Inducible types of cyclooxygenase and nitric oxide synthase in adaptive cytoprotection in rat stomachs

The Apelin-Apela Receptor APJ is Necessary for Formation and Healing of Ischemia Reperfusion-Induced Gastric Ulcer in Rats

The apelinergic system, widely expressed and regulates hormone-enzyme secretion, motility, and protective mechanisms of the stomach. This system consists of the apelin receptor (APJ) and two peptides known as apela and apelin. The IR-induced experimental gastric ulcer model, is a well-known and commonly used one that induces hypoxia and causes the release of proinflammatory cytokines. Expressions of apelin and its receptor APJ are induced by hypoxia and inflammation in the gastrointestinal tract. Apelin has been shown to affect angiogenesis positively, considered the most critical component of the healing process. Although it is known that apelin and AJP expressions are induced by inflammatory stimuli and hypoxia, stimulate endothelial cell proliferation and have a role in regenerative angiogenesis, no information or has been found in the literature regarding the role of APJ in the formation and healing of gastric mucosal lesions induced by I/R. So, we conducted a study to clarify the role of APJ in formation and healing mechanisms of IR-induced gastric lesions. Male Wistar rats were divided into five groups; control, sham-operated, IR, APJ antagonist treated-IR group (F13A+IR), and the healing groups. F13A was intravenously given to the animals. Gastric lesion index, mucosal blood flow, PGE₂, NOx, 4-HNE-MDA, HO activity, and protein expressions of VEGF and HO-1 were measured. F13A application before the IR increased the mucosal injury, F13A application following the ischemia delayed the mucosal healing during the reperfusion period. Consequently, blocking apelin receptors may worsen gastric injury due to the IR and delay mucosal healing.

Alendronate induces gastric damage by reducing nitric oxide synthase expression and NO/cGMP/K(ATP) signaling pathway

Chronic use of alendronate has been linked to gastrointestinal tract problems. Our objective was to evaluate the role of the NO/cGMP/KATP signaling pathway and nitric oxide synthase expression in alendronate-induced gastric damage. Rats were either treated with the NO donor, sodium nitroprusside (SNP; 1, 3, and 10 mg/kg), or the NO synthase (NOS) substrate, L-arginine (L-Arg; 50, 100, and 200 mg/kg). Some rats were pretreated with either ODQ (a guanylate cyclase inhibitor; 10 mg/kg) or glibenclamide (KATP channels blocker; 10 mg/kg). In other experiments, rats were pretreated with L-NAME (non-selective NOS inhibitor; 10 mg/kg), 1400 W (selective inducible NOS [iNOS] inhibitor; 10 mg/kg), or L-NIO (a selective endothelial NOS [eNOS] inhibitor; 30 mg/kg). After 1 h, the rats were treated with alendronate (30 mg/kg) by gavage for 4 days. SNP and L-Arg prevented alendronate-induced gastric damage in a dose-dependent manner. Alendronate reduced nitrite/nitrate levels, an effect that was reversed with SNP or L-Arg treatment. Pretreatment with ODQ or glibenclamide reversed the protective effects of SNP and L-Arg. L-NAME, 1400 W, or L-NIO aggravated the severity of alendronate-induced lesions. In addition, alendronate reduced the expression of iNOS and eNOS in the gastric mucosa. Gastric ulcerogenic responses induced by alendronate were mediated by a decrease in NO derived from both eNOS and iNOS. In addition, our findings support the hypothesis that activation of the NO/cGMP/KATP pathway is of primary importance for protection against alendronate-induced gastric damage.

Gastroprotective effect of desmosdumotin C isolated from Mitrella kentii against ethanol-induced gastric mucosal hemorrhage in rats: possible involvement of glutathione, heat-shock protein-70, sulfhydryl compounds, nitric oxide, and anti-Helicobacter pylori activity

BACKGROUND

Mitrella kentii (M. kentii) (Bl.) Miq, is a tree-climbing liana that belongs to the family Annonaceae. The plant is rich with isoquinoline alkaloids, terpenylated dihydrochalcones and benzoic acids and has been reported to possess anti-inflammatory activity. The purpose of this study is to assess the gastroprotective effects of desmosdumotin C (DES), a new isolated bioactive compound from M. kentii, on gastric ulcer models in rats.

METHODS

DES was isolated from the bark of M. kentii. Experimental rats were orally pretreated with 5, 10 and 20 mg/kg of the isolated compound and were subsequently subjected to absolute ethanol-induced acute gastric ulcer. Gross evaluation, mucus content, gastric acidity and histological gastric lesions were assessed in vivo. The effects of DES on the anti-oxidant system, non-protein sulfhydryl (NP-SH) content, nitric oxide (NO)level, cyclooxygenase-2 (COX-2) enzyme activity, bcl-2-associated X (Bax) protein expression and Helicabacter pylori (H pylori) were also investigated.

RESULTS

DES pre-treatment at the administered doses significantly attenuated ethanol-induced gastric ulcer; this was observed by decreased gastric ulcer area, reduced or absence of edema and leucocytes infiltration compared to the ulcer control group. It was found that DES maintained glutathione (GSH) level, decreased malondialdehyde (MDA) level, increased NP-SH content and NO level and inhibited COX-2 activity. The compound up regulated heat shock protein-70 (HSP-70) and down regulated Bax protein expression in the ulcerated tissue. DES showed interesting anti-H pylori effects. The efficacy of DES was accomplished safely without any signs of toxicity.

CONCLUSIONS

The current study reveals that DES demonstrated gastroprotective effects which could be attributed to its antioxidant effect, activation of HSP-70 protein, intervention with COX-2 inflammatory pathway and potent anti H pylori effect.

Moderate ethanol ingestion and cardiovascular protection: from epidemiologic associations to cellular mechanisms

While ethanol intake at high levels (3-4 or more drinks), either in acute (occasional binge drinking) or chronic (daily) settings, increases the risk for myocardial infarction and stroke, an inverse relationship between regular consumption of alcoholic beverages at light to moderate levels (1-2 drinks per day) and cardiovascular risk has been consistently noted in a large number of epidemiologic studies. Although initially attributed to polyphenolic antioxidants in red wine, subsequent work has established that the ethanol component contributes to the beneficial effects associated with moderate intake of alcoholic beverages regardless of type (red versus white wine, beer, spirits). Concerns have been raised with regard to interpretation of epidemiologic evidence for this association including heterogeneity of the reference groups examined in many studies, different lifestyles of moderate drinkers versus abstainers, and favorable risk profiles in moderate drinkers. However, better controlled epidemiologic studies and especially work conducted in animal models and cell culture systems have substantiated this association and clearly established a cause and effect relationship between alcohol consumption and reductions in tissue injury induced by ischemia/reperfusion (I/R), respectively. The aims of this review are to summarize the epidemiologic evidence supporting the effectiveness of ethanol ingestion in reducing the likelihood of adverse cardiovascular events such as myocardial infarction and ischemic stroke, even in patients with co-existing risk factors, to discuss the ideal quantities, drinking patterns, and types of alcoholic beverages that confer protective effects in the cardiovascular system, and to review the findings of recent experimental studies directed at uncovering the mechanisms that underlie the cardiovascular protective effects of antecedent ethanol ingestion. Mechanistic interrogation of the signaling pathways invoked by antecedent ethanol ingestion may point the way towards development of new therapeutic approaches that mimic the powerful protective effects of socially relevant alcohol intake to limit I/R injury, but minimize the negative psychosocial impact and pathologic outcomes that also accompany consumption of ethanol.

Regulatory mechanism of duodenal bicarbonate secretion: Roles of endogenous prostaglandins and nitric oxide

The secretion of HCO(3)(-) in the duodenum is increased by exogenous prostaglandin (PG) E(2) and mucosal acidification, the latter being accompanied by a rise in mucosal PGE(2) content and nitric oxide (NO) release. The stimulatory effect of PGE(2) is mediated intracellularly by both Ca(2+) and 3',5'-adenosine cyclic adenosine monophosphate (cAMP), and this action is inhibited by EP3 and EP4 antagonists. The secretion is also increased by NOR3 (NO donor), and this response is mimicked by dibutyryl 3',5'-cyclic guanosine monophosphate (dbcGMP) and attenuated by indomethacin. Mucosal acidification stimulates HCO(3)(-) secretion with concomitant increases in mucosal PGE(2) production and NO release. The effects on HCO(3)(-) secretion and PGE(2) production are inhibited by indomethacin [nonselective cyclooxygenase (COX) inhibitor] and SC-560 (selective COX-1 inhibitor) but not rofecoxib (selective COX-2 inhibitor). N(G)-nitro-l-arginine methyl ester [l-NAME: nonselective NO synthase (NOS) inhibitor], but not aminoguanidine [selective inducible NOS inhibitor], attenuates the acid-induced HCO(3)(-) secretion and NO release in an l-arginine-sensitive manner. In addition, the response to PGE(2) is potentiated by vinpocetine [phosphodiesterase (PDE) 1 inhibitor] and cilostamide (PDE3 inhibitor), while the response to NOR3 is increased by vinpocetine. We conclude that endogenous PGs and NO are both involved in the local regulation of acid-induced duodenal HCO(3)(-) secretion; COX-1 and constitutive NOS are key enzymes responsible for the production of PGs and NO, respectively; NO stimulates HCO(3)(-) secretion by increasing PG production; PGE(2) stimulates HCO(3)(-) secretion via activation of EP3/EP4 receptors; and both PDE1 and PDE3 are involved in the regulation of duodenal HCO(3)(-) secretion.

Taurocholate-induced nitric oxide signaling and the ensuing production of reactive oxygen species lead to an increase in epithelial permeability in cultivated mouse gastric epithelium

We have here elucidated whether ulcerogenic agents affect the production of NO and reactive oxygen species (ROS). The ulcerogenic agents dose dependently induced NO and ROS production in mouse gastric epithelial cells. Taurocholate (TC, 5 mM) exposure did not affect cell viability, but it increased inducible nitric oxide synthase (iNOS) expression, NO production, ROS production, and epithelial permeability. Epithelial permeability was inhibited with NOS inhibitors or antioxidants. Oxidative stress induced by acetylsalicylic acid (ASA) and ethanol was not inhibited with NOS inhibitors. ASA induced ROS production even at low concentrations (1 mM), which did not affect cell viability. Ethanol-induced ROS production was linked to cell viability, suggesting direct oxidative stress caused by ethanol. Taurocholate-induced NO signaling and the ensuing production of ROS might contribute to initiation of defensive or adaptive cellular mechanisms. ASA-induced ROS signaling might have similar effects, whereas ethanol induced direct oxidative stress, having an influence on cell viability.

Nonsteroidal antiinflammatory drugs and the small intestine

PURPOSE OF REVIEW

The small intestine may be a more common site for nonsteroidal antiinflammatory drug toxicity than the gastroduodenal mucosa. Two-thirds of regular nonsteroidal antiinflammatory drug users develop subclinical small bowel enteropathy. This review highlights this emerging issue in patients requiring antiinflammatory drugs.

RECENT FINDINGS

Nonsteroidal antiinflammatory drug enteropathy is a stepwise process involving direct mucosal toxicity, mitochondrial damage, breakdown of intercellular integrity, enterohepatic recirculation and neutrophil activation by luminal contents including bacteria. Unlike upper gastrointestinal toxicity, cyclooxygenase-mediated mechanisms are probably less important. Newer imaging modalities such as capsule endoscopy studies demonstrate nonsteroidal antiinflammatory drug-induced small bowel erosions, but the clinical implications are unclear.

SUMMARY

Nonsteroidal antiinflammatory drug toxicity to the small intestine is common. Useful research tools have been developed to indirectly measure intestinal inflammation and permeability, but these are not generally available to the clinician, although enteroscopy and capsule endoscopy can be illuminating. Anaemia or hypoalbuminaemia are useful indications of nonsteroidal antiinflammatory drug enteropathy. Cessation of the drug would be the preferred option, alternatively there are experimental data to support the use of sulphasalazine and metronidazole. Animal models are unravelling new mechanisms for mucosal toxicity beyond the cyclooxygenase model, including mucosal oxidative injury and nitric oxide mediated pathways.

Role of endogenous nitric oxide (NO) and NO synthases in healing of indomethacin-induced intestinal ulcers in rats

We examined the roles of nitric oxide (NO) and NO synthase (NOS) isozymes in the healing of indomethacin-induced small intestinal ulcers in rats. Animals were given indomethacin (10 mg/kg, s.c.) and killed 1, 4 and 7 days after the administration. Indomethacin (2 mg/kg), N(G)-nitro-L-arginine methyl ester (L-NAME: a nonselective NOS inhibitor: 10 mg/kg) and aminoguanine (a relatively selective iNOS inhibitor: 20 mg/kg) were given s.c. once daily for 6 days, the first 3 days or the last 3 days during a 7-day experimental period. Both indomethacin and L-NAME significantly impaired healing of these lesions, irrespective of whether they were given for 6 days, first 3 days or last 3 days. The healing was also impaired by aminoguanine given for the first 3 days but not for the last 3 days. Expression of iNOS mRNA in the intestine was up-regulated after ulceration, persisting for 2 days thereafter, and the Ca(2+)-independent iNOS activity also markedly increased with a peak response during 1-2 days after ulceration. Vascular content in the ulcerated mucosa as measured by carmine incorporation was decreased when the healing was impaired by indomethacin and L-NAME given for either the first or last 3 days as well as aminoguanidine given for the first 3 days. These results suggest that endogenous NO plays a role in healing of intestinal lesions, in addition to prostaglandins, yet the NOS isozyme mainly responsible for NO production differs depending on the stage of healing: iNOS in the early stage and cNOS in the late stage.

Role of endogenous nitric oxide in mucosal defense of inflamed rat stomach following iodoacetamide treatment

Nitric oxide (NO) plays a role in regulating the mucosal integrity of the stomach. However, its part in the mucosal defense of the inflamed stomach remains unclear. In the present study, we examined the effects of various NO synthase (NOS) inhibitors on gastric ulcerogenic and acid secretory responses following daily exposure of the stomach to iodoacetamide and investigated the role of each NOS isozyme in gastric protection from subchronic mucosal irritation. Gastric mucosal irritation was induced in rats by addition of 0.1% iodoacetamide to drinking water, and the gastric mucosa was examined on the 6th day. L-NAME (a nonselective NOS inhibitor: 20 mg/kg) or aminoguanidine (a selective iNOS inhibitor: 20 mg/kg) was given s.c. twice 24 h and 3 h before the termination of iodoacetamide treatment. Giving iodoacetamide in drinking water for 5 days produced minimal damage in the stomach with an increase in myeloperoxidase (MPO) activity and lipid peroxidation. Iodoacetamide treatment up-regulated the expression of iNOS mRNA and NO production in the stomach, without affecting nNOS expression. Both L-NAME and aminoguanidine markedly aggravated gastric lesions induced by iodoacetamide treatment, with a further enhancement in MPO activity and lipid peroxidation. Basal acid secretion as determined in pylorous-ligated stomachs was decreased following iodoacetamide treatment, but the response was significantly restored by both L-NAME and aminoguanidine. These results suggest that endogenous NO derived from both cNOS and iNOS is involved in mucosal defense of the inflamed stomach, partly by decreasing acid secretion, and contributes to maintaining mucosal integrity under such conditions.

Less irritative action of wine and Japanese sake in rat stomachs: a comparative study with ethanol

The ingestion of alcohol, especially in excess, causes acute gastric lesions and gastritis in humans, yet the mucosal irritative action of alcoholic beverages remains largely unknown. We examined the mucosal irritative action of whiskey, wine and Japanese sake in the rat stomach both ex vivo and in vitro, in comparison with ethanol. Under urethane anesthesia, a rat stomach was mounted in an ex vivo chamber, then superfused with saline, and the transmucosal potential difference (PD) was measured. After the basal PD had stabilized, the mucosa was exposed for 30 min to 2 ml of 15% ethanol, whiskey (containing 15% ethanol), white wine, or Japanese sake (the ethanol concentration of the latter two is 12-15%). In the in vitro study, rat epithelial cells (RGM1) were treated with the alcoholic beverages for 5 min, and the cell viability was determined with crystal violet. Ethanol or whiskey applied to the chamber caused a decrease in PD, while wine or Japanese sake did not. Histologically, surface epithelial damage was observed after exposure to both ethanol and whiskey, yet no damage was induced by white wine and Japanese sake. Likewise, both ethanol and whiskey markedly reduced the viability of RGM1 cells after 5 min of incubation, while neither white wine nor Japanese sake had any effect. In addition, supplementation of glucose significantly prevented the reduction in both PD and cell viability caused by ethanol. These results suggest that the mucosal irritative action of Japanese sake and white wine is much less pronounced than that of ethanol or whiskey and that the less damaging action of Japanese sake and white wine may be, at least partly, accounted for by the glucose contained in these alcoholic beverages.

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.

Cyclooxygenase 2, pS2, inducible nitric oxide synthase and transforming growth factor alpha in gastric adaptation to stress

AIM

To determine the role of mucosal gene expression of cyclooxygenase 2 (COX-2), pS2 (belongs to trefoil peptides), inducible nitric oxide synthase (iNOS) and transforming growth factor alpha (TGFalpha) in gastric adaptation to water immersion and restraint stress (WRS) in rats.

METHODS

Wistar rats were exposed to single or repeated WRS for 4 h every other day for up to 6 d. Gastric mucosal blood flow (GMBF) was measured by laser Doppler flowmeter-3. The extent of gastric mucosal lesions were evaluated grossly and histologically and expressions of COX-2, pS2,iNOS and TGFalpha were determined by reverse transcriptase polymerase chain reaction (RT-PCR) and Western blot.

RESULTS

The damage to the surface of gastric epithelium with focal areas of deep haemorrhagic necrosis was induced by repeated WRS. The adaptative cytoprotection against stress was developed with activation of cell proliferation in the neck regions of gastric glands. The ulcer index (UI) in groups II, III and IV was markedly reduced as compared with group I (I: 47.23+/-1.20; IV: 10.39+/-1.18,P<0.01). GMBF significantly decreased after first exposure to WRS with an adaptive increasement of GMBF in experimental groups after repetitive challenges with WRS. After the 4th WRS, the value of GMBF almost restored to normal level (I: 321.87+/-8.85; IV: 455.95+/-11.81, P<0.01). First WRS significantly decreased the expression of pS2 and significantly increased the expressions of COX-2, iNOS and TGFalpha. After repeated WRS, pS2 and TGFalpha expressions gradually increased (pS2: I: 0.37+/-0.02; IV: 0.77+/-0.01; TGFalpha: I: 0.86+/-0.01; IV: 0.93+/-0.03, P<0.05) with a decrease in the expressions of COX-2 and iNOS (COX-2: I: 0.45+/-0.02; IV: 0.22+/-0.01; iNOS: I: 0.93+/-0.01; IV: 0.56+/-0.01, P<0.01). Expressions of pS2, COX-2, iNOS and TGFalpha showed regular changes with a good relationship among them.

CONCLUSION

Gastric adaptation to WRS injury involves enhanced cell proliferation, increased expression of pS2 and TGFalpha, and reduced expression of COX-2 and iNOS. These changes play an important role in adaptation of gastric mucosa after repeated WRS.

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.

Ulcerogenic influence of selective cyclooxygenase-2 inhibitors in the rat stomach with adjuvant-induced arthritis

Cyclooxygenase (COX)-2 inhibitors have been developed as new gastric sparing anti-inflammatory drugs. We previously reported that the ulcerogenic response to conventional nonselective COX inhibitors, such as indomethacin and aspirin, was markedly increased in arthritic rats. The ulcerogenic effect of selective COX-2 inhibitors in arthritic animals, however, remains unknown. The present study was designed to examine the influence of selective COX-2 inhibitors, such as rofecoxib and celecoxib, on gastric mucosal integrity in rats with adjuvant-induced arthritis. Arthritis was induced in male dark Agouti rats by injection of Freund's complete adjuvant into the right hind paw. Two weeks after the injection, the animals were fasted for 18 h, various COX inhibitors were administered orally, and the mucosa was examined for lesions 4 h later. Oral administration of indomethacin caused hemorrhagic gastric lesions in both normal and arthritic rats, although the severity of lesions was significantly greater in the latter group. In contrast, neither rofecoxib nor celecoxib caused any gastric damage in normal rats, but both drugs provoked hemorrhagic gastric lesions in arthritic rats. The expression of COX-2 mRNA and immuno-positive cells was observed in the gastric mucosa of arthritic but not normal rats. The gastric mucosal prostaglandin (PG) E(2) content was significantly elevated in arthritic rats in a rofecoxib-sensitive manner. In conclusion, COX-2 inhibitors produce gastric lesions in arthritic rats, similar to the nonselective COX-inhibitors. COX-2 is up-regulated in the stomach of arthritic rats, and PGs produced by COX-2 play a role in maintaining the integrity of the gastric mucosa.

Gastroprotective effects of amtolmetin guacyl: a new non-steroidal anti-inflammatory drug that activates inducible gastric nitric oxide synthase

BACKGROUND

The novel non-steroidal anti-inflammatory drug amtolmetin guacyl has been shown to possess markedly reduced ulcerogenic effects and nitric oxide-mediated gastroprotective activity against the damage induced by ethanol in the rat.

AIMS

To investigate, in the rat, the role of nitric oxide and of inducible nitric oxide synthase isoform in the protective effect of amtolmetin guacyl against the gastric damage induced by ethanol.

METHODS

The effects of amtolmetin guacyl on gastric transmucosal potential difference and on gastric mucosal blood flow were investigated in the anaesthetised rat; myeloperoxidase activity, inducible and endothelial nitric oxide synthase protein content were determined in rat gastric mucosal homogenates. The anti-inflammatory drug tolmetin and the bacterial lipopolysaccharide from Escherichia coli were studied for comparison.

RESULTS

In the anaesthetised rat, amtolmetin guacyl, but not tolmetin, reduced by approximately 50% the fall in gastric potential difference and, to a lesser extent, the macroscopic damage induced by ethanol. The effect of amtolmetin guacyl on transmucosal potential difference was prevented by the selective inducible nitric oxide synthase inhibitor 1400W. In amtolmetin guacyl-treated rats, 1400W decreased gastric mucosal blood flow, whereas it was inactive in vehicle- and tolmetin-treated animals. In gastric mucosal homogenates, both amtolmetin guacyl and lipopolysaccharide, but not tolmetin, increased inducible, but not endothelial, nitric oxide synthase protein content, as revealed by Western immunoblotting.

CONCLUSIONS

These data confirm that amtolmetin guacyl is a non-steroidal anti-inflammatory agent devoid of gastrolesive properties, that can actually reduce the damaging effects of ethanol through the increase in nitric oxide production, via the inducible isoform of nitric oxide synthase.

Alteration of gastric ulcerogenic and healing responses in rats with adjuvant-induced arthritis

Gastroenteropathy is the most common among patients who use non-steroidal anti-inflammatory drugs (NSAIDs) for treatment of inflammatory disorders. It is known that rheumatoid arthritic patients are more susceptible to NSAID-induced gastropathy than other NSAID users. This article reviewed our recent studies concerning the influence of arthritic conditions on gastric ulcerogenic response to NSAID and healing response of chronic gastric ulcers in rats. Gastric lesions induced by indomethacin, one of the conventional NSAIDs, were markedly aggravated in arthritic rats. This increased ulcerogenic response in arthritic rats was attributable to nitric oxide production due to up-regulation of inducible nitric oxide synthase. In arthritic rat stomachs, cyclooxygenase (COX)-2 was also up-regulated, where COX-2 selective inhibitors such as rofecoxib or celecoxib provoked gross lesions, although they caused no damage in normal rats. In addition, the healing of chronic gastric ulcers was also delayed in arthritic rats because of less expression of various growth factors such as basic fibroblast growth factors or insulin-like growth factors. Based on these findings, it is concluded that arthritic conditions alter the mucosal ulcerogenic and healing responses in the stomach. Especially, caution should be paid on the use of COX-2 selective inhibitors in rheumatoid arthritic patients.

[Changes in ulcerogenic response to non-steroidal anti-inflammatory drugs (NSAIDs) in adjuvant arthritic rats]

Gastroenteropathy is the most common among patients who use non-steroidal anti-inflammatory drugs (NSAIDs) for the treatment of inflammatory disorders. It is known that rheumatoid arthritic (RA) patients are more susceptible to NSAID-induced gastropathy than other NSAID users. This article reviewed our recent studies concerning the influence of arthritis on gastric mucosal integrity in adjuvant-induced arthritic rats. The gastric mucosal lesions induced by indomethacin, one of conventional NSAIDs, were markedly aggravated in arthritic rats. Likewise, the healing of chronic gastric ulcers induced by thermal cauterization was significantly delayed in arthritic rats. The underlying mechanisms of these phenomena observed in arthritic rats may be attributable to the enhancement of iNOS/NO pathway in the former and the less expression of various growth factors in the ulcerated mucosa, such as basic fibroblast growth factors (bFGF) or insulin-like growth factors (IGF-1) in the latter. In addition, we recently found that cyclooxygenase-2 (COX-2) selective inhibitors, such as rofecoxib or celecoxib, induced apparent gastric lesions in arthritic rats, suggesting that a caution should be paid on the use of COX-2 selective inhibitors in RA patients.

[Gastrointestinal sparing anti-inflammatory drugs--COX-2 selective inhibitors and NO-releasing NSAIDs]

The use of NSAIDs is associated with a wide array of alterations in the gastrointestinal integrity and function. Various approaches have been taken to develop NSAIDs with reduced gastrointestinal toxicity, and few have successfully reduced the incidence of adverse reactions. These include COX-2 selective inhibitors and NO-releasing NSAIDs. Much has been written about the potential of COX-2 inhibitors as antiinflammatory agents that lack the gastrointestinal side effects of traditional NSAIDs. COX-2 expression is most evident at sites of inflammation, while COX-1 accounts for most of the PG synthesis in the normal gastrointestinal tract. However, there are distinct examples of circumstances in which COX-2-derived PGs play a role in the maintenance of the mucosal integrity, and the differentiation of COX-1 and COX-2 is not quite as clear as has been suggested. On the other hand, the rational behind the NO-releasing NSAIDs is that NO released from the derivatives exerts beneficial effects on the gastrointestinal mucosa. The present article overviews the roles of COX and NO in housekeeping functions of the gastrointestinal mucosa in various circumstances and the effects of gastrointestinal sparing NSAIDs, such as COX-2 selective inhibitors and NO-releasing NSAIDs, on the ulcerogenic and healing responses in the gastrointestinal mucosa.