Effects of inhibition of prostaglandin endoperoxide synthase-2 in chronic gastro-intestinal ulcer models in rats

Nonsteroidal anti-inflammatory drugs induce hypermotilinemia and disturbance of interdigestive migrating contractions in instrumented dogs

Nonsteroidal anti-inflammatory drugs (NSAIDs) induce gastric ulcers due to inhibition of prostaglandin production. Prostaglandins have an influence on physiological gastrointestinal motility, but the relationships between NSAID-induced gastric ulcer, gastrointestinal motility and motilin are unknown. Fifteen dogs were allocated randomly to three groups in which either gelatin, meloxicam or indomethacin was administered. Fecal occult blood and gastrointestinal motility were monitored continuously for 6 days. In addition, analyses of the plasma motilin concentration, gastrointestinal endoscopy and gastric emptying, and detection of motilin cells were performed. Gastrointestinal motility was disturbed in the indomethacin group, presenting as disappearance of interdigestive migrating contractions (IMCs) 3 days before gastric ulcers were detected. Delayed gastric emptying and hypermotilinemia were observed significantly more often in the indomethacin group compared with the other groups. Motilin cell-crypt/villi ratio in the indomethacin group significantly decreased in the duodenum and jejunum, compared with the other groups. No significant changes in any tests were observed in the meloxicam group, when compared with the gelatin group. These findings suggest that the disturbance of IMCs caused by hypermotilinemia, with changes in motilin cell distribution, and delayed gastric emptying induced by indomethacin may contribute to the development of gastric ulcers.

Targeted cyclooxygenase gene (ptgs) exchange reveals discriminant isoform functionality

The prostaglandin G/H synthase enzymes, commonly termed COX-1 and COX-2, differ markedly in their responses to regulatory stimuli and their tissue expression patterns. COX-1 is the dominant source of "housekeeping" prostaglandins, whereas COX-2 synthesizes prostaglandins of relevance to pain, inflammation, and mitogenesis. Despite these distinctions, the two enzymes are remarkably conserved, and their subcellular distributions overlap considerably. To address the functional interchangeability of the two isozymes, mice in which COX-1 is expressed under COX-2 regulatory elements were created by a gene targeting "knock-in" strategy. In macrophages from these mice, COX-1 was shown to be lipopolysaccharide-inducible in a manner analogous to COX-2 in wild-type macrophages. However, COX-1 failed to substitute effectively for COX-2 in lipopolysaccharide-induced prostaglandin E2 synthesis at low concentrations of substrate and in the metabolism of the endocannabinoid 2-arachidonylglycerol. The marked depression of the major urinary metabolite of prostacyclin in COX-2 null mice was only partially rescued by COX-1 knock-in, whereas the main urinary metabolite of prostaglandin E2 was rescued totally. Replacement with COX-1 partially rescued the impact of COX-2 deletion on reproductive function. The renal pathology consequent to COX-2 deletion was delayed but not prevented, whereas the corresponding peritonitis was unaltered. Insertion of COX-1 under the regulatory sequences that drive COX-2 expression indicated that COX-1 can substitute for some COX-2 actions and rescue only some of the consequences of gene disruption. Manipulation of COX-2 also revealed a preference for coupling with distinct downstream prostaglandin synthases in vivo. These mice will provide a valuable reagent with which to elucidate the distinct roles of the COX enzymes in mammalian biology.

Effects of cyclooxygenase inhibition on the gastrointestinal tract

Cyclooxygenase (COX) is a rate-limiting enzyme that catalyzes the conversion of arachidonic acid, an essential fatty acid present in cell membrane phospholipids and liberated by phospholipase, into prostaglandins (PGs) and prostanoids. COX has two distinct membrane-anchored isoenzymes; COX-1 and COX-2. COX-1 is a constitutively expressed and found in most normal body tissues; COX-2 is expressed in normal tissues at low levels and is highly induced by pro-inflammatory mediators in the setting of inflammation, injury, and pain. Inhibitors of COX activity include: (1) conventional non-selective non-steroidal anti-inflammatory drugs (ns-NSAIDs); (2) selective COX-2 inhibitors (COXIBs); and (3) COX-1 inhibitors. Non-selective NSAIDs, at therapeutic doses, inhibit both COX-1 and COX-2. The anti-inflammatory benefits of these drugs are primarily derived from COX-2 inhibition, while inhibition of COX-1 often elicits gastrointestinal (GI) toxicity. Therefore, COXIBs were developed to provide a selective COX-2 agent, i.e., one, that at fully therapeutic doses demonstrated comparable therapeutic benefit to non-selective NSAIDs, without the attendant COX-1-mediated GI toxicities. In this review, we evaluate available literature describing the pathophysiologic role of cyclooxygenases and the effects of their inhibition in GI system in experimental and domestic animal species.

Heregulin-alpha and heregulin-beta expression is linked to a COX-2-PGE2 pathway in human gastric fibroblasts

We have previously shown heregulin (HRG)-alpha expression in human gastric fibroblasts and its stimulation of gastric epithelial cell growth. Although cyclooxygenase (COX)-2 has also been shown to stimulate growth factor production in these cells, the interaction between COX-2 and HRG remains unknown. Conditioned media (CM) from gastric fibroblasts incubated with PGE(2) or interleukin (IL)-1beta, a well known COX-2 inducer, were analyzed for their effect on erbB3 tyrosine phosphorylation in MKN28 gastric epithelial cells. HRG protein expression in fibroblast lysates and CM was also examined by western blot. HRG-alpha and HRG-beta mRNA expression in gastric fibroblasts and human gastric tissue was examined by real-time quantitative PCR. HRG and COX-2 expressions in surgical resections of human gastric ulcer tissue were examined immunohistochemically. CM from fibroblasts incubated with PGE(2), or IL-1beta, stimulated erbB3 phosphorylation in MKN28 cells. Preincubation of the fibroblasts with celecoxib, a selective COX-2 inhibitor, suppressed CM-induced erbB3 phosphorylation. This inhibition was reversed by exogenous PGE(2). As with erbB3 phophorylation, IL-1beta stimulated both HRG-alpha and HRG-beta mRNA expression, as well as HRG release into gastric fibroblast CM. IL-1beta-stimulated HRG expression and release were also inhibited by celecoxib, and exogenous PGE(2) restored this inhibitory effect, suggesting the activation of an IL-1beta-COX-2-PGE(2) pathway that culminates in the release of HRG from fibroblasts. HRG-alpha and HRG-beta mRNA levels were significantly higher in gastric ulcer tissue than in normal gastric mucosa. HRG immunoreactivity was found in interstitial cells of the gastric ulcer bed and coexpressed with COX-2. These results suggest that HRG might be a new member of the growth factor family involved in the COX-2-dependent ulcer repair process.

Gastroprotective action of glucocorticoid hormones during NSAID treatment

In this article we present an overview of the results of our studies suggesting that endogenous glucocorticoid hormones play a role as natural defensive factors in maintaining the integrity of the gastric mucosa during treatment with non-steroidal anti-inflammatory drugs (NSAIDs). In-domethacin and aspirin at ulcerogenic doses induce a rise in corticosterone, which helps the gastric mucosa to resist the harmful actions of these ulcerogenic agents. The gastroprotective action of glucocorticoids during NSAID treatment may be mediated by multiple actions, including maintenance of glucose homeostasis, mucus production and attenuation of enhanced gastric motility and microvascular permeability. According to our findings, glucocorticoid hormones also participate in the healing processes of NSAID-induced gastric injury. It was demonstrated that there is some cooperative interaction between glucocorticoids and prostaglandins (PGs) in gastroprotection, in a way that a deficiency of one protective factor can lead to an apparently compensatory increase of the other. The gastric mucosa becomes more susceptible to injury during deficiency of both glucocorticoids and PGs.

Dexamethasone Impairs the Gastric Mucosal Integrity in Rats Treated with a Cyclooxygenase-1 but Not with a Cyclooxygenase-2 Inhibitor

In rats, neither the cyclooxygenase-1 inhibitor SC-560 nor the cyclooxygenase-2 inhibitor rofecoxib damages the gastric mucosa. Coadministration of dexamethasone induced injury in SC-560- but not in rofecoxib-treated rats. High levels of cyclooxygenase-1 protein occurred in the gastric mucosa of control rats, with no change after administration of SC-560. In contrast, the gastric cyclooxygenase-2 protein levels were low in control rats, but increased in a time-dependent manner after administration of SC-560. Dexamethasone prevented the increase in cyclooxygenase-2 protein levels. Our findings show that inhibition of cyclooxygenase-1 upregulates cyclooxygenase-2. When the upregulation is prevented by dexamethasone, gastric damage develops, suggesting that induction of cyclooxygenase-2 represents a compensatory mechanism that counteracts the injurious effect of cyclooxygenase-1 inhibition.

Role of the different isoforms of cyclooxygenase and nitric oxide synthase during gastric ulcer healing in cyclooxygenase-1 and -2 knockout mice

Traditional NSAIDs, selective cyclooxygenase (COX)-2 inhibitors, and inhibitors of nitric oxide synthase (NOS) impair the healing of preexisting gastric ulcers. However, the role of COX-1 (with or without impairment of COX-2) and the interaction between COX and NOS isoforms during healing are less clear. Thus we investigated healing and regulation of COX and NOS isoforms during ulcer healing in COX-1 and COX-2 deficiency and inhibition mouse models. In this study, female wild-type COX-1(-/-) and COX-2(-/-) mice with gastric ulcers induced by cryoprobe were treated intragastrically with vehicle, selective COX-1 (SC-560), COX-2 (celecoxib, rofecoxib, and valdedoxib), and unselective COX (piroxicam) inhibitors. Ulcer healing parameters, mRNA expression, and activity of COX and NOS were quantified. Gene disruption or inhibition of COX-1 did not impair ulcer healing. In contrast, COX-2 gene disruption and COX-2 inhibitors moderately impaired wound healing. More severe healing impairment was found in dual (SC-560 + rofecoxib) and unselective (piroxicam) COX inhibition and combined COX impairment (in COX-1(-/-) mice with COX-2 inhibition and COX-2(-/-) mice with COX-1 inhibition). In the ulcerated repair tissue, COX-2 mRNA in COX-1(-/-) mice, COX-1 mRNA in COX-2(-/-) mice, and, remarkably, NOS-2 and NOS-3 mRNA in COX-impaired mice were more upregulated than in wild-type mice. This study demonstrates that COX-2 is a key mediator in gastric wound healing. In contrast, COX-1 has no significant role in healing when COX-2 is unimpaired but becomes important when COX-2 is impaired. As counterregulatory mechanisms, mRNA of COX and NOS isoforms were increased during healing in COX-impaired mice.

Emerging roles for cyclooxygenase-2 in gastrointestinal mucosal defense

The development of selective inhibitors of cyclooxygenase-2 (COX-2) was based on the concept that this enzyme played little, if any, role in modulating the ability of the gastrointestinal (GI) tract to resist and respond to injury. There is now overwhelming evidence that this is far from true. Indeed, COX-2 mediates several of the most important components of 'mucosal defense', contributes significantly to the resolution of GI inflammation and plays a crucial role in regulating ulcer healing. COX-2 also contributes to long-term changes in GI function after bouts of inflammation.

Effects of cyclooxygenase-1 and -2 inhibition on gastric acid secretion and cardiovascular functions in rats

The discovery of a second isoform of cyclooxygenase has led to a re-evaluation of the mechanisms underlying the adverse effects of nonsteroidal anti-inflammatory drugs, focusing in particular on the gastrointestinal system. We investigated the involvement of cyclooxygenase-1 and -2 in the regulation of gastric acid secretion and cardiovascular functions in anesthetized rats, after acute intravenous administration of the selective cyclooxygenase-1 inhibitor SC-560, the selective cyclooxygenase-2 inhibitor celecoxib and the nonselective inhibitor indomethacin. Indomethacin, celecoxib and SC-560 did not significantly modify basal acid secretion. Indomethacin and celecoxib were also ineffective on the acid secretion stimulated by pentagastrin; by contrast, SC-560 significantly enhanced the acid secretion stimulated by pentagastrin, electrical vagal stimulation or histamine. The stimulatory effects of SC-560 were prevented by cervical vagotomy, atropine and famotidine. Indomethacin caused either no change, increasing or decreasing effects on mean arterial pressure and heart rate. By contrast, SC-560 was unable to change cardiovascular parameters at 5 mg/kg, while inducing a marked bradycardia at 10 mg/kg. Celecoxib was ineffective. Our findings indicate that cyclooxygenase-1-derived prostaglandins are involved in the regulation of stimulated acid secretion and of basal heart rate; the role of prostaglandins in the acute control of systemic blood pressure under resting conditions seems to be negligible.

(2E,6Z,10E)-7-hydroxymethyl-3,11,15-trimethyl-2,6,10,14-hexadecatetraen-1-ol (Plaunotol) increases cyclooxygenase-2 expression via nuclear factor kappaB and cyclic AMP response element in rat gastric epithelial cells

Plaunotol, [(2E,6Z,10E)-7-hydroxymethyl-3,11,15-trimethyl-2,6,10,14-hexadecatetraen-1-ol], a gastroprotective agent, increases the prostaglandin production in the gastric mucosa and accelerates ulcer healing. The precise mechanisms underlying the gastroprotective actions by plaunotol are not known. On the other hand, cyclooxygenase (COX)-2 is a key enzyme in PGE(2) production and its induction is thought to have an important role in ulcer healing. We investigated the mechanism of plaunotol-mediated COX-2 induction in rat gastric epithelial (RGM1) cells. We used a PGE(2) enzyme-linked immunoassay kit and Western blot analysis to measure PGE(2) production and COX-2 induction with plaunotol treatment in serum-starved RGM1 cells. In addition, gel-shift assay, Western blot analysis and a reporter assay were performed to observe which Cox-2 promoter was involved in plaunotol-induced Cox-2 expression. The findings indicated that plaunotol treatment dose-dependently increased COX-2 expression and PGE(2) production. The nuclear factor kappaB (NF-kappaB) and cyclic AMP response element (CRE) sites of the COX-2 gene promoter were critical to plaunotol-mediated COX-2 expression. In conclusion, plaunotol induced COX-2 expression and increased PGE(2) production in serum-starved RGM1 cells via activation of the NF-kappaB and CRE sites of Cox-2 gene promoters.

Cyclo-oxygenase-2 expression and prostaglandin E2 production in experimental chronic gastric ulcer healing

Prostaglandin, a key molecule that stimulates the complex array of ulcer healing mechanism, gets synthesized in the mucosal cells by cyclooxygenase (COX) enzymes: COX-1 and COX-2. High expression level of COX-2 protein at healing ulcer margins highlights its role in ulcer healing and hypothesized to be an important contributing factor in healing mechanism of anti-ulcer drugs. In the present study we have compared the expression profile of COX-2 protein, prostaglandin E2 (PGE2) levels and myeloperoxidase activity in acetic acid induced chronic gastric ulcer model in rats treated with omeprazole, misoprostol and COX-2 selective nonsteroidal anti-inflammatory drug (NSAID) celecoxib. Both COX-2 expression and PGE2 level have shown differential pattern in different treated groups parallel to the differential effects of these drugs on ulcer healing. Omeprazole has significantly elevated the expression level of COX-2 protein, PGE2 level (19.37%), and decreased myeloperoxidase activity (81.92%), thereby causing the most effective ulcer healing (89.74%). Similar trend was observed with misoprostol, but with relatively less pronounced ulcer healing and COX-2 expression. Celecoxib has retarded COX-2 expression and delayed ulcer healing. Therefore, induction of COX-2 expression leading to higher level of prostaglandin appears to be an important contributing factor in drug mediated ulcer healing apart from the respective mechanisms of different drugs.

Cyclooxygenase-2 inhibition selectively attenuates bone morphogenetic protein-6 synthesis and bone formation during guided tissue regeneration in a rat model

OBJECTIVES

Bone formation during guided tissue regeneration is a tightly regulated process involving cells, extracellular matrix and growth factors. The aims of this study were (i) to examine the expression of cyclooxygenase-2 (COX-2) during bone regeneration and (ii) the effects of selective COX-2 inhibition on osseous regeneration and growth factor expression in the rodent femur model.

MATERIAL AND METHODS

A standardized transcortical defect of 5 x 1.5 mm was prepared in the femur of 12 male rats and a closed half-cylindrical titanium chamber was placed over the defect. The expression of COX-2 and of platelet-derived growth factor-B (PDGF-B), bone morphogenetic protein-6 (BMP-6) and insulin-like growth factor-I/II (IGF-I/II) was analyzed at Days 3, 7, 21 and 28 semiquantitatively by reverse transcriptase-polymerase chain reaction and immunohistochemistry. The effects of COX-2 inhibition by intraperitoneal injection of NS-398 (3 mg/kg/day) were analyzed in five additional animals sacrificed at Day 14.

RESULTS

Histomorphometry revealed that new bone formation occurred in the cortical defect area as well as in the supracortical region, i.e. region within the chamber by Day 7 and increased through Day 28. Immunohistochemical evidence of COX-2 and PDGF-B levels were observed early (i.e. Day 3) and decreased rapidly by Day 7. BMP-6 expression was maximal at Day 3 and slowly declined by Day 28. In contrast, IGF-I/II expression gradually increased during the 28-day period. Systemic administration NS-398 caused a statistically significant reduction (P<0.05) in new bone formation (25-30%) and was associated with a statistically significant reduction in BMP-6 protein and mRNA expression (50% and 65% at P<0.05 and P<0.01, respectively). PDGF-B mRNA or protein expression was not affected by NS-398 treatment.

CONCLUSION

COX-2 inhibition resulted in reduced BMP-6 expression and impaired osseous regeneration suggesting an important role for COX-2-induced signaling in BMP synthesis and new bone formation.

Rebamipide reduces delay in gastric ulcer healing in cyclooxygenase-2-deficient mice

Rebamipide is an antiulcer drug capable of various actions including the induction of cyclooxygenase-2 (COX-2). In this study, we investigated the effect of rebamipide on gastric ulcer healing in COX-2-deficient mice. Wild-type (N=34) and COX-2-deficient mice (N=28) with gastric ulcers were administered 30 mg/kg of rebamipide or the vehicle. Ulcerous tissues were subjected to measurements of ulcer size, immunohistochemical staining of CD31 (an endothelial cell marker), and mRNA levels. COX-2 deficiency delayed ulcer healing and inhibited angiogenesis and bFGF mRNA expression in the granulation tissue. In wild-type mice, rebamipide accelerated ulcer healing and increased COX-2 mRNA expression. In COX-2-deficient mice, rebamipide prevented delayed ulcer healing and reversed the inhibition in angiogenesis and bFGF mRNA expression. The effect of rebamipide on the enhancement of ulcer healing, angiogenesis, and induction of bFGF expression was more prominent in wild-type mice than in COX-2-deficient mice. In conclusion, rebamipide may accelerate gastric ulcer healing through both COX-2-dependent and COX-2-independent mechanisms.

Resveratrol as an anti-inflammatory and anti-aging agent: mechanisms and clinical implications

Resveratrol is a phytoalexin polyphenolic compound found in various plants, including grapes, berries, and peanuts. Multiple lines of compelling evidence indicate its beneficial effects on neurological, hepatic, and cardiovascular systems. Also one of the most striking biological activities of resveratrol soundly investigated during the late years has been its cancer-chemopreventive potential. In fact, recently it has been demonstrated that this stilbene blocks the multistep process of carcinogenesis at various stages: tumor initiation, promotion, and progression. One of the possible mechanisms for its biological activities involves downregulation of the inflammatory response through inhibition of synthesis and release of pro-inflammatory mediators, modification of eicosanoid synthesis, inhibition of activated immune cells, or inhibiting such as inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) via its inhibitory effects on nuclear factor (kappa)B (NF-(kappa)B) or the activator protein-1 (AP-1). More recent data provide interesting insights into the effect of this compound on the lifespan of yeast and flies, implicating the potential of resveratrol as an anti-aging agent in treating age-related human diseases. It is worthy to note that the phenolic compound possesses a low bioavailability and rapid clearance from the plasma. As the positive effects of resveratrol on inflammatory response regulation may comprise relevant clinical implications, the purpose of this article is to review its strong anti-inflammatory activity and the plausible mechanisms of these effects. Also, this review is intended to provide the reader an up-date of the bioavailability and pharmacokinetics of resveratrol and its impact on lifespan.

COX-1 and COX-2 conversely promote and suppress ischemia-reperfusion gastric injury in mice

OBJECTIVE

Neutrophil activation followed by free radical production is a feature that is common to the various forms of gastric injury. However, the roles of cyclooxygenase (COX)-1 and -2 in neutrophil activation have yet to be clarified in the gastric mucosa. We examined the roles of both COX-1 and COX-2 in neutrophil activation and free radical production in ischemia-reperfusion (IR) injury in the gastric mucosa of mice.

MATERIAL AND METHODS

Ischemia was induced by clamping the celiac artery for 30 min, then removing the clamp for 90 min. SC-560, a selective COX-1 inhibitor; NS-398, a selective COX-2 inhibitor; or rebamipide, a mucoprotective agent, was administered to mice 60 min before ischemia. Gastric damage was evaluated histologically and by measuring myeloperoxidase (MPO) activity. Expressions of COX protein and intercellular adhesion molecule (ICAM)-1 were evaluated by Western blot analysis and ELISA, respectively. Effects of these drugs on thiobarbituric acid reactive substances (TBARS) and gastric blood flow were also evaluated.

RESULTS

COX-2 expression was induced in gastric mucosa 60 min after reperfusion, whereas COX-1 expression remained unaltered. Localization of COX-1 and ICAM-1 in IR-injured mucosa was observed mainly in endothelial cells, while COX-2 expression was detected in mesenchymal cells such as mononuclear cells, spindle-like cells and endothelial cells. SC-560 significantly decreased gastric blood flow at the reperfusion point and reduced gastric mucosal injury in IR mice. Furthermore, SC-560 pretreatment significantly reduced MPO activity, TBARS levels and ICAM-1 expression. In contrast, NS-398 significantly increased ICAM-1 expression, MPO activity and TBARS levels, and aggravated gastric damage in IR mice. Rebamipide pretreatment reduced both COX-2 expression and IR injury.

CONCLUSIONS

In IR mice, COX-2 protects the gastric mucosa by down-regulating ICAM-1 expression, whereas COX-1 is involved in up-regulating reperfusion flow, thereby aggravating the mucosa.

Role of cyclooxygenase isoforms in gastric mucosal defense and ulcer healing

The rationale for the development of selective inhibitors of cyclooxygenase-2 (COX-2) was the proposal that this enzyme plays an important role in inflammation but does not contribute to the resistance of the gastrointestinal mucosa against injury. However, studies from several groups have established that both COX-1 and COX-2 have important functions in the maintenance of gastrointestinal mucosal integrity. Thus, in the normal rat stomach lesions only develop when both COX-1 and COX-2 are inhibited. On the other hand, in specific pathophysiological situations the isolated inhibition of either COX-1 or COX-2 without simultaneous suppression of the other COX isoenzyme is ulcerogenic. Furthermore, COX-2 plays an important role in the healing of gastric ulcers and inhibition of COX-2 delays ulcer healing. From these findings the initial concept that only inhibition of COX-1 interferes with gastrointestinal defense has to be re-evaluated.

Differential expression of COX-1 and COX-2 in the gastrointestinal tract of the rat

The aim of this study was to use immunohistochemistry with morphometry to investigate COX-1 and COX-2 expression in the normal rat gastrointestinal (GI) tract and examine if sites of ulceration previously observed with long-term COX-2 inhibitor administration in mice correlate with differential COX-1/COX-2 expression. COX-2 positive cells were observed predominantly in the apical lamina propria of intestinal villi with fewer cells in the mucosal epithelium. The highest level of COX-2 expression was observed at the ileocaecal junction (ICJ). COX-2 expression was also present in parasympathetic ganglia of the submucosa and muscularis. In the stomach, the highest grade of COX-2 expression was observed in the apical lamina propria of the fundus adjacent to the junctional ridge. In contrast, COX-1 positive cells within the lamina propria were evenly distributed along the GI tract but were present in higher numbers than COX-2 positive cells. The mean level of COX-1 expression at the ICJ was not significantly different from the ileum and caecum. Evidence that the highest level of COX-2 expression in normal rats is located on the ileal side of the ICJ provides the first mechanism to explain spontaneous ulceration and perforation of the distal ileum in COX-2 -/- animals.

Small bowel cyclooxygenase 2 (COX-2) expression in patients with IgA nephropathy

BACKGROUND

Clinical manifestation of IgA nephropathy (IgAN) strikingly occurs after respiratory tract infections. An intestinal inflammation has also been described. We hypothesized that the intestinal inflammation should manifest itself as an increase in inflammatory cells and mucosal cyclooxygenase 2 (COX-2) expression.

METHODS

By using immunohistochemistry, we determined the phenotype and quantity of inflammatory cells in duodenal biopsy specimens from 17 IgAN patients. Control material comprised 18 patients undergoing gastroscopy because of dyspepsia.

RESULTS

All the biopsy specimens disclosed normal villous architecture. In IgAN, CD3(+) cells and COX-2-positive cells were significantly increased and J chain-producing plasma cells were significantly decreased. CD3(+) cells coexpressed COX-2 protein and COX-2-positive cells also expressed CD45RO antigen. The number of lymphocytes correlated significantly with serum IgA and COX-2-expression with serum IgA and the degree of hematuria. COX-2-positive subepithelial fibroblasts were a conspicuous finding in IgAN. In CD68(+) and CD15(+) cells, a significant increase was seen. Many of these cells also expressed COX-2 protein. CD15(+) positivity correlated significantly with proteinuria in IgAN.

CONCLUSION

Our results indicate that small bowel inflammation in IgAN shows itself as an increased number of mucosal inflammatory cells. However, polymeric IgA production is significantly decreased. An increased mucosal COX-2 expression suggests activation of the inflammatory cells and the degree of inflammation significantly correlates with serum IgA and the amount of proteinuria and hematuria. Subepithelial fibroblasts seem also to be involved in the inflammatory reaction.

Pharmacology in rehabilitation: nonsteroidal anti-inflammatory agents

Nonsteroidal anti-inflammatory agents (NSAIDs) are the most commonly encountered over-the-counter (OTC) and prescription medications in physical therapy practice. Worldwide, over 73000000 prescriptions for nonsteroidal agents are written yearly. NSAIDs produce a wide range of beneficial effects to the physical therapy patient, enhancing the outcome of treatment. Helpful effects of NSAIDs include analgesia, antipyretic, anti-inflammatory, and antithrombotic properties. However, NSAIDs are also associated with frequent and significant side effects that are deleterious to treatment outcome, including delay in soft tissue and bone healing, renal and liver toxicity, hemorrhagic events, gastric irritation and ulceration, and central nervous system effects. Understanding of the pharmacological properties of these drugs, exemplified by aspirin, and the individual pharmacokinetics of specific preparations will help the therapist to screen patients for potential side effects, develop more effective plans of care, and, where allowed, effectively and safely prescribe NSAIDs.

Angiogenesis, cell proliferation and apoptosis in gastric ulcer healing. Effect of a selective cox-2 inhibitor

To elucidate the role of cyclooxygenase-2, we compared the effects of rofecoxib, a selective cyclooxygenase-2 inhibitor, and ibuprofen, a nonselective cyclooxygenase inhibitor, on the evolution of acetic-acid-induced gastric ulcers in rats, evaluating growth factor expression, the angiogenic process, cell proliferation and cell apoptosis. Levels of basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF), angiogenesis and cell proliferation were analysed by immunohistochemical methods, and apoptosis was evaluated by an enzyme immunoassay. Both growth factors and microvessels appeared to be abundant in the granulation tissue of the ulcer bed. Rofecoxib (2.5 mg/kg/day) and ibuprofen (100 mg/kg/day) delayed ulcer healing, but only rofecoxib treatment provoked a reduction of bFGF expression and inhibition of the development of new microvessels. No changes in VEGF expression were detected. Results also showed that proliferation and apoptosis were increased in control ulcerated animals. Rofecoxib reduced significantly both processes. These findings demonstrate that a reduction of bFGF expression and an antiangiogenic action, as well as proliferation/apoptosis inhibition, are some of the mechanisms possibly implicated in the delay in ulcer healing seen after the administration of the highly selective COX-2 inhibitor rofecoxib.

Chemoprevention of 4-NQO-induced oral carcinogenesis by co-administration of all-trans retinoic acid loaded microspheres and celecoxib

All-trans retinoic acid (atRA) is one of the most potential chemopreventive agents for head and neck squamous cell carcinoma (HNSCC). However, the induced metabolism of atRA by cytochrome P450s in the liver limits its clinical applications. To overcome such limitation, we had developed atRA-loaded microspheres designed to release atRA for a long period. Unfortunately, the atRA-loaded microspheres severely induced inflammatory responses: that is, atRA released from the microspheres significantly induced the proliferation of fibroblasts and collagen deposition, thereby causing a permeability barrier for drugs from entering the blood stream. In the present study, the effects of celecoxib as an anti-inflammatory drug are investigated when it is concurrently used with atRA-loaded microspheres to treat 4-NQO-induced oral carcinogenesis. We investigated if it might influence the plasma concentration of atRA and its metabolism by preventing the fibroblast proliferation and collagen deposition, reduce the toxicity level of atRA, and improve the chemopreventive efficacy of atRA-loaded microspheres. The concurrently administered celecoxib prevented inflammatory responses and suppressed the number of fibroblasts and collagen deposition in the fibrous capsules for 14 days. The atRA concentration in plasma was also increased and the metabolism of atRA was significantly decreased within 2 weeks. In the 4-NQO-induced oral carcinogenesis study, the incidence of invasive SCC was above 44% when F344 rats were treated with atRA-loaded microspheres. However, the treatment using atRA-loaded microspheres and celecoxib concurrently could reduce the incidence of invasive SCC up to 28%, and three of 25 rats were found to have no tongue lesions. In conclusion, the concurrent use of celecoxib could maintain the atRA concentration in plasma at a higher level while reducing its metabolism by preventing inflammatory responses, thereby improving their chemopreventive effects against 4-NQO-induced oral carcinogenesis.

Current approaches to prevent NSAID-induced gastropathy--COX selectivity and beyond

Gastrointestinal (GI) toxicity associated with nonsteroidal anti-inflammatory drugs (NSAIDs) is still an important medical and socio-economic problem--despite recent pharmaceutical advances. To prevent NSAID-induced gastropathy, three strategies are followed in clinical routine: (i) coprescription of a gastroprotective drug, (ii) use of selective COX-2 inhibitors, and (iii) eradication of Helicobacter pylori. Proton pump inhibitors are the comedication of choice as they effectively reduce gastrointestinal adverse events of NSAIDs and are safe even in long-term use. Co-medication with vitamin C has only been little studied in the prevention of NSAID-induced gastropathy. Apart from scavenging free radicals it is able to induce haeme-oxgenase 1 in gastric cells, a protective enzyme with antioxidant and vasodilative properties. Final results of the celecoxib outcome study (CLASS study) attenuated the initial enthusiasm about the GI safety of selective COX-2 inhibitors, especially in patients concomitantly taking aspirin for cardiovascular prophylaxis. Helicobacter pylori increases the risk for ulcers particularly in NSAID-naive patients and therefore eradication is recommended prior to long-term NSAID therapy at least in patients at high risk. New classes of COX-inhibitors are currently evaluated in clinical studies with very promising results: NSAIDs combined with a nitric oxide releasing moiety (NO-NSAID) and dual inhibitors of COX and 5-LOX. These drugs offer extended anti-inflammatory potency while sparing gastric mucosa.

Mucosal expression of cyclooxygenase isoforms 1 and 2 is increased with worsening damage to the gastric mucosa

AIMS

To test the hypothesis that both COX-1 and COX-2 expression in human gastric mucosa is up-regulated in the presence of inflammation as seen in patients with gastritis and gastric ulcers.

METHODS AND RESULTS

We performed immunohistochemistry using COX-1 and COX-2 monoclonal antibodies on gastric biopsies from 59 patients with normal mucosa, gastritis and gastric ulcers. Expression of COX-1 and COX-2 was quantified using an intensity proportion scoring system. Expression of COX-1 was primarily seen in the lamina propria mononuclear cells with some expression in deep gastric glands in the ulcer group. Expression of COX-2 was primarily seen in the deep gastric glands with focal expression in the lamina propria mononuclear cells. We found a stepwise increase in the expression of both COX-1 and COX-2 as mucosal damage progressed from normal to gastritis to gastric ulcer.

CONCLUSIONS

We conclude that both COX-1 and COX-2 expression in the gastric mucosa are increased in the setting of gastritis and gastric ulceration. Although this increased expression may be due, at least in part, to an increase in inflammatory cell numbers, this study raises the possibility that both COX-1 and COX-2 are inducible, contrary to the traditionally held view of only COX-2 being inducible.

Gastrointestinal effects of COX-2 inhibitors

The developing popularity of non-steroidal anti-inflammatory drugs (NSAIDs) over the last 100 years has been paralleled by an increase in associated complications, particularly affecting the gastrointestinal (GI) tract [1]. Over this period, there have been several attempts to develop less toxic NSAIDs, most of which have been unsuccessful. Since the discovery that the enzyme cyclooxygenase (COX) exists as two isoforms, the largely constitutive COX-1 and the mainly inducible COX-2, much interest has centred on the development of drugs capable of selectively inhibiting COX-2. Early studies that investigated specific COX-2 inhibitors (with no effect on the COX-1 isoform over the whole range of concentrations achieved in clinical usage) are encouraging, as they demonstrate that these drugs have fewer effects on gastroduodenal mucosa than standard NSAIDs given at equivalent doses. Further clinical experience with these agents outside trial settings and additional studies to assess the role of COX-2 when induced in the GI tract are needed, before such agents can be safely recommended for widespread prescribing.

COX expression and PGE2 and PGD2 production in experimental acute and chronic gastric lesions

Prostaglandin E(2) and D(2) (PGE(2) and PGD(2)) production and cyclooxygenase-2 (COX-2) expression during the resolution of acute and chronic gastric inflammatory lesions in Wistar rats have been investigated. Differences between ibuprofen, nonselective COX inhibitor, and rofecoxib, specific COX-2 inhibitor, on the development of the induced responses were also analysed. In an acute model, by instillation of HCL, the greatest injury was observed early with a rapid and progressive restoration. Maximal up-regulation of COX-2 protein was detected at 6 h and was accompanied by increase of PGE(2) synthesis but not PGD(2). Both drugs stimulated COX-2 expression in accordance to their capacity of inhibiting this enzymatic activity, driving to delay in the healing. In a chronic model, by acetic acid-induced gastric ulcers, COX-2 was expressed at 7 days and was also associated with PGE(2) increase. Ibuprofen and rofecoxib also augmented COX-2 protein and inhibited PGE(2) levels. However, PGD(2) production was augmented when none signal of COX-2 protein could be detected. Together, this study confirms the role played by COX-2 enzyme in the resolution of acute and chronic gastric inflammatory process, PGE(2) being the principal product. The antiinflammatory effect of nonsteroidal antiinflammatory drugs (NSAIDs) could be mediated not only through the inhibition of COX activity but also through the induction of antiinflammatory PGs production-such as PGD(2)-although further studies would be needed to clarify the mechanisms of this activity and the possible implicated processes.

Survivin: a novel target for indomethacin-induced gastric injury

BACKGROUND & AIMS

Nonsteroidal anti-inflammatory drugs (NSAIDs) cause gastrointestinal erosions and ulcers. Apoptosis is one of the mechanisms. The role of survivin, an antiapoptosis protein, in NSAID-induced gastric injury is unknown. We examined the role of survivin in NSAID-induced gastric mucosal and gastric cell injury.

METHODS

We examined: (1) the effects of indomethacin (nonselective NSAID), celecoxib and NS-398 (cyclooxygenase [COX]-2-selective NSAIDs), SC-560 (a COX-1-selective NSAID), and SC-560 plus celecoxib on survivin expression and extent of injury in rat gastric mucosa; (2) the effects of indomethacin, NS-398, SC-560, and SC-560 plus NS-398 on survivin expression and injury in gastric epithelial (RGM-1) cells; and (3) the effects of survivin suppression with small interfering RNA (siRNA) on RGM-1 cell integrity at baseline and following indomethacin injury.

RESULTS

Indomethacin treatment dose-dependently reduced survivin protein levels and caused severe injury of gastric mucosa and RGM-1 cells. Suppression of survivin expression with siRNA in RGM-1 cells caused cell damage and increased susceptibility to injury by indomethacin. Celecoxib treatment caused exfoliation of the mucosal surface epithelium, but neither caused deep erosions or altered survivin expression. Neither NS-398 nor SC-560 treatment altered survivin levels or produced injury in vivo or in vitro. COX-1 and COX-2 inhibitor combination caused injury in vivo and in vitro but did not decrease survivin expression.

CONCLUSIONS

(1) Indomethacin, but not selective COX-1 or COX-2 inhibitors alone or in combination, reduces survivin expression in gastric mucosal cells and (2) significant reduction of survivin precedes greater severity of gastric injury.

Cyclooxygenase 1 is required for pH control at the mouse gastric surface

BACKGROUND

Endogenous cyclooxygenase (COX) activity is required to maintain a relatively alkaline surface pH at the gastric luminal surface.

AIMS

The purpose of this study was to determine which COX isoform, COX-1 or COX-2, is responsible for regulating the protective surface pH gradient and to test if COX inhibitors also had non-COX mediated effects in vivo.

METHODS

Immunofluorescence and western blot analysis showed constitutive expression of both COX isoforms in the normal mouse stomach. We used in vivo confocal microscopy to measure pH near the mucosal surface of anaesthetised COX-1 (-/-), COX-2 (-/-), or wild-type mice of the same genetic background.

RESULTS

When the gastric mucosal surface was exposed and superfused (0.2 ml/min) with a weakly buffered saline solution (pH 3) containing the pH indicator Cl-NERF, the pH directly at the gastric surface and thickness of the pH gradient were similar in wild-type and COX-2 (-/-) mice, but COX-1 (-/-) mice had a significantly thinner pH gradient. Addition of indomethacin had minimal effects on the residual surface pH gradient in COX-1 (-/-) mice, suggesting no role for COX-2 in surface pH regulation. Whole stomach perfusion studies demonstrated diminished net alkali secretion in COX-1 (-/-) mice, and application of SC-560 or rofecoxib to wild-type mice and mutant mice confirmed that only COX-1 inhibition reduced alkali secretion.

CONCLUSION

COX-1 is the dominant isoform regulating the normal thickness of the protective surface pH gradient in mouse stomach.

Effects of a selective cyclo-oxygenase 2 inhibitor on colonic anastomotic and skin wound integrity

BACKGROUND

Selective inhibitors of inducible cyclo-oxygenase (COX-2) are of potential benefit in the perioperative period for both their analgesic and, perhaps, antineoplastic actions. However, their effects on laparotomy and intestinal wound healing are unknown.

METHODS

Forty adult Sprague-Dawley rats underwent laparotomy, descending colonic transection and handsewn reanastomosis. The animals were randomized to receive either a selective COX-2 inhibitor (rofecoxib, 10 mg/kg) or an equal volume of water by gavage before operation and then daily after surgery. Animals were killed after 3 or 7 days, and their wounds were evaluated by means of tensiometry (skin and colonic wounds) and bursting pressure measurement (colonic anastomoses). In addition, haematoxylin and eosin-stained intestinal sections were examined and scored by a blinded independent observer.

RESULTS

Five animals that received rofecoxib had anastomotic leaks by day 7 compared with none in the control group (P = 0.048). Intact colonic suture lines were also significantly weaker in this group (tensile strength at day 3, P = 0.043; bursting pressure on days 3 and 7, both P = 0.019). Skin wound strengths were similar in the two groups at both time points.

CONCLUSION

Although beneficial in the treatment of pathological inflammation, selective COX-2 inhibitors may adversely affect colonic anastomotic healing.

Toxic effects of nonsteroidal antiinflammatory drugs on the small bowel, colon, and rectum

The gastrointestinal toxicity of conventional nonsteroidal antiinflammatory drugs (NSAIDs) is not confined to the stomach and proximal duodenum but extends also to the rest of the small bowel, colon, and rectum. Long-term NSAID therapy usually induces clinically silent enteropathy characterized by increased intestinal permeability and inflammation. Chronic occult bleeding and protein loss may result in iron-deficiency anemia and hypoalbuminemia. NSAIDs can also induce small bowel ulcers that infrequently lead to acute bleeding, perforation, or chronic scarring responsible for diaphragm-like strictures. At the colon and rectum, NSAID use can result in de novo lesions such as nonspecific colitis and rectitis, ulcers, and diaphragm-like strictures. NSAIDs have been implicated in the development of segmental ischemic colitis. In patients with diverticular disease, NSAID use increases the risk of severe diverticular infection and perforation. NSAIDs can trigger exacerbations of ulcerative colitis or Crohn's disease. With selective COX-2 inhibitors, the risk of gastrointestinal toxicity is reduced as compared to conventional NSAIDs but is not completely eliminated. Experimental studies suggest that long-term COX-2 inhibitor therapy may cause damage to the previously healthy small bowel. Similar to conventional NSAIDs, COX-2 inhibitors may be capable of triggering exacerbations of inflammatory bowel disease.

Gastrointestinal and hepatic toxicity of selective and non-selective cyclooxygenase-2 inhibitors in pregnant and non-pregnant rats

The aim of the study was to evaluate the toxicity of non-selective (tolmetin, ibuprofen and piroxicam) and selective (DFU) cyclooxygenase-2 inhibitors on pregnant and non-pregnant rats. The drugs were administered orally once (DFU, piroxicam) or three times (tolmetin, ibuprofen) a day from days 8 through 21 of gestation experiment in three doses. The initial dose was similar to the human antiinflammatory one and set as 8.5 mg/kg (tolmetin, ibuprofen), 0.3 mg/kg (piroxicam) and 0.2 mg/kg (DFU). The middle dose was increased 10 times and the highest one 100 times the initial dose. The highest dose for ibuprofen was set at 200mg/kg due to high mortality. On gestation/experimental day 21 animals were sacrificed, blood was collected and abdominal organs were taken for pathological examination. Activity of alanine and asparate aminotransferases and levels of total protein and urea were determined. Stomach, small and large intestines, and liver were grossly and histologically examined. Dose-dependent mortality, signs of gastrointestinal toxicity, and significant changes of biochemical parameters were found in groups exposed to non-selective COX inhibitors in both pregnant and non-pregnant rats. Mild regressive structural hepatic changes were observed. Significant decrease of protein level in non-pregnant rats treated with high DFU dose, and occasionally observed gastrointestinal changes were the only changes noted in groups exposed to the selective COX-2 inhibitor. Tolerability of non-selective COX inhibitors was lower in both pregnant and non-pregnant groups when compared with DFU. Insignificant mortality and histological changes were noted between pregnant and non-pregnant groups.

Analgesic Comparison of Meloxicam or Ketoprofen for Orthopedic Surgery in Dogs

OBJECTIVE

To compare the safety and efficacy of 2 analgesic protocols (preoperative meloxicam or intraoperative ketoprofen administration) during the first 24 hours after orthopedic surgery in dogs.

STUDY DESIGN

Double-blind, prospective randomized clinical trial.

ANIMALS

Sixty client-owned dogs.

METHODS

Dogs with surgical orthopedic disorders were randomly separated into 2 groups: 30 dogs were administered 0.2 mg/kg meloxicam intravenously (IV) immediately before induction and 30 dogs were administered 2 mg/kg ketoprofen IV, 30 minutes before the end of surgery. Pain was assessed with a visual analog scale (VAS) and a cumulative pain score (CPS) preoperatively and at 30 minutes, 1, 2, 3, 4, 6, 8, and 24 hours after extubation. Selected serum biochemical variables were measured before and 24 hours after surgery and, buccal mucosal bleeding time (BMBT) and whole blood clotting time (WBCT) were measured before and 8 hours after surgery. Dogs were anesthetized with propofol and maintained on halothane in oxygen. Any complications were documented for 7 days after surgery. Results were compared between the 2 groups for significant differences in VAS scores (2-sample t-test) and in CPS (Wilcoxon's 2-sample test). Moreover, results were analyzed for significant differences in area under the curve (AUC) for VAS (2-sample t-test) and CPS (Wilcoxon's 2-sample test) among groups. To assess the effects of treatments on biochemical and coagulation functions, pre- and postoperative mean values of BMBT and WBCT were compared within both treatment groups (paired t-tests) and between both groups (2-sample t-test).

RESULTS

No significant differences in pain response or coagulation were found between meloxicam- and ketoprofen-treated dogs. In both groups, alkaline phosphatase and alanine aminotransferase concentrations were significantly increased compared with baseline. No serious complications occurred.

CONCLUSIONS

Preoperative administration of meloxicam is a safe and effective method of controlling postoperative pain for up to 24 hours in dogs undergoing orthopedic surgery.

CLINICAL RELEVANCE

Analgesia after administration of preoperative meloxicam was comparable with administration of ketoprofen at the end of the surgery.

COX-1, COX-2 and the topical effect in NSAID-induced enteropathy

The side effects of NSAIDs are equally evident in the stomach and the small bowel. The latter is increasingly seen as being clinically significant, contributing substantially to the iron-deficiency anaemia that is so common in patients with rheumatoid arthritis. Furthermore, NSAID-enteropathy may be associated with life-threatening events. The pathogenesis of NSAID-enteropathy is uncertain but inhibition of COX-1 is believed to be of pivotal importance. However there is increasing evidence that COX-2 inhibition and the topical effect may have a synergistic detrimental action. We examined the role of COX-1, COX-2 and the so called topical effect of acidic NSAIDs. We found that COX-1 or COX-2 inhibition and the topical effect alone do not damage the GI tract. Dual inhibition of COX-1 and COX-2 results in intestinal inflammation similar to that caused by Indomethacin. The topical effect may act synergistically in this damage. The conventional view that the mechanism of gastrointestinal damage is principally caused by COX-1 inhibition needs to be revised in view of recent studies using selective inhibitors of the COX enzymes and COX knockout animals.

Impaired gastric ulcer healing in diabetic rats: role of heat shock protein, growth factors, prostaglandins and proinflammatory cytokines

Gastric mucosa of diabetic rats is highly vulnerable to acute injury, but little is known about the influence of diabetic conditions on the healing of gastric ulcers. In this study, streptozotocin (70 mg/kg injected intraperitoneally) was used to induce diabetes mellitus in rats. Four weeks after streptozotocin injection, gastric ulcers were induced using the acetic acid method, and 10 days later, the healing rate and the gastric blood flow (GBF) were measured by planimetry and hydrogen (H(2))-gas clearance method, respectively. Six major groups of rats with gastric ulcers were used: (1) vehicle (saline); (2) streptozotocin alone; (3) insulin (4 IU/day intraperitoneally); (4) streptozotocin plus insulin; (5) pentoxifylline, an inhibitor of synthesis and release of tumor necrosis factor-alpha (TNF alpha); and (6) aspirin, a non-selective inhibitor of cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2), and rofecoxib, the highly selective COX-2. In the diabetic rats, a significant delay in ulcer healing ( approximately by 300%), accompanied by a decrease in the gastric mucosal blood flow was observed. The prolongation of the healing in diabetic animals was associated with an increase in gastric mucosal expression and release of TNFalpha, interleukin-1 beta (IL-1 beta), suppression of the vascular endothelial growth factor (VEGF), platelet endothelial cell adhesion molecule-1 (PECAM-1) and the mucosal overexpression of heat shock protein 70 (HSP 70). Administration of insulin reversed the delay in ulcer healing and significantly decreased the expression of IL-1 beta and TNF-alpha, while producing the rise in the expression of VEGF and PECAM. Pentoxifylline, an inhibitor of TNF-alpha, which by itself accelerated ulcer healing in non-diabetic rats, counteracted the increase in the area of gastric ulcer induced by streptozotocin, raised significantly gastric blood flow and suppressed the plasma TNF-alpha levels. Aspirin and rofecoxib, that significantly suppressed the mucosal prostaglandin E(2) generation in ulcer area, delayed significantly the rate of ulcer healing and decreased the GBF at ulcer margin in non-diabetic rats, and these changes were significantly augmented in diabetic animals. We conclude that: (1) Experimental diabetes dramatically impairs ulcer healing, depending upon the increased release of proinflammatory cytokines and the attenuation of angiogenesis that can limit the ulcer healing effects of locally produced HSP 70 and TNF-alpha. (2) Insulin reversed this impairment of ulcer healing in diabetic rats, mainly due to the enhancement of angiogenesis and reduction in expression of cytokines in the ulcer area. (3) Classic non-steroidal anti-inflammatory drugs such as aspirin prolonged ulcer healing under diabetic conditions due to suppression of endogenous prostaglandins and the fall in the microcirculation at the ulcer margin and these effects were mimicked by selective, so called "safe" COX-2 inhibitor, rofecoxib, suggesting that both COX isoforms are important sources of prostaglandins that are essential in the ulcer healing in diabetes.

Ulcer formation with low-dose enteric-coated aspirin and the effect of COX-2 selective inhibition: a double-blind trial

BACKGROUND & AIMS

We assessed the risk of ulcers with low-dose aspirin and the interaction of low-dose aspirin with a COX-2 selective inhibitor in a double-blind trial that compared placebo, low-dose aspirin, rofecoxib + low-dose aspirin, and ibuprofen.

METHODS

Osteoarthritis patients > or =50 years of age without ulcers or erosive esophagitis at baseline endoscopy were assigned randomly to placebo, enteric-coated aspirin 81 mg/day, rofecoxib 25 mg combined with aspirin 81 mg/day, or ibuprofen 800 mg 3 times a day. Repeat endoscopies were performed at 6 and 12 weeks.

RESULTS

The 12-week cumulative incidence of ulcers was placebo (N = 381) 5.8%, aspirin (N = 387) 7.3%, rofecoxib combined with aspirin (N = 377) 16.1%, and ibuprofen (N = 374) 17.1% (P < 0.001 for rofecoxib combined with aspirin and for ibuprofen vs. each of placebo and aspirin). Over 12 weeks, mean increases in the number of erosions were placebo 0.17, aspirin 0.85 (P = 0.002 vs. placebo), rofecoxib combined with aspirin 1.67, and ibuprofen 1.91 (both P < 0.001 vs. aspirin and placebo).

CONCLUSIONS

Low-dose aspirin alone did not significantly increase ulcer incidence. Addition of a cyclooxygenase-2 (COX-2) selective inhibitor to low-dose aspirin increased ulcer incidence, to a rate not significantly less than a nonselective nonsteroidal anti-inflammatory drug (NSAID) alone. Determining the relative impact of COX-2 selective inhibitors and nonselective NSAIDs on gastrointestinal mucosal injury in low-dose aspirin users will require further study.

The effects of aspirin on gastric mucosal integrity, surface hydrophobicity, and prostaglandin metabolism in cyclooxygenase knockout mice

BACKGROUND & AIMS

Insight into the role of the different cyclooxygenase isoforms in prostaglandin biosynthesis, surface hydrophobicity, and gastric mucosal barrier integrity can be gained by comparing the effects of luminal damaging agents in wild-type and cyclooxygenase knockout mice.

METHODS

Fasted wild-type, cyclooxygenase-1, and cyclooxygenase-2 knockout mice were intragastrically administered saline, 0.6N HCl, or aspirin (aspirin 20 mmol/L) in combination with 0.6N HCl and killed 1 hour later, at which time the gastric lesion score was assessed and biopsy samples were taken for surface, biochemical, and morphological analyses.

RESULTS

The gastric mucosa of cyclooxygenase-1 knockout mice was more severely injured by both HCl alone and aspirin/HCl than that of wild-type and cyclooxygenase-2 knockout mice. HCl alone and aspirin/HCl also induced a more profound decrease in surface hydrophobicity in cyclooxygenase-1 knockout mice than in wild-type mice, whereas this surface property was unaffected in cyclooxygenase-2 knockout mice. The gastric injury induced by aspirin/HCl in cyclooxygenase-1 knockout mice could be prevented if the animals were treated with phosphatidylcholine-associated aspirin. Aspirin/HCl, in comparison to saline or HCl alone, induced a 4-6-fold increase in gastric mucosal prostaglandin E(2) concentration in the cyclooxygenase-1 knockout mice, whereas it decreased prostaglandin E(2) levels in wild-type and cyclooxygenase-2 knockout mice. This paradoxical aspirin-induced increase in gastric prostaglandin E(2) in cyclooxygenase-1 knockout mice seemed to correspond to an increase in cyclooxygenase-2 messenger RNA and protein expression. The gastric lesion score seemed to be significantly associated with alterations in surface hydrophobicity but not with mucosal prostaglandin E(2) concentration.

CONCLUSIONS

Our evidence on cyclooxygenase knockout mice suggests that aspirin predominantly causes gastric injury by a non-prostaglandin mechanism, perhaps by attenuating surface hydrophobicity, a possibility supported by the low gastric toxicity of phosphatidylcholine/aspirin. However, prostaglandins generated by cyclooxygenase-1 may play an important permissive role in maintaining gastric mucosal barrier integrity. Aspirin seems to paradoxically increase the gastric mucosal prostaglandin E(2) concentration in cyclooxygenase-1 knockout mice, possibly by the induction of cyclooxygenase-2.

Effects of celecoxib on acid-challenged gastric mucosa of rats: comparison with metamizol and piroxicam

Selective COX-2 inhibitors have been shown to produce fewer gastrointestinal adverse reactions than classical NSAIDs. Nevertheless, these new agents may worsen and delay the healing of experimentally induced gastric ulcers in animals. In this study, we compared the effects of a selective COX-2 inhibitor (celecoxib), a preferential COX-1 inhibitor (piroxicam), and a nonnarcotic analgesic (metamizol) on normal gastric mucosa of rats and, on the other hand, in a setting of preexisting acute gastric lesions induced by 0.6 N hydrochloric acid. Under normal conditions, only piroxicam produced appreciable gastric lesions. However, after acid challenge the three assayed drugs induced significant macroscopic and microscopic damage. Myeloperoxidase activity as an index of neutrophil infiltration was elevated with celecoxib and piroxicam on normal gastric mucosa. On inflamed mucosa, celecoxib augmented enzymatic activity at the lower dose, which was parallelled by an increase in the interleukin 1beta level. Acid instillaton produced a significant rise in PGE2 content at 7 hr. Drug treatment after acid challenge decreased prostaglandin values in all cases, although to a lesser extent than after single drug dose administration. COX-2 mRNA expression was visible 1 hr after acid application, whereas COX-2 protein could only be detected at 7 hr. Piroxicam increased both expression levels. All NSAIDs enhanced transforming growth factor alpha and epidermal growth factor receptor immunoreactivity around the acid-induced lesions. It is concluded that selective COX-2 inhibitors, like conventional NSAIDs, impair the healing of gastric damage, and therefore special attention should be paid in patients with gastric pathologies.

NSAIDs: gastroprotection or selective COX-2 inhibitor?

Conventional nonsteroidal anti-inflammatory drugs (NSAIDs) are effective adjuvant analgesics commonly encountered in palliative care. However, these drugs are associated with adverse effects that are primarily due to gastrointestinal toxicity, with resultant serious complications such as gastroduodenal perforations, ulcers and bleeds. This toxicity has been attributed to inhibition of cyclooxygenase-1 (COX-1). Factors known to increase this risk of toxicity include age above 65 years, classification of NSAID in terms of COX-1/COX-2 selectivity, previous history of complications and coadministration of aspirin, anticoagulants and corticosteroids. Selective inhibitors of cyclooxygenase-2 (COX-2) were developed in an attempt to reduce this association; trials to date confirm that these drugs do indeed have reduced incidence of gastroduodenal toxicity. Prior to the introduction of the COX-2 selective inhibitors, patients at high risk were often coprescribed a gastroprotective agent (such as misoprostol or a proton pump inhibitor) with a conventional NSAID. This review discusses the merits of both options and devises a treatment strategy for the safe and cost-effective use of these drugs in the palliative care population.

Physiopathologie des lésions gastro-duodénales induites par les anti-inflammatoires non stéroïdiens

The pathogenesis of the gastroduodenal lesions induced by non-steroidal anti-inflammatory drugs and aspirin is primarily caused by a reduction in mucosal blood flow, which is the consequence of inhibition of cyclooxygenase-producing vasodilator prostaglandins. The subsequent phase is adherence of leukocytes to the endothelium, which may depend on cyclooxygenase-2. Endothelial lesions accentuate the fall of mucosal blood flow and promote the inflammatory process in the gastric mucosa. The inflammatory process is amplified by expression of TNFalpha in polymorphonuclears induced by non-steroidal anti-inflammatory drugs. A few days after starting treatment, epithelial proliferation and increased mucosal blood flow, partly dependent on cyclooxygenase-2 and nitric oxide expression, compensates for the damaging process. Selective inhibitors of inducible cyclooxygenase-2 have reduced gastrointestinal toxicity, which could partially be explained by the protection effect of cyclooxygenase-2 on the gastrointestinal mucosa during inflammation or epithelial repair. Selective inhibitors may worsen inflammatory bowel disease. Non-steroidal inflammatory drugs and aspirin, but perhaps not selective inhibitors, increase the mucosal lesions associated with Helicobacter pylori-induced gastritis. Co-administration of selective inhibitors and aspirin leads to gastrointestinal toxicity equivalent to that of non-specific anti-inflammatory drugs.

Gastric effects of the selective cyclooxygenase-2 inhibitor, celecoxib, in the rat

BACKGROUND

Recent studies have revealed that cyclooxygenase-2 is involved in the protection of the damaged gastric mucosa, mediating, in particular, the acceleration of ulcer healing and angiogenesis; therein, it has been suggested that selective cyclooxygenase-2 inhibitors, although safe in healthy stomach, may have deleterious effects on the injured gastric mucosa. Moreover, no information is available about direct effects of these drugs on gastric surface epithelium.

AIMS

To investigate the gastric effects of the selective cyclooxygenase-2 inhibitor, celecoxib, in healthy and damaged rat gastric mucosa.

METHODS

Gastric toxicity was studied in the rat by measuring gastric potential difference and mucosal lesions. Celecoxib was administered intragastrically, either in basal conditions or in combination with damaging (acetylsalicylic acid and ethanol) or protective (sodium nitroprusside and lipopolysaccharides from Escherichia coli) agents. The anti-inflammatory activity was evaluated in the carrageenan-induced paw oedema assay. The non-selective inhibitors indomethacin and acetylsalicylic acid were used for comparison.

RESULTS

In conscious rats celecoxib, indomethacin and acetylsalicylic acid significantly reduced the paw oedema induced by carrageenan. While acetylsalicylic acid and indomethacin significantly reduced basal gastric potential difference and caused gastric mucosal lesions, celecoxib was ineffective; moreover, it did not aggravate the direct damaging effect of intragastric ethanol or aspirin. Pretreatment with the non-selective nitric oxide synthase inhibitor N-nitro-L-argynine methyl ester did not significantly change the gastric effects of celecoxib. Both celecoxib and indomethacin prevented the gastroprotective effects induced by sodium nitroprusside (nitric oxide donor) or by bacterial lipopolysaccharides (inducer of nitric oxide synthesis). CONCLUSIONS. These data indicate that the selective cyclooxygenase-2 inhibitor celecoxib did not alter gastric mucosal barrier nor induced mucosal lesions in the healthy or nitric oxide-deficient rat gastric mucosa. However, cyclooxygenase-2 inhibition impaired nitric oxide-dependent gastroprotection, indicating that cyclooxygenase-2 derived prostaglandins may be involved in the gastric mucosal defence.

Expression of functional neurokinin-1 receptors in regenerative glands during gastric wound healing in rodents

BACKGROUND & AIMS

Although functions of the neurokinin-1 receptor have been well explored in neurogenic inflammation and immunoinflammatory responses, little is known about neurokinin-1 receptors during gastric wound healing. The aim of this study was to assess whether neurokinin-1 receptors play a role in gastric wound healing.

METHODS

In vitro neurokinin-1 receptor autoradiography and immunohistochemistry were performed to identify, locate, and quantify neurokinin-1 receptors during wound healing in rodents with cryoulcers in the gastric corpus and antrum. Moreover, to assess the functionality of these receptors, the effect of the neurokinin-1 receptor antagonist NKP608 on gastric wound healing was quantified in vivo in wild-type and cyclooxygenase-2(-/-) mice.

RESULTS

Regenerative glands of the mucosal ulcer margin of rat cryoulcers of the gastric corpus showed strong expression of neurokinin-1 receptors in binding studies between days 3 and 22, with little expression on days 29-84. In addition, strong immunoreactivity for neurokinin-1 receptors was detected on the cell membrane of these regenerative glands. Expression of neurokinin-1 receptors in regenerative glands was confirmed in the rat antrum and the mouse gastric corpus. Moreover, in vivo functional tests during gastric ulcer healing showed that cell proliferation in the regenerative epithelia of the ulcer margin was significantly decreased by NKP608 compared with placebo; furthermore, gastric ulcer healing was significantly delayed by NKP608 both in wild-type and cyclooxygenase-2(-/-) mice.

CONCLUSIONS

This report shows the time-limited overexpression of neurokinin-1 receptors in the mucosal repair tissue of the corpus and antrum. Our in vitro and in vivo data suggest that neurokinin-1 receptors are involved in gastric wound healing.

Mucosal damage induced by preferential COX-1 and COX-2 inhibitors: role of prostaglandins and inflammatory response

Nonsteroidal anti-inflammatory drugs (NSAID) are well known to induce gastric mucosal damage including bleeding, ulceration and perforation in humans and animals too. These effects are related with the inhibition of the enzyme cyclooxygenase, which is the main established mechanism of action for these drugs. Fasted rats were given piroxicam, preferential COX-1 inhibitor (10-20 mg/kg) or meloxicam, preferential COX-2 inhibitor (7.5-15 mg/kg) orally. Six or nine hours (h) later, respectively, the stomach was excised, the severity of the damage assessed and myeloperoxidase (MPO) activity measured, as well as prostaglandin PGE(2) content. Furthermore, in order to assess the effects of these oxicams over previously damaged gastric mucosa, 1 ml of 0.6 N HCl was administered p.o. followed, 1 h after, of the correspondent dose of each NSAID, and the same parameters were determined. Oral administration of both drugs dose-dependently caused acute gastric haemorrhage erosions. Myeloperoxidase activity was significantly increased by piroxicam administration. In addition, PGE(2) content was significantly reduced. The association between the administration of the acid and NSAID caused a worsening of the damage and, while myeloperoxidase activity did not modify by both piroxicam and meloxicam, PGE(2) levels were reduced. These results suggest that the PG derived from both COX-1 and COX-2 pathway plays a beneficial role in the gastroprotection, and thus caution should be exercise in the clinical use of preferential COX-2 inhibitors.

The role of cyclooxygenase selective inhibitors in the gastrointestinal tract

This article reviews the gastrointestinal manifestations of traditional nonsteroidal anti-inflammatory drugs (NSAIDs) and the improved gastrointestinal safety profile of cyclooxygenase selective (COX)-2 inhibitors. By inhibiting the COX enzyme, NSAIDs provide effective analgesia and suppress inflammation in a variety of conditions. Most NSAIDs (nonselective or traditional) not only inhibit prostaglandins at sites of inflammation but also inhibit prostaglandins that have important normal functions in other parts of the body. This may be harmful when normal gastrointestinal mucosal function is impaired and mucosal damage occurs. Although such damage is often trivial and usually not symptomatic, gastrointestinal ulceration may produce pain and, more ominously, lead to bleeding, perforation, or obstruction. A new approach to the gastrointestinal complications of NSAIDs became feasible with the discovery of two isoforms of COX, COX-1 and COX-2, with COX-1 expressed mainly in the gastrointestinal tract. The development of NSAIDs that preferentially inhibit COX-2 offers the promise of relieving pain and inflammation without the side effects attendant to COX-1 blockade. In prospective studies evaluating gastrointestinal ulceration with COX-2-specific NSAIDs, rates of endoscopic ulceration have been equivalent to those with placebo and much lower than those with nonselective NSAIDs. In the recently released studies of gastrointestinal outcomes (perforated, painful, or bleeding ulcers), incidence of clinically relevant ulceration with COX-2 NSAIDs is much lower than that of traditional NSAIDs.

COX-2 is essential for EGF induction of cell proliferation in gastric RGM1 cells

Growth factors upregulate cyclooxygenase-2 (COX-2) expression and extracellular signal-regulated kinase (ERK) activity, yet little is known regarding the interaction between COX-2 and ERK in terms of mitogenic signal transduction pathways in gastric epithelial cells. Therefore, we examined the role of COX-2 in EGF-induced proliferation of gastric epithelial RGM1 cells. EGF treatment significantly induced ERK activity (peaked at 30 min) and significantly increased COX-2 protein (peaked at 6 hr), production of prostaglandin E2 (PGE2), and cell proliferation. MEK inhibitor (PD98059) decreased ERK activity and cell proliferation induced by EGF. The selective COX-2 inhibitor (NS-398) significantly reduced EGF-induced cell proliferation. Exogenous PGE2 partly reversed the NS-398-induced inhibitory action on cell proliferation, clearly indicating the importance of PGE2 in mitogenic pathway. The induction of COX-2 protein by EGF was completely blocked by preincubation with MEK inhibitor. These results suggest that the ERK-COX-2 pathway is critical for EGF-induced proliferation of gastric epithelial cells.

Cyclooxygenase expression during Helicobacter pylori infection in Mongolian gerbils

We investigated the expression of cyclooxygenase-2 (COX-2) and COX-1 mRNAs during longterm Helicobacter pylori infection of the Mongolian gerbil (18 months) as well as the effect of eradication therapy and the cag pathogenicity island on COX mRNA expression. COX mRNA levels were determined by reverse transcription-polymerase chain reaction. Pyloric channel ulcers were noted in one of 10 gerbils (10%) at 3 months, 33% at 6 months, 50% at 9 months, 17% at 10 months, 40% at 12 months and 25% at 18 months after inoculation of parental strains. Nineteen of 21 gerbils had successful H. pylori eradication and showed significant reduction of inflammation and no ulcerations. There were no significant differences in COX-1 mRNA expression between the groups. COX-2 mRNA expression was significantly increased 1 and 3 months after inoculation and then decreased to basal levels. In control animals, COX-2 mRNA expression was significantly higher at 12 and 18 months compared to younger animals. cagE knockout mutants did not induce gastric inflammation and induced significantly lower COX-2 mRNA expression compared to parental strains. COX-2 mRNA was induced early in H. pylori infection and then declined. COX-2 mRNA expression was also induced with aging.

Interaction of cyclooxygenase isoenzymes, nitric oxide, and afferent neurons in gastric mucosal defense in rats

The cyclooxygenase (COX)-2 inhibitors 5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulfonyl)phenyl-2(5II)-furanone (DFU) (0.02-2 mg/kg) and N-[2-(cyclohexyloxy)-4-nitrofenyl]-methanesulfonamide (NS-398) (0.01-1 mg/kg), the COX-1 inhibitor 5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-trifluoromethylpyrazole (SC-560) (0.05-5 mg/kg), and dexamethasone (1 mg/kg) were studied in rats challenged with intragastric acid (300 mM HCl). All compounds induced severe gastric damage when rats were treated concurrently with the inhibitor of constitutive and inducible nitric-oxide (NO) synthase N(G)-monomethyl-L-arginine methyl ester (L-NAME) (3 or 40 mg/kg). DFU and NS-398 caused significantly less damage in rats receiving the selective inhibitor of inducible NO synthase N-(3-(aminomethyl)benzyl)acetamidine (1400W) (0.3 mg/kg). The COX-1 inhibitor SC-560 induced moderate damage in the acid-challenged stomach even without suppression of NO, but damage was aggravated by L-NAME. The COX-3 inhibitor phenacetin (400 mg/kg) did not injure the gastric mucosa despite suppression of NO. Furthermore, DFU, NS-398, SC-560, and dexamethasone caused severe injury in the acid-challenged stomach of rats pretreated with capsaicin to ablate afferent neurons. The mucosal damage induced by the COX-1 inhibitor, the COX-2 inhibitors, and dexamethasone in L-NAME- or capsaicin-treated rats was reversed by coadministration of 16,16-dimethyl-prostaglandin E2 (2 x 8 ng/kg). Gross mucosal damage was paralleled by histology. Our results support the concept that endogenous NO, prostaglandins, and afferent neurons act in concert in the regulation of gastric mucosal integrity. The prostaglandins necessary for mucosal defense in the face of NO suppression, and afferent nerve ablation can be derived either from COX-1 or COX-2. The data do not propose a protective role for a phenacetin-sensitive COX-3. Our findings suggest that not only COX-1 but also COX-2 has important functions in the maintenance of gastric integrity.

Effects of aspirin and indomethacin on endothelial cell proliferation in vitro

BACKGROUND AND AIM

Non-steroidal anti-inflammatory drugs (NSAID) are associated with delayed peptic ulcer healing. Ulcer healing is dependent on angiogenesis, which requires endothelial cell (EC) proliferation. The present study aimed to determine whether NSAID and prostaglandin E2 (PGE2) inhibited EC proliferation in vitro.

METHODS

Effects of 50 micro L aspirin (10 micro M-1 mM), indomethacin (10 micro M-1 mM) and PGE2 (1 micro M-0.1 mM) on the proliferation, viability and cell cycle of human dermal microvascular (HuDMEC) and human umbilical vein (HUVEC) EC were assessed using dual staining cell viability, 3-(4,5-dimethyl-2 thiazoyl)-2,5-diphenyl-2H-tetrazolium bromide and flow cytometry assays.

RESULTS

Proliferation of HuDMEC and HUVEC was significantly inhibited by 0.1 mM/1 mM indomethacin, 1 mM aspirin and 100 micro M PGE2, with a significant (P < 0.05) increase in EC necrosis with 1 mM indomethacin and 100 micro M PGE2. No effects on cell cycle were demonstrated.

CONCLUSIONS

High concentrations of NSAID inhibit both HuDMEC and HUVEC proliferation in vitro by cytotoxic (indomethacin) or cytostatic (aspirin and indomethacin) mechanisms. Interestingly, PGE2 was also antiproliferative. Inhibition of EC proliferation may prevent angiogenesis at the ulcer site, which may in part explain the delayed ulcer healing associated with NSAID.

Inhibition of angiogenesis by NSAIDs: molecular mechanisms and clinical implications

Angiogenesis, the formation of new capillary blood vessels, is a fundamental process essential for reproduction and embryonic development. It is crucial to the healing of tissue injury because it provides essential oxygen and nutrients to the healing site. Angiogenesis is also required for cancer growth and progression since tumor growth requires an increased nutrient and oxygen supply. Nonsteroidal anti-inflammatory drugs (NSAIDs) are the most widely used drugs worldwide for treating pain, arthritis, cardiovascular diseases, and more recently for colon cancer prevention. However, NSAIDs produce gastrointestinal ulcers and delay ulcer healing. Recently NSAIDs have been demonstrated to inhibit angiogenesis, but the underlying mechanisms are only beginning to be elucidated. The inhibition of angiogenesis by NSAIDs is a causal factor in the delay of ulcer healing, and it is becoming clear that this is also likely to be one of the mechanisms by which NSAIDs can reduce or prevent cancer growth. Based on the experimental data and the literature, the mechanisms by which NSAIDs inhibit angiogenesis appear to be multifactorial and likely include local changes in angiogenic growth factor expression, alteration in key regulators and mediators of vascular endothelial growth factor (VEGF), increased endothelial cell apoptosis, inhibition of endothelial cell migration, recruitment of inflammatory cells and platelets, and/or thromboxane A2 mediated effects. Some of these mechanisms include: inhibition of mitogen-activated protein (Erk2) kinase activity; suppression of cell cycle proteins; inhibition of early growth response (Egr-1) gene activation; interference with hypoxia inducible factor 1 and VEGF gene activation; increased production of the angiogenesis inhibitor, endostatin; inhibition of endothelial cell proliferation, migration, and spreading; and induction of endothelial apoptosis.