Investigation of the vasodilator and antisecretory role of prostaglandins in the rat gastric mucosa by use of non-steroidal anti-inflammatory drugs

Roles of endothelial prostaglandin I2 in maintaining synchronous spontaneous Ca2+ transients in rectal capillary pericytes

In hollow visceral organs, capillary pericytes appear to drive spontaneous Ca2+ transients in the upstream arterioles. Here, mechanisms underlying the intercellular synchrony of pericyte Ca2+ transients were explored. Ca2+ dynamics in NG2 chondroitin sulphate proteoglycan (NG2)-expressing capillary pericytes were examined using rectal mucosa-submucosa preparations of NG2-GCaMP6 mice. Spontaneous Ca2+ transients arising from endoplasmic reticulum Ca2+ release were synchronously developed amongst capillary pericytes in a gap junction blocker (3 μM carbenoxolone)-sensitive manner and could spread into upstream vascular segments. Spontaneous Ca2+ transients were suppressed by the Ca2+ -activated Cl- channel (CaCC) blocker niflumic acid and their synchrony was diminished by a TMEM16A inhibitor (3 μM Ani9) in accordance with TMEM16A immunoreactivity in pericytes. In capillaries where cyclooxygenase (COX)-2 immunoreactivity was expressed in endothelium but not pericytes, non-selective COX inhibitors (1 μM indomethacin or 10 μM diclofenac) or COX-2 inhibitor (10 μM NS 398) disrupted the synchrony of spontaneous Ca2+ transients and raised the basal Ca2+ level. Subsequent prostaglandin I2 (PGI2 ; 100 nM) or the KATP channel opener levcromakalim restored the synchrony with a reduction in the Ca2+ level. PGI2 receptor antagonist (1 μM RO1138452) also disrupted the synchrony of spontaneous Ca2+ transients and increased the basal Ca2+ level. Subsequent levcromakalim restored the synchrony and reversed the Ca2+ rise. Thus, the synchrony of spontaneous Ca2+ transients in pericytes appears to be developed by the spread of spontaneous transient depolarisations arising from the opening of TMEM16A CaCCs. Endothelial PGI2 may play a role in maintaining the synchrony, presumably by stabilising the resting membrane potential in pericytes. KEY POINTS: Capillary pericytes in the rectal mucosa generate synchronous spontaneous Ca2+ transients that could spread into the upstream vascular segment. Spontaneous Ca2+ release from the endoplasmic reticulum (ER) triggers the opening of Ca2+ -activated Cl- channel TMEM16A and resultant depolarisations that spread amongst pericytes via gap junctions, establishing the synchrony of spontaneous Ca2+ transients in pericytes. Prostaglandin I2 (PGI2 ), which is constitutively produced by the endothelium depending on cyclooxygenase-2, appears to prevent premature ER Ca2+ releases in the pericytes allowing periodic, regenerative Ca2+ releases. Endothelial PGI2 may maintain the synchrony of pericyte activity by stabilising pericyte resting membrane potential by opening of KATP channels.

Gastroprotective activity and pharmacological safety evaluation of Eupatorium aschenbornianum

Eupatorium aschenbornianum has been widely used in traditional Mexican and folk medicine for the treatment of wounds, skin lesions, hemorrhages and gastric ulcers in humans. Phytochemical studies have indicated that hexane extracts of E. aschenbornianum have anti-microbial and anti-fungal activities. In the present study, an accurate and reliable approach using a murine model was pursued to evaluate the anti-ulcer activity, lipid peroxidation properties and acute toxicity of powdered dried stem of E. aschenbornianum. The results indicated that administration of E. aschenbornianum exerted an anti-ulcerative effect and decreased lipid peroxidation in gastric ulcers induced by acetylsalicylic acid. An acute toxicity assay indicated normal behavior and no significant variations in the weight and food consumption of animals. In addition, quantitative analysis of biochemical parameters did not indicate any liver or kidney damage. The results indicated that E. aschenbornianum may be a safe therapeutic agent for the prevention of gastric ulcers.

Radical scavenging and gastroprotective activity of methanolic extract of Gmelina arborea stem bark

BACKGROUND

Gmelina arborea (GA) is widely used in traditional medicine for treating a number of ailments including gastrointestinal tract disorders.

OBJECTIVE

To evaluate the gastroprotective effect of GA stem bark against ethanol-induced gastric ulcer in Wistar rats.

MATERIALS AND METHODS

All animals were fasted for 36 h and received GA extract 250 and 500 mg/kg body weight (bw), 1 h before the administration of ethanol. The animals received ranitidine 50 mg/kg bw which served as the standard. The rats were sacrificed after 4 h. Then, the injuries to the gastric mucosa were estimated through gross evaluation of ulcer lesions and histology. The antioxidant parameters such as level of lipid peroxidation, superoxide dismutase (SOD), reduced glutathione (GSH), and glutathione peroxidase (GPx) in gastric tissue were also determined.

RESULTS

GA treatment at a dose of 500 mg/kg bw offered 91.98% inhibition of ulcer formation, which is higher than that of ranitidine. The ethanol treatment extensively increased lipid peroxidation and it was significantly (P < 0.01) reduced in GA-treated group that eventually helped to prevent free radical accumulation. The GA enhanced the gastric mucosal antioxidant system, as indicated by a dose-dependent increase in the level/activities of GSH, GPx, and SOD. GA also attenuated the severity of histological signs of cell damage. Further, GA extract showed in-vitro 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity with IC50 value of 124.39 μg/ml.

CONCLUSION

The results indicate that the gastroprotective effect of GA is probably related to its antioxidant activities that protect gastric mucosa against oxidative damage and antilipid peroxidative activity that maintain membrane integrity.

Nonsteroidal anti-inflammatory drugs and inflammatory bowel disease: pathophysiology and clinical associations

Nonsteroidal anti-inflammatory drugs (NSAIDs) produce significant gastrointestinal (GI) adverse events. Laboratory and clinical studies suggest that NSAIDs have the potential to trigger the onset or relapse of inflammatory bowel disease. In this review, the currently available information on the mechanism of action of NSAID injury of the GI tract and the pathophysiology of GI effects of NSAIDs, including immune dysregulation will be assessed. A detailed description of NSAID effects on individual GI organs will be discussed. This is followed by a MEDLINE review of clinical literature on the relationship between NSAID ingestion and the development and worsening of inflammatory bowel disease.

beta-Amyrin and alpha-amyrin acetate isolated from the stem bark of Alstonia boonei display profound anti-inflammatory activity

CONTEXT

Alstonia boonei De Wild (Apocyanaceae) is used in ethnomedicine for the management of malaria, ulcer, rhematic pain, toothache, and inflammatory disorders.

OBJECTIVE

To investigate the anti-inflammatory potential of β-amyrin and α-amyrin acetate isolated from the stem bark of Alstonia boonei using animal models.

MATERIALS AND METHODS

Chromatographic purification of the crude methanol extract led to the isolation and structure elucidation of β-amyrin and α-amyrin acetate. Their anti-inflammatory activities were evaluated in rodents using egg albumen-induced paw edema and xylene-induced ear edema models. The gastric ulcerogenic, in vivo leucocyte migration, and RBC membrane stabilization tests were also investigated.

RESULTS

α-Amyrin acetate at 100 mg/kg showed significant (p < 0.05) inhibition of egg albumen-induced paw edema with % inhibition of 40 at the 5th hour. Oral administration up to 100 mg/kg did not produce significant (p > 0.01) irritation of the gastric mucosa while significant (p < 0.01) ulceration was recorded for indomethacin at 40 mg/kg compared with the negative control. At 100 μg/mL, both β-amyrin and α-amyrin acetate inhibited heat-induced hemolysis to as much 47.2 and 61.5%, respectively, while diclofenac sodium (100 μg/mL) evoked only 40.5% inhibition. Both compounds at 100 µg/ear produced significant (p < 0.01) inhibition of ear edema in mice by 39.4 and 55.5%, respectively. Also at 100 mg/kg (p.o.) α-amyrin acetate evoked 60.3% reduction in total leucocyte count and significant (p < 0.05) suppression (47.9%) of neutrophil infiltration.

DISCUSSION AND CONCLUSION

This study generally provided evidence of profound anti-inflammatory activity of β-amyrin and α-amyrin acetate isolated from the Alstonia boonei stem bark.

Protective effects of Punica granatum in experimentally-induced gastric ulcers

In the present investigation standardized aqueous methanolic extract of Punica (AMP) was used for its possible ulcer protective activity in wistar rats against different experimental models. Preliminary phytochemical screening of AMP reveals the presence of saponin, tannins, and flavonoids, which may be responsible for its activity. HPTLC finger prints of AMP showed the presence of 12 spots at different (retention factor) rf values. Oral administration of AMP (490 and 980 mg/kg bw) significantly reduced the ulcer lesion index produced by alcohol, indomethacin, and aspirin, at both doses in rats. Further, in pylorus-ligated rats AMP significantly reduces the ulcer lesions, gastric volume, and total acidity. It prevents the ulceration by increasing the pH and mucus secretion in pylorus ligated rats. The present study shows the anti-ulcer activity of AMP in experimentally-induced gastric ulcers.

Tyrosine and glycine derivatives as potential prodrugs: design, synthesis, and pharmacological evaluation of amide derivatives of mefenamic acid

This study deals with the synthesis, pharmacological activity, and kinetic studies of mefenamic acid (MA) prodrugs of tyrosine and glycine. The synthesis involved a series of protection and deprotection reactions. The hydrolysis of these prodrugs in the intestine was confirmed by hydrolysis kinetics studies in simulated gastric fluid, simulated intestinal fluid, and 80% plasma. The prodrugs were also evaluated for analgesic, anti-inflammatory, and ulcerogenic activities. The glycine prodrug showed maximum analgesic activity of 86%, and both tyrosine and glycine prodrugs showed better anti-inflammatory activity of 74% and 81%, respectively, when compared to the 40% of MA. Further, the prodrugs showed fewer gastric ulcers compared to MA; tyrosine and glycine prodrugs had an average ulcer index of 9.1 and 4.5, respectively, while an average ulcer index of 24.2 was observed with MA. These findings suggest that both prodrugs are better in action as compared to MA, and are advantageous in having fewer gastrointestinal side effects.

Evaluation of antiulcer and antisecretory potential of Linum usitatissimum fixed oil and possible mechanism of action

The aim of the study was to evaluate the antiulcer activity of Linum usitatissimum fixed oil against aspirin-, indomethacin-, ethanol-, reserpine-, serotonin- and stress-induced gastric ulceration in rats and histamine-induced gastric ulceration in guinea pigs. Attempts were also made to evaluate the in vitro anticholinergic and antihistaminic activity and in vivo antisecretary and antiulcer activity of oil following pylorus ligation in rats. L. usitatissimum fixed oil exhibited significant antiulcer activity against different ulcerogens in experimental animal models. The fixed oil significantly inhibited acetylcholine- and histamine-induced contraction of guinea pig and rat ileums, respectively, suggesting its anticholinergic and antihistaminic activity. The oil also exhibited significant inhibitory effect on gastric secretion/total acidity and aspirin-induced gastric ulceration in pylorus-ligated rats. The lipoxygenase inhibitory, histamine antagonistic and antisecretory (anticholinergic) effects of the oil could probably have contributed towards antiulcer activity. L. usitatissimum fixed oil may be considered to be a drug of natural origin which possesses significant antiulcer activity. The present observation is the first experimental data showing antiulcer activity of L. usitatissimum fixed oil.

Evaluation of Myrtus communis Linn. berries (common myrtle) in experimental ulcer models in rats

The present study was conducted to investigate the protective effect of the dried berries of Myrtus communis L. in gastric ulcer against ethanol, indomethacin and pyloric ligation induced models in Wistar rats. Two doses of aqueous extracts of M. communis (AE( 1) and AE(2)) at the dose 105 and 175 mg/kg, respectively, and methanolic extracts (ME(1) and ME(2)) at the dose of 93 and 154 mg/kg, respectively, were administered orally to animals prior to the exposure of ulcerogens. The parameters taken to assess anti-ulcer activity were ulcer index, gastric juice volume, gastric pH, total acidity, gastric wall mucus and histopathological studies. Oral administration of AE(1) and AE(2) significantly reduced the ulcer index in all models of ulcers. Low dose of aqueous extract and high dose of methanolic extract of M. communis exhibited more significant effect in comparison to omeprazole (standard drug) in ethanol-induced ulcer model. Both the doses of aqueous and methanolic extracts also reduced the gastric juice volume, total acidity and increased the gastric pH and gastric wall mucus content in all the models of ulcers used in the present study. Histopathological examinations of gastric tissues of rats treated with the aqueous and methanolic extracts in indomethacin-induced ulcer exhibited significant ulcer-protective effect at both the dose levels.

Reduced conscious blood flow in the stomach during non-steroidal anti-inflammatory drugs administration assessed by flash echo imaging

OBJECTIVE

Harmonic flash echo imaging, which is an intermittent second harmonic imaging technique, has recently been developed for the evaluation of blood flow. The present study was designed to investigate human gastric blood flow during administration of non-steroidal anti-inflammatory drugs (NSAIDs) by harmonic flash echo imaging.

MATERIAL AND METHODS

Eight healthy volunteers were enrolled in the study. After an overnight fast, the volunteers were requested to drink 400 ml water and remain in the sitting position. Seven milliliters (300 mg/ml) Levovist (SHU508A) was then injected intravenously at the rate of 1 ml/s, and intermittent harmonic scanning was carried out at 1-s intervals. A similar examination was carried out one hour after each subject took an oral tablet of diclofenac sodium (50 mg). To minimize the effect of variations in acoustic attenuation among patients, the ratio of the maximum amplitude in the gastric wall to that in the portal vein was expressed as the gastric perfusion index.

RESULTS

Strong ultrasonographic contrast enhancement of the gastric wall and portal vein was observed. The area under the curve was significantly reduced in the images obtained after ingestion of the diclofenac sodium tablet. The gastric perfusion index was significantly reduced from 0.617+/-0.114 to 0.480+/-0.127 in the antrum and from 0.659+/-0.103 to 0.509+/-0.107 in the lower gastric corpus after ingestion of the diclofenac sodium tablet (p<0.05).

CONCLUSIONS

A reduction in the human conscious gastric transmural blood flow following ingestion of an NSAID is revealed by harmonic flash echo imaging.

Cytoprotective effects ofBergenia ciliata Sternb, extract on gastric ulcer in rats

Bergenia ciliata is used for the treatment of stomach disorders in the folk medicine of some areas of South East Asia. This study was designed to evaluate its gastroprotective effects on ethanol/HCl, indomethacin and pylorus ligation-induced gastric ulcers in rats. Doses of 15, 30 and 60 mg/kg b/w of the aqueous and methanol extracts of the rhizome were administered 1 h after ulcerogenic treatment. The animals were killed 3 h later, their stomachs removed and the mean area of ulcer lesion was determined. The weight of mucus and gastric acidity were also measured. The aqueous extract decreased the ulcer lesion (p < 0.05) in all models to a greater extent than the methanol extract, but at the higher doses the effect was reduced. In addition, the antiulcer activity appears to be mediated via cytoprotective effects conferred by enhancement of the mucosal barrier, rather than by prevention of gastric acid secretion or the lowering of pH and acidity.

Gastroprotective effect of cardamom, Elettaria cardamomum Maton. fruits in rats

Cardamom, the fruits of Elettaria cardamomum Maton. (Zingiberaceae) commonly known as "Heel khurd" is used in Unani system of medicine to treat gastrointestinal disorders. A crude methanolic extract (TM), essential oil (EO), petroleum ether soluble (PS) and insoluble (PI) fractions of methanolic extract, were studied in rats at doses of 100-500, 12.5-50, 12.5-150 and 450 mg/kg, respectively for their ability to inhibit the gastric lesions induced by aspirin, ethanol and pylorous ligature. In addition their effects on wall mucus and gastric acid output were recorded. All fractions (TM, EO, PS, PI) significantly inhibited gastric lesions induced by ethanol and aspirin but not those induced by pylorus ligation. TM proved to be active reducing lesions by about 70% in the EtOH-induced ulcer model at 500 mg/kg. The PS fraction reduced the lesions by 50% at 50 and 100mg/kg (no dose response was observed) with similar effect than the PI fraction at 450 mg/kg. In the aspirin-induced gastric ulcer, the best gastroprotective effect was found in the PS fraction, which inhibited lesions by nearly 100% at 12.5mg/kg. In our experimental conditions, the PS extract at doses >or=12.5mg/kg proved to be more active than ranitidine at 50mg/kg.

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

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

The inhibition of gastric mucosal injury by Punicagranatum L. (pomegranate) methanolic extract

Administration of 70% methanolic extract of Punicagranatum fruit rind (250 mg/kg and 500 mg/kg) shows a percentage of inhibition in 22.37, 74.21 and 21.95, 63.41 in aspirin- and ethanol-induced gastric ulceration, respectively. In treated groups of animals, the in vivo antioxidant levels such as superoxide dismutase (SOD), catalase, glutathione (GSH) and glutathione peroxidase (GPx) levels were increased and found more or less equal to the normal values. The tissue lipid peroxidation level was found to be decreasing in treated groups of animals as compared to the control group. The histopathological examination of the stomach of the ulcerated animals shows severe erosion of gastric mucosa, sub-mucosal edema and neutrophil infiltration. All of these symptoms were found to be normal in treated groups. In general, the results of the present investigation revealed the gastroprotective activity of the extract through antioxidant mechanism.

On the mechanisms underlying histamine induction of gastric mucosal lesions in rats with partial gastric vascular occlusion

Although it is well known that histamine induces gastric mucosal lesions in laboratory animals, the fundamental mechanisms remain unclear. In order to further analyze the vascular mechanisms underlying histamine-induced lesions, a new model was developed in the glandular stomach via administration of histamine (40 mg/kg, s.c.) twice to rats with partial gastric vascular occlusion (ligated left gastric artery and vein) also subjected to pylorus ligation. Both antagonists of histamine H(2)-receptors (roxatidine and famotidine) and H(1)-receptors (epinastine and tripelennamine) significantly inhibited lesion formation at doses that did not inhibit acid secretion. Combined treatment of tripelennamine and famotidine synergistically inhibited lesion formation. Nitro L-arginine methyl ester inhibited lesion development; inhibition was reversed by concomitantly administered L-arginine. Indomethacin, diclofenac, and SC-560 (a selective COX-1 inhibitor), but not rofecoxib (a selective COX-2 inhibitor), significantly inhibited lesion formation. In addition, sodium bicarbonate, pirenzepine, S-0509 (a gastrin/CCK(2) inhibitor), omeprazole, sucralfate, and a prostaglandin analog also significantly inhibited lesion formation. It was concluded that the mechanism by which histamine induces gastric lesions in rats with partial gastric vascular occlusion appears to involve extensive vasodilation resulting from histamine acting on microvasculature histamine H(1)- and H(2)-receptors, generation of endogenous nitric oxide and prostaglandins, with the presence of gastric acid.

Gastrointestinal effects of nonsteroidal anti-inflammatory drugs

Non-steroidal anti-inflammatory drugs (NSAIDs) causes extensive damage to the gastrointestinal (GI) tract. The underlying mechanisms of gastric injury include topical irritant actions that disrupt the epithelial barrier, as well as the inhibition of cyclo-oxygenase (COX), which is predominantly the COX-1 isoform in the mucosa. This damage can be attenuated by antisecretory agents or by mucosal protective agents such as the synthetic prostanoids or nitric oxide (NO) donors. Compounds designed to attenuate topical irritancy, or have protective agents incorporated, such as NO-containing NSAIDs, the CINODs (cyclo-oxygenase-inhibiting NO-donating drugs) show reduced mucosal injury. NSAIDs also cause injury in the small intestine, which appears to result from initial COX inhibition, with subsequent translocation of indigenous bacteria, induction of NO synthase and production of the cytotoxic moiety, peroxynitrite. The COX-2 selective agents, the coxibs, which inhibit prostanoid biosynthesis at inflammatory sites, but not the endogenous protective prostanoids in the gut formed by COX-1, have proved so far to be a successful therapeutic approach to reducing NSAIDs GI damage. The clinical outcome of the use of the second generation of coxibs, and the newer NO NSAIDs is now awaited.

Non-steroidal anti-inflammatory drug, nabumetone, prevents indometacin-induced gastric damage via inhibition of neutrophil functions

Nabumetone is a non-steroidal anti-inflammatory drug (NSAID). It works as a prodrug and is extensively metabolized to an active metabolite, 6-methoxy-2-naphthylacetic acid (6MNA). It is well known that neutrophil infiltration and activation are critical in the pathogenesis of NSAID-induced gastric injury, and nabumetone shows less incidence of gastrointestinal irritancy. We examined the effects of nabumetone on neutrophil activation and on indometacin-induced gastric damage. In the indometacin-induced gastric mucosal injury, rats were treated with indometacin and then nabumetone or 6MNA was orally administered. Nabumetone prevented gastric damage accompanied by the reduction of neutrophil infiltration into gastric mucosa, but such an effect was not observed with 6MNA. Nabumetone reduced the formyl methionyl leucyl phenylalanine (fMLP)-induced respiratory burst of human neutrophils to 30% of the control level in-vitro, but 6MNA did not. In addition, nabumetone prevented the fMLP-induced migration of neutrophils. Nabumetone did not inhibit O2- generation in the xanthine-xanthine oxidase system. These results suggest that nabumetone prevents gastric damage induced by the active metabolite, 6MNA, via the suppression of neutrophil activation in gastric mucosa.

Aspirin effects on gastric epithelial cell proliferation and cytokine expression

Aspirin is known to cause gastric injury and to delay ulcer healing. The effects of aspirin on gastric epithelial cell function are heterogeneous; in contrast to injuring the mucosa, aspirin may also act beneficially by inducing adaptation; a mechanism that is poorly understood. We aimed to document the effects of different doses of aspirin on gastric epithelial cell function defined as proliferation, and secretion as well as mRNA expression of cytokines. Furthermore, we studied the effects of aspirin pretreatment on cytokine secretion as a potential element of gastric adaptation. The proliferative activity of three different gastric epithelial cell lines (AGS, KATO III, RGM-1) was assessed by (3)H-thymidine incorporation; secretion of growth factors PDGF-AB and VEGF into culture supernatant was documented by ELISA. mRNA transcripts of both cytokines were quantified by real time RT-PCR. Low doses of aspirin did not alter the proliferative dynamics in two of the three studied cell lines; high doses abolished proliferation. Secretion of PDGF-AB and VEGF increased during the first days of low dose aspirin exposition; higher concentrations led to a depletion of cytokines after an initial liberation in the case of VEGF, mRNA of which was also dose-dependently increased by aspirin. Seven-day pretreatment with low amounts of aspirin did not alter the secretory response of the epithelia caused by higher doses of this drug. The secretion of cytokines and proliferation of gastric epithelial cells are adversely effected by aspirin in a similarly dose-dependent fashion as the intended effects of this drug on platelet function and pain relief.

Evaluation of the gastric antiulcerogenic effect of large cardamom (fruits of Amomum subulatum Roxb)

Large cardamom (fruit of Amomum subulatum Roxb, N.O. Zingiberaceae) commonly known as 'Heel kalan' or 'Bari Ilaichi' is used in Unani system of medicine in gastrointestinal disorders. A crude methanolic extract and its different fractions, viz. essential oil, petroleum ether (60-80 degrees ), ethyl acetate and methanolic fractions, were studied in rats for their ability to inhibit the gastric lesions induced by aspirin, ethanol and pylorus ligature. In addition their effects on wall mucus, output of gastric acid and pepsin concentration were recorded. The crude methanolic extract of A. subulatum and its fractions, viz. essential oil, petroleum ether and ethyl acetate, inhibited gastric lesions induced by ethanol significantly, but not those which were induced by pylorus ligation and aspirin. However, ethyl acetate fraction increased the wall mucus in pylorus ligated rats. The results suggest a direct protective effect of ethyl acetate fraction on gastric mucosal barrier. While the observation of decrease in gastric motility by essential oil and petroleum ether fractions suggests the gastroprotective action of the test drug. These investigations validate the use of 'Heel kalan' in gastrointestinal disorders by Unani physicians.

The mechanism of action of amtolmetin guacyl, a new gastroprotective nonsteroidal anti-inflammatory drug

Amtolmetin guacyl (2-methoxyphenyl-1-methyl-5-p-methylbenzoyl-pyrrol-2-acetamido acetate) (MED15) is a new nonsteroidal anti-inflammatory drug (NSAID) with anti-inflammatory, analgesic and antipyretic properties similar to the traditional drugs, but with unexpected gastroprotective effects. In an in vivo rat model, amtolmetin guacyl administered orally demonstrates inhibition of gastric acid secretion following stimulation by various agonists, and up-regulation of gastric bicarbonate production. Pretreatment with MED15 also shows a significant reduction of indomethacin-induced gastric damage in the rat. The reason behind this behaviour appears to be bound to the presence in the MED15 molecule of a vanillic moiety known to stimulate capsaicin receptors. In fact, the antisecretive effect of MED15 is blocked by capsazepine (a specific capsaicin receptor antagonist). This effect is confirmed by the interference found with anti-histamine H(1) drugs. Owing to the connection between capsaicin and calcitonin gene-related peptide (CGRP), a possible effect of MED15 on CGRP receptors was hypothesized, considering the leading role played on gastric mucosa by the predominant sensory neuropeptide of the stomach wall, CGRP. In fact, the anti-secretive and gastroprotective effect of MED15 is abolished by CGRP-(8-37) (the specific CGRP receptor antagonist). The unmodified MED15 molecule is found throughout the gastroenteric tract for long periods of time following oral administration, as further confirmation of the mechanism of action being based on the presence of the vanillic moiety at receptor level.

Potassium channel modulators and indomethacin-induced gastric ulceration in rats

BACKGROUND

Different mechanisms have been proposed for the pathophysiology of indomethacin-induced gastric ulceration (IIGU), including changes in gastric mucosal blood flow, motility, and acidity. It seems probable that adenosine 5'-triphosphate (ATP)-dependent potassium channels (K(ATP)) have a regulatory effect on the above factors. The aim of the present study was to investigate the effects of K(ATP) channel modulators, diazoxide as a channel opener and glibenclamide as a K(ATP) antagonist, on IIGU.

METHODS

Male rats were starved for 24 h. Groups of 10 animals were used. Diazoxide at doses of 5, 15, and 45 mg/kg and glibenclamide at doses of 2, 6, and 18 mg/kg were injected intraperitoneally 30 min before the subcutaneous injection of 30 mg/kg of indomethacin. To assess the effects of indomethacin on the gastric mucosal vascular bed, different doses of enalapril and hydralazine, two vasodilators with mechanisms of action independent of K(ATP), were also studied. Gastric mucosal ulceration was noted, and fasting blood sugar was assayed. The data were compared between the groups.

RESULTS

Indomethacin produced gastric ulceration in 100% of rats with a severity rating of 2.15/10. This was prevented by diazoxide and aggravated by glibenclamide. Diazoxide increased and glibenclamide decreased fasting blood sugar. Neither enalapril nor hydralazine showed any effect on IIGU and/or fasting blood sugar.

CONCLUSION

K(ATP) modulators may play an important role in the pathophysiology of IIGU through a peripheral action on mucosal and submucosal blood flow of the stomach, gastric motility, acidity, or an action on the vagus complex center of the brain.

Evaluation of the gastric antiulcer activity of fixed oil of Ocimum sanctum (Holy Basil)

The fixed oil of Ocimum sanctum L. (Labiatae) was found to possess significant antiulcer activity against aspirin-, indomethacin-, alcohol-, histamine-, reserpine-, serotonin- and stress-induced ulceration in experimental animal models. Significant inhibition was also observed in gastric secretion and aspirin-induced gastric ulceration in pylorus ligated rats. The lipoxygenase inhibitory, histamine antagonistic and antisecretory effects of the oil could probably have contributed towards antiulcer activity. O. sanctum fixed oil may be considered to be a drug of natural origin which possesses both anti-inflammatory and antiulcer activity.

Expression of endothelial cell-derived nitric oxide synthase (eNOS) is increased during gastric adaptation to chronic aspirin intake in humans

BACKGROUND

Gastric adaptation to aspirin is well-documented. However, the mechanisms underlying the reduction of aspirin-induced mucosal damage despite continued ingestion of the drug remain poorly understood.

METHODS

Eight healthy volunteers who received aspirin 1 g b.d. for 14 days were compared with eight placebo-dosed controls. Gastroscopy with mucosal biopsy was performed, and gastric mucosal blood flow was measured before and following 3, 7 and 14 days of aspirin treatment. At the same time points, tissue concentration and the content of prostaglandin E2 in the gastric juice were determined and expression of endothelial cell-derived nitric oxide synthase (eNOS) in mucosal biopsies was measured using Western blot analysis.

RESULTS

Aspirin-induced mucosal damage that reached a maximum on day 3, declining significantly by day 14. Concomitantly, mucosal blood flow significantly increased on day 3 and returned to initial values on day 14. Aspirin intake led to a significant decrease in prostaglandin E2 concentration in the gastric mucosa and in gastric juice during the whole period of aspirin consumption. eNOS expression started to increase on day 7 in oxyntic mucosa and on day 3 in antral mucosa, reaching its highest values at the end of the consumption of aspirin.

CONCLUSIONS

The human gastric mucosa adapts to prolonged aspirin intake, and this is accompanied by an increase in mucosal blood flow and reduced prostaglandin synthesis. Increase of mucosal eNOS expression might compensate for reduced prostaglandin synthesis and be responsible for gastric adaptation to chronic aspirin intake in humans.

Evaluation of Nigerian traditional medicines: II. Effects of some Nigerian folk remedies on peptic ulcer

Antiulcer activity of four medicinal plants, Diodia sarmentosa (whole plant), Cassia nigricans (leaves), Ficus exasperata (leaves) and Synclisia scabrida (leaves), which are commonly used by the Nigerian traditional healers for the treatment of peptic ulcer were investigated. Acute toxicity tests were also carried out. The results revealed that the four extracts possess significant anti-ulcerogenic properties in a dose-dependent way. They protected rats from aspirin-induced ulcerogenesis, delayed intestinal transit, increased the pH, and decreased both the volume and acidity of gastric secretion. These results correlate with local use of the plants.

Infection of Helicobacter pylori in gastric adaptation to continued administration of aspirin in humans

BACKGROUND & AIMS

Involvement of Helicobacter pylori in aspirin-induced gastropathy and adaptation to aspirin remains unclear. The aim of this study was to compare gastric damage and adaptation after repeated exposures to acetylsalicylic acid in the same subjects before and after eradication of H. pylori.

METHODS

Before and after H. pylori eradication, 8 volunteers were given aspirin, 2 g/day during 14 days. Mucosal damage was evaluated by endoscopy and histological analysis of biopsy samples. Gastric microbleeding, DNA synthesis, prostaglandin E2 generation, and luminal contents of transforming growth factor alpha and its immunohistochemical expression were determined on days 0, 3, 7, and 14 of aspirin course.

RESULTS

In all subjects, aspirin-induced gastric damage that reached maximum on day 3. In H. pylori-positive subjects, this damage was maintained at a similar level up to day 14. After H. pylori eradication, the damage was significantly lessened both in endoscopy and histology at day 14 and accompanied by increased mucosal expression and luminal release of transforming growth factor alpha. Prostaglandin E2 generation was significantly greater in H. pylori-positive subjects than after H. pylori eradication, but aspirin treatment resulted in >90% reduction of this generation independent of H. pylori status.

CONCLUSIONS

Gastric adaptation to aspirin is impaired in H. pylori-positive subjects, but eradication of this bacterium restores this process.

Evaluation of chronic oral toxicity and carcinogenic potential of lornoxicam in rats

As part of the preclinical development program for lornoxicam, a novel non-steroidal anti-inflammatory drug (NSAID), its chronic oral toxicity and carcinogenic potential was assessed in Sprague-Dawley rats. Male and female rats were administered lornoxicam by oral gavage at 0, 0.06, 0.16 or 0.40 mg/kg/day for 12 months or at 0, 0.01 or 0.06 mg/kg/day in a supplementary low-dose study of the same duration (main group: 20/sex/group; 4-wk recovery: five/sex/group; satellites for electrocardiography and toxicokinetics: five/sex/group). Drug-related toxicity mainly comprised mortality, reduced body weight gain, clinico-pathological changes indicative of anaemia resulting from blood loss, and renal damage, renal papillary necrosis and gastrointestinal mucosal lesions. The kidney-associated changes were not completely reversible during the recovery period. Toxicokinetic investigations demonstrated a dose-linear absorption of the drug. In female rats the terminal half-life was about twice that in males which led to a higher exposure of this gender to lornoxicam. A dose of 0.01 mg/kg/day was established as no-observed-effect level. In a 104-wk carcinogenicity study, lornoxicam was administered by oral gavage to male and female rats (50/sex/group) at 0 (control 1), 0 (control 2), 0.0625, 0.125 or 0.250 mg/kg/day. In females only, the high dose was reduced twice during the study due to toxicity observed (0.250 to 0.200 to 0.160 mg/kg/day). Drug-related changes were similar to those in the chronic studies and consistent with the anticipated side-effects of NSAIDs. No carcinogenic potential was revealed.

Indomethacin-induced morphological changes in the rat gastric mucosa, with or without prior treatment with two proton pump inhibitors

BACKGROUND

The mechanisms responsible for the gastric ulcerogenic effect of indomethacin are unclear. The importance of basal acid secretion on morphological changes by indomethacin was investigated.

METHODS

Gastric lesions were macroscopically evaluated 6 h after indomethacin, 20 mg/kg intragastrically, in rats pre-treated with omeprazole (10-100 mumol/kg intragastrically) or lansoprazole (3-30 mumol/kg intragastrically). Glandular mucosa was processed for light, scanning and transmission electron microscopy 3 and 6 h after indomethacin in rats pre-treated with omeprazole (100 mumol/kg) or lansoprazole (30 mumol/kg).

RESULTS

After 3 h, indomethacin caused extensive vasocongestion, oedema in the subepithelial region and superficial erosions. After 6 h, deeply extending focal necrosis involved 11% of the tissue. Leukocyte margination was occasionally seen at 3 h and consistently present at 6 h. Only at 6 h were endothelial cells altered. In rats pre-treated with omeprazole (100 mumol/kg) or lansoprazole (30 mumol/kg) grossly visible lesions were prevented. Oedema, erosions and necrosis were absent. Vasocongestion, vascular leakage and leukocytic margination were seen both at 3 and 6 h while no major damage of endothelial cells was observed.

CONCLUSION

Indomethacin appears primarily to alter microcirculation, and microcirculation damage is dependent on acid for the progression to haemorrhagic lesions.

Role of prostaglandins and histamine in hyperemic response to superficial and deep gastric mucosal injury and H+ back-diffusion in cats

This study was undertaken to examine the role of prostaglandins and histamine in the hyperemic response to gastric mucosal damage followed by H+ back-diffusion. Cat stomachs were exposed to 2 mol/liter NaCl for 10 min followed by luminal perfusion at pH 1. Hypertonic saline caused extensive (microscopic) damage to the surface epithelium, increased gastric mucosal blood flow, and increased release of histamine, PGE2, and 6-keto PGF1 alpha (prostacyclin) into portal venous blood. The effect of indomethacin and histamine blockers (H1 + H2) on the hyperemic response to acid back-diffusion was related to the depth of the mucosal injury and the region of the stomach. In the corpus, indomethacin enhanced mucosal injury. In areas with superficial damage, the hyperemia was inhibited by indomethacin and antihistamines and eliminated by the combination of both. In corpus areas with indomethacin-induced deep lesions, the blood flow was very high, and this hyperemia was partly inhibited by antihistamines. In the antrum the hyperemic response was reduced by antihistamines. Indomethacin increased the release of histamine into portal venous blood (baseline recordings) and reduced basal gastric mucosal blood flow.

The role of gastric muscle relaxation in cytoprotection induced by san-huang-xie-xin-tang in rats

We examined the mechanism of the protective effect of San-huang-xie-xin-tang (SHXT), a traditional oriental drug, on the gastric mucosa. SHXT, given intraduodenally, inhibited the gastric secretion in pylorus-ligated rats. SHXT, given orally 30 min before the administration of aspirin, HCl-aspirin and ethanol, protected the gastric mucosa from these agent-induced gastric lesions, although it had no effect on the gastric lesions induced by indomethacin and water immersion stress. Oral administration of SHXT increased gastric contents (muscle relaxation) when they were measured 30 min after SHXT administration. SHXT also inhibited carbachol-contracted gastric muscle in vitro. Neither increased gastric contents nor inhibited ethanol lesions of SHXT were observed when these were tested 4 h after SHXT administration. Pretreatment with indomethacin which is a prostaglandin synthesis inhibitor, and N-ethylmaleimide which is a sulfhydryl blocker did not influence either the increased gastric contents or inhibited ethanol lesions of SHXT. These results indicate that gastric muscle relaxation plays an important role in the gastric protective mechanisms of SHXT, and the endogenous prostaglandins and the sulfhydryl compounds are not necessary for the action of SHXT.

Role of endogenous nitric oxide in the control of gastric acid secretion, blood flow and gastrin release in conscious dogs

Nitric oxide (NO) was shown to mediate gastric hyperemia following secretory stimulation but its role in the control of gastric secretion has not been clarified. Secretory studies were carried out on conscious dogs with chronic gastric fistula, Heidenhain pouch and esophageal fistula, while changes in gastric blood flow were measured in the mucosa of Heidenhain pouuch by laser Doppler flowmetry. Plasma gastrin was determined by radioimmunoassay. Infusion of NG-nitro-L-arginine (L-NNA) (bolus i.v. injection of 2.5 mg/kg followed by infusion of 0.5 mg/kg/h), a potent inhibitor of nitric oxide synthase, failed to affect basal gastric secretion or plasma gastrin level but suppressed an increase of this secretion induced by sham-feeding, ordinary meat feeding or i.v. infusion of bombesin (0.5 microgram/kg/h), pentagastrin (4 micrograms/kg/h) or histamine (40 micrograms/kg/h). In tests with feeding and bombesin infusion, L-NNA caused a significant and dose-dependent reduction in plasma gastrin levels. The inhibition by L-NNA of gastric acid secretory response to pentagastrin, histamine or feeding was accompanied by a decline in blood flow. Addition of L-arginine (bolus i.v. dose of 50 mg/kg followed by infusion of 5 mg/kg/h) significantly attenuated the L-NNA induced inhibition of gastric secretion and the reduction in plasma gastrin response as well as in the fall of gastric blood flow. We conclude that endogenous nitric oxide affects the gastric secretion and that this effect is mediated, at least in part, by the changes in the gastrin release and gastric blood flow.

Mucosal adaptation to aspirin induced gastric damage in humans. Studies on blood flow, gastric mucosal growth, and neutrophil activation

The gastropathy associated with the ingestion of non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin is a common side effect of this class of drugs, but the precise mechanisms by which they cause mucosal damage have not been fully explained. During continued use of an injurious substance, such as aspirin, the extent of gastric mucosal damage decreases and this phenomenon is named gastric adaptation. To assess the extent of mucosal damage by aspirin and subsequent adaptation the effects of 14 days of continuous, oral administration of aspirin (2 g per day) to eight healthy male volunteers was studied. To estimate the rate of mucosal damage, gastroscopy was performed before (day 0) and at days 3, 7, 14 of aspirin treatment. Gastric microbleeding and gastric mucosal blood flow were measured using laser Doppler flowmeter and mucosal biopsy specimens were taken for the estimation of tissue DNA synthesis and RNA and DNA concentration. In addition, the activation of neutrophils in peripheral blood was assessed by measuring their ability to associate with platelets. Aspirin induced acute damage mainly in gastric corpus, reaching at day 3 about 3.5 on the endoscopic Lanza score but lessened to about 1.5 at day 14 pointing to the occurrence of gastric adaptation. Mucosal blood flow increased at day 3 by about 50% in the gastric corpus and by 88% in the antrum. The in vitro DNA synthesis and RNA concentration, an index of mucosal growth, were reduced at day 3 but then increased to reach about 150% of initial value at the end of aspirin treatment. It is concluded that the treatment with aspirin in humans induces gastric adaptation to this agent, which entails the increase in mucosal blood flow, the rise in neutrophil activation, and the enhancement in mucosal growth.

Review article: controversies in NSAID-induced gastroduodenal damage--do they matter?

BACKGROUND

This article reviews various issues surrounding NSAID-induced gastroduodenal ulceration, about which there appear to be conflicting views and data in the literature. These issues include the size, clinical relevance and main site of the problem; when complications occur (early or late?); the relevance of non-ulcer lesions and whether adaptation is a clinically relevant phenomenon.

METHOD

A comprehensive literature search was carried out to identify relevant new data published since 1987.

RESULTS

NSAIDs are causally associated with more gastric than duodenal ulcers but their use may be associated with duodenal ulcers or complications. Erosive lesions may progress to more severe damage. The theories of early or late onset of complications during a course of NSAID therapy may not be mutually exclusive.

CONCLUSIONS

Available data indicate that NSAID ulcers are at least as dangerous as classic peptic ulcers, and result in significant morbidity and mortality which in the patient population does not appear to be significantly reduced by processes such as adaptation.

Gastric mucosal blood flow and neutrophil activation in aspirin-induced gastric mucosal damage in man

Gastric and intestinal injury induced by nonsteroidal anti-inflammatory agents (NSAIDs) such as aspirin (ASA) is a common side effect of this class of drugs, but the mechanism by which these drugs act is not fully explained. In this study the effects of 3 days of continuous oral ASA administration (1 g twice daily) to eight healthy male volunteers were studied. To estimate the extent of mucosal damage, gastroscopy was performed before and after 3 days of ASA treatment, during which the mucosal blood flow was measured by means of laser-Doppler flowmetry. Before each endoscopy gastric microbleeding was measured. Since neutrophil activation has recently been suggested to be involved in the pathogenesis of ASA-induced gastric mucosal damage, we examined the influence of ASA treatment on the activation of leukocytes by determining their association with platelets in the blood. Aspirin-induced acute gastric damage reached about 3.5 in the endoscopic Lanza score. Mucosal blood flow increased significantly after ASA treatment, by about 50% in the oxyntic gland area and by 87% in the antral area. Gastric microbleeding rose from about 0.38 ml/day in the intact stomach to about 7.7 ml/day after ASA treatment. The platelet/neutrophil adherence increased significantly in both thrombin-unstimulated and thrombin-stimulated platelets. We conclude that acute 3 days' administration of ASA in man produces well-defined areas of gastric damage accompanied by a significant increase in gastric microbleeding and gastric blood flow and that ASA promotes platelet/neutrophil adhesion that may resemble the neutrophil/endothelium interaction in the gastric mucosa.

Thirteenth Gaddum Memorial Lecture. Neuronal and endothelium-derived mediators in the modulation of the gastric microcirculation: integrity in the balance

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Gastroprotective capability of exogenous phosphatidylcholine in experimentally induced chronic gastric ulcers in rats

Phosphatidylcholine (PC) is a main component of the hydrophobic gastric mucosal barrier. Exogenously administered, it prevents acute lesions. We evaluated the gastroprotective capacity of exogenous PC in both acute (ethanol- and indomethacin-induced) and chronic (indomethacin-induced) lesions in rats. Polyunsaturated (PPC) or hydrogenated PC in different concentrations were given intragastrically, before or after the injury factor, in single or repeated doses. Mucosal lesions were significantly reduced by a single dose of PPC, given before or after the injury factor, in both acute models. In the chronic model a single dose of PPC or hydrogenated PC significantly reduced lesions evaluated 6 h after ulcer induction, whereas after 72 h no protective effect was noticed. Repeated doses of PC were ineffective. In conclusion, in acute models exogenous PC reduces lesions in a dose-dependent manner and contributes to the mucosal defense. In chronic models an incomplete and temporary protection might be due to complex pathogenesis that requires activation of all levels in the mucosal defense. Strengthening of only one level was insufficient to restrict injury.

Mechanism of gastric hyperemia induced by intragastric hypertonic saline in rats

BACKGROUND

Intragastric hypertonic (2 mol/L) saline produces injury in the gastric mucosa and a significant increase in gastric blood flow (hyperemia) in anesthetized rats. We studied the mechanism of this hyperemia.

METHODS

Rats were treated with intravenous boluses of NG-nitro-L-arginine methyl ester (3 mg/kg) to block synthesis of endogenous nitric oxide, pyrilamine (1 mg/kg) to inhibit H1 receptors, or indomethacin (5 mg/kg) to block synthesis of endogenous prostaglandins during blood flow studies or with subcutaneous capsaicin (125 mg/kg) 10-14 days before blood flow studies to ablate capsaicin-sensitive afferent nerves. Gastric mucosal blood flow was measured by hydrogen gas clearance before and during intragastric administration of 2 mol/L saline.

RESULTS

The gastric hyperemia induced by intragastric 2 mol/L saline was completely blocked only by indomethacin. The associated gastric mucosal damage was increased significantly.

CONCLUSIONS

In the rat stomach, the gastric hyperemia induced by intragastric 2 mol/L saline is mediated by endogenous prostaglandins and plays a protective role. Endogenous nitric oxide, H1 receptors, and capsaicin-sensitive afferent nerves are not involved in this protective hyperemia.

Effects of acute normovolemic anemia on gastric mucosal blood flow in rats: role of nitric oxide

The present study investigates the effects of acute normovolemic anemia induced by isovolemic hemodilution on gastric mucosal blood flow (GMBF), measured by hydrogen gas clearance, and on the oxygen and hemoglobin content in the gastric mucosa, estimated by reflectance spectrophotometry. GMBF significantly increased after 3 and 6 mL of isovolemic hemodilution (from 50 +/- 5 to 70 +/- 7 and 77 +/- 6 mL.min-1.100 g-1, respectively; P less than 0.05) compared with basal values (50 +/- 5.mL-1.min-1.100 g-1; P less than 0.05). Oxygen content remained unchanged, whereas hemoglobin concentration decreased in parallel with the decrease in hematocrit. In a second set of experiments, the role of endogenous nitric oxide (NO) as a possible mediator of the gastric vascular changes induced by hemodilution was investigated by using the specific inhibitor of NO biosynthesis, NG-monomethyl-L-arginine (L-NMMA). The increase in GMBF induced by 3 mL of isovolemic hemodilution (delta 23 +/- 7 mL.min-1.100 g-1) was attenuated in a dose-related manner with L-NMMA, 6.25 mg/kg IV (delta 15 +/- 4 mL.min-1.100 g-1) or 50 mg/kg IV (delta 5 +/- 2 mL.min-1.100 g-1 g; P less than 0.05). The concurrent administration of L-arginine (the precursor of NO biosynthesis) abolished the effects of L-NMMA on GMBF changes. The current findings show that acute normovolemic anemia causes an increase in GMBF that is dependent on the endogenous formation of NO.