NSAID-induced Gastric Lesions Research Articles

Structure–activity relationship of celecoxib and rofecoxib for the membrane permeabilizing activity

Non-steroidal anti-inflammatory drugs (NSAIDs) achieve their anti-inflammatory effect by inhibiting cyclooxygenase activity. We previously suggested that in addition to cyclooxygenase-inhibition at the gastric mucosa, NSAID-induced gastric mucosal cell death is required for the formation of NSAID-induced gastric lesions in vivo. We showed that celecoxib exhibited the most potent membrane permeabilizing activity among the NSAIDs tested. In contrast, we have found that the NSAID rofecoxib has very weak membrane permeabilizing activity. To understand the membrane permeabilizing activity of coxibs in terms of their structure–activity relationship, we separated the structures of celecoxib and rofecoxib into three parts, synthesized hybrid compounds by substitution of each of the parts, and examined the membrane permeabilizing activities of these hybrids. The results suggest that the sulfonamidophenyl subgroup of celecoxib or the methanesulfonylphenyl subgroup of rofecoxib is important for their potent or weak membrane permeabilizing activity, respectively. These findings provide important information for design and synthesis of new coxibs with lower membrane permeabilizing activity.

Co-administration of Water Containing Magnesium Ion Prevents Loxoprofen-Induced Lesions in Gastric Mucosa of Adjuvant-Induced Arthritis Rat

Non-steroidal anti-inflammatory drugs (NSAIDs) comprise one of the most frequently used classes of medicines in the world; however, NSAIDs have significant side effects, such as gastroenteropathy, and rheumatoid arthritis patients taking NSAIDs are more susceptible to NSAID-induced gastric lesions as compared to patients with other diseases. In Asian countries, loxoprofen has been used clinically for many years as a standard NSAID. We demonstrate the preventive effect of the co-administration of water containing magnesium ion (magnesium water, 1-200 µg/kg) on the ulcerogenic response to loxoprofen in adjuvant-induced arthritis (AA) rats. Oral administration of loxoprofen (100 mg/kg) caused hemorrhagic lesions in the gastric mucosa of AA rats 14 d after adjuvant injection, and, following loxoprofen administration, the lesion score of AA rats was significantly higher than that of normal rats. The expression of inducible nitric oxide synthase (iNOS) mRNA and nitric oxide (NO) production in the gastric mucosa of AA rats were also increased by the administration of loxoprofen, and the increase in lesions and NO were prevented by the administration of aminoguanidine, an iNOS inhibitor. The co-administration of magnesium water decreased the ulcerogenic response to loxoprofen in AA rats. In addition, the co-administration of magnesium water attenuated the increase in iNOS mRNA expression and NO production in AA rats receiving loxoprofen. These results suggest that the oral co-administration of magnesium water to AA rats has a potent preventive effect on the ulcerogenic response to loxoprofen, probably by inhibiting the rise in iNOS and NO levels in the gastric mucosa.

Synthesis and biological evaluation of loxoprofen derivatives

Non-steroidal anti-inflammatory drugs (NSAIDs) achieve their anti-inflammatory actions through an inhibitory effect on cyclooxygenase (COX). Two COX subtypes, COX-1 and COX-2, are responsible for the majority of COX activity at the gastrointestinal mucosa and in tissues with inflammation, respectively. We previously suggested that both gastric mucosal cell death due to the membrane permeabilization activity of NSAIDs and COX-inhibition at the gastric mucosa are involved in NSAID-induced gastric lesions. We have also reported that loxoprofen has the lowest membrane permeabilization activity among the NSAIDs we tested. In this study, we synthesized a series of loxoprofen derivatives and examined their membrane permeabilization activities and inhibitory effects on COX-1 and COX-2. Among these derivatives, 2-{4′-hydroxy-5-[(2-oxocyclopentyl)methyl]biphenyl-2-yl}propanoate 31 has a specificity for COX-2 over COX-1. Compared to loxoprofen, oral administration of 31 to rats produced fewer gastric lesions but showed an equivalent anti-inflammatory effect. These results suggest that 31 is likely to be a therapeutically beneficial and safer NSAID.

Suppression of Expression of Endoplasmic Reticulum Chaperones by Helicobacter pylori and Its Role in Exacerbation of Non-steroidal Anti-inflammatory Drug-induced Gastric Lesions

Both the use of non-steroidal anti-inflammatory drugs (NSAIDs), such as indomethacin, and infection with Helicobacter pylori are major causes of gastric ulcers. Although some clinical studies suggest that infection with H. pylori increases the risk of developing NSAID-induced gastric lesions, the molecular mechanism governing this effect is unknown. We recently found that in cultured gastric cells, expression of endoplasmic reticulum (ER) chaperones (such as 150-kDa oxygen-regulated protein (ORP150) and glucose-regulated protein 78 (GRP78)) is induced by NSAIDs and confers protection against NSAID-induced apoptosis, which is important in the development of NSAID-induced gastric lesions. In this study we have found that co-culture of gastric cells with H. pylori suppresses the expression of ER chaperones. This suppression was regulated at the level of transcription and accompanied by a reduction in the level of activating transcription factor 6 (ATF6), one of the transcription factors for ER chaperone genes. In vivo, inoculation of mice with H. pylori suppressed the expression of ER chaperones at gastric mucosa both with and without administration of indomethacin. Inoculation with H. pylori also stimulated formation of indomethacin-induced gastric lesions and mucosal cell death. In addition, we found that heterozygous ORP150-deficient mice are sensitive to the development of indomethacin-induced gastric lesions and mucosal cell death. The results of this study suggest that H. pylori exacerbates NSAID-induced gastric lesions through suppression of expression of ER chaperones, which stimulates NSAID-induced mucosal cell death.

Properties and Synthesis of 2-{2-Fluoro (or Bromo)-4-[(2-oxocyclopentyl)methyl]phenyl}propanoic Acid: Nonsteroidal Anti-inflammatory Drugs with Low Membrane Permeabilizing and Gastric Lesion-Producing Activities

We previously proposed that membrane permeabilization activity of NSAIDs is involved in NSAID-induced gastric lesions. We here synthesized derivatives of loxoprofen that have lower membrane permeabilization activity than other NSAIDs. Compared to loxoprofen, the derivatives 10a and 10b have lower membrane permeabilization activity and their oral administration produced fewer gastric lesions but showed an equivalent anti-inflammatory effect. These results suggest that 10a and 10b are likely to be therapeutically beneficial as safer NSAIDs.

Low Direct Cytotoxicity of Loxoprofen on Gastric Mucosal Cells

Pro-drugs of non-steroidal anti-inflammatory drugs (NSAIDs), such as loxoprofen are widely used for clinical purposes because they are not so harmful to the gastrointestinal mucosa. We recently showed that NSAIDs such as indomethacin and celecoxib have direct cytotoxicity (ability to induce necrosis and apoptosis in gastric mucosal cells) due to their membrane permeabilizing activities, which is involved in NSAID-induced gastric lesions. We show here that under conditions where indomethacin and celecoxib clearly induce necrosis and apoptosis, loxoprofen and its active metabolite loxoprofen-OH, do not have such effects in primary culture of guinea pig gastric mucosal cells. Loxoprofen and loxoprofen-OH induced apoptosis more effectively in cultured human gastric cancer cells than in the primary culture. Loxoprofen and loxoprofen-OH exhibited much lower membrane permeabilizing activities than did indomethacin and celecoxib. We thus consider that the low direct cytotoxicity of loxoprofen observed in vitro is involved in its relative safety on production of gastric lesions in clinical situation.

Geranylgeranylacetone Protects against Diclofenac-Induced Gastric and Small Intestinal Mucosal Injuries in Healthy Subjects: A Prospective Randomized Placebo-Controlled Double-Blind Cross-Over Study

Background and Aims: Little information is available regarding the prevention and treatment of small intestinal mucosal injuries caused by non-steroidal anti-inflammatory drugs (NSAIDs). We planned a pilot study to investigate the protective effects of geranylgeranylacetone (GGA) against NSAID-induced small intestinal injuries using video capsule endoscopy (VCE). Subjects and Methods: Ten healthy male volunteers took oral GGA 300 mg/day (regimen A) or placebo (regimen B) in addition to diclofenac 75 mg/day + rabeprazole 20 mg/day for 7 days. We conducted a cross-over trial of regimens A and B with a 2-week washout period. All subjects underwent VCE before and after each administration period, and were evaluated for NSAID-induced gastric and small intestinal mucosal lesions. Results: The number of mucosal lesions (erosions, ulcers and a red spot with possible bleeding) detected in both stomach and small bowel changed between prior to and immediately after administration period, with significantly fewer lesions for regimen A after administration period (mean ± SD A:B = 2.6 ± 3.2:9.5 ± 8.5; p = 0.027). Conclusions: Combination therapy with GGA and rabeprazole reduced the incidence of gastroenteropathy induced by 1-week administration of diclofenac. Our findings suggest this therapy as a candidate for protecting patients on long-term NSAID therapy.

A Role for HSP70 in Protecting against Indomethacin-induced Gastric Lesions

A major clinical problem encountered with the use of nonsteroidal anti-inflammatory drugs (NSAIDs), such as indomethacin, is gastrointestinal complications. Both NSAID-dependent cyclooxygenase inhibition and gastric mucosal apoptosis are involved in NSAID-produced gastric lesions, and this apoptosis is mediated by the endoplasmic reticulum stress response and resulting activation of Bax. Heat shock proteins (HSPs) have been suggested to protect gastric mucosa from NSAID-induced lesions; here we have tested this idea genetically. The severity of gastric lesions produced by indomethacin was worse in mice lacking heat shock factor 1 (HSF1), a transcription factor for hsp genes, than in control mice. Indomethacin administration up-regulated the expression of gastric mucosal HSP70. Indomethacin-induced gastric lesions were ameliorated in transgenic mice expressing HSP70. After indomethacin administration, fewer apoptotic cells were observed in the gastric mucosa of transgenic mice expressing HSP70 than in wild-type mice, whereas the gastric levels of prostaglandin E(2) for the two were indistinguishable. This suggests that expression of HSP70 ameliorates indomethacin-induced gastric lesions by affecting mucosal apoptosis. Suppression of HSP70 expression in vitro stimulated indomethacin-induced apoptosis and activation of Bax but not the endoplasmic reticulum stress response. Geranylgeranylacetone induced HSP70 at gastric mucosa in an HSF1-dependent manner and suppressed the formation of indomethacin-induced gastric lesions in wild-type mice but not in HSF1-null mice. The results of this study provide direct genetic evidence that expression of HSP70 confers gastric protection against indomethacin-induced lesions by inhibiting the activation of Bax. The HSP inducing activity of geranylgeranylacetone seems to contribute to its gastroprotective activity against indomethacin.

Development of new type of NSAIDs with lower gastric side effects

Non-steroidal anti-inflammatory drugs (NSAIDs) are a useful family of therapeutics. The anti-inflammatory actions of NSAIDs are mediated through their inhibitory effects on cyclooxygenase (COX) activity and resulting decrease in prostaglandins (PGs). On the other hand, NSAID use is associated with gastrointestinal complications. Although PGs have a strong protective effect on gastrointestinal mucosa, the inhibition of COX by NSAIDs is not the sole explanation for the gastrointestinal side effects of NSAIDs. In this study, we examined the COX-independent mechanism involved in NSAID-induced gastric lesions. Using DNA microarray analysis, we found that CHOP, a transcription factor with apoptosis-inducing ability is induced by NSAIDs and treatment of cells with NSAIDs caused apoptosis in wild-type cells but not in CHOP-knock out cells. We also found that NSAIDs have membrane permeabilization activity. Furthermore, intracellular Ca2+ chelator, BAPTA-AM inhibited the NSAID-induced apoptosis and induction of CHOP. In vivo, we proposed that both COX inhibition at gastric mucosa and direct gastric mucosal cell damage (such as induction of apoptosis) by NSAIDs are required for the production of gastric lesions. Results showed that NSAID-induced apoptosis is mediated by permeabilization of cytoplasmic membranes, increase in the intracellular Ca2+ levels and induction of CHOP. Furthermore, results suggest that NSAIDs without membrane permeabilizing activity have reduced aastrointestinal side effects.

The aerial parts of Guazuma ulmifolia Lam. protect against NSAID-induced gastric lesions

Guazuma ulmifolia Lam., a member of the Sterculiaceae family, is used in folk medicine because of its antioxidant, antimicrobial and antihypertensive properties. Most of the research work carried out on this plant has focused on the bark because of its high concentration of antioxidant proanthocyanidins. The flowers and leaves of Guazuma ulmifolia, though less studied, are also used as a remedy for different conditions, such as kidney and gastrointestinal diseases, fever and diabetes. The aim of this study was to assess the gastroprotective effects of an aqueous suspension of the ethanolic extract from leaves and flowers of Guazuma ulmifolia in a model of acute gastric ulcer induced by diclofenac as ulcerogenic agent, using the proton pump inhibitor omeprazole as a protection reference. Therefore, the extract was administered two times orally to three groups of Wistar rats at doses of 500, 250 and 125 mg/kg, with a 24-h interval between doses. Diclofenac (100 mg/kg) was given 1 h after the last administration of the extract. Pretreatment with Guazuma ulmifolia or omeprazole decreased the ulcerated area in a dose-dependent way. Myeloperoxidase activity as a marker of neutrophil infiltration was slightly reduced in vivo, whereas in vitro, anti-inflammatory activity was clearly inhibited in a dose-dependent way. The lowest doses of the extract significantly decreased the levels of lipoperoxides, and superoxide dismuthase activity increased to a similar extent as with omeprazole ( P < 0.001). Examination of glutathione metabolism reflected a significant rise in glutathione peroxidase activity at the highest dose of Guazuma ulmifolia. Finally, there was a faint elevation in prostaglandin E 2 levels with all doses, though the depletion induced by diclofenac could not be reverted. We conclude that the aerial parts of Guazuma ulmifolia protect gastric mucosa against the injurious effect of NSAIDs mainly by anti-inflammatory and radical-scavenging mechanisms.

Various stress proteins protect gastric mucosal cells against non-steroidal anti-inflammatory drugs

Gastric mucosal cell death induced by non-steroidal anti-inflammatory drugs (NSAIDs) is suggested to be involved in NSAID-induced gastric lesions. Therefore, cellular factors that suppress this cell death are important for protection of the gastric mucosa from NSAIDs. When cells are exposed to various stressors, including NSAIDs, they induce a number of proteins, so-called stress proteins, in order to protect themselves against such stressors. Stress proteins contain cytosolic molecular chaperons (such as heat shock proteins), endoplasmic reticulum molecular chaperons (such as glucose-regulated proteins) and heme oxygenase-1. We recently showed that (i) these stress proteins are up-regulated by NSAIDs both in vitro and in vivo; (ii) these up-regulation make gastric mucosal cells resistant to NSAIDs in vitro; (iii) these up-regulation protects the gastric mucosa from NSAID-induced gastric lesions in vivo. In this review, I summarize these results and propose that non-toxic inducers of these stress proteins are therapeutically beneficial as anti-ulcer drugs.

Heme Oxygenase-1 Protects Gastric Mucosal Cells against Non-steroidal Anti-inflammatory Drugs

Gastric mucosal cell death by non-steroidal anti-inflammatory drugs (NSAIDs) is suggested to be involved in NSAID-induced gastric lesions. Therefore, cellular factors that suppress this cell death are important for protection of the gastric mucosa from NSAIDs. Heme oxygenase-1 (HO-1) is up-regulated by various stressors and protects cells against stressors. Here, we have examined up-regulation of HO-1 by NSAIDs and the contribution of HO-1 to the protection of gastric mucosal cells against NSAIDs both in vitro and in vivo. In cultured gastric mucosal cells, all NSAIDs tested up-regulated HO-1. In rats, orally administered indomethacin up-regulated HO-1, induced apoptosis, and produced lesions at gastric mucosa. An inhibitor of HO-stimulated NSAID-induced apoptosis in vitro and in vivo and also stimulated NSAID-produced gastric lesions, suggesting that NSAID-induced up-regulation of HO-1 protects the gastric mucosa from NSAID-induced gastric lesions by inhibiting NSAID-induced apoptosis. Indomethacin activated the HO-1 promoter and caused nuclear accumulation of NF-E2-related factor 2 (Nrf2), a transcription factor for the HO-1 gene. Examination of phosphorylation of p38 mitogen-activated protein kinase (MAPK) and experiments with its inhibitor strongly suggest that the nuclear accumulation of Nrf2 and resulting up-regulation of HO-1 by NSAIDs is mediated through NSAID-dependent activation (phosphorylation) of p38 MAPK. This is the first report showing the protective role of HO-1 against irritant-induced gastric lesions.

Low Direct Cytotoxicity of Nabumetone on Gastric Mucosal Cells

Prodrugs of non-steroidal anti-inflammatory drugs (NSAIDs) are widely used for clinical purposes because they are not harmful to the gastrointestinal mucosa. We recently showed that NSAIDs have direct cytotoxicity in NSAID-induced gastric lesions. We show here that under conditions where the NSAIDs indomethacin and celecoxib clearly induce cell death, an NSAID prodrug, nabumetone, and its active metabolite 6-methoxy-2-naphthylacetic acid (6MNA), did not have such effects. Moreover, nabumetone and 6MNA exhibited much lower membrane permeabilizing activities than did indomethacin and celecoxib. We recently reported that when an orally administered NSAID was used in combination with a low dose of intravenously administered indomethacin, the severity of gastric lesions produced in rats depended on the cytotoxicity of the orally administered NSAID. Using a similar protocol, we show here that gastric lesions were produced when the orally administered NSAID was celecoxib, but not when nabumetone was used. We thus propose that the low direct cytotoxicity of nabumetone observed in vitro is maintained in vivo, and that the use of nabumetone does not harm the gastric mucosa.

Geranylgeranylacetone Protects Membranes against Nonsteroidal Anti-Inflammatory Drugs

Direct gastric mucosal cell damage mediated by nonsteroidal anti-inflammatory drugs (NSAIDs) is involved in the formation of NSAID-induced gastric lesions. We recently suggested that this direct cytotoxicity of NSAIDs is caused by their membrane-permeabilization activity. Geranylgeranylacetone (GGA), a clinically used antiulcer drug, can protect gastric mucosa against lesion formation mediated by NSAIDs. However, the mechanism by which this occurs is not fully understood. In this study, we show that GGA acts to stabilize membranes against NSAIDs. GGA suppressed NSAID-induced permeabilization of calcein-loaded liposomes and NSAID-induced stimulation of K(+)-efflux across the cytoplasmic membrane in cells. GGA was effective even when coadministered with NSAIDs and was also able to restore membrane fluidity that had been compromised by NSAIDs. This mechanism seems to play an important role in the antiulcer activity of GGA.

Membrane permeabilization by non-steroidal anti-inflammatory drugs

The cytotoxicity of non-steroidal anti-inflammatory drugs (NSAIDs) is involved in the formation of NSAID-induced gastric lesions. The mechanism(s) behind these cytotoxic effects, however, is not well understood. We found here that several NSAIDs tested caused hemolysis when employed at concentrations similar to those that result in cytotoxicity. Moreover, these same NSAIDs were found to directly permeabilize the membranes of calcein-loaded liposomes. Given the similarity in NSAID concentrations for cytotoxic and membrane permeabilization effects, the cytotoxic action of these NSAIDs may be mediated through the permeabilization of biological membranes. Increase in the intracellular Ca2+ level can lead to cell death. We here found that all of NSAIDs tested increased the intracellular Ca2+ level at concentrations similar to those that result in cytotoxicity. Based on these results, we consider a possibility that membrane permeabilization by NSAIDs induces cell death through increase in the intracellular Ca2+ level.

Endoplasmic reticulum stress response is involved in nonsteroidal anti-inflammatory drug-induced apoptosis.

Apoptosis induced by nonsteroidal anti-inflammatory drugs (NSAIDs) is involved not only in the production of NSAID-induced gastric lesions but also in the antitumor activity of these drugs. The endoplasmic reticulum (ER) stress response is a cellular mechanism that aids in protecting the ER against ER stressors and is involved in ER stressor-induced apoptosis. Here, we examine the relationship between this response and NSAID-induced apoptosis in cultured guinea-pig gastric mucosal cells. Exposure of cells to indomethacin, a commonly used NSAID, induced GRP78 as well as CHOP, a transcription factor involved in apoptosis. Three factors that positively regulate CHOP expression (ATF6, ATF4 and XBP-1) were activated and/or induced by indomethacin. NSAIDs other than indomethacin (diclofenac, ibuprofen and celecoxib) also induced CHOP. Monitoring of the transcriptional activities of ATF6 and CHOP by luciferase assay revealed that both were stimulated in the presence of indomethacin. Furthermore, indomethacin-induced apoptosis was suppressed in cultured guinea-pig gastric mucosal cells by expression of the dominant-negative form of CHOP, or in peritoneal macrophages from CHOP-deficient mice. These results suggest that ER stress response-related proteins, particularly CHOP, are involved in NSAID-induced apoptosis.

Role of direct cytotoxic effects of NSAIDs in the induction of gastric lesions

A major clinical problem encountered with the use of non-steroidal anti-inflammatory drugs (NSAIDs), is gastrointestinal complications. We previously reported that NSAIDs induce both necrosis and apoptosis in vitro. We here examined the cyclooxygenase (COX) dependency of this cytotoxic effect of NSAIDs and its involvement in NSAID-induced gastric lesions. Necrosis and apoptosis by NSAIDs was observed with all selective COX-2 inhibitors except rofecoxib and was not inhibited by exogenously added prostaglandin E 2, suggesting that cytotoxicity of NSAIDs seems to be independent of the inhibition of COX. Intravenously administered indomethacin, which completely inhibited COX activity at gastric mucosa, did not produce gastric lesions. Orally administered selective COX-2 inhibitors, which did not inhibit COX at gastric mucosa, also did not produce gastric lesions. Interestingly, a combination of the oral administration of each of all selective COX-2 inhibitors except rofecoxib with the intravenous administration of indomethacin clearly produced gastric lesions. These results suggest that in addition to COX inhibition by NSAIDs, direct cytotoxicity of NSAIDs may be involved in NSAID-induced gastric lesions.

Up-regulation of COX-2 by inhibition of COX-1 in the rat: a key to NSAID-induced gastric injury.

A recent study demonstrated that inhibition of both cyclooxygenase (COX)-1 and COX-2 is required for the development of nonsteroidal anti-inflammatory drug (NSAID)-induced gastric lesions. However, the role of COX-1 or COX-2 inhibition in the pathogenisis of these lesions remains unclear. To examine the gastric ulcerogenic properties of selective COX-1 and COX-2 inhibitors in rats and to investigate further the relationship of COX inhibition to various events involved in the process of NSAID-induced gastric lesions. Animals were given various COX inhibitors p.o., either alone or in combination, and killed 8 h later. Under the treatment, gastric damage, prostaglandin (PG) E2 content, mucosal permeability, myeloperoxidase (MPO) activity as well as gastric motility were examined. The nonselective COX inhibitor indomethacin inhibited PGE2 production, enhanced gastric motility, and provoked severe lesions in the stomach, with an increase in mucosal permeability and MPO activity. In contrast, the selective COX-2 inhibitor rofecoxib did not induce any damage in the stomach and had no effect on mucosal PGE2 content. Similarly, the selective COX-1 inhibitor SC-560 also caused no gastric damage, despite inhibiting PGE2 production. The combined administration of SC-560 and rofecoxib, however, provoked gross damage in the gastric mucosa, in a dose-dependent manner for each drug. SC-560, but not rofecoxib, caused marked gastric hypermotility and an increase in mucosal permeability, although an increase in MPO activity was observed only when rofecoxib was coadministered. The normal gastric mucosa expressed COX-1 mRNA and not COX-2 mRNA, but COX-2 mRNA was expressed in the stomach after administration of SC-560 as well as indomethacin but not rofecoxib. These results suggest that the gastric ulcerogenic properties of NSAIDs are not accounted for solely by COX-1 inhibition, but require the inhibition of both COX-1 and COX-2. The inhibition of COX-1 up- regulates COX-2 expression, and COX-2/PGs may, in turn, counteract the deleterious affects of gastric hypermotility due to COX-1 inhibition.

Prevention by parenteral aspirin of indomethacin-induced gastric lesions in rats: mediation by salicylic acid.

Nonsteroidal antiinflammatory drugs (NSAIDs) produce gastric damage in experimental animals, irrespective of the route of administration. However, aspirin (ASA) causes damage only when it is given orally. In the present study, we examined the gastric ulcerogenic effect of subcutaneously administered ASA in rats, in comparison with various NSAIDs, and investigated the reason why ASA does not cause damage in the stomach, in relation to its metabolite salicylic acid (SA). Since the antiinflammatory action of SA is known to be mediated, partly, by endogenous adenosine (AD), we also examined the possible involvement of AD in the protective action of SA. Various NSAIDs (indomethacin, flurbiprofen, naproxen, diclrofenac, ASA, SA) were administered subcutaneously, and the gastric mucosa was examined macroscopically 4 hr later. All NSAIDs tested, except ASA and SA, caused hemorrhagic lesions in the stomach, with a marked gastric hypermotility and a decrease of mucosal PGE2 contents. These ulcerogenic and motility responses caused by NSAIDs were blocked by pretreatment with atropine or PGE2. ASA, although inhibiting PGE2 generation, caused neither hypermotility nor damage in the stomach. On the other hand, SA alone inhibited basal gastric motility without any effect on mucosal PGE2 contents, and this agent, when given together with indomethacin, prevented gastric hypermotility and lesion formation in response to indomethacin, without affecting the reduced PGE2 contents. Likewise, ASA inhibited these responses to indomethacin, yet the effects appeared later than those of SA. Following administration of ASA, the blood SA levels reached a peak within 30 min and remained elevated for 4 hr. In addition, the protective effect of SA was not significantly influenced by either the AD deaminase or the AD-receptor antagonists. These results suggest that the failure of parenteral ASA to induce gastric damage may be explained by a protective action of SA metabolized from ASA. SA has a cytoprotective action against NSAID-induced gastric lesions, and this action is not mediated by endogenous AD but may be functionally associated with inhibition of the gastric motility response.

3441 Autofluorescence and tissue peroxidation in nsaids-induced acute gastric mucosal lesions in human volunteers.

Background and Aims:We have already reported that gastric mucosal autofluorescence intensity increased in accordance with gastric mucosal lesions formation induced by dicrofenac sodium administration in rats. In this study, we have established an endoscopic apparatus composed with an image processor and a highly-sensitive camera for fluorescence observation named SEFAS: a simultaneous endoscopic fluorescence analyzing system. Using this system, we clarified whether NSAID-treatment increased gastric mucosal fluorescence intensity in human volunteers or not. Moreover, we examined relations of distributions between tissue peroxidation and fluorescent substance. Methods: Healthy human volunteers who completely agreed to take part in this study were administrated 50 mg dicrofenac per os. Mucosal fluorescence intensity were measured with SEFAS before and 1, 2 hour(s) after the dicrofenac treatment. Moreover, volunteers were also administrated 50 mg teprenone, a mucosal prostaglandin inducing agent, 30 min before the dicrofenac treatment, and were also measured mucosal intensities. In each study, some pieces of mucosa were taken from each area of the mucosal fluorescence measurement. These biopsies were rapidly made into specimens of cryosections. They were immunohistochemicaly stained with anti-4-hydroxynonenal antibody, a specific monoclonal antibody for peroxidized tissue, and analyzed distributions of tissue peroxidation. Distributions of autofluorescent substance were also observed. Moreover, autofluorescent substance was analyzed with HPLC. Results: The dicrofenac treatment increased mucosal fluorescence intensity. The administrations of teprenone completely restrained this phenomenon. Fluorescence substances were porphyrins. These fluorescence substances were localized at the disrupted surface layer of the gastric mucosa. Peroxidized tissue was located in middle part of the mucosa. Conclusions: It suggested that tissue peroxidation was induced before mucosal injury formation, and fluorescent porphyrins were generated with tissue disruption. Mucosal fluorescence observations with SEFAS can diagnose NSAID-induced gastric lesions.