Diclofenac delays healing of gastroduodenal mucosal lesions. Double-blind, placebo-controlled endoscopic study in healthy volunteers

Synergistic Action of Diclofenac with Endotoxin-Mediated Inflammation Exacerbates Intestinal Injury in Vitro

Intestinal homeostasis is tightly regulated by the orchestrated actions of a multitude of cell types, including enterocytes, goblet cells, and immune cells. Disruption of intestinal barrier function can increase susceptibility to pathogen invasion and destabilize commensal microbial-epithelial-immune interaction, manifesting in various intestinal and systemic pathologies. However, a quantitative understanding of how these cell types communicate and collectively contribute to tissue function in health and disease is lacking. Here, we utilized a human intestinal epithelial-dendritic cell model and multivariate analysis of secreted factors to investigate the cellular crosstalk in response to physiological and/or pathological cues (e.g., endotoxin, nonsteroidal anti-inflammation drug (NSAID)). Specifically, we demonstrated that treatment with diclofenac (DCF), an NSAID commonly used to treat inflammation associated with acute infection and other conditions, globally suppressed cytokine secretion when dosed in isolation. However, the disruption of barrier function induced by DCF allowed for luminal lipopolysaccharide (LPS) translocation and activation of resident immune cells that overrode the anti-inflammatory influence of DCF. DCF-facilitated inflammation in the presence of LPS was in part mediated by upregulation of macrophage migration inhibitory factor (MIF), an important regulator of innate immunity. However, while neutralization of MIF activity normalized inflammation, it did not lead to intestinal healing. Our data suggest that systems-wide suppression of inflammation alone is insufficient to achieve mucosal healing, especially in the presence of DCF, the target of which, the COX-prostaglandin pathway, is central to mucosal homeostasis. Indeed, DCF removal postinjury enabled partial recovery of intestinal epithelium functions, and this recovery phase was associated with upregulation of a subset of cytokines and chemokines, implicating their potential contribution to intestinal healing. The results highlight the utility of an intestinal model capturing immune function, coupled with multivariate analysis, in understanding molecular mechanisms governing response to microbial factors, supporting application in studying host-pathogen interactions.

Meloxicam and Study of Their Antimicrobial Effects against Phyto- and Human Pathogens

Recently, the design of new biological metal-ligand complexes has gained a special interest all over the world. In this research, new series of mixed ligand complexes from meloxicam (H₂mel) and glycine (Gly) were synthesized. Structures of the compounds were investigated employing elemental analyses, infrared, electronic absorption, ¹H NMR, thermal analyses, effective magnetic moment and conductivity. The estimated molar conductivity of the compounds in 1 × 10^-3 M DMF solution indicates the non-electrolyte existence of the examined complexes. Additionally, the effective magnetic moment values refer to the complexes found as octahedral molecular geometry. The data of the infrared spectra showed the chelation of H₂mel and Gly with metal ions from amide oxygen and nitrogen of the thyizol groups of H₂mel and through nitrogen of the amide group and oxygen of the carboxylic group for Gly. Thermal analyses indicated that the new complexes have good thermal stability and initially lose hydration water molecules followed by coordinated water molecules, Gly and H₂mel. The kinetic parameters were calculated graphically using Coats-Redfern and Horowitz-Metzeger methods at n = 1 and n ≠ 1. The density functional theory (DFT) calculations were performed at B3LYP levels. The optimized geometry of the ligand and its complexes were obtained based on the optimized structures. The data indicated that the complexes are soft with η value in the range 0.114 to 0.086, while η = 0.140 for free H₂mel. The new prepared complexes were investigated as antibacterial and antifungal agents against some phyto- and human pathogens and the minimum inhibitory concentration (MIC) data showed that complex (A) has the lowest MIC for Listeria and E. coli (10.8 µg/mL).

Enhanced chemopreventive effects of a hydrogen sulfide-releasing anti-inflammatory drug (ATB-346) in experimental colorectal cancer

Regular use of nonsteroidal anti-inflammatory drugs is associated with a significantly lower incidence of several types of cancer, particularly those affecting the gastrointestinal tract. However, the propensity of these drugs to cause ulcers and bleeding in the stomach and small intestine limits their utility for chemoprevention of cancer. In the present study, we evaluated the effectiveness of a novel hydrogen sulfide-releasing derivative of naproxen in reducing the incidence of pre-cancerous lesions (aberrant crypt foci) in mice treated with the carcinogen azoxymethane. Weekly administration of azoxymethane over a 4-week period resulted in formation of an average of ∼50 aberrant crypt foci in the colon. Twice-daily treatment with naproxen at high doses significantly reduced the number of aberrant crypt foci. However, a significantly greater effect was observed with ATB-346 (H2S-releasing naproxen) and it was also effective at much lower doses, where naproxen was ineffective. The H2S-releasing moiety of ATB-346 did not significantly affect the number of aberrant crypt foci, suggesting that both the inhibition of cyclooxygenase activity and release of H2S were necessary for the enhanced chemopreventative effect. ATB-346 suppressed colonic prostaglandin synthesis and whole blood thromboxane synthesis as effectively as naproxen, but did not induce any gastrointestinal injury. These results demonstrate that ATB-346 exerts superior chemopreventive effects to those of naproxen, while sparing the gastrointestinal tract of the injury normally associated with use of the parent drug. ATB-346 may therefore be an attractive agent for chemoprevention of colon cancer, and possibly of cancers in other tissues.

The anti-inflammatory drug indomethacin alters nanoclustering in synthetic and cell plasma membranes

The nonsteroidal anti-inflammatory drug indomethacin exhibits diverse biological effects, many of which have no clear molecular mechanism. Membrane-bound receptors and enzymes are sensitive to their phospholipid microenvironment. Amphipathic indomethacin could therefore potentially modulate cell signaling by changing membrane properties. Here we examined the effect of indomethacin on membrane lateral heterogeneity. Fluorescence lifetime imaging of cells expressing lipid-anchored probes revealed that treatment of BHK cells with therapeutic levels of indomethacin enhances cholesterol-dependent nanoclustering, but not cholesterol-independent nanoclustering. Immuno-electron microscopy and quantitative spatial mapping of intact plasma membrane sheets similarly showed a selective effect of indomethacin on promoting cholesterol-dependent, but not cholesterol-independent, nanoclustering. To further evaluate the biophysical effects of indomethacin, we measured fluorescence polarization of the phase-sensitive probe Laurdan and FRET between phase-partitioning probes in model bilayers. Therapeutic levels of indomethacin enhanced phase separation in DPPC/DOPC/Chol (1:1:1) and DPPC/Chol membranes in a temperature-dependent manner, but had minimal effect on the phase behavior of pure DOPC at any temperature. Taken together, the imaging results on intact epithelial cells and the biophysical assays of model membranes suggest that indomethacin can enhance phase separation and stabilize cholesterol-dependent nanoclusters in biological membranes. These effects on membrane lateral heterogeneity may have significant consequences for cell signaling cascades that are assembled on the plasma membrane.

Markedly reduced toxicity of a hydrogen sulphide-releasing derivative of naproxen (ATB-346)

BACKGROUND AND PURPOSE

Hydrogen sulphide is an important mediator of gastric mucosal defence. The use of non-steroidal anti-inflammatory drugs continues to be limited by their toxicity, particularly in the upper gastrointestinal tract. We evaluated the gastrointestinal safety and anti-inflammatory efficacy of a novel hydrogen sulphide-releasing derivative of naproxen, ATB-346 [2-(6-methoxy-napthalen-2-yl)-propionic acid 4-thiocarbamoyl-phenyl ester].

EXPERIMENTAL APPROACH

The ability of ATB-346 versus naproxen to cause gastric damage was evaluated in healthy rats and in rats with compromised gastric mucosal defence. Effects on the small intestine and on the healing of ulcers were also assessed. The ability of ATB-346 to inhibit cyclooxygenase-1 and 2 and to reduce inflammation in vivo was also evaluated.

KEY RESULTS

ATB-346 suppressed gastric prostaglandin E(2) synthesis as effectively as naproxen, but produced negligible damage in the stomach and intestine. In situations in which the gastric mucosa was rendered significantly more susceptible to naproxen-induced damage (e.g. ablation of sensory afferent nerves, inhibition of endogenous nitric oxide or hydrogen sulphide synthesis, co-administration with aspirin, antagonism of K(IR)6.x channels), ATB-346 did not cause significant damage. Unlike naproxen and celecoxib, ATB-346 accelerated healing of pre-existing gastric ulcers. In a mouse airpouch model, ATB-346 suppressed cyclooxygenase-2 activity and inhibited leukocyte infiltration more effectively than naproxen. ATB-346 was as effective as naproxen in adjuvant-induced arthritis in rats, with a more rapid onset of activity. Unlike naproxen, ATB-346 did not elevate blood pressure in hypertensive rats.

CONCLUSIONS AND IMPLICATIONS

ATB-346 exhibits anti-inflammatory properties similar to naproxen, but with substantially reduced gastrointestinal toxicity.

The nonsteroidal anti-inflammatory drug indomethacin induces heterogeneity in lipid membranes: potential implication for its diverse biological action

Background

The nonsteroidal anti-inflammatory drug (NSAID), indomethacin (Indo), has a large number of divergent biological effects, the molecular mechanism(s) for which have yet to be fully elucidated. Interestingly, Indo is highly amphiphilic and associates strongly with lipid membranes, which influence localization, structure and function of membrane-associating proteins and actively regulate cell signaling events. Thus, it is possible that Indo regulates diverse cell functions by altering micro-environments within the membrane. Here we explored the effect of Indo on the nature of the segregated domains in a mixed model membrane composed of dipalmitoyl phosphatidyl-choline (di16∶0 PC, or DPPC) and dioleoyl phosphatidyl-choline (di18∶1 PC or DOPC) and cholesterol that mimics biomembranes.

Methodology/Principal Findings

Using a series of fluorescent probes in a fluorescence resonance energy transfer (FRET) study, we found that Indo induced separation between gel domains and fluid domains in the mixed model membrane, possibly by enhancing the formation of gel-phase domains. This effect originated from the ability of Indo to specifically target the ordered domains in the mixed membrane. These findings were further confirmed by measuring the ability of Indo to affect the fluidity-dependent fluorescence quenching and the level of detergent resistance of membranes.

Conclusion/Significance

Because the tested lipids are the main lipid constituents in cell membranes, the observed formation of gel phase domains induced by Indo potentially occurs in biomembranes. This marked Indo-induced change in phase behavior potentially alters membrane protein functions, which contribute to the wide variety of biological activities of Indo and other NSAIDs.

A randomized, placebo-controlled study of the effects of naproxen, aspirin, celecoxib or clopidogrel on gastroduodenal mucosal healing

BACKGROUND

Many individuals with gastroduodenal ulcers require on-going, non-steroidal anti-inflammatory drug (NSAID) or anti-platelet therapy.

AIMS

To evaluate the effects of these agents on gastroduodenal mucosal healing.

METHODS

Helicobacter pylori-negative volunteers were randomized to receive naproxen, celecoxib, aspirin, clopidogrel or placebo. Antral and duodenal lesions were created endoscopically with a biopsy forceps. After 7 days of medication dosing, each lesion was scored [from 0 (low) to 8 (high)] using a validated methodology. The primary endpoint was the mean injury score. The secondary endpoint was the percentage of subjects with > or = 1 unhealed lesion.

RESULTS

In all, 108 subjects completed the study. Naproxen impaired antral lesion healing more than placebo, clopidogrel, aspirin or celecoxib (mean injury score of 4.3 vs. 3.0, 2.7, 3.2, and 3.2, respectively, P < 0.05). Naproxen impaired duodenal lesion healing more than placebo, clopidogrel or aspirin (mean injury score of 4.0 vs. 2.4, 2.6, and 2.2, respectively, P < 0.05). More subjects taking naproxen than placebo or clopidogrel had > or =1 unhealed antral lesions (72.2% vs. 36.0% and 32.0%, respectively, P < 0.05) and unhealed duodenal lesions (61.1% vs. 16.0% and 28.0%, respectively, P < 0.05).

CONCLUSIONS

Naproxen may impair gastroduodenal healing more than aspirin or celecoxib in H. pylori negative subjects. Clopidogrel did not impair mucosal healing.

Hydrogen sulfide enhances ulcer healing in rats

Hydrogen sulfide is an endogenous mediator that relaxes vascular smooth muscle, exhibits several antiinflammatory activities, and contributes to gastric mucosal defense. This study was performed to examine the role of hydrogen sulfide in the resolution of injury; specifically, the healing of gastric ulcers. Ulcers were induced in rats by serosal application of acetic acid. This elicited a marked increase in gastric expression of the two key enzymes in hydrogen sulfide synthesis (cystathionine-beta-synthase and cystathionine-gamma-lyase) and in hydrogen sulfide synthesis. Twice-daily treatment for a week with hydrogen sulfide donors significantly increased the extent of healing of gastric ulcers as compared to vehicle-treatment. Similar treatment with L-cysteine, a precursor for hydrogen sulfide, also accelerated healing of the ulcers, and the effect was abolished by cotreatment with an inhibitor of cystathionine-gamma-lyase. The beneficial effects of hydrogen sulfide on ulcer healing were not dependent on nitric oxide synthesis, nor did they appear to occur through activation of ATP-sensitive K+ channels. These results suggest that hydrogen sulfide is produced in the gastric mucosa in response to injury and acts to promote healing. The results further suggest that drugs releasing hydrogen sulfide could be employed to accelerate healing of gastric ulcers, and possibly of other wounds.

Modulation of prostaglandin biosynthesis by nitric oxide and nitric oxide donors

The biosynthesis and release of nitric oxide (NO) and prostaglandins (PGs) share a number of similarities. Two major forms of nitric-oxide synthase (NOS) and cyclooxygenase (COX) enzymes have been identified to date. Under normal circumstances, the constitutive isoforms of these enzymes (constitutive NOS and COX-1) are found in virtually all organs. Their presence accounts for the regulation of several important physiological effects (e.g. antiplatelet activity, vasodilation, and cytoprotection). On the other hand, in inflammatory setting, the inducible isoforms of these enzymes (inducible NOS and COX-2) are detected in a variety of cells, resulting in the production of large amounts of proinflammatory and cytotoxic NO and PGs. The release of NO and PGs by the inducible isoforms of NOS and COX has been associated with the pathological roles of these mediators in disease states as evidenced by the use of selective inhibitors. An important link between the NOS and COX pathways was made in 1993 by Salvemini and coworkers when they demonstrated that the enhanced release of PGs, which follows inflammatory mechanisms, was nearly entirely driven by NO. Such studies raised the possibility that COX enzymes represent important endogenous "receptor" targets for modulating the multifaceted roles of NO. Since then, numerous papers have been published extending the observation across various cellular systems and animal models of disease. Furthermore, other studies have highlighted the importance of such interaction in physiology as well as in the mechanism of action of drugs such as organic nitrates. More importantly, mechanistic studies of how NO switches on/off the PG/COX pathway have been undertaken and additional pathways through which NO modulates prostaglandin production unraveled. On the other hand, NO donors conjugated with COX inhibitors have recently found new interest in the understanding of NO/COX reciprocal interaction and potential clinical use. The purpose of this article is to cover the advances which have occurred over the years, and in particular, to summarize experimental data that outline how the discovery that NO modulates prostaglandin production has impacted and extended our understanding of these two systems in physiopathological events.

The role of prostaglandins and other eicosanoids in the gastrointestinal tract

Nonsteroidal anti-inflammatory drugs (NSAIDs) are generally prescribed to ameliorate symptoms associated with acute pain and chronic inflammatory diseases such as arthritis. Recent epidemiologic studies and clinical trials indicate that use of NSAIDs and cyclooxygenase (COX)-2 selective inhibitors are associated with a reduced risk of certain malignancies, especially gastrointestinal cancer. The cyclooxygenase enzymes are the best known targets of NSAIDs; this diverse class of compounds blocks conversion of arachidonic acid to prostanoids. Prostaglandins and other eicosanoids derived from COX-1 and COX-2 are involved in a variety of physiologic and pathologic processes in the gastrointestinal tract. Recent efforts to identify the molecular mechanisms by which COX-2-derived prostanoids exert their proneoplastic effects have provided a rationale for the possible use of NSAIDs alone or in a combination with conventional or experimental anticancer agents for the treatment or prevention of gastrointestinal cancers.

Meta-analysis of dyspepsia and nonsteroidal antiinflammatory drugs

OBJECTIVE

Nonsteroidal antiinflammatory drug (NSAID) use is a known risk factor for gastrointestinal (GI) perforations, ulcers, and bleeds, but there are limited data on its association with the very common symptom of dyspepsia. Using published and unpublished data sources, we sought to determine estimates of the risks of dyspepsia associated with NSAIDs.

METHODS

We searched computerized databases (1966-1998) for primary studies of NSAIDs reporting on GI complications. We also obtained Food and Drug Administration (FDA) new drug application reviews for the 5 most common NSAIDs. We included studies reporting defined upper GI outcomes among subjects (>17 years old) who used oral NSAIDs for more than 4 days. Two reviewers evaluated 4,881 published titles, identifying 55 NSAID versus placebo randomized controlled trials (RCTs), 37 unpublished (FDA data) placebo-controlled RCTs; 86 NSAID versus NSAID RCTs (sample size >or=50); and 103 observational studies.

RESULTS

The majority of clinical trials were of good quality. Meta-regression identified an increased risk of dyspepsia for users of specific NSAIDs (adjusted odds ratio [OR] of indomethacin, meclofenamate, piroxicam = 2.8), and for high dosages of other NSAIDs (OR = 3.1), but not for other NSAIDs regardless of dosage (OR = 1.1). Dyspepsia was not reported as an outcome in the case control or cohort studies.

CONCLUSIONS

Clinical trial data indicate that high dosages of any NSAID along with any dosage of indomethacin, meclofenamate, or piroxicam increase the risk of dyspepsia by about 3-fold. Other NSAIDs at lower dosages were not associated with an increased risk of dyspepsia.

How useful are unpublished data from the Food and Drug Administration in meta-analysis?

The goals of this systematic review and meta-analysis were to ascertain whether studies of nonsteroidal anti-inflammatory drugs (NSAIDs) summarized in the FDA reviews are ultimately published, to compare the methodologic and population characteristics of studies summarized in the FDA reviews with those reported in peer reviewed literature, and to compare the pooled relative risk of dyspepsia from NSAIDs in each data source. Summary measures of risk difference were calculated with a random effects model; meta-regression was used to assess the effect of study covariates. Among 37 studies described in the FDA reviews, one was published. Sample size, gender distribution, indication for drug use, and methodologic quality did not vary significantly between the published and FDA data. The pooled risk ratio for dyspepsia obtained using published data (1.21) or FDA data (1.07) did not differ significantly or practically. Data from FDA reviews may be a viable data source for systematic reviews and meta-analyses but only after being subjected to the same methodologic scrutiny as published data.

Do NSAIDs cause dyspepsia? A meta-analysis evaluating alternative dyspepsia definitions

OBJECTIVE

Nonsteroidal anti-inflammatory drugs (NSAIDs) may be associated with dyspepsia, but the relationship is obscured by variations in the terminology used to report GI symptoms. Using alternative definitions, we assessed the relationship between NSAID use and dyspepsia.

METHODS

We searched MEDLINE, EMBASE, HEALTHSTAR, and BIOSIS databases (1966-1997) and New Drug Application reviews, identifying randomized, placebo-controlled trials (5 days or more duration) of any NSAID, reporting original data on GI complications. Based upon reported terms describing upper GI symptoms, we derived three definitions: strict, using terms synonymous with epigastric pain/discomfort; loose, (containing the strict definition plus terms for heartburn, nausea, bloating, anorexia, and vomiting); and a loose definition without heartburn terms (the loose-less-heartburn definition). Using each definition, we performed a random-effects model meta-analysis of the relationship between NSAID exposure and dyspepsia.

RESULTS

Fifty-five published and 37 unpublished controlled NSAID trials met our inclusion criteria. The mean duration of the trials was 33.2 days (SD 40 days). Application of the strict definition resulted in a pooled risk ratio of dyspepsia for NSAIDs compared with placebo of 1.36 (95% CI = 1.11-1.67). For the loose definition, the pooled risk ratio was 1.13 (95% CI = 0.98-1.32). The loose-less-heartburn definition yielded a pooled risk ratio of 1.19 (95% CI = 1.03-1.39). In the placebo-treated control groups, the percent of patients reporting dyspepsia ranged from 2.3% (strict definition) to 4.2% (loose and loose-less-heartburn definitions).

CONCLUSIONS

Using the strict definition, based solely on epigastric pain-related symptoms, NSAIDs increased the risk of dyspepsia by 36% (p < 0.05). These findings may be useful in creating a standardized definition of NSAID-related dyspepsia.

Pathogenesis of NSAID-induced gastroduodenal mucosal injury

The use of non-steroidal anti-inflammatory drugs (NSAIDs), even in the era of selective COX-2 inhibitors, remains limited by the ability of these agents to cause gastroduodenal ulceration and bleeding. This damage is caused mainly through the ability of these agents to inhibit prostaglandin synthesis, which has a negative impact on several components of mucosal defence. Many NSAIDs also have topical irritant effects on the epithelium which may be particularly important in the production of small intestinal injury. While the presence of acid in the lumen of the stomach may not be a primary factor in the pathogenesis of NSAID-induced gastroenteropathy it can make an important contribution to the chronicity of these lesions and to bleeding by impairing the restitution process, interfering with haemostasis and inactivating several growth factors that are important in mucosal defence and repair. Through better understanding of the pathogenesis of ulcers induced by NSAIDs, some new approaches to the development of more effective and safer anti-inflammatory drugs have been taken in recent years.

Nonsteroidal anti-inflammatory drugs and the gastrointestinal tract. Mechanisms of protection and healing: current knowledge and future research

The resistance of the gastric mucosa to injury is attributable to a series of factors collectively known as "mucosal defense." Many components of mucosal defense are regulated by prostaglandins and nitric oxide (NO). Thus, inhibition of the production of these mediators predisposes the stomach to injury. Administration of these agents, as synthetic prostaglandins or NO donors, can restore mucosal defense and thereby prevent damage induced by several irritants. Repair of gastric ulcers is also influenced by NO and prostaglandins. Furthermore, a variety of growth factors appear to play critical roles in stimulating the formation of granulation tissue (the "foundation" for repair), the formation of new blood vessels, and the proliferation of epithelial cells. Better understanding of the factors that regulate ulcer healing should provide clues for the development of drugs that can produce better "quality" healing of ulcers.

Role of cyclooxygenase-2 in modulating gastric acid secretion in the normal and inflamed rat stomach

Nonsteroidal anti-inflammatory drugs elevate gastric acid secretion, possibly contributing to their ability to interfere with gastric ulcer healing. Inhibitors of cyclooxygenase-2 have been shown to delay experimental gastric ulcer healing. In the present study, we tested the hypothesis that cyclooxygenase-2-derived prostaglandins modulate gastric acid secretion. Studies were performed in normal rats and in rats with iodoacetamide-induced gastritis. Inflammation in the latter group was confirmed histologically and by a threefold increase in tissue levels of the granulocyte marker myeloperoxidase and was also associated with overexpression of cyclooxygenase-2 in the stomach. Basal acid secretion in both groups of rats was not affected by pretreatment with DuP-697, a selective inhibitor of cyclooxygenase-2. A nonselective cyclooxygenase inhibitor, indomethacin, had no effect on acid secretion in normal rats but caused a doubling of acid secretion in the rats with gastritis. DuP-697 had no effect on pentagastrin-induced secretion in either group of rats. Gastritis itself was associated with significantly increased pentagastrin-induced acid secretion, and this was further increased in rats pretreated with indomethacin. These results suggest that in a setting of gastric inflammation, prostaglandins derived from cyclooxygenase-1, not cyclooxygenase-2, exert inhibitory effects on acid secretion.

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.

The effects of omeprazole on healing and appearance of small gastric and duodenal lesions during dosing with diclofenac in healthy subjects

BACKGROUND

Non-steroidal anti-inflammatory drugs (NSAIDs) are associated with gastrointestinal mucosal damage. Omeprazole prevents the formation, and accelerates the healing, of NSAID-induced ulcers.

AIM

To test whether omeprazole accelerates healing of standardized gastroduodenal lesions in the presence of diclofenac.

METHODS

In a double-blind, double-dummy, placebo-controlled, crossover study, 12 healthy volunteers received consecutive, 2-week courses of omeprazole (40 mg o.d.) and placebo, in random order, with an intervening, 4-week washout period; diclofenac (50 mg t.d.s.), was given for the second week of each course. Five endoscopies were performed, one at the outset and the others before and after each course of diclofenac. Biopsies were taken from the endoscopically normal mucosa of the corpus, antrum and duodenum and also from any new mucosal lesion that developed after diclofenac. The sites of biopsies taken before each course of diclofenac were evaluated endoscopically after each course to assess the extent of healing according to a predetermined healing score scale.

RESULTS

The healing scores observed after administration of placebo/diclofenac (median=0; range 0-6) and after omeprazole/diclofenac (median=0; range 0-6; P=0.17) did not differ. Small gastroduodenal lesions developed de novo in six subjects during placebo/diclofenac and in seven during omeprazole/diclofenac. Focal chemical gastropathy was observed only in close proximity to macroscopic lesions.

CONCLUSIONS

In healthy subjects, omeprazole does not accelerate the healing of pre-existing mucosal lesions or prevent the development of small diclofenac-induced mucosal lesions.

How do NSAIDs cause ulcer disease?

Gastroduodenal ulceration and bleeding are the major limitations to the use of non-steroidal anti-inflammatory drugs (NSAIDs). The development of safer NSAIDs or of effective therapies for the prevention of the adverse effects of existing NSAIDs requires a better understanding of the pathogenesis of NSAID-induced ulcer disease. NSAIDs can cause damage to the gastroduodenal mucosa via several mechanisms, including the topical irritant effect of these drugs on the epithelium, impairment of the barrier properties of the mucosa, suppression of gastric prostaglandin synthesis, reduction of gastric mucosal blood flow and interference with the repair of superficial injury. The presence of acid in the lumen of the stomach also contributes to the pathogenesis of NSAID-induced ulcers and bleeding, by impairing the restitution process, interfering with haemostasis and inactivating several growth factors that are important in mucosal defence and repair. In recent years, a fuller understanding of the pathogenesis of NSAID-induced ulcer disease has facilitated some new, very promising approaches to the development of stomach-sparing NSAIDs.

Distribution and expression of cyclooxygenase (COX) isoenzymes, their physiological roles, and the categorization of nonsteroidal anti-inflammatory drugs (NSAIDs)

The molecular identification of a second isoform of cyclooxygenase-2 (COX-2) led to a major investment by several pharmaceutical companies in the development of selective inhibitors. The central tenets of the rationale for developing selective COX-2 inhibitors are that prostaglandins that contribute to inflammation are derived from COX-2, whereas prostaglandins that are involved in normal physiological processes are derived from the constitutively expressed isoform COX-1. There is now considerable evidence that COX-2 is actually expressed constitutively in many tissues and performs important physiological functions. Thus, suppression of COX-2 with selective inhibitors should not be expected to be without some adverse consequences. Moreover, there is strong evidence that COX-1 contributes to inflammation and pain, so selective inhibition of COX-2 will not necessarily produce the same degree of efficacy that is seen with mixed inhibitors of COX-1 and COX-2.

Exacerbation of inflammation-associated colonic injury in rat through inhibition of cyclooxygenase-2

Cyclooxygenase type 1 is constitutively expressed and accounts for synthesis of prostaglandins in the normal gastrointestinal tract. Cyclooxygenase-2 is expressed at sites of inflammation. Selective inhibitors of cyclooxygenase-2 have been suggested to spare gastrointestinal prostaglandin synthesis, and therefore lack the ulcerogenic effects associated with standard nonsteroidal antiinflammatory drugs. However, the effects of cyclooxygenase-2 inhibitors on inflamed gastrointestinal mucosa have not been examined. We examined cyclooxygenase-2 mRNA and protein expression before and after induction of colitis in the rat, the contribution of cyclooxygenase-2 to colonic prostaglandin synthesis during colitis and the effects of selective inhibitors of cyclooxygenase-2 on colonic injury in this model. Cyclooxygenase-2 mRNA expression increased three to sixfold during the period 24 h to 1 wk after induction of colitis, with marked increases in cyclooxygenase-2 protein expression in the lamina propria and muscularis of the colon during colitis. Cyclooxygenase-1 expression (mRNA and protein) was not affected by the induction of colitis. The prostaglandins produced during colitis were largely derived from cyclooxygenase-2. Treatment with selective cyclooxygenase-2 inhibitors resulted in exacerbation of colitis, with perforation occurring when the compounds were administered for a week. These studies demonstrate that suppression of cyclooxygenase-2 can result in exacerbation of inflammation-associated colonic injury.

Review article: new insights into prostaglandins and mucosal defence

A role for prostaglandins in maintaining mucosal integrity in the gastrointestinal tract is well documented. While traditionally the effects of prostaglandins on mucosal blood flow and epithelial function have been regarded as critical in the mechanism of action of these fatty acids, recent evidence that mucosal ulceration is almost invariably associated with mucosal inflammation has caused a re-evaluation of the role of prostaglandins in mucosal defence. This review focuses on the ability of prostaglandins to exert anti-inflammatory, and therefore anti-ulcerogenic, effects in the gastrointestinal tract. These effects of prostaglandins are attributable to their ability to suppress the release of inflammatory mediators and reactive oxygen metabolites from a number of immunocytes, stromal cells and inflammatory cells. There is emerging evidence for cooperative interactions between prostaglandins and nitric oxide in maintaining mucosal integrity. Recent work on the inducible isoform of prostaglandin synthase as it pertains to mucosal defence is also reviewed.

Prospective multicentre study of risk factors associated with delayed healing of recurrent duodenal ulcers (RUDER). RUDER Study Group

Risk factors for delayed duodenal ulcer healing during treatment with ranitidine (300 mg daily) were examined in a multicentre German study of 1923 patients with endoscopically proved, recurrent duodenal ulceration. Healing rates, per protocol, were 39.5% at two weeks, 70.9% at four weeks, and 93.2% at eight weeks. Prospective testing of five, predefined risk factors indicated that smoking (p = 0.0039) was associated with a decreased healing rate at two weeks. Frequent prior recurrence (p = 0.464), a heavy physical workload (p = 0.145), and psychological stress (p = 0.062) were not associated with a decreased healing rate and there were too few patients at risk to allow assessment of the effect of regular NSAID intake. Exploratory analysis identified prior slow healing, a large ulcer, multiple ulcers, and prior ulcer complications, in addition to smoking, as markers of slow healing. In the absence of these risk factors, the mean healing time was 3.3 weeks (95% confidence interval 3.0, 3.5), rising to 3.7 weeks (3.5, 3.9) for one, 4.4 weeks (4.1, 4.7) for two, and 5.1 weeks (4.5, 5.6) for three to five risk factors. Delayed duodenal ulcer healing is associated with multiple factors whose effect is cumulative; for patients with two or more of five easily identified risk factors, more than four weeks' treatment with a histamine H2 receptor antagonist is required to achieve ulcer healing.

Do the pharmacodynamics of the nonsteroidal anti-inflammatory drugs suggest a role in the management of postoperative pain?

Until recently, nonsteroidal anti-inflammatory drugs (NSAIDs) were regarded as weak analgesic agents with a potent antiplatelet effect that severely limited their perioperative usefulness. However, the recent development of injectable NSAIDs has stimulated a re-evaluation of the potential role of this class of drugs in postoperative pain management. In general surgery, NSAIDs have been shown to be effective analgesics when administered after surgery, as judged by either a reduction in pain scores and/or by an opioid sparing effect. Parenteral NSAIDs alone, notably ketorolac and diclofenac, may be adequate or even preferred analgesic agents after minor surgery. In dental surgery, NSAIDs produce greater initial analgesia than steroids, although the latter produce greater suppression of swelling and less functional loss. NSAID pretreatment results in only modest suppression of swelling compared with placebo. These data suggest that the acute analgesic effects of NSAIDs in oral surgery and probably other models result from suppression of a nociceptive process, rather than a generalised anti-inflammatory effect. This view challenges the traditional association between inhibition of prostaglandin synthesis and the therapeutic effects of these drugs. The variety of NSAIDs leads to a range in half-lives from short, e.g. diclofenac (1 h), intermediate, e.g. ketorolac (5h), to long, e.g. tenoxicam (60h), which has implications for both convenience of the dosage regimen and drug accumulation. For some racemic NSAIDs (e.g. ibuprofen), metabolic 'activation' of the inactive R-enantiomer to the active S-enantiomer occurs. Renal dysfunction may increase both the plasma concentration and body residence time of NSAIDs, thereby increasing the risk of adverse effects. The concomitant effects of anaesthesia have not yet been studied. The principal concern regarding the use of perioperative NSAIDs is the risk of decreased haemostasis and wound healing. Although it has been found that NSAIDs prolong bleeding times in patients, values generally remain below the upper limits of those in generally healthy patients. Healing of gastrointestinal anastomoses may be compromised by NSAID administration but corneal healing and bone remodelling are not. There is a need for further research into the potential for renal side effects with NSAIDs in the perioperative setting, where the effects of anaesthesia and surgery may increase the risk of side effects, particularly in elderly patients. The main benefits of NSAIDs derive from opioid sparing (e.g. reduction in perioperative nausea and vomiting and improvement in ventilation), although some studies allude to an enhanced quality of analgesia from the combination compared with either NSAID or opioid alone. The question of pre- vs postinjury treatment with NSAIDs remains unresolved.