A new gastric ulcer model in rats produced by ferrous iron and ascorbic acid injection

Particularities of Experimental Models Used to Induce Gastric Ulcer

Introduction: Gastric ulcer is one of the most common gastrointestinal diseases, therefore the constant interest for new treatments is due to adverse effects induced by current therapy. The restricted number of in vivo experimental models is a challenge for researchers. Objectives: Identifying the particularities of different types of experimentally induced gastric ulcer in laboratory animals to facilitate their choise for the study of new antiulcer drugs.

Material and method: A search in PubMed and Scopus using keywords ( “experimentally” AND “gastric ulcer” AND “rats/mice”) to include experimental studies with the description of local-induced changes. Review articles and in vitro studies were excluded.

Results and discussions: Experimental researches on new drugs for gastric ulcer use chemical or surgical methods to induce gastric lesions in rats. Non-steroidal anti-inflammatory drugs (NSAIDs) and acetic acid models to investigate antisecretory and cytoprotective effects; ethanol models evaluate cytoprotective and/or antioxidant effects; pylorus ligature models to evaluate the effects on the secretion of aggressive gastric factors (hydrochloric acid or pepsin). NSAIDs (indomethacin, acetylsalicylic acid or ibuprofen) inhibit cyclooxygenase activity, resulting from reduced mucus and bicarbonate secretion, decreased mucosal blood flow, alteration of microvascular structures, causing epithelial damage Ethanol enhances the proteolytic and hydrolytic action of hydrochloric acid and pepsin; in addition, stimulates the acid secretion and disruptes vascular endothelium. Pylorus ligature determines the accumulation of gastric acid resulting in gastric ulcers due to the autodigestion of the mucosa.

Conclusion: The knowledge of the mechanisms to induce experimental gastric ulcers is essential for choosing the model to evaluate new antiulcer agents.

The Probiotic Lactobacillus rhamnosus for Alleviation of Helicobacter pylori-Associated Gastric Pathology in East Africa

The probiotic Lactobacillus rhamnosus GG (LGG) can play a role in establishing a harmless relationship with Helicobacter pylori and reduce gastric pathology in East African populations. H. pylori has the ability to inhabit the surface of the mucous layer of the human stomach and duodenum. In the developing world, an estimated 51% of the population is carrier of H. pylori, while in some Western countries these numbers dropped below 20%, which is probably associated with improved sanitation and smaller family sizes. Colonization by H. pylori can be followed by inflammation of the gastric mucus layer, and is a risk factor in the development of atrophic gastritis, peptic ulcers and gastric cancer. Notwithstanding the higher prevalence of H. pylori carriers in developing countries, no equal overall increase in gastric pathology is found. This has been attributed to a less pro-inflammatory immune response to H. pylori in African compared to Caucasian populations. In addition, a relatively low exposure to other risk factors in certain African populations may play a role, including the use of non-steroidal anti-inflammatory drugs, smoking, and diets without certain protective factors. A novel approach to the reduction of H. pylori associated gastric pathology is found in the administration of the probiotic bacterium Lactobacillus rhamnosus yoba 2012 (LRY), the generic variant of LGG. This gastro-intestinal isolate inhibits H. pylori by competition for substrate and binding sites as well as production of antimicrobial compounds such as lactic acid. In addition, it attenuates the host's H. pylori-induced apoptosis and inflammation responses and stimulates angiogenesis in the gastric and duodenal epithelium. The probiotic LRY is not able to eradicate H. pylori completely, but its co-supplementation in antibiotic eradication therapy has been shown to relieve side effects of this therapy. In Uganda, unlike other African countries, gastric pathology is relatively common, presumably resulting from the lack of dietary protective factors in the traditional diet. Supplementation with LRY through local production of probiotic yogurt, could be a solution to establish a harmless relationship with H. pylori and reduce gastric pathology and subsequent eradication therapy treatment.

Ulceration of the oral mucosa following direct contact with ferrous sulfate in elderly patients: a case report and a review of the French National Pharmacovigilance Database

Objective

To report a series of cases of ulceration of the oral mucosa linked to direct contact with ferrous sulfate in elderly patients.

Case summary

The first case report concerns the occurrence of widespread oral ulceration in an 87-year-old woman with Alzheimer’s disease. The ulceration extended from the side of the tongue to the floor of the mouth. No clear explanation was found and various local treatments were ineffective. Once it was realized that the ferrous sulfate tablets (given as an iron supplement) were crushed prior to administration (due to the patient’s deglutition disorder), withdrawal of this treatment led to rapid resolution of the ulceration. Nine other cases of oral ulcerations associated with ferrous sulfate were identified in the French National Pharmacovigilance Database. All but one of the patients were over 80 years of age and the youngest patient (a 54-year-old) had dysphagia associated with facial paralysis.

Discussion

Only two other reports of oral ulceration due to ferrous sulfate have been published to date. Mucosal toxicity of ferrous sulfate (which is probably related to oxidative stress) has previously been reported for the hypopharynx, the esophageal lumen, and (after inhalation of a tablet) the tracheobronchial tree.

Conclusion

The mucosal toxicity of ferrous sulfate must be taken into account when deglutition disorders are present (as in elderly patients) and appropriate pharmaceutical formulations (such as syrups) should be administered to at-risk patients. The use of iron salts other than ferrous sulfate could be considered.

Lipid hydroperoxide-derived modification of proteins in gastrointestinal tract

Role of lipid peroxidation in the pathogenesis of gastrointestinal diseases has been evaluated by measuring the tissue levels of lipid peroxides as thiobarbituric acid-reactive substances in the animal models as well as human. Recently, N (ε)-(hexanoyl)lysine (HEL) and 4-hydroxy-2-nonenal (HNE) are recognized as reliable and sensitive biomarkers for the early phase and the late phase of lipid peroxidation, respectively. The presence of HNE- and HEL-modified proteins has been demonstrated in in vivo models of several gastrointestinal diseases. In the present review, we introduced HNE-modification of TRPV1 channel in esophageal epithelial cells, HEL-modification of tropomyosin 1 (TMP1) in gastric cancer cells, and HEL-modification of gastrokine 1 in the healing of gastric ulcer.

In Vivo Models Used for Evaluation of Potential Antigastroduodenal Ulcer Agents

Peptic ulcer is among the most serious gastrointestinal diseases in the world. Several orthodox drugs are employed for the treatment of the disease. Although these drugs are effective, they produce many adverse effects thus limiting their use. In recent years, there has been a growing interest in alternative therapies, especially those from plants due to their perceived relative lower side effects, ease of accessibility, and affordability. Plant medicines with ethnomedicinal use in peptic ulcer management need to be screened for their effectiveness and possible isolation of lead compounds. This requires use of appropriate animal models of various ulcers. The limited number of antiulcer models for drug development against gastric and duodenal ulcer studies has hindered the progress of targeted therapy in this field. It is, therefore, necessary to review the literature on experimental models used to screen agents with potential antigastroduodenal ulcer activity and explain their biochemical basis in order to facilitate their use in the development of new preventive and curative antiulcer drugs. Clinical trials can then be carried out on agents/drugs that show promise. In this paper, current in vivo animal models of ulcers and the pathophysiological mechanisms underlying their induction, their limitations, as well as the challenges associated with their use have been discussed.

Dual role of selected antioxidants found in dietary supplements: crossover between anti- and pro-oxidant activities in the presence of copper

Overproduction of reactive oxygen species (ROS) in vivo can result in damage associated with many aging-associated diseases. Defenses against ROS that have evolved include antioxidant enzymes, such as superoxide dismutases, peroxidases, and catalases, which can scavenge ROS. In addition, endogenous and dietary antioxidants play an important role in moderating damage associated with ROS. In this study, we use four common dietary antioxidants to demonstrate that, in the presence of copper (cupric sulfate and cupric gluconate) and physiologically relevant levels of hydrogen peroxide, these antioxidants can also act as pro-oxidants by producing hydroxyl radicals. Using electron spin resonance (ESR) spin trapping techniques, we demonstrate that the level of hydroxyl radical formation is a function of the pH of the medium and the relative amounts of antioxidant and copper. On the basis of the level of hydroxyl radical formation, the relative pro-oxidant potential of these antioxidants is cysteine > ascorbate > EGCG > GSH. It has been reported that copper sequestered by protein ligands, as happens in vivo, loses its redox activity (diminishing/abolishing the formation of free radicals). However, in the presence of hydrogen peroxide, cysteine and GSH efficiently react with cupric sulfate sequestered with bovine serum albumin to generate hydroxyl radicals. Overall, the results demonstrate that in the presence of copper, endogenous and dietary antioxidants can also exhibit pro-oxidative activity.

Iron supplements: the quick fix with long-term consequences

Co-supplementation of ferrous salts with vitamin C exacerbates oxidative stress in the gastrointestinal tract leading to ulceration in healthy individuals, exacerbation of chronic gastrointestinal inflammatory diseases and can lead to cancer. Reactive oxygen and nitrogen species (RONS) have been ascribed an important role in oxidative stress. Redox-active metal ions such as Fe(II) and Cu(I) further activate RONS and thus perpetuate their damaging effects. Ascorbic acid can exert a pro-oxidant effect by its interaction with metal ions via a number of established RONS generating systems which are reviewed here. Further studies are required to examine the detrimental effects of nutraceuticals especially in chronic inflammatory conditions which co-present with anaemia.

[An overview of acetic acid ulcer models and their utility for drug screening]

Since Takagi et al. reported an experimental chronic gastric ulcer model [acetic acid ulcers induced by submucosal injection of acetic acid (Type 1)], we further modified the methodology and subsequently devised three more models. The second model involves inducing ulcers by serosal application of an acetic acid solution (Type 2) and the third model achieves ulcer induction by intragastric application of an acetic acid solution (Type 3). The forth model was modification of the third model by giving the acetic acid solution and the same volume of air to make one ulcer in the stomach (Type 4). In general, animals accepted the procedures without problems and no undesirable effects were noticed. More importantly, this experimental animal model allows production of ulcers that highly resemble human ulcers in terms of both pathology and healing. Indeed, relapse is even endoscopically observed for 360 days after ulceration. The ulcers produced not only respond well to various anti-ulcer medications, such as antisecretory and mucosal protective drugs and growth factors, but also demonstrate appropriate responses to ulcerogenic agents such as NSAIDs. In addition, we have recently demonstrated that H. pylori infection resulted in delayed ulcer healing and recurrence of healed acetic acid ulcers induced in Mongolian gerbils. The present article gives a brief summary of the ulcer history before establishment of acetic acid ulcers and characteristic features of acetic acid ulcer, including both their merits and shortcomings.

Reactive oxygen species activity, mucosal lipoperoxidation and glutathione in Helicobacter pylori-infected gastric mucosa

BACKGROUND AND AIM

Helicobacter pylori is considered as the major pathogen in Helicobacter pylori-associated gastroduodenal disease, but the mechanism of its action has not been fully explained. This study was performed to assess the reactive oxygen species activity and the damage in Helicobacter pylori-infected gastric mucosa.

METHODS

Gastric biopsy specimens were obtained from 308 patients undergoing endoscopy. Gastric mucosal damage was assessed by using luminol enhanced chemiluminescence, thiobarbituric acid-reactive substance, and mucosal glutathione.

RESULTS

The chemiluminescence and thiobarbituric acid-reactive substance-equivalent levels in the mucosa of patients with Helicobacter pylori-positive gastric mucosa (43.8 +/- 134.9 c.p.m./microg tissue, 157.0 +/- 96.2 nmol/g tissue, respectively) were significantly higher than in those with Helicobacter pylori-negative mucosa (6.8 +/- 20.3 c.p.m./microg tissue, 110.0 +/- 51.6 nmol/g tissue, respectively; P=0.000, P=0.016, respectively). The glutathione levels in the mucosa of patients with Helicobacter pylori-positive gastric mucosa (159.3 +/- 76.6 nmol/microg tissue) were significantly lower than in those with Helicobacter pylori-negative gastric mucosa (212.3 +/- 134.3 nmol/microg tissue; P=0.008). After the data were divided according to the presence of Helicobacter pylori, there were no significant differences in chemiluminescence, thiobarbituric acid-reactive substance, and glutathione among the different macroscopic findings within Helicobacter pylori-positive and -negative gastric mucosa.

CONCLUSIONS

Helicobacter pylori infection plays a pathological role in many gastrointestinal diseases through excessive mucosal-reactive oxygen species production, pronounced membrane damage, and the depletion of gastric anti-oxidants.

Anxiety and helplessness in the face of stress predisposes, precipitates, and sustains gastric ulceration

When an organism is subjected to stress, gastric ulcers or ulcerations commonly develop but the vulnerability to and amount of pathology induced varies considerably between individuals. The role of psychological factors in determining the occurrence and severity of these ulcerations is amply demonstrated in the studies reviewed here. The present paper (a) gives a brief history of the search for the causes of gastric ulcer, (b) provides a review of our own research which reveals that vulnerability to gastric ulceration is modulated by psychologically meaningful experiences, and (c) offers a multifactorial perspective on the causes of gastric ulceration and the future of research on it.

Deferiprone, an oral iron chelator, ameliorates experimental colitis and gastric ulceration in rats

Iron is pivotal is producing tissue-damaging reactive oxygen metabolites. Our aim is to determine the antiinflammatory activity of deferiprone, an oral iron chelator, in experimental colitis and gastritis. Colitis was induced by intraceccal administration of 2 ml 5% acetic acid or by intracolonic administration of 0.1 ml 3% iodoacetamide, with or without cotreatment with deferiprone. Gastritis was induced by intragastric administration of ethanol or hydrochloric acid (HCl) and by subcutaneous injection of indomethacin, with and without deferiprone. Rats were killed 24 hours after acetic acid and iodoacetamide, 30 minutes after ethanol, one hour after HCl, and three hours after indomethacin administration. The colon or stomach was isolated, macroscopic damage was measured, and mucosal samples were obtained for determination of eicosanoid generation, myeloperoxidase (MPO), and nitric oxide synthase (NOS) activities. Deferiprone decreased iodoacetamide and acetic acid-induced macroscopic colonic damage by 67% and 69%, respectively, and macroscopic gastric damage by 91%, 68%, and 46% induced by ethanol, HCl, and indomethacin, respectively. The effect of deferiprone was accompanied by significant decrease in colonic and gastric, MPO and NOS activities, and colonic prostaglandin E2 (PGE2) generation, in acetic acid, ethanol, and indomethacin models, whereas in the iodoacetamide and HCl models attenuation of the decrease in PGE2 generation was seen. Deferiprone is protective in experimental colitis and gastritis, probably due to decreased production of iron-dependent oxygen-free radicals. Oral iron chelators may constitute a novel approach to ameliorate gastrointestinal inflammatory disorders.

Mechanisms underlying gastric antiulcerative activity of nitroxides in rats

Reactive oxygen-derived species and redox-active metals are implicated in mediation of the pathogenesis of gastric mucosal damage and ulceration. Therefore, common strategies of intervention employ metal chelators, antioxidative enzymes, and low-molecular-weight antioxidants (LMWA). The aim of the present study was to elaborate the mechanism(s) responsible for the protection provided by nitroxide radicals in the experimental model of gastric ulceration. Fasted male rats were treated ig with 1 ml 96% ethanol, with or without ig pretreatment with nitroxide or hydroxylamine. In several experiments, rats were injected ip or iv with iron(III) or iron(II) prior to ethanol administration. Rats were sacrificed 10 min after ethanol administration, the stomach was removed, washed and lesion area measured. Pretreatment with iron(III) complexed to nitrilotriacetate or citrate, aggravated the extent of the gastric injury. Conversely, iron(II) inhibited the formation of lesions. The nitroxides were rapidly reduced to their respective hydroxylamines and demonstrated antiulcerative activity for rats treated with iron. However, injecting the hydroxylamine resulted in a similar tissue distribution of nitroxide/hydroxylamnine but did not provide protection. The results show that: (a) the nitroxide radicals, rather than their respective non-radical reduced form, are the active species responsible for protection; (b) nitroxides protect by dismutating O2*- and possibly indirectly increasing the NO level; (c) unlike classical LMWA which are reducing agents, nitroxides inhibit gastric damage by acting as mild oxidants, oxidizing reduced metals and pre-empting the Fenton reaction; and (d) the nitroxides act catalytically as recycling antioxidants.

Gastric ulcer, atrophic gastritis, and intestinal metaplasia caused by Helicobacter pylori infection in Mongolian gerbils

BACKGROUND

Helicobacter pylori infection is associated with gastroduodenal disease in humans. In this study we aimed to show this relationship directly in Mongolian gerbils.

METHODS

The animals were challenged orally with H. pylori and killed 1, 2, 3, and 6 months after inoculation for histologic and anti-H. pylori antibody titer examination.

RESULTS

The spiral bacteria were observed in the mucus and gastric pits of all infected animals. A severe infiltration of the lamina propria by polymorphonuclear and mononuclear cells was seen 1 month after H. pylori inoculation. The submucosa was infiltrated by mainly mononuclear cells with formation of lymphoid follicles. Erosion of the gastric mucosa appeared soon after inoculation, whereas gastric ulcers, gastritis cystica profunda, and atrophy with goblet cell metaplasia occurred between 3 and 6 months after inoculation. In the duodenal mucosa a mild inflammatory cell infiltration with ballooning and diminished number of duodenal glands was seen. The IgG anti-H. pylori antibody titer increased gradually after 2 months of inoculation.

CONCLUSIONS

Since the gastritis, gastric ulcers, atrophic gastritis, and intestinal metaplasia that developed in Mongolian gerbils were similar to those observed in humans, this model may be useful to study the therapy of gastric ulcer and, with a longer observation period, to confirm a possible relationship between H. pylori and malignancy.

Role of lipid peroxidation and antioxidants in gastric mucosal injury induced by the hypoxanthine-xanthine oxidase system in rats

Free radical-induced gastric mucosal injury was caused by severe depletion of glutathione and alpha-tocopherol. Intravenous infusion of hypoxanthine (HX) via the jugular vein and local intra-arterial infusion of xanthine oxidase (XO) via the left gastric artery caused marked gastric mucosal injury in the antrum and the corpus. This study was performed to determine whether antioxidants in the gastric mucosa are mobilized during oxidative stress in the rat stomach. The level of thiobarbituric acid (TBA) reactive substance in the gastric mucosa was not significantly changed. The levels of total glutathione and alpha-tocopherol in the gastric mucosa significantly decreased. Total superoxide dismutase (Cu/Zn-and Mn-SOD) and glutathione peroxidase activities were not significantly changed. Administration of SOD reversed the glutathione level but not the alpha-tocopherol level in the gastric mucosa. To determine the role of glutathione and alpha-tocopherol in oxidative stress, the stomach was removed from a normal, alpha-tocopherol supplemented, and glutathione-depleted rat and used for experimentation. Frozen slices of the rat stomach were infused with HX-XO then examined histochemically using cold Schiff's reagent for signs of lipid peroxidation. It was found that the alpha-tocopherol supplemented stomach inhibited lipid peroxidation induced by HX-XO. Biochemical measurements and histochemical examination showed that the glutathione-depleted frozen tissue section and the homogenate had increased by lipid peroxidation induced by HX-XO. These findings suggested that alpha-tocopherol and glutathione may play a role in protecting the gastric mucosa against oxygen free radicals.