion and restraint stress (WRS) applied every other day for up to 8 days (series B). When the adaptation to ASA or WRS was fully developed, rats of series A and B were challenged with strong irritants such as 100% ethanol, 200 mM acidified taurocholate (TC), or 25% NaCl for 1 h or with WRS for 3.5 h.

RESULTS

ASA or WRS applied once produced numerous gastric lesions and deep histologic necrosis accompanied by a decrease in gastric blood flow. With repeated application of ASA or stress the mucosal adaptation to ASA and WRS developed; the area of gastric lesions was reduced by 86% and 56%, respectively, and this was accompanied by a marked decrease of superficial and deep necrosis, and increase in gastric blood flow (GBF) and the enhancement of mucosal regeneration. An increase in mucosal and luminal contents of epidermal growth factor (EGF) and in mucosal expression of EGF receptors was also observed in the mucosa adapted to ASA or stress. In rats adapted to ASA or stress and then challenged with 100% ethanol, 200 mm TC, 25% NaCl, stress or ASA, the areas of macroscopic gastric lesions and deep histologic necrosis were remarkable reduced as compared with those in non-adapted vehicle-treated rats. This was also accompanied by a significant decrease in (GBF), a marked increase of mucosal and luminal contents of EGF and expression of its receptors, and enhanced mucosal cell proliferation.

CONCLUSIONS

Gastric adaptation to ASA or stress enhances mucosal resistance to the injury induced by strong irritants, and this appears to be mediated by mucosal regeneration, probably resulting from increased luminal and mucosal contents of EGF and excessive expression of its receptors.

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.

Do non-steroidal anti-inflammatory drugs have an effect on gastric cell turnover?

AIM

To study the effect of non-steroidal anti-inflammatory drugs (NSAIDs) on gastric cell turnover using an in vitro immunohistochemical method of bromodeoxyuridine (BrDU) uptake.

METHODS

Thirty patients undergoing routine upper gastrointestinal endoscopy were studied. Sixteen had taken NSAIDs daily for more than 3 months and there were 14 age-matched controls. Endoscopic gastric antral biopsies were obtained and stained immediately using the BrDU technique. Cell proliferation was expressed as a labelling index percentage (LI%) defined as the number of BrDU-labelled nuclei in 10 gastric glands, expressed as a percentage of the total cells in the gastric gland.

RESULTS

Gastric infection with Helicobacter pylori was excluded in all patients. Of the 16 patients on NSAIDs, four had gastritis, four had erosions or ulceration and eight had a normal examination. Endoscopy was normal in all patients in the control group. The LI% (mean +/- S.E.M.) in the entire NSAID group was 4.09 +/- 0.29 and in the control group 3.57 +/- 0.29. No significant difference was observed. In the NSAID patients with gastritis and erosions or ulceration, the LI% was 4.99 +/- 0.61 and 3.07 +/- 0.32, respectively. There was no significant difference in LI% between the endoscopic subgroups of patients on NSAIDs or between patients on NSAIDs who had normal endoscopy and the control patients.

CONCLUSION

These results provide evidence that refutes the hypothesis that the prevalence of NSAID gastropathy is due to an effect on gastric cell turnover.

Histological findings in gastric mucosa in patients treated with non-steroidal anti-inflammatory drugs

AIMS

To identify distinguishing and general histological features related to the use of non-steroidal anti-inflammatory drugs (NSAID).

METHODS

Slides from gastric antral biopsies of 50 patients with osteoarthritis taking NSAID were compared with slides from antral biopsies of 50 control cases matched for age, sex, and race. Semithin sections stained with toluidine blue were used.

RESULTS

Chronic gastritis was seen in 76% of the patients taking NSAID and in 58% of the control cases; active inflammation was detected in 10% of the NSAID treated patients and in 24% of the control cases, and it appeared closely related with Helicobacter pylori infection. Some histological features common to all slides of patients taking NSAID were recognised. These consisted of focal erosions of the gastric epithelium and macroerosions, and they seemed to represent successive steps of a process of "desquamation".

CONCLUSIONS

Some distinguishing morphological aspects appeared prominent; it is suggested that these may be related to the pathogenesis of NSAID linked peptic ulceration. On the other hand, epithelial damage due to NSAID appears very different from that due to Helicobacter pylori, another important factor involved in the aetiopathogenesis of peptic disease.

Do infiltrating leukocytes contribute to the adaptation of human gastric mucosa to continued aspirin administration?

BACKGROUND

Aspirin (ASA)-induced gastropathy decreases with continued ASA ingestion due to the development of gastric mucosal tolerance. However, the mechanism of the gastric mucosal adaptation to repeated ASA challenge is unknown.

METHODS

The aim of the present study was to determine the density of leukocytes infiltrating the gastric mucosa in healthy subjects during prolonged treatment with ASA. In eight healthy volunteers ASA treatment (2 g/day) was continued for 14 days. Endoscopy was performed before medication, on the 3rd, 7th, and 14th day of ASA treatment, and on the 16th and 18th day (2 and 4 days after medication was stopped). Gastric damage was scored (Lanza score), and gastric biopsy specimens were taken from both the oxyntic and antral mucosa.

RESULTS

ASA administration resulted in the development of hemorrhagic erosions, which were most severe on the 3rd day of the medication; later significant reduction of severity of the damage was observed. ASA administration caused an increased mucosal infiltration of leukocytes; leukocyte margination and adherence to endothelia were commonly observed in the gastric mucosa, particularly on the 3rd day of ASA treatment but not later on. Mast cell density increased significantly on the 3rd day of ASA treatment. Density of mast cells later decreased in the antral mucosa but continued to be significantly increased in the oxyntic mucosa up to the 14th day. There was a striking correspondence between mast cell density and endoscopic score of the mucosal damage. Eosinophil density increased significantly during ASA treatment and remained high even after medication was withdrawn.

CONCLUSIONS

1) Initial mucosal damage by ASA is followed by gastric adaptation on continuous exposure to this agent; 2) infiltrating leukocytes appear to contribute to the development of gastric mucosal adaptation to ASA; and 3) mast cell density reflects the endoscopic score of gastric damage by ASA.

Gastric mucosal blood flow and neutrophil activation in aspirin-induced gastric mucosal damage in man

Gastric and intestinal injury induced by nonsteroidal anti-inflammatory agents (NSAIDs) such as aspirin (ASA) is a common side effect of this class of drugs, but the mechanism by which these drugs act is not fully explained. In this study the effects of 3 days of continuous oral ASA administration (1 g twice daily) to eight healthy male volunteers were studied. To estimate the extent of mucosal damage, gastroscopy was performed before and after 3 days of ASA treatment, during which the mucosal blood flow was measured by means of laser-Doppler flowmetry. Before each endoscopy gastric microbleeding was measured. Since neutrophil activation has recently been suggested to be involved in the pathogenesis of ASA-induced gastric mucosal damage, we examined the influence of ASA treatment on the activation of leukocytes by determining their association with platelets in the blood. Aspirin-induced acute gastric damage reached about 3.5 in the endoscopic Lanza score. Mucosal blood flow increased significantly after ASA treatment, by about 50% in the oxyntic gland area and by 87% in the antral area. Gastric microbleeding rose from about 0.38 ml/day in the intact stomach to about 7.7 ml/day after ASA treatment. The platelet/neutrophil adherence increased significantly in both thrombin-unstimulated and thrombin-stimulated platelets. We conclude that acute 3 days' administration of ASA in man produces well-defined areas of gastric damage accompanied by a significant increase in gastric microbleeding and gastric blood flow and that ASA promotes platelet/neutrophil adhesion that may resemble the neutrophil/endothelium interaction in the gastric mucosa.

Nonsteroidal anti-inflammatory drugs--the clinical dilemmas

Physicians using nonsteroidal anti-inflammatory drugs (NSAIDs) are concerned that effective anti-inflammatory doses cause few gastrointestinal side effects. Among the causes of discontinuing therapy, upper gastrointestinal symptoms and the development of 'ulcer' complications are major concerns; endoscopic findings in asymptomatic users are not. Initial symptoms, poorly correlated with endoscopic findings, are relieved by anti-ulcer drugs and ameliorate with time of NSAID use in most patients. Symptoms accompanied by epigastric tenderness, or unrelieved by H2 antagonists, or resulting in cessation of NSAID therapy are more predictive of underlying ulcers. Complications probably arise in several ways, including as hemorrhages due to interference with platelet function, and as complications due to exacerbations of underlying ulcer disease or of ulcers caused by the NSAIDs. Pathogenesis and effective prophylaxis (yet to be established) may therefore vary in different patients, a clinical dilemma.

Gastric adaptation to nonsteroidal anti-inflammatory drugs in man

Adaptation describes the phenomenon in which visible gastric mucosal injury lessens or resolves completely despite continued administration of an injurious substance such as aspirin. Adaptation occurs in man although the mechanism remains unclear. Recent evidence suggests increased cell proliferation and correction of nonsteroidal anti-inflammatory drug induced reduction in gastric blood flow as possibly being important. Gastric erosions and ulcers in chronic nonsteroidal anti-inflammatory drug users represent failed adaptation. Gastric erosions and ulcers in chronic nonsteroidal anti-inflammatory drug users represent failed adaptation. The factors responsible for failure of adaptation are unknown but one clue is that there appears to be a dose-response effect relating anti-inflammatory dose and effectiveness of adaptation (i.e., adaptation is delayed, or less effective, when higher anti-inflammatory doses are administered). Gastric adaptation can be enhanced by co-therapy with synthetic prostaglandins but not with sucralfate or H2-receptor antagonists.