Effects of cimetidine, atropine and prostaglandin E2 on rat mucosal erosions produced by intragastric distension

Strawberry polyphenols attenuate ethanol-induced gastric lesions in rats by activation of antioxidant enzymes and attenuation of MDA increase

Background and Aim

Free radicals are implicated in the aetiology of gastrointestinal disorders such as gastric ulcer, colorectal cancer and inflammatory bowel disease. Strawberries are common and important fruit due to their high content of essential nutrient and beneficial phytochemicals which seem to have relevant biological activity on human health. In the present study we investigated the antioxidant and protective effects of three strawberry extracts against ethanol-induced gastric mucosa damage in an experimental in vivo model and to test whether strawberry extracts affect antioxidant enzyme activities in gastric mucosa.

Methods/Principal Findings

Strawberry extracts were obtained from Adria, Sveva and Alba cultivars. Total antioxidant capacity and radical scavenging capacity were performed by TEAC, ORAC and electron paramagnetic resonance assays. Identification and quantification of anthocyanins was carried out by HPLC-DAD-MS analyses. Different groups of animals received 40 mg/day/kg body weight of strawberry crude extracts for 10 days. Gastric damage was induced by ethanol. The ulcer index was calculated together with the determination of catalase and SOD activities and MDA contents. Strawberry extracts are rich in anthocyanins and present important antioxidant capacity. Ethanol caused severe gastric damage and strawberry consumption protected against its deleterious role. Antioxidant enzyme activities increased significantly after strawberry extract intake and a concomitantly decrease in gastric lipid peroxidation was found. A significant correlation between total anthocyanin content and percent of inhibition of ulcer index was also found.

Conclusions

Strawberry extracts prevented exogenous ethanol-induced damage to rats' gastric mucosa. These effects seem to be associated with the antioxidant activity and phenolic content in the extract as well as with the capacity of promoting the action of antioxidant enzymes. A diet rich in strawberries might exert a beneficial effect in the prevention of gastric diseases related to generation of reactive oxygen species.

Antiulcerogenic effect and acute toxicity of a hydroethanolic extract from the cashew (Anacardium occidentale L.) leaves

The antiulcerogenic effect of a hydroethanolic extract of Anacardium occidentale L. leaves was investigated. The extract inhibited gastric lesions induced by HCl/ethanol in female rats. A dose-response effect study showed that the ED50 was 150 mg/kgb.w. Extract doses higher than 100 mg/kgb.w. were more effective than 30 mg/kg of lansoprazol in inhibiting gastric lesions. A methanolic fraction (257.12 mg/kg) which reduced gastric lesion at 88.20% is likely to contain the active principle of the antiulcer effect. No signs of acute toxicity were observed when mice were treated with extract dose up to 2000 mg/kgb.w. A chemical analysis of the extract allowed the identification of phenolic compounds as the major components. Glycosylated quercetin, amentoflavone derivate and a tetramer of proanthocyanidin were identified by liquid chromatography coupled to mass spectrometry. The level of total phenolics in the extract was evaluated at 35.5% and flavonoid content was 2.58%.

Targeted disruption of histamine H1-receptor attenuates regulatory effects of leptin on feeding, adiposity, and UCP family in mice

Histamine neurons are widely distributed in the brain and suppress food intake through the histamine H1 receptor (H1-R) in the hypothalamus. To examine the role of neuronal histamine in leptin signaling pathways, we investigated the effects of H1-R knockout (H1KO) mice on both food intake and mRNA expressions of uncoupling proteins (UCPs) as regulated by leptin, and concomitantly on basal changes in both expression of hypothalamic neuropeptides and diet-induced fat deposition in adipose tissues. H1KO mice showed no change in daily food intake, growth curve, body weight, or adiposity. Reflecting no specificity in these parameters, H1KO mice induced no basal changes in mRNA expression of hypothalamic neuropeptides, ob gene, or peripheral UCPs. Loading H1KO mice with a high-fat diet accelerated fat deposition and ob gene expression compared with the controls. Leptin-induced feeding suppression was partially attenuated in H1KO mice, indicating involvement of histamine neurons in feeding regulation as a downstream signal of leptin. Upregulation of fat UCP mRNA and reduction of body fat induced by central infusion of leptin were attenuated in the H1KO mice. These results show that H1KO mice are a novel leptin-resistant model and that H1-R is a key receptor for downstream signaling of leptin in the brain that contributes to regulation of feeding, fat deposition, and UCP mRNA expression.

The plant kingdom as a source of anti-ulcer remedies

Phytogenic agents have traditionally been used by herbalists and indigenous healers for the prevention and treatment of peptic ulcer. This article reviews the anti-acid/anti-peptic, gastro-protective and/or anti-ulcer properties of the most commonly employed herbal medicines and their identified active constituents. Botanical compounds with anti-ulcer activity include flavonoids (i.e. quercetin, naringin, silymarin, anthocyanosides, sophoradin derivatives) saponins (i.e. from Panax japonicus and Kochia scoparia), tannins (i.e. from Linderae umbellatae), gums and mucilages (i.e. gum guar and myrrh). Among herbal drugs, liquorice, aloe gel and capsicum (chilli) have been used extensively and their clinical efficacy documented. Also, ethnomedical systems employ several plant extracts for the treatment of peptic ulcer. Despite progress in conventional chemistry and pharmacology in producing effective drugs, the plant kingdom might provide a useful source of new anti-ulcer compounds for development as pharmaceutical entities or, alternatively, as simple dietary adjuncts to existing therapies.

Effect of D-002 on gastric mucus composition in ethanol-induced ulcer

This study was designed to determine the effect of D-002, a natural product isolated and purified from beeswax (Apis mellifera), on gastric mucus composition on ethanol-induced ulcer in rats. The morphology of the lesions was analysed histologically, and morphometric analysis of gastric-gland content in total glycoprotein and sulphated macromolecules were done. Oral pretreatment with D-002 at 5 and 25 mgkg(-1)1 before oral administration of ethanol at 60%, produced a significant increase in the amount of gastric mucus and total protein. The histomorphometric evaluation of the gastric damage at the same doses showed a significant increase in neutral glycoproteins and sulfated macromolecules. It is concluded that enhancement of the quantity and quality of the mucus could partly explain the gastroprotective effect of D-002.

Neuroinflammatory reactions in experimental gastric ulcer: Target for mucosal protection

The effect of different opioids receptor agonists-morphine, DAGO (mu-agonists), DADLE, DPDPE and deltorphin II (delta-agonists)-on gastric mucosal damage induced by either acidified ethanol or acidified aspirin was studied following subcutaneous (sc) administration of these agonists. The results indicate that both mu and delta receptors are involved in gastroprotection. Morphine, DAGO and DADLE, injected intracerebroventricularly, were also effective in both ulcer models. This suggests that gastric cytoprotection can be induced also be central action, since gastric acid secretion is not involved in the pathomechanism of mucosal damage induced by acidified ethanol. Interaction between the opioids and alpha(2)-adrenoceptors in gastroprotection is suggested by the findings that the gastroprotective effect of clonidine (0.09 mumol/kg orally) was antagonized by opioid antagonists. As both naloxone (1.38 mumol/kg sc) and naltrindole (12 mumol/kg sc) exerted antagonist effects, both mu and delta receptors are likely to be involved in presynaptic alpha(2)-receptor-mediated gastroprotection.

Antacids: new perspectives in cytoprotection

There is increasing evidence that aluminum-containing antacids are able to protect the gastric mucosa against various ulcerogenic and necrotizing agents including 0.6 M HCl, 0.2 M NaOH, and absolute alcohol. Since gastric mucosal necrosis produced by alcohol is independent of luminal acid and cannot be reduced by H2-receptor antagonists, the protective action of antacids is accomplished by mechanism(s) other than acid-neutralizing ability. In addition, since acidified antacids can protect the gastric mucosa even better than an antacid with intact neutralizing capacity, it is clear that such action is independent of acid-neutralizing ability and therefore has all the features of cytoprotection. Whereas the cytoprotective action of antacids in experimental conditions is well established, the mechanisms of antacid-induced mucosal protection are not known. The clinical relevance of antacid-induced protection also requires further elucidation. Antacids have advantages over the H2 blockers in protecting the gastric mucosa against alcohol-induced necrosis and in preventing stress-induced ulcers in critically ill patients. Although more work is needed to clarify the mechanisms of cytoprotective action of antacids, the recent experimental findings gave a new life to and new potential clinical applications for antacids.

Damage and protection of the human gastric mucosa. A multiparameter assessment

Studies in animals and humans have indicated that endogenous prostaglandins as well as synthetic prostaglandin analogues can prevent gastric mucosal damage induced by various agents. Methods were developed to assess induced damage and the effects of potentially protective agents (synthetic prostaglandin analogues and the histamine [H2]-receptor antagonist cimetidine) on the human gastric mucosa by measuring ion fluxes and transmucosal potential difference, as well as by observations with gastrointestinal endoscopy. Commonly ingested agents, such as aspirin, 1,300 mg, and 20 percent ethanol increased hydrogen ion and sodium ion fluxes, decreased potential difference, and caused gross mucosal damage, as observed by endoscopy. Conversely, acetaminophen, 2,600 mg, and 10 percent ethanol did not have any significant effects. Hyperosmolar solutions (1,800 and 3,600 mOsm/kg) also produced acute damage. Sodium taurocholate (10 mmol/liter) when instilled into the stomach, either at pH 1.1 or 7.0, produced both functional and structural damage. When given as a single dose, neither 15(R)15-methyl PGE2 nor the synthetic PGE1 analogue, misoprostol, prevented mucosal damage induced by aspirin and taurocholate (pH 1.1), respectively. Cimetidine, 400 mg orally, however, did reduce aspirin-induced mucosal damage, and this effect was independent of gastric acid inhibition.

Mucosal coating agents and other nonantisecretory agents. Are they cytoprotective?

Gastric cytoprotection is protection against gross and histological gastric mucosal injury by a mechanism other than inhibition of neutralization of gastric acid secretion. Animal studies have shown that a variety of agents afford such a protective effect. With some of these agents, a similar protective effect has been shown in man. This protective effect must be distinguished from an action that enhances healing of an already established mucosal lesion as an ulcer. It is yet to be established that the cytoprotective effect of an agent enhances ulcer healing. Agents other than prostaglandins that have been shown to possess such a cytoprotective effect in animals are reviewed. Some, such as sucralfate, act via stimulation of endogenous prostaglandin synthesis, while others, such as DeNol, neomycin, and meciadanol, do not. Investigation of the mechanism through which these agents enhance gastric mucosal defense is a fertile field for investigation.

Cytoprotective drugs. Focus on essential fatty acids and sucralfate

Cytoprotection has been defined as an ability of prostaglandins to prevent gastric mucosal injury produced by a variety of ulcerogenic and necrotizing agents without inhibition of gastric acid secretion or without neutralizing intragastric acidity. Since the first demonstration of cytoprotection by prostaglandins many other agents have been claimed to be cytoprotective. Essential fatty acids: arachidonic and linoleic, licorice products, sucralfate, antacids and sulfhydryl compounds all possess cytoprotective properties. All of these compounds are able to prevent or reduce gastric mucosal necrosis produced by absolute ethanol, a necrotizing agent which injures mucosa independently of the luminal pH. Gastric mucosal protection by essential fatty acids is mediated by their conversion by the gastric mucosa to protective prostaglandins. Sucralfate and antacids are also cytoprotective compounds which stimulate release of endogenous prostaglandins from the gastric mucosa.

Short term treatment of gastric ulcer: a comparison of sucralfate and cimetidine

A double blind randomised study was undertaken to compare sucralfate and cimetidine in short term treatment of gastric ulcer. The study included 149 patients with endoscopically confirmed gastric ulcerations. Patients with prepyloric ulcers 2 cm or less from the pyloric ring were not accepted for participation in the trial. Ulcer healing was assessed endoscopically at four week intervals. A total of 134 patients completed the study. The cumulative healing rates after 12 weeks were 98% for sucralfate and 94% for cimetidine treated patients. After four and eight weeks, the healing rates were 61% and 94% for sucralfate and 69% and 94% for the cimetidine-treated group respectively. No statistically significant differences in healing rates were seen. The 95% confidence interval was calculated for the difference between the ulcer healing rates of sucralfate and cimetidine. This interval was found to range between +11% and -2% after 12 weeks of treatment - that is, the healing efficacy of sucralfate was calculated to be at most 11% better or 2% worse than that of cimetidine. No significant differences in symptom relief, side effects or antacid intake were found.

Protection of gastric mucosa in rats. Differences between vagotomy, atropine, and PGE2

We have studied the protective effects of truncal vagotomy, atropine, and PGE2 against gastric mucosal injury produced by necrotizing agents (0.2 N NaOH, 0.6 N HCl, absolute ethanol), acetylsalicylic acid (ASA) and HCl, or serotonin (5HT). Vagotomy, atropine, and PGE2 prevent the effects of different noxious agents. Vagotomy is protective only against 5HT and against ASA + 0.15 N or 0.35 N HCl, whereas atropine and PGE2 are also protective against the necrotizing agents. The effectiveness of vagotomy against ASA + 0.35 N HCl does not depend on the inhibition of acid secretion and supports the hypothesis that removal of the vagal drive counteracts the effect of H+ back-diffusion.

Effect of intragastric pH, prostaglandins and prostaglandin synthesis inhibitors on the release of gastrin and somatostatin into the gastric lumen of anaesthetized rats

The object of the present work was to study the influence of antral pH, of aspirin and indomethacin, and of prostaglandins A2, E1 and E2 on the intragastric output of somatostatin and gastrin induced by electrical vagal stimulation (5 V, 2 ms, 2, 5 and 10 Hz). Experiments were performed on anaesthetized rats in which the stomach was perfused with a dextran solution (pH approximately 1.5 to approximately 6). To assess the effect of vagal stimulations on gastric acid secretion and on gastrin and somatostatin release, pH as well as somatostatin and gastrin levels was recorded in the perfusate effluent. During perfusion of the stomach with dextran solution, pH approximately 6, vagal stimulation at 10 Hz decreased perfusate pH to 1.3 and gastrin and somatostatin were released at a ratio of 2:1. Less gastrin and more somatostatin (ratio 0.1:1) was released by the same stimulation when the stomach was pre-perfused with acid solution (pH approximately 1.5), although also in these experiments the pH of the perfusate fell to 1.3. When vagal stimulations were performed after the rats had been pretreated with aspirin or indomethacin, more somatostatin than gastrin was detected in the perfusate independently of the perfusate pH. The vagally induced intraluminal release of somatostatin occurring in aspirin-treated animals was abolished by a low dose of atropine (0.05 mg kg-1) or by a simultaneous infusion of prostaglandin E1 (30 micrograms kg-1 h-1).

Effects of zinc acexamate on gastric mucosal resistance factors

The effects of zinc acexamate on gastric defensive systems were evaluated in the rat. Gastric ulcers induced by oral administration of three necrotic agents (0.6 N HCl, 25% NaCl, 100% ethanol) were markedly reduced by different pretreatments with zinc acexamate. This cytoprotective effect was not modified by previous treatment with indomethacin (30 mg/kg orally). Zinc acexamate pretreatment also prevents the disruption of the gastric mucosal barrier induced by aspirin (40 mM) and increases mucus production in the gastric glands and tracheal walls. These observations suggest that the antiulcer effects described for zinc salts could be the result, at least partly, of an action increasing gastric mucosal defensive systems.

Protection of the gastroduodenal mucosa by prostaglandins

Like other nucleated cell populations in the body, the cells of the gastroduodenal mucosa are capable to metabolise arachidonic acid into prostaglandins, with prostaglandin E2 as the probable major metabolite. The production increases on demand and can be followed in the gastric lumen, where the output of prostaglandin E2 increases two to fourfold after exposure of the mucosa to hydrochloric acid. Exogenous prostaglandins, in particular of the E series, stimulate several identified mucosal defense factors in the upper gastrointestinal tract. Prostaglandins of the E series stimulate the transport of bicarbonate and the production and release of mucus glycoproteins from the gastroduodenal mucosa. They have trophic effects on gastrointestinal epithelia by increasing the survival time of mucosal cells and have cytoprotective properties. In addition, E2 prostaglandins suppress the gastric acid secretion and accelerate peptic ulcer healing. Non steroidal antiinflammatory drugs, which block the biosynthesis of prostaglandins, suppress the bicarbonate secretion, the production of mucus glycoproteins and cytoprotective properties. They interfere with the inhibitory feedback regulation of the gastric acid secretion and are ulcerogenic in experimental and clinical situations. These actions of PG biosynthesis blockers provide indirect information on the importance of local prostaglandin formation for maintenance of gastrointestinal mucosal integrity. It is hypothesised that biosynthesis of prostaglandins in the gastroduodenal mucosa is of importance and may be a key event in triggering the different components of the mucosal defense.

Effect of cimetidine and carbenoxolone on cysteamine-induced ulcers: a study of gastric mucosal histamine and histamine formation capacity in rat

Cysteamine-induced ulcers in rat were used to study the effect of ulcer-healing agents with different modes of action on ulcer formation and mucosal histamine. Male Wistar rats were divided into 5 groups. Group I had cysteamine injection; group II had cimetidine followed by cysteamine injection; group III had carbenoxolone before cysteamine injection; group IV had carbenoxolone as group III and cimetidine and cysteamine injections; group V had saline injections (controls). In group I 20/29; group II 17/30; group III 15/29; and group IV 23/30 developed ulcers. No significant differences were found. No ulcers were found in group V. Comparison between all groups and controls showed an increase in gastric mucosal histamine and HFC. The increase in histamine was related to ulcer formation. Duodenal and oesophageal histamine did not change significantly. Gastric mucosal histamine and HFC were directly correlated.

Do prostaglandins mediate the somatostatin preventive effect on gastric lesion?

The inhibition of endogenous prostaglandin synthesis by indomethacin treatment blocks the somatostatin preventive effect on the gastric lesions induced in a stress model and has no preventive effect on an intragastric distension model.

Effects of beta-adrenoceptor drug stimulation on various models of gastric ulcer in rats

1. Experiments were designed to evaluate the effect of the pharmacological activation of beta-adrenoceptors on various models of gastric ulcer in the rat. 2. Pretreatment with the beta-adrenoceptor stimulant drugs, isoprenaline or salbutamol, significantly inhibited stress-induced gastric ulcers. This anti-ulcer effect was abolished by propranolol but not by atenolol, suggesting that beta 2-adrenoceptors mediate this response. 3. In the pylorus-ligation model, salbutamol inhibited lesion formation and reduced the intragastric content of hydrogen ions, histamine and pepsin although the latter was only affected with the higher dose of salbutamol. 4. Salbutamol also prevented the ulcerogenic action on the gastric mucosa of an exogenously perfused artificial gastric juice, showing that the anti-ulcer effect is not necessarily dependent on acid inhibition. 5. Salbutamol also reduced the formation of acute ulcers induced by various iatrogenic means (histamine, polymyxin B, reserpine and indomethacin). 6. Long-term treatment with salbutamol accelerated the healing of experimental chronic gastric ulcer. 7. In anaesthetized rats, salbutamol produced a dose-related increase in mucosal blood flow which may contribute to its mode of action. 8. It is concluded that beta-adrenoceptor agonists exert preventive and curative effects on gastric damage induced in the rat. This effect seems specific and mediated through beta-adrenoceptor activation.