Protection by amylin of gastric erosions induced by indomethacin or ethanol in rats

Protective effect of chrysin on indomethacin induced gastric ulcer in rats: role of multi-pathway regulation

We investigated the potential gastroprotective effects of chrysin on indomethacin induced gastric ulcers in rats. We used six groups of animals: control; indomethacin (Indo); reference (Ulcuran®); indomethacin + 25 mg/kg chrysin (Indo + CHR25); indomethacin + 50 mg/kg chrysin (Indo + CHR50); indomethacin + 100 mg/kg chrysin (Indo + CHR100). All doses of chrysin were given orally to rats before indomethacin. Gastric lesions were examined macroscopically and microscopically. The effects of treatment with chrysin were assessed versus a single dose of 30 mg/kg Ulcuran® (generic ranitidine) as reference standard. We also investigated gastric mucosal superoxide dismutase (SOD), glutathione (GSH), glutathione peroxidase (GPx), catalase (CAT), malonaldehyde (MDA) and arginase activities, and COX-2, PGE₂, iNOS, TNF-α, IL-1β, NFκB, MPO, Bax, caspase-3 and 8-OHdG levels. We assessed caspase-3 and Bax levels using immunohistochemistry. Compared to the control and reference groups, SOD, CAT, GPx and arginase activities and GSH levels decreased, and MDA levels increased in the indomethacin induced gastric ulcer group. iNOS, TNF-α, IL-1β, NFκB, MAPK-14, MPO, Bax and 8-OHdG levels were increased in the indomethacin treated gastric group, while COX-2 activity and PGE₂ levels were decreased. The three doses of chrysin co-administered with indomethacin increased COX-2 activity and PGE₂ levels in rats with ulcers. Chrysin exhibited gastroprotective effects on indomethacin induced gastric ulcer due to its antioxidant, anti-inflammatory and anti-apoptotic activities.

Malvidin Protects against and Repairs Peptic Ulcers in Mice by Alleviating Oxidative Stress and Inflammation

Peptic ulcer episodes cause damage to the stomach and intestine, with inflammatory cell infiltration and oxidative stress as the main players. In this study, we investigated the potential of anthocyanidin malvidin for preventive and curative peptic ulcer treatment. The anthocyanidin effects were examined in gastric ulcer mouse models induced by ethanol, non-steroidal anti-inflammatory drugs (NSAIDs), ischemia-reperfusion (IR), acetic acid and duodenal ulcer induced by polypharmacy. Expression levels of oxidative and inflammatory genes were measured to investigate the mechanism of anthocyanin activity. At a dose of 5 mg·kg⁻¹, Malvidin prevented gastric ulcer induction by ethanol, NSAID and repaired the tissue after 6 days of IR. Moreover, the anthocyanidin accelerated the healing of acetic acid-induced ulcer, increased the gene expression of EGF and COX-1, and downregulated MMP-9. Anthocyanin treatment mitigated the effect of polypharmacy on inflammation and oxidative stress observed in the intestine. Additionally, the compound downregulated cytokine expression and TLR4 and upregulated HMOX-1 and IL-10, exhibiting protective activity in the mouse gut. Malvidin thus prevented gastric and duodenal ulcers due to prominent anti-inflammatory and antioxidative effects on the gastrointestinal tract that were related to gene expression modulation and an increase in endogenous defense mechanisms.

Medical image recognition and segmentation of pathological slices of gastric cancer based on Deeplab v3+ neural network

OBJECTIVE

In order to improve the efficiency of gastric cancer pathological slice image recognition and segmentation of cancerous regions, this paper proposes an automatic gastric cancer segmentation model based on Deeplab v3+ neural network.

METHODS

Based on 1240 gastric cancer pathological slice images, this paper proposes a multi-scale input Deeplab v3+ network, _and compares it with SegNet, ICNet in sensitivity, specificity, accuracy, and Dice coefficient.

RESULTS

The sensitivity of Deeplab v3+ is 91.45%, the specificity is 92.31%, the accuracy is 95.76%, and the Dice coefficient reaches 91.66%, which is more than 12% higher than the SegNet and Faster-RCNN models, and the parameter scale of the model is also greatly reduced.

CONCLUSION

Our automatic gastric cancer segmentation model based on Deeplab v3+ neural network has achieved better results in improving segmentation accuracy and saving computing resources. Deeplab v3+ is worthy of further promotion in the medical image analysis and diagnosis of gastric cancer.

Indomethacin can induce cell death in rat gastric parietal cells through alteration of some apoptosis- and autophagy-associated molecules

In clinical medicine, indomethacin (IND, a non-steroidal anti-inflammatory drug) is used variously in the treatment of severe osteoarthritis, rheumatoid arthritis, gouty arthritis or ankylosing spondylitis. A common complication found alongside the therapeutic characteristics is gastric mucosal damage. This complication is mediated through apoptosis and autophagy of the gastrointestinal mucosal epithelium. Apoptosis and autophagy are critical homeostatic pathways catalysed by caspases downstream of the gastrointestinal mucosal epithelial injury. Both act through molecular signalling pathways characterized by the initiation, mediation, execution and regulation of the cell regulatory cycle. In this study we hypothesized that dysregulated apoptosis and autophagy are associated with IND-induced gastric damage. We examined the spectra of in vivo experimental gastric ulcers in male Sprague-Dawley rats through gastric gavage of IND. Following an 18-hour fast, IND was administered to experimental rats. They were sacrificed at 3-, 6- and 12-hour intervals. Parietal cells (H⁺ , K⁺ -ATPase β-subunit assay) and apoptosis (TUNEL assay) were determined. The expression of apoptosis-signalling caspase (caspases 3, 8, 9 and 12), DNA damage (anti-phospho-histone H2A.X) and autophagy (MAP-LC3, LAMP-1 and cathepsin B)-related molecules in gastric mucosal cells was examined. The administration of IND was associated with gastric mucosal erosions and ulcerations mainly involving the gastric parietal cells (PCs) of the isthmic and upper neck regions and a time-dependent gradual increase in the number of apoptotic PCs with the induction of both apoptotic (upregulation of caspases 3 and 8) cell death and autophagic (MAP-LC3-II, LAMP-1 and cathepsin B) cell death. Autophagy induced by fasting and IND 3 hours initially prompted the degradation of caspase 8. After 6 and 12 hours, damping down of autophagic activity occurred, resulting in the upregulation of active caspase 8 and its nuclear translocation. In conclusion we report that IND can induce time-dependent apoptotic and autophagic cell death of PCs. Our study provides the first indication of the interactions between these two homeostatic pathways in this context.

Machaerium hirtum (Vell.) Stellfeld Alleviates Acute Pain and Inflammation: Potential Mechanisms of Action

Machaerium hirtum (Vell.) Stellfeld (Fabaceae) known in Brazil as “jacaranda de espinho” or “espinheira santa nativa” is a medicinal plant commonly used in folk medicine to treat ulcers, cough and diarrhea. This study aimed to investigate the anti-inflammatory and antinociceptive effects of hydroalcoholic extracts from M. hirtum twig (HEMh) using in vivo experimental models of nociception through the involvement of transient receptor potential channels, acid-sensing ion channel (ASIC), nitrergic, opioidergic, glutamatergic, and supraspinal pathways. Our results revealed an antinociceptive effect of HEMh mediated by the opioidergic, l-arginine-nitric oxide and glutamate systems, as well as by interactions with TRPA1/ASIC channels. The anti-inflammatory effect of HEMh evaluated with a xylene-induced ear edema and by the involvement of arachidonic acid and prostaglandin E2 (PGE₂) showed involvement of the COX pathway, based on observed decreases in PGE₂ levels. A phytochemical investigation of the HEMh led to the isolation of α-amyrin, β-amyrin, allantoin, apigenin-7-methoxy-6-C-β-d-glucopyranoside, and apigenin-6-C-β-d-glucopyranosyl-8-C-β-d-xylopyranoside. In conclusion, the acute oral administration of HEMh inhibits the nociceptive behavioral response in animals through the nitrergic, opioid, glutamatergic pathways, and by inhibition of the TRPA1 and ASIC channels, without causing locomotor dysfunction. In addition, its anti-inflammatory effect is associated with the COX pathway and decreased PGE₂ levels.

Effects of intracerebroventricularly injected glucagon-like peptide-2 on ethanol-induced gastric mucosal damage in rats

PURPOSE

The present study aims to investigate the effects of intracerebroventricularly (i.c.v.)-injected glucagon-like peptide-2 (GLP-2) on ethanol-induced gastric mucosal damage and to reveal the mechanisms involved in this effect.

MATERIALS AND METHODS

Rats received absolute ethanol orally via an orogastric tube 30 minutes after GLP-2 (1-200 ng/10 µl; i.c.v.) or saline (10 µl) injections. They were decapitated 1 hour later, their stomachs were removed, and the gastric mucosal damage was scored.

RESULTS

A total of 100 ng GLP-2 inhibited the gastric mucosal damage by 67%. This effect was abolished by the calcitonin gene-related peptide (CGRP) receptor antagonist CGRP-(8-37) (10 µg/kg; s.c.), but was not affected by either the nitric oxide (NO) synthase inhibitor L-NAME (30 mg/kg; s.c.) or the cyclooxygenase inhibitor indomethacin (5 mg/kg; i.p.). The most effective gastroprotective dose of GLP-2 (100 ng/10 µl; i.c.v.), but not the higher doses (150 or 200 ng/10 µl; i.c.v.) prevented the decrease in gastric mucosal blood flow caused by ethanol. In conclusion, i.c.v. GLP-2 protects against ethanol-induced gastric mucosal damage and this effect is mediated by CGRP receptor activation and gastric mucosal blood flow, but not by NO or prostaglandins.

Investigation of antiulcer and antioxidant activity of moclobemide in rats

OBJECTIVE

Even though there are many drugs for the treatment of gastric ulcers, these drugs sometimes cannot succeed. Since the 1950s, antidepressant drugs have been used for several non-psychiatric indications. Many antidepressant drugs have been shown experimentally to produce antiulcer activity in various ulcer models. Moclobemide is an antidepressant drug which inhibits monoamine oxidase-A (MAO) enzyme selectively. When it is compared to the classic antidepressants drugs, moclobemide is the first choice in depression treatment because of its effectiveness and less side effects. This study aimed to investigate the antiulcer effects of moclobemide and to determine its relationship with antioxidant mechanisms in rat gastric tissue.

MATERIALS AND METHODS

The antiulcer activities of 10, 20, 40, 80, 150 mg/kg moclobemide and 20 mg/kg famotidine have been investigated on indomethacin-induced ulcers in rats, and the results have been compared with that of the control group.

RESULTS

Moclobemide decreased the indomethacin-induced ulcers significantly at all doses used. While used doses of moclobemide increased the glutathione (GSH), nitric oxide (NO) level and superoxide dismutase (SOD) activity, it decreased the malondialdehyde (MDA) level and myeloperoxidase (MPO) activity in stomach tissue when compared to the control group.

CONCLUSION

It is determined that an antidepressant drug, moclobemide is a potent anti-ulcer agent. Inhibition of toxic oxidant radicals and activation of antioxidant mechanisms play a role in its anti-ulcer effect mechanisms.

Antinociceptive, anti-inflammatory and gastroprotective effects of a hydroalcoholic extract from the leaves of Eugenia punicifolia (Kunth) DC. in rodents

ETHNOPHARMACOLOGICAL RELEVANCE

An ethnopharmacological survey indicated that leaves from Eugenia punicifolia (Kunth) DC. (Myrtaceae) are popularly used as a natural therapeutic agent to treat pain and inflammation.

AIM OF THE STUDY

The overall objective of the present study was to evaluate the antinociceptive, anti-inflammatory and gastroprotective activities of a hydroalcoholic extract of leaves from Eugenia punicifolia (HEEP) in rodents.

MATERIAL AND METHODS

The antinociceptive effects of HEEP were evaluated in mice after oral administration in chemical (formalin and glutamate) and thermal (hot-plate) tests. We evaluated the involvement of the glutamatergic, opioidergic and nitrergic pathways in the antinociception of HEEP and the effect of HEEP on the inhibition of p38α MAPK. The anti-inflammatory effect of HEEP was evaluated in mice and rats using xylene-induced ear edema and carrageenan-induced paw edema, respectively. Furthermore, the gastroprotective effect of HEEP was evaluated in rats with acute gastric lesions induced by ethanol or indomethacin. Finally, we performed a phytochemical analysis of HEEP.

RESULTS

The oral administration of HEEP (125, 250 and 500mg/kg, p.o.) significantly inhibited the neurogenic and inflammatory phases of formalin-induced licking, and HEEP (250mg/kg, p.o.) also significantly inhibited the nociception caused by glutamate. The antinociceptive effects of HEEP were significantly reversed by l-arginine (500mg/kg, i.p.) but not by naloxone (1mg/kg, i.p.) in the formalin test. HEEP did not affect animal motor performance in the rotarod model. In addition, HEEP also increased the paw withdraw latency in the hot-plate test. HEEP significantly inhibited ear edema induced by xylene (64%) and paw edema induced by carrageenan (50%) compared to the control group. Furthermore, HEEP (3-30mg/mL) also inhibited the phosphorylation of p38α MAPK by approximately 90%. In addition, HEEP (125, 250 and 500mg/kg, p.o.) protected the rats against ethanol (88.4-99.8%) and indomethacin (53-72.3%) and increased the mucus levels of the gastric mucosa without producing an antisecretory effect. The phytochemical profile of HEEP obtained using HPLC-PDA showed secondary metabolites already reported for the genus, mostly flavonoids, gallotannins and proanthocyanidins.

CONCLUSIONS

These data show for the first time that HEEP has significant antinociceptive and anti-inflammatory effects, which appear to be related to the inhibition of the glutamatergic system, the synthesis of nitric oxide and the inhibition of the phosphorylation of p38α MAPK. HEEP also has interesting gastroprotective effects related to the maintenance of protective factors, such as mucus production. These results support the use of Eugenia punicifolia in popular medicine and demonstrate that this plant has therapeutic potential for the development of phytomedicines with antinociceptive, anti-inflammatory and gastroprotective properties.

Brain neuropeptides in gastric mucosal protection

The centrally induced gastroprotective effect of neuropeptides has been intensively studied. Besides many similarities, however, differences can also be observed in their gastroprotective actions. The gastroprotective dose-response curve proved to be either sigmoid, or bell-shaped. Additional gastrointestinal effects of neuropeptides can contribute to their mucosal protective effect. Part of the neuropeptides induces gastroprotection by peripheral administration as well. Besides vagal nerve the sympathetic nervous system may also be involved in conveying the central effect to the periphery. Better understanding of the complex mechanism of the maintenance of gastric mucosal integrity may result in the development of new strategy to enhance gastric mucosal resistance against injury.

Hymenaea stigonocarpa Mart. ex Hayne: a Brazilian medicinal plant with gastric and duodenal anti-ulcer and antidiarrheal effects in experimental rodent models

ETHNOPHARMACOLOGICAL RELEVANCE

Hymenaea stigonocarpa Mart. ex Hayne (Fabaceae) is a medicinal species commonly found in the Brazilian savannah. The stem bark of this medicinal plant, popularly known as "jatobá-do-cerrado", is widely used in tea form to treat gastric pain, ulcers, diarrhoea and inflammation, whereas its fruits pulp is edible.

AIM OF THE STUDY

The aim of this study was to investigate the antidiarrheal and anti-ulcer effects of a methanolic extract derived from the stem bark (MHs) and diet with fruit pulp of H. stigonocarpa.

MATERIALS AND METHODS

The antidiarrheal action of MHs was measured against the intestinal motility and diarrhoea induced by castor oil in mice. The preventive action of MHs (50, 100, 150 and 200mg/Kg, by oral route (p.o.)) against peptic ulcers was evaluated in experimental rodent models challenged with absolute ethanol, non-steroidal anti-inflammatory drugs (NSAIDs), ischemia-reperfusion (I/R) (200mg/Kg, p.o.) and cysteamine (200mg/Kg, p.o.). The main anti-ulcer mechanisms of action of MHs were analysed as follows: evaluation of the gastric juice parameters, assessment of mucus adherence to the gastric wall, determination of the role of nitric oxide (NO) and sulfhydryl compounds (SH), glutathione (GSH) levels and myeloperoxidase (MPO) activity. The healing effects from MHs (200mg/Kg) and diet with fruit pulp (10%) against gastric and duodenal ulcers induced by acetic acid were also evaluated by treating rats over 7 or 14 consecutive days of treatment.

RESULTS

The phytochemical profile of MHs and fruit pulp indicated the presence of phenolic compounds (mainly flavonoids and condensed tannins). MHs (200mg/Kg, p.o.) displayed an antidiarrheal effect and were able to protect gastric mucosa against absolute ethanol (68% protection) and also against the injurious effect of NSAIDs (86% protection) when compared to the group treated with vehicle. These results were accompanied by the prevention of GSH depletion and an inhibition of MPO activity when compared to animals treated with vehicle (P<0.05). MHs markedly protected duodenal mucosa against injuries caused by cysteamine (98%) and also against I/R induced gastric ulceration (80%) when compared to the group treated with vehicle. Furthermore, MHs also prevented the GSH depletion of gastric mucosa relative to the control group treated with vehicle. NO appeared to be involved in this gastroprotective effect. MHs and diet with fruit pulp clearly demonstrated gastric healing actions after treatment for 7 (MHs - 53% inhibition) or 14 days (MHs - 60% inhibition and fruit pulp - 61% inhibition). Treatment with diet with fruit pulp for 7 days demonstrates a significant duodenal healing effect (71% inhibition) without any signs of toxicity.

CONCLUSIONS

MHs clearly demonstrate antidiarrheal, gastroprotective and cicatrising effects in experimental gastric and duodenal ulcers, and the diet with fruit pulp displays duodenal healing effects. The observed effects may be associated with the antioxidant effect, which may be due the presence of condensed tannins and flavonoids in the bark and fruit of H. stigonocarpa.

Brainstem neuropeptides and vagal protection of the gastric mucosal against injury: role of prostaglandins, nitric oxide and calcitonin-gene related peptide in capsaicin afferents

Earlier experimental studies indicated that the integrity of vagal pathway was required to confer gastric protection against damaging agents. Several peptides located in the brainstem initially identified to influence vagal outflow to the stomach, as assessed by electrophysiological approach or by vagal dependent alterations of gastric secretory and motor function, were investigated for their influence in the vagal regulation of the resistance of the gastric mucosa to injury. Thyrotropin releasing hormone (TRH), or its stable TRH analog, RX-77368, injected at low doses into the cisterna magna or the dorsal motor nucleus (DMN) was the first peptide reported to protect the gastric mucosa against ethanol injury through stimulation of vagal cholinergic pathways, inducing the release of gastric prostaglandins/nitric oxide (NO) and the recruitment of efferent function of capsaicin sensitive afferent fibers containing calcitonin-gene related peptide (CGRP). Activation of endogenous TRH-TRH1 receptor signaling located in the brainstem plays a role in adaptive gastric protection against damaging agents. Since then, an expanding number of peptides, namely peptide YY, CGRP, adrenomedullin, amylin, glugacon-like peptide, opioid peptides acting on µ, δ1 or δ2 receptors, nocicpetin, nocistatin, ghrelin, leptin and TLQP-21, a peptide derived from VGF prohormone, have been reported to act in the brainstem to afford gastric protection against ethanol injury largely through similar peripheral effectors mechanisms than TRH. Therefore gastric prostaglandins and CGRP/NO pathways represent a common final mechanism through which brain peptides confer vagally mediated gastroprotection against injury. A better understanding of brain circuitries through which these peptides are released will provide new strategies to recruit integrated and multifaceted gastroprotective mechanisms.

Gastric anti-ulcerative and anti-inflammatory activity of metyrosine in rats

In this study, the anti-inflammatory and anti-ulcerative effects of metyrosine, a selective tyrosine hydroxylase enzyme inhibitor, were investigated in rats. For ulcer experiments, indomethacin-induced gastric ulcer tests and ethanol-induced gastric ulcer tests were used. For these experiments, rats were fasted for 24 h. Different doses of metyrosine and 25 mg/kg doses of ranitidine were administered to rats, followed by indomethacin at 25 mg/kg for the indomethacin-induced ulcer test, or 50% ethanol for the ethanol-induced test. Results have shown that at all of the doses used (50, 100 and 200 mg/kg), metyrosine had significant anti-ulcerative effects in both indomethacin and ethanol-induced ulcer tests. Metyrosine doses of 100 and 200 mg/kg (especially the 200 mg/kg dose) also inhibited carrageenan-induced paw inflammation even more effectively than indomethacin. In addition, to characterize the anti-inflammatory mechanism of metyrosine we investigated its effects on cyclooxygenase (COX) activity in inflammatory tissue (rat paw). The results showed that all doses of metyrosine significantly inhibited high COX-2 activity. The degree of COX-2 inhibition correlated with the increase in anti-inflammatory activity. In conclusion, we found that metyrosine has more anti-inflammatory effects than indomethacin and that these effects can be attributed to the selective inhibition of COX-2 enzymes by metyrosine. We also found that adrenalin levels are reduced upon metyrosine treatment, which may be the cause of the observed gastro-protective effects of this compound.

Adaptation of rat gastric tissue against indomethacin toxicity

Indomethacin is used in the treatment of inflammatory diseases. But the drug toxicity limits its usage. This study investigated whether adaptation occurred after various dosages of repeated (chronic) indomethacin in rats to the gastro-toxic effects of indomethacin. It also examined whether the adaptation was related to oxidant-antioxidant mechanisms and oxidative DNA damage in gastric tissue. To illuminate the adaptation mechanism in the gastric tissue of rats given various dosages of chronic indomethacin, the levels of oxidants and antioxidants (GSH, MDA, NO, SOD and MPO), activities of COX-1 and COX-2 enzymes and oxidative DNA damage (8-OHd Gua/10(5) Gua) were measured. Results were compared to 25-mg/kg single-dose indomethacin group, and the role of oxidant and antioxidant parameters and oxidative DNA damage in the adaptation mechanism was evaluated. The average ulcer areas of gastric tissue of the 0.5-, 1-, 2-, 3-, 4-, and 5-mg/kg dosages of chronic indomethacin given to rats were 19.5+/-3.7, 12.5+/-3.3, 10+/-5.2, 4.5+/-3.6, 8.6+/-2.4, and 9.5+/-2.1mm(2), respectively. This rate was measured as 21.3+/-2.6mm(2) in the single-dose indomethacin group. Consequently, after various dosages of repeated (chronic) indomethacin administration in rats, it was observed that a clear adaptation developed against gastric damage and that gastric damage was reduced. The best adaptation was observed in the gastric tissue of the 3-mg/kg chronic indomethacin group. In parallel with the damage reduction, the oxidant parameters (MDA and MPO) and oxidative DNA damage (8-OHd Gua/10(5) Gua) were reduced, and the antioxidant parameters (GSH, NO and SOD) were increased. There is no relation between COX enzymes and adaptation mechanism. This circumstance shows that not COX-1 and COX-2 enzymes, oxidant and antioxidant parameters may play a role in the adaptation mechanism.

Protective effect of mirtazapine on indomethacin-induced ulcer in rats and its relationship with oxidant and antioxidant parameters

Even though there are many drugs for the treatment of gastric ulcers, these drugs sometimes cannot succeed. Since the 1950s, antidepressant drugs have been used for several non-psychiatric indications. A lot of antidepressant drugs have been shown experimentally to produce antiulcer activity in various ulcer models. This study aimed to investigate the antiulcer effects of mirtazapine and to determine its relationship with antioxidant mechanisms. The antiulcer activities of 15, 30, and 60 mg/kg mirtazapine have been investigated on indomethacin-induced ulcers in rats, and the results have been compared with that of the control group. Mirtazapine decreased the indomethacin-induced ulcers significantly at all doses used. Mirtazapine significantly increased the glutathione (GSH) level, which decreased in the control group given only indomethacin. All doses of mirtazapine significantly decreased the catalase (CAT) level in stomach tissue compared to the control. Additionally, all doses of mirtazapine reversed the decrease in the superoxide dismutase (SOD) level in the stomach tissue of control rats. And finally, all doses of mirtazapine decreased malondialdehyde (MDA) and myeloperoxidase (MPO) levels significantly compared to the control. In conclusion, the activation of enzymatic and non-enzymatic antioxidant mechanisms and the inhibition of some toxic oxidant mechanisms play a role in the antiulcer effect mechanism of mirtazapine. This new indication of mirtazapine will make it the first-choice drug in depressive patients with gastric ulcers.

Gastroprotective and antioxidant effects of opipramol on indomethacin-induced ulcers in rats

Tricyclic antidepressants are particularly useful in the treatment of endogenous depression. Since the 1950s, tricyclic antidepressants (TCAs) have also been used for the treatment of gastric ulcer disease. Many TCAs have been evaluated for their antiulcer effects, but there are presently no data in the literature specifically concerning the antidepressant opipramol. This study aimed to investigate the antiulcer effects of opipramol and to determine its potential relationship with oxidant and antioxidant systems. The antiulcer activities of 25, 50 and 100 mg/kg opipramol have been investigated on indomethacin-induced ulcers in rats. Compared with a control group (indomethacin alone), opipramol decreased indomethacin-induced ulcers significantly at all doses used (52%, 71% and 76% respectively). Opipramol also significantly increased the glutathione (GSH), superoxide dismutase (SOD) and nitric oxide (NO) levels in the stomach tissue, all of which were decreased in the control group given only indomethacin. All doses of opipramol also significantly decreased myeloperoxidase (MPO), malondialdehyde (MDA) and catalase (CAT) levels in stomach tissue compared to the control. In conclusion, the activation of enzymatic and non-enzymatic antioxidant mechanisms, as well as the inhibition of some toxic oxidant mechanisms, appear to play a role in the antiulcer effect of opipramol. This new indication for opipramol prompts a rethinking about the possible clinical application of opipramol, particularly for peptic ulcer patients also presenting depression.

Antiulcer activity of fluvoxamine in rats and its effect on oxidant and antioxidant parameters in stomach tissue

Background

Although many drugs are available for the treatment of gastric ulcers, often these drugs are ineffective. Many antidepressant drugs have been shown to have antiulcer activity in various models of experimental ulcer. One such drug, the antidepressant mirtazapine, has been reported to have an antiulcer effect that involves an increase in antioxidant, and a decrease in oxidant, parameters. To date, however, there is no information available regarding the antiulcer activity for a similar antidepressant, fluvoxamine. This study aimed to investigate the antiulcer effects of fluvoxamine and to determine its relationship with antioxidants.

Methods

Groups of rats fasted for 24 h received fluvoxamine (25, 50, 100 and 200 mg/kg), ranitidine (50 mg/kg) or distilled water by oral gavage. Indomethacin (25 mg/kg) was orally administered to the rats as an ulcerative agent. Six hours after ulcer induction, the stomachs of the rats were excised and an ulcer index determined. Separate groups of rats were treated with the same doses of fluvoxamine and ranitidine, but not with indomethacin, to test effects of these drugs alone on biochemical parameters. The stomachs were evaluated biochemically to determine oxidant and antioxidant parameters. We used one-way ANOVA and least significant difference (LSD) options for data analysis.

Results

The 25, 50, 100 and 200 mg/kg doses of fluvoxamine exerted antiulcer effects of 48.5, 67.5, 82.1 and 96.1%, respectively, compared to the control rat group. Ranitidine showed an 86.5% antiulcer effect. No differences were observed in the absence of indomethacin treatment for any dose of fluvoxamine or for ranitidine. The levels of antioxidant parameters, total glutathione and nitric oxide, were increased in all fluvoxamine groups and in the ranitidine group when compared with the indomethacin-only group. In addition, fluvoxamine and ranitidine decreased the levels of the oxidant parameters, myeloperoxidase and malondialdeyhyde, in the stomach tissues of the rats when compared to indomethacin group.

Conclusion

We conclude that fluvoxamine has antiulcer effects, and that these occur by a mechanism that involves activation of antioxidant parameters and inhibition of some toxic oxidant parameters.

Role of alpha-2 adrenergic receptors in anti-ulcer effect mechanism of estrogen and luteinising hormone on rats

OBJECTIVE

To evaluate anti-ulcer effect of estrogen and luteinising hormone (LH) on indomethacin-induced ulcer model in female rats.

STUDY DESIGN

Ovariectomy in healthy adult famale rats. Acute administration of estradiol to ovariectomised rats. Acute administration of LH to intact rats. Combined administration of tamoxifen with estradiol or LH to intact rats. Combined administration of yohimbin with estradiol or LH to intact rats. Combined administration of piperoxan with estradiol or LH to intact rats. Indomethacin administration to all rats.

RESULTS

Results have shown that LH exerted anti-ulcer activity at all doses we used but estradiol at 5 and 10 mg/kg. In rats administered yohimbine and piperoxan estradiol and LH could not prevent indomethacin-induced ulcers. In rats administered tamoxifen, estradiol and LH could prevent indomethacin-induced ulcers.

CONCLUSIONS

LH is a very potent endogen anti-ulcer factor, and the anti-ulcerative activities of estrogen and LH are mediated via alpha-2 adrenergic receptors, but not es receptors. The resistance of gastric mucosa to aggressive factors may decrease as a result of LH inhibition when estrogen is secreted chronically in the human body.

Comparative study on the gastroprotective potential of some antidepressants in indomethacin-induced ulcer in rats

Clinical studies have shown that anxiolytic and antidepressant drug therapy benefits patients with ulcers. Many antidepressant drugs have been shown experimentally to produce antiulcer activity in various ulcer models. This study investigated the antiulcer activities of tianeptine, trazodone, and venlafaxine on indomethacin-induced ulcers in rats; and evaluated tianeptine's effects on oxidant and antioxidant parameters in rat stomach tissue. The results show that trazodone and venlafaxine did not prevent indomethacin-induced ulcers. Tianeptine, however, decreased indomethacin-induced ulcers significantly at all doses used (6, 12, and 25 mg/kg). Famotidine, an H(2) receptor blocker, showed the highest antiulcer activity. Tianeptine significantly prevented the decrease in glutathione (GSH) content that occurred in the indomethacin-only group's damaged stomach tissues. All doses of tianeptine, but especially the 25 mg/kg dose, significantly decreased catalase (CAT) activity in stomach tissue, compared to the control. All doses of tianeptine eliminated the decrease in superoxide dismutase (SOD) activity in the stomach tissue of rats given indomethacin. Although all doses of tianeptine significantly decreased the malondialdehyde (MDA) content, all doses of tianeptine, except 6 mg/kg, decreased myeloperoxidase (MPO) activities significantly compared to the control. Our results indicate that activating enzymatic and non-enzymatic antioxidant mechanisms and inhibiting some toxic oxidant mechanisms play a role in tianeptine's antiulcer effect mechanism.

Gastroprotective and antioxidant effects of amiodarone on indomethacin-induced gastric ulcers in rats

Reactive oxygen species (ROS) have been implicated in the etiology of indomethacin-induced gastric mucosal damage. This study investigated amiodarone's protective effects against oxidative gastric mucosal damage induced by indomethacin. Amiodarone is a widely used antiarrhythmic agent. We have investigated alterations in the glutathione level, and the activities of antioxidative enzymes [superoxide dismutase, catalase, glutathione s-transferase glutathione reductase and myeloperoxidase], as markers for ulceration process following oral administration of amiodarone and ranitidine in rats with indomethacin-induced ulcers. In the present study we found that 1) amiodarone, lansoprazole and ranitidine reduced the development of indomethacin-induced gastric damages, at a greater magnitude for amiodarone and lansoprazole than for ranitidine; 2) amiodarone and ranitidine alleviated increases in the activities of catalase and glutathione s-transferase enzymes resulting from ulcers; 3) amiodarone and ranitidine ameliorated depressions in the glutathione level and the activities of superoxide dismutase and glutathione reductase enzymes caused by indomethacin administration; and 4) all doses of amiodarone amplified the myeloperoxidase activity resulting from indomethacin-induced gastric ulcers. The results indicate that the gastroprotective activity of amiodarone, which may be linked to its intrinsic antioxidant properties, cannot be attributed to its effect on myeloperoxidase activity.

Gastroprotective and anti-oxidative properties of ascorbic acid on indomethacin-induced gastric injuries in rats

Reactive oxygen species (ROS) have been implicated in the etiology of indomethacin-induced gastric mucosal damage. This study investigated ascorbic acid (vitamin C)'s protective effects against oxidative gastric mucosal damage induced by indomethacin. Ascorbic acid is a powerful antioxidant because it can donate a hydrogen atom and form a relatively stable ascorbyl free radical. We have investigated alterations in the levels of myeloperoxidase, antioxidant system enzymes (glutathione S-transferase, superoxide dismutase, glutathione reductase, catalase, glutathione peroxidase), lipid peroxidation and glutathione, as markers for ulceration process following oral administration of ascorbic acid, famotidine, lansoprazole, and ranitidine in rats with indomethacin-induced ulcers. In the present study, we found that (1) ascorbic acid, famotidine, lansoprazole and ranitidine reduced the development of indomethacin-induced gastric damages; (2) the administration of indomethacin caused a significant decrease in the levels of superoxide dismutase, glutathione peroxidase, glutathione S-transferase and glutathione, and an increase in the lipid peroxidation level; (3) the administration of ascorbic acid reversed the trend, inducing a significant increase of these enzymes' levels and a reduction in lipid peroxidation level in tissues; and (4) catalase, glutathione reductase and myeloperoxidase activities, increased by indomethacin, were found to be lower in the ascorbic acid, famotidine, lansoprazole and ranitidine-treated groups. The results indicate that the gastroprotective properties of ascorbic acid could be related to its positive effects on the antioxidant system and myeloperoxidase activity in indomethacin-induced gastric ulcers in rats.

Gastroprotective and antioxidant effects of montelukast on indomethacin-induced gastric ulcer in rats

Montelukast, a selective reversible cysteinyl leukotriene D(4)-receptor (LTD(4) receptor) antagonist, is used in the treatment of asthma. We have investigated alterations in the glutathione (GSH) and activity levels of antioxidative enzymes [superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), and glutathione reductase (GR)] and myeloperoxidase (MPO), as markers of the ulceration process following oral administration of montelukast, lansoprazole, famotidine, and ranitidine, respectively, in rats with indomethacin-induced ulcers. In the present study, we found that 1) montelukast, lansoprazole, famotidine, and ranitidine all reduced the development of indomethacin-induced gastric damage, with this reduction occurring at a greater magnitude for montelukast, famotidine, and lansoprazole than for ranitidine; 2) montelukast and ranitidine both alleviated increases in the activity levels of CAT and GST enzymes resulting from gastric injury; 3) montelukast and ranitidine both ameliorated depressions in the GSH and activity levels of SOD and GR enzymes caused by indomethacin administration; and 4) all doses of montelukast, lansoprazole, and ranitidine decreased amplification of MPO activity resulting from induced gastric injuries. These results suggest that the gastroprotective effects of montelukast on indomethacin-induced ulcerations can be attributed to its ameliorating effect on oxidative damage and MPO activity.

Amylin causes anorexigenic effects via the hypothalamus and brain stem in chicks

This study was conducted to determine the effects of amylin on appetite-related processes in chicks. Broiler chicks were centrally and peripherally injected with amylin, and feed and water intake were quantified. Feed intake was reduced after both central and peripheral amylin, but water intake was not affected. To determine if the hypothalamus and brainstem were involved in the anorexigenic effect, chicks were centrally and peripherally injected with amylin, and c-Fos immunoreactivity was quantified in the lateral hypothalamus (LH), ventromedial hypothalamus (VMH), area postrema (AP) and the nucleus of the solitary tract (NTS). Amylin decreased c-Fos immunoreactivity in the LH, did not affect the VMH, and increased c-Fos immunoreactivity in the AP and NTS. To determine if alimentary transit time was affected, chicks received central amylin and were gavaged with chicken feed slurry containing a visible marker. Amylin-treated chicks had increased alimentary canal transit time. Chicks also responded to central amylin with increased anxiety-related behaviors and increased plasma corticosterone concentration. These results demonstrate that amylin affects feeding, alimentary canal transit, and behavior through hypothalamic and brainstem mechanisms in chicks.

Characterisation of alpha2-adrenoceptor subtypes involved in gastric emptying, gastric motility and gastric mucosal defence

The effect of clonidine on ethanol-induced gastric mucosal damage, gastric emptying and gastric motility was compared. The clonidine-induced gastroprotective effect (0.03-0.09 micromol/kg, s.c.) was antagonised by yohimbine (5 micromol/kg, s.c.), prazosin (0.23 micromol/kg; alpha2B-adrenoceptor antagonist) and naloxone (1.3 micromol/kg, s.c.). Clonidine also inhibited the gastric emptying of liquid meal (0.75-3.75 micromol/kg, s.c.) and gastric motor activity (0.75 micromol/kg, i.v.) stimulated by 2-deoxy-D-glucose (300 mg/kg, i.v.). Inhibition of gastric emptying and motility was reversed by yohimbine (5 and 10 micromol/kg, s.c., respectively), but not by prazosin (0.23 micromol/kg, s.c.) or naloxone (1.3 micromol/kg, s.c.). Oxymetazoline-an alpha2A-adrenoceptor agonist-inhibited both gastric emptying (0.67-6.8 micromol/kg, s.c.) and motility (0.185-3.4 micromol/kg, i.v.), whereas it failed to affect gastric mucosal lesions. The results indicate that in contrast to the gastroprotective effect, which is mediated by alpha2B-adrenoceptor subtype, alpha2A-adrenoceptor subtype may be responsible for inhibition of gastric emptying and motility. However, the site of action (central, peripheral, both) remains to be established.

Investigation of the mechanisms involved in the central effects of glucagon-like peptide-1 on ethanol-induced gastric mucosal lesions

The aim of this study was to investigate the effects of intracerebroventricularly injected glucagon-like peptide-1 (GLP-1) on ethanol-induced gastric mucosal damage and to elucidate the mechanisms involved. Absolute ethanol was administered through an orogastric cannula 5 min before GLP-1 (1 microg/10 microl) injection. One hour later, the rats were decapitated, their stomachs were removed and scored for mucosal damage. GLP-1 inhibited the ethanol-induced gastric mucosal damage by 92%. Centrally injected atropine sulphate, a muscarinic receptor antagonist (5 microg/10 microl), prevented the gastroprotective effect of GLP-1, while mecamylamine, a nicotinic receptor antagonist (25 microg/10 microl), was ineffective. Peripherally injected atropine methyl nitrate (1 mg/kg) did not change the effect of GLP-1, but mecamylamine (5 mg/kg) blocked it. Cysteamine, a somatostatin depletor (280 mg/kg, s.c.), did not affect the protective activity of GLP-1, while inhibition of nitric oxide (NO) synthesis by L-NAME (3 mg/kg, i.v.) significantly abolished the protective effect of GLP-1 on ethanol-induced gastric mucosal lesions. We conclude that central muscarinic and peripheral nicotinic cholinergic receptors and NO, but not somatostatin, contribute to the protective effect of intracerebroventricularly injected GLP-1 on ethanol-induced gastric mucosal damage.

Effects of water extract of Usnea longissima on antioxidant enzyme activity and mucosal damage caused by indomethacin in rats

In this study, the antiulcerogenic effect of a water extract obtained from the lichen species Usnea longissima was investigated using indomethacin-induced ulcer models in rats. Experimental groups consisted of six rats. Antiulcerogenic activities of 50, 100 and 200mg/kg body wt. doses of the water extract were determined by comparing the negative (treated only with indomethacin) and positive (ranitidine) control groups. Although all doses of the water extract of U. longissima showed significant antiulcerogenic activity as compared to negative control groups, the highest activity was observed with 100 mg/kg body wt. doses (79.8%). The water extract of U. longissima showed moderate antioxidant activity when compared with trolox and ascorbic acids used as positive antioxidants. In addition, the activities of antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST)] were determined in the stomach tissues of rats and compared with those of the negative and positive control groups to expose the effects of antioxidant enzymes on antiulcerogenic activity. SOD and GST enzymes activities in indomethacin-administrated tissues were reduced significantly by indomethacin in comparison to control groups. These enzymes were activated, however, by the water extracts of U. longissima. In contrast to SOD and GST activities, CAT activity was increased by indomethacin and reduced by all doses of U. longissima and ranitidine. The present results indicate that the water extract of U. longissima has a protective effect in indomethacin-induced ulcers, which can be attributed to its antioxidant potential.

The protective effect of vitamin C, vitamin E and selenium combination therapy on ethanol-induced duodenal mucosal injury

In this study, the effect of a combination of vitamin C, vitamin E and selenium on ethanol-induced duodenal mucosal damage in rats was investigated morphologically and biochemically. The duodenal mucosal injury was produced by oral administration of 1 mL of absolute ethanol to each rat. Animals received vitamin C (250 mg/ kg), vitamin E (250 mg/kg) and selenium (0.5 mg/kg) for 3 days and absolute ethanol 1 hour after last antioxidant administration and were sacrificed 1 hour after absolute ethanol. Extreme degeneration in intestinal mucosa of rats given ethanol was observed morphologically. In addition, an increase in neuronal nitric oxide synthase immunoreactive areas was observed in the rats of the group given ethanol. On the other hand, a normal morphological appearance and a decrease in neuronal nitric oxide synthase immunoreactive areas were detected in the rats given ethanol+vitamin C+vitamin E+ selenium. In the group to which ethanol was administered, an increase in serum cholesterol and a decrease in serum albumin levels were determined. On the other hand, in the group to which ethanol+vitamin C+vitamin E+selenium were administered, serum cholesterol value decreased, and the serum albumin level increased. As a result, we can say that the combination of vitamin C, vitamin E and selenium has a protective effect on ethanol-induced duodenal mucosal injury.

Effects on digestive secretions

Rat amylin subcutaneously injected into rats dose-dependently inhibits pentagastrin-stimulated gastric acid secretion and protects the stomach from ethanol-induced gastritis. The ED50s for these actions (0.050 and 0.036 microg, respectively) are the lowest for any dose-dependent effect of amylin thus far described, and their similar potencies are consistent with a mechanistic (causal) association. At higher amylin doses, inhibition of gastric acid secretion was almost complete (93.4%). Gastric injury (measured by a subjective analog scale) was inhibited by up to 67%. The observation that effective doses of amylin result in plasma concentrations of 7-10 pM (i.e., within the reported range; Pieber et al., 1994) supports the interpretation that inhibition of gastric acid secretion and maintenance of gastric mucosal integrity are physiological actions of endogenous amylin. The pharmacology of these responses fits with one mediated via amylin-like receptors. Rat amylin inhibited CCK-stimulated secretion of pancreatic enzymes,amylase, and lipase by up to approximately 60% without having significant effect in the absence of CCK. ED50s for the effect were in the 0.1-0.2 microg range, calculated to produce plasma amylin excursions within the physiological range. Effects of informative ligands are consistent with the concept of amylin receptor mediation. Amylin was effective in ameliorating the severity of pancreatitis in a rodent model. The amylin analog pramlintide inhibited gallbladder emptying in mice as measured by total weight of acutely excised gallbladders. Amylin inhibition of gastric acid secretion, pancreatic enzyme secretion, and bile secretion likely represents part of an orchestrated control of nutrient appearance. Modulation of digestive function fits with a general role of amylin in regulating nutrient uptake. Rate of ingestion, rate of release from the stomach, and rate of digestion of various food groups appear to be under coordinate control.

Amylin and the integrated control of nutrient influx

The most potent actions of amylin that occur at physiological plasma concentrations include inhibition of food intake, gastric emptying, acid and digestive enzyme secretion, and glucagon secretion. These actions share a common outcome; they each help regulate the rate at which nutrients (including glucose) appear in the blood (Ra). Amylin physiologically orchestrates, via several parallel processes, the rate of entry of nutrient into the circulation, as shown schematically in Fig. 1. In this way, amylin's function may be viewed as complementary to that of insulin (secreted from the same pancreatic beta-cells), which orchestrates the exit of nutrient from blood and its storage in peripheral tissues. The following discussion addresses the emerging picture that, although amylin is co-secreted with an endocrine hormone from endocrine tissue (the pancreatic islets), the target for its most potent and physiologically relevant effects appears to be the central nervous system. Amylin thus may be primarily regarded as a neuroendocrine hormone (Young et al., 2000).

Effects of centrally injected GLP-1 in various experimental models of gastric mucosal damage

Glucagon-like peptide-1 (GLP-1) is accepted to be a peptide involved in the central regulation of gastrointestinal function, but its potential gastroprotective effect is not clear. The aim of this study was to investigate whether intracerebroventricularly injected GLP-1 has protective effects on gastric mucosal lesions induced by several models, and if yes, whether these effects are due to the gastric antisecretory effect of the peptide. GLP-1 which was injected in three different doses (1, 10, 100 ng/10 microl; i.c.v.) to conscious rats prevented the mucosal lesions induced by reserpine and ethanol, but did not prevent the gastric mucosal lesions induced by pyloric ligation. In addition, 1 ng/10 microl dose of centrally injected GLP-1 inhibited gastric acid secretion in pylorus-ligated rats. As a result, we conclude that intracerebroventricularly injected GLP-1 may play a role in the prevention of gastric mucosal lesions induced by certain experimental models and this gastroprotective effect may be independent from its antisecretory effect.

Antiulcer effects of amylin: a review

Amylin belongs to the calcitonin peptide family. Amylin is a peptide synthesized not only in the beta cells of pancreatic islets, but in small quantities also in other organs like in the intestinal and gastric mucosa, lungs and central nervous system. It is located in the same secretory granules as insulin. Amylin participates in the maintenance of glucose and calcium homeostasis. It also inhibits food intake and decreases body weight. Furthermore, amylin inhibits gastric acid secretion. It protects the gastric mucosa in ulcer models like stress, vagal stimulation, ethanol, acetic acid, reserpine and serotonine administration and pylorus ligation. This protective antiulcer is seen not only at pharmacological but also at near-physiological doses-0.5mkg/kg. Moreover amylin also exerts curative properties in the acetic acid and indomethacin ulcer models. Amylin decreases the aggressive factors like acid-pepsin secretion, increases mast cell stability and increases protective mechanisms like bicarbonate gastric secretion, dilates blood vessels, and it increases lymphatic mesenteric activity. Amylin seems to be a powerful protector of gastric mucosa in animals by increasing the stability of gastric mucosa. Further research remains, however, to be done.

Antioxidant effect of T-type calcium channel blockers in gastric injury

It is known that calcium ion has an important role in the cellular function. For this reason, calcium channel blockers may have a protective action against gastric injury which is induced by various stimuli. In this study, the influence of mibefradil on ethanol-induced gastric injury was investigated in rats. Mibefradil was given at a dose 50 mg/kg intraperitoneally 30 min before administration of 1 ml absolute ethanol given by gavage. We compared this effect of mibefradil with that of omeprazol. Ethanol-induced mucosal damage was evaluated using three different approaches: analysis of biochemical parameters and pathologic and macroscopic investigation. It was found that pretreatment with mibefradil significantly reduced ethanol-induced macroscopic, pathologic, and biochemical changes in the gastric mucosa. In conclusion, it is speculated that this findings may prove important in the development of new and improved therapies for the treatment and prevention of gastric ulcers in humans.

Melatonin prevents ethanol-induced gastric mucosal damage possibly due to its antioxidant effect

Oxygen radical release has been proposed as a pathogenic factor of the ethanol-induced acute gastric injury. Melatonin, a pineal hormone, is known to scavenge oxygen free radicals. We investigated whether parenteral administration of melatonin prevented ethanol-induced macroscopic damage, polymorphonuclear (PMN) leukocyte infiltration, depletion of total glutathione (tGSH) concentration, and glutathione reductase (GSSG-Rd) activity in the rat gastric mucosa. We compared the effects of melatonin with those of omeprazole. Ethanol-induced mucosal damage was evaluated using three different parameters: gastric total glutathione (tGSH) concentration and glutathione reductase (GSSG-Rd) activity, the number of PMN leukocytes, and macroscopic investigation. Gatric tGSH concentration and GSSG-Rd activity decreased and the number of PMNs increased after ethanol administration. It was found that pretreatment with melatonin increased both tGSH concentration and GSSG-Rd activity. Melatonin also reduced ethanol-induced PMN infiltration in the stomach. Ethanol administration damaged the entire gastric mucosa. Melatonin significantly decreased the extent of ethanol-induced macroscopic injury. In conclusion, these findings support the conclusion that the protection conferred by melatonin in gastric ulcer is presumably due to its antioxidant activity.

A comparative study on the activity of lansoprazole, omeprazole and PD-136450 on acidified ethanol- and indomethacin-induced gastric lesions in the rat

1. The proton pump inhibitors lansoprazole (LP) and omeprazole (OP) and the cholecystokinin (CCK)-receptor antagonist PD-136450 (PD) provide a broad spectrum of activities in their ability to inhibit gastric acid secretion and protect the stomach against ulcerogens. In the present study, we investigated the protective effects of these compounds against gastric ulcers induced by acidified ethanol (AE) and indomethacin. 2. Both AE (60% ethanol in 150 mmol/L HCl, 1 mL/rat) and indomethacin (30 mg/kg) produced gastric haemorrhagic lesions in the rat 1 and 6 h after oral administration, respectively. 3. The gastric mucosal protective effects of LP (1-20 mg/kg), OP (0.5-10 mg/kg) and PD (1-20 mg/kg), administered either orally or subcutaneously (s.c.) 30 min before the administration of AE or indomethacin, were dose dependent against both models of ulcer induction. 4. To determine whether the cytoprotective effect of LP, OP and PD (each 10 mg/kg) was mediated by endogenous prostaglandins (PG), indomethacin (10 mg/kg, s.c.) was administered 15 min before AE to inhibit prostanoids biosynthesis. Indomethacin reduced the cytoprotective effects of OP, but not LP, administered either orally or s.c. Indomethacin reduced the cytoprotective effect of PD administered orally, although the effect was much less significant than when PD was administered s.c. The results exclude the role of PG in mediating the protective effects of LP, whereas the possibility exists for PG to have a role in mediating the protective effects of OP and PD. 5. To investigate the possible involvement of endogenous nitric oxide (NO) in the cytoprotective action of LP, OP and PD, we treated rats with a selective inhibitor of NO synthesis, namely NG-nitro-L-arginine methyl ester (L-NAME; 25 mg/kg, s.c.). Administration of L-NAME 15 min prior to LP, OP or PD (each 10 mg/kg) orally or s.c. and challenge with AE or indomethacin did not significantly increase the degree of the ulcer index and L-NAME was not able to antagonize the protective effects of LP, OP and PD, thus excluding the role of NO in mediating the protective effects of these drugs. However, the effects of PD in reducing the indomethacin-induced ulcer index were less significant in the presence than the absence of L-NAME (P < 0.05 vs P < 0.001, respectively), suggesting a role for NO. 6. In conclusion, the results of the present study suggest that LP and OP are equally effective against AE- as well as indomethacin-induced gastric ulcers and were more potent than PD in protecting the stomach against ulcer formation. Lansoprazole, OP and PD bring about their cytoprotective action through the reduction of acid secretion and some other unknown mechanisms. However, OP and PD may exert their cytoprotective action through PG and NO pathways.

The effect of nimesulide on the indomethacin- and ethanol-induced gastric ulcer in rats

In the present study, we investigated the effects of nimesulide, indomethacin, naproxene, ibuprofen and diclofenac, at anti-inflammatory doses, on the rat gastric tissue (total number = 102). In addition, the effect of nimesulide at doses of 100, 300 and 500 mg kg(-1) on indomethacin-induced and ethanol-induced damage (ulcer) was examined. The potency of nimesulide was compared with that of ranitidine (at 150 mg kg(-1)). Results indicated that nimesulide did not produce any gastric damage. Additionally, it has a therapeutic effect on indomethacin- and ethanol-induced gastric lesions. Ulcer areas were measured in the rats given nonsteroidal anti-inflammatory drugs (NSAIDs). Nimesulide (at doses of 100, 300 and 500 mg kg(-1)) and ranitidine (at a dose of 150 mg kg(-1)) treated completely indomethacin-induced ulcer. The mean ulcer area was 21.9 +/- 8.9 mm(2)in the indomethacin-given control group. Nimesulide and ranitidine reduced the ethanol-induced gastric ulcer. The ulcer area was 114.3 +/- 10.3 mm(2) in the ethanol-given group and it was 4.5 +/- 4.8, 20.1 +/- 1.66, 15.16 +/- 4.05 mm(2) for nimesulide (at doses of 100, 300 and 500 mg kg(-1)), respectively, and 64.16 +/- 3.97 mm(2) for ranitidine.

The role of sensory neurons in the antiulcer effect of centrally injected amylin in rat

Central administration of amylin (2.2 microg/rat, i.c.v.) reduces (from a minimum of 67% to 83%) indomethacin (Indo, 20 mg Kg(-1), orally) induced ulcers in rats. The anti-ulcer effect of the peptide is not removed by the administration of prokinetic drugs like domperidone or neostigmine but it is reduced by 35% in rats treated with capsaicin or with the CGRP antagonist, CGRP(8-37). These data indicate that amylin gastroprotection involves capsaicin-sensitive nerve fiber leading to CGRP-dependent gastric vasodilatory effect. Additional mechanisms could involve noradrenergic alpha(2) receptors as the peptide gastroprotective activity is reduced from 67% to 20% by the alpha(2) antagonist yohimbine.

Gastroprotections of escins Ia, Ib, IIa, and IIb on ethanol-induced gastric mucosal lesions in rats

Effects of escins Ia, Ib, IIa, and IIb isolated from horse chestnuts on ethanol-induced gastric mucosal lesions and the roles of capsaicin-sensitive afferent neurons, endogenous nitric oxide (NO), sulfhydryls, prostaglandins, as well as gastric secretion and the sympathetic nervous system, were investigated in rats. Test samples were given orally to fasted rats 1 h before ethanol (1.5 ml/rat, p.o.) treatment or ligation of the pylorus. Escins Ia-IIb (10-50 mg/kg) potently inhibited ethanol-induced gastric mucosal lesions, whereas desacylescins I and II (50 mg/kg) showed no such effect. These active saponins (10 and 20 mg/kg) did not decrease the gastric secretion. The gastroprotections of escins Ia-IIb were attenuated by the pretreatment with capsaicin, N(G)-nitro-L-arginine methyl ester, and indomethacin, but not by N-ethylmaleimide. The effects of escins Ia-IIb were also attenuated in streptozotocin-induced diabetic rats, in which the activity of the sympathetic nervous system was abnormal. These results suggest that the gastroprotections of escins Ia-IIb on ethanol-induced gastric mucosal lesions are acid-independent, whereas endogenous prostaglandins, NO, capsaicin-sensitive afferent neurons, and the sympathetic nervous system participate.

Investigation on the mechanisms involved in the central protective effect of amylin on gastric ulcers in rats

1. The mechanisms involved in the protective effect of amylin (administered into the brain ventricle, i.c.v.) on gastric ulcers induced by the oral administration of ethanol 50% (EtOH, 2 ml/rat) or indomethacin (indomethacin, 20 mg kg(-1), at a dosing volume of 5 ml) were investigated in rats. 2. The possible involvement of endogenous nitric oxide (NO) in the beneficial effect of amylin against EtOH-induced ulcers was examined. The inhibitor of NO-synthesis, NG-nitro-L-arginine methyl ester (L-NAME, 70 mg kg(-1), s.c.) was injected 30 min before amylin (2.2 microg/rat, i.c.v.) followed by EtOH after a further 30 min. Rats were sacrificed 1 h after EtOH. L-NAME completely removed the protective effect of amylin. 3. The interaction between amylin and gastric nonprotein sulfhydryl groups was studied. The rats were treated with N-ethyl-maleimide (NEM, 25 mg kg(-1), s.c.) 30 min before amylin (2.2 microg/rat, i.c.v.) followed by EtOH 30 min after or by indomethacin 5 min after amylin. Rats were sacrificed 1 h or 6 h respectively after EtOH or indomethacin. NEM counteracted the protective effect of amylin against EtOH-induced ulcers but not against those provoked by indomethacin. 4. To determine whether amylin was able to promote ulcer healing, the peptide was injected 5 min after EtOH or 1 h after indomethacin. In the case of EtOH, the beneficial effect of amylin was lost whereas it was still effective on indomethacin-induced ulcers. 5. The results indicate that: the mechanisms involved in the antiulcer effects of amylin are different in these two types of gastric lesions probably because of the different etiopathology of various types of ulcers. Endogenous NO and nonprotein sulfhydryl groups are involved in the mucosal protective effects of amylin on EtOH and not on indomethacin-induced ulcers. Furthermore the effectiveness of amylin against indomethacin-induced lesions when administered after the ulcerogenic process has started suggests that amylin is involved not only in the protection but also in the healing mechanisms in this type of ulcer.

Amylin and gastrointestinal activity

1. Amylin is a new pancreatic islet peptide with a role in the maintenance of glucose homeostasis. 2. Amylin is predominantly present in the beta cells of the pancreas and to a lesser extent in the gastrointestinal tract and in the nervous system, where amylin mRNA is also present along with specific binding sites. 3. Amylin given peripherally or centrally inhibits acid gastric secretion in a dose-dependent manner and has a protective effect against indomethacin- or ethanol-induced ulcers only when injected centrally. 4. Subcutaneous or central injection of amylin produces a dose-dependent inhibition of gastric emptying, which may contribute to the activity of amylin in the regulation of carbohydrate absorption. In addition amylin inhibits food intake both when injected peripherally or centrally. 5. Amylin may thus be considered a novel brain-gut peptide taking part in the rapid endocrine response during digestion to maintain euglycemia.