Acceleration of gastric ulcer healing by omeprazole in portal hypertensive rats. Is its action mediated by gastrin release and the stimulation of epithelial proliferation?

Management of portal hypertensive gastropathy and other bleeding

A major cause of cirrhosis related morbidity and mortality is the development of variceal bleeding, a direct consequence of portal hypertension. Less common causes of gastrointestinal bleeding are peptic ulcers, malignancy, angiodysplasia, etc. Upper gastrointestinal bleeding has been classified according to the presence of a variceal or non-variceal bleeding. Although non-variceal gastrointestinal bleeding is not common in cirrhotic patients, gastroduodenal ulcers may develop as often as non-cirrhotic patients. Ulcers in cirrhotic patients may be more severe and less frequently associated with chronic intake of non-steroidal anti-inflammatory drugs, and may require more frequently endoscopic treatment. Portal hypertensive gastropathy (PHG) refers to changes in the mucosa of the stomach in patients with portal hypertension. Patients with portal hypertension may experience bleeding from the stomach, and pharmacologic or radiologic interventional procedure may be useful in preventing re-bleeding from PHG. Gastric antral vascular ectasia (GAVE) seems to be different disease entity from PHG, and endoscopic ablation can be the first-line treatment.

The type 2 CCK/gastrin receptor antagonist YF476 acutely prevents NSAID-induced gastric ulceration while increasing iNOS expression

YF476 differs from the proton pump inhibitor (PPI) esomeprazole in mode of action by antagonizing the type 2 receptor of cholecystokinin/gastrin (CCK-2R). YF476 protection against diclofenac-induced gastric ulcers was compared to esomeprazole and correlated with plasma levels of hormones related to gastric pH (gastrin, ghrelin, and somatostatin), gastric gene expression of these hormones, their receptors, and inducible nitric oxide synthase (iNOS). YF476 or esomeprazole pretreatments were followed by diclofenac. Four hours later, gastric tissue was excised and analyzed for ulcer index. An intragastrically implanted Bravo capsule measured pH for 5 days during YF476 plus pentagastrin treatment. Changes in gene expression were assayed for gastrin, ghrelin, and somatostatin; their receptors; and iNOS. YF476 acutely (within 4 h) protected against diclofenac-induced gastric ulcers equivalent to esomeprazole. Gastric pH recorded during 5 days in the presence of pentagastrin was 1.83 (±0.06). YF476 raised pH to 3.67 (±0.09) and plasma ghrelin, gastrin, and somatostatin increased. YF476 increased gene expression of somatostatin receptor and gastrin, while ghrelin receptor decreased; transcripts coding ghrelin, somatostatin, and CCK-2R remained unchanged. In the presence of diclofenac, esomeprazole increased expression of all these transcripts and that of iNOS, while YF476 yielded only decreased CCK-2R and increased iNOS transcripts. YF476 is a potential new preventative treatment for patients at risk of nonsteroidal antiinflammatory drug (NSAID)-induced ulceration. Gastric gene expressions of ghrelin, gastrin, and somatostatin and their receptors differ between esomeprazole and YF476. Despite these differences and different modes of action to raise gastric pH, both drugs acutely increase iNOS, suggesting iNOS expression parallels pH.

Protective effect of a cysteine prodrug and antioxidant, L-2-oxothiazolidine-4-carboxylate, against ethanol-induced gastric lesions in rats

Earlier studies have suggested an important role of glutathione (GSH) in cytoprotection against free radicals induced oxidative damage. This study reports gastroprotective effects of a cysteine precursor, L-2-oxothiazolidine-4-carboxylate (OTC), in experimental models of gastric secretion and ulceration. Acid secretion studies (volume and acidity) were undertaken in pylorus-ligated rats whereas the gastric lesions were induced by ethanol. Different groups of animals were treated with OTC (0, 100, 200 and 400 mg/kg). The levels of gastric wall mucus, nonprotein sulfhydryls (NP-SH) and myeloperoxidase (MPO) were measured in the glandular stomach of rats following ethanol-induced gastric lesions. Both medium and high doses of OTC significantly reduced the volume and acidity of gastric secretion in pylorus-ligated rats. Pretreatment with OTC significantly and dose-dependently attenuated the formation of ethanol-induced gastric lesion. OTC significantly protected the gastric mucosa against ethanol-induced depletion of gastric wall mucus, NP-SH and MPO. The gastroprotective effects of OTC may be attributed to its ability to inhibit neutrophils activity and replenish GSH demand.

Risk factors for gastrointestinal complications in aspirin users: review of clinical and experimental data

This paper reviews recent clinical evidence that suggests that aspirin prophylaxis against cardiac and cerebral vascular ischemia is associated with significant gastrointestinal complications. The clinical and experimental evidence to confirm the role of risk factors of concomitant use of nonsteroidal anti-inflammatory drugs (NSAID), tobacco cigarette smoking, and alcohol consumption are discussed. The limitations of long-term acid suppression treatment for the prevention of these complications are considered. Future experimental studies to guide the clinical approach to develop novel and potentially cost-effective management strategies are discussed.

Gastric antisecretory and antiulcer effects of simvastatin in rats

BACKGROUND AND AIM

Recently, statins have appeared to have additional benefits beyond their lipid lowering effects, which has led to the interest in the use of this class of drugs outside the realm of cardiovascular disease. Simvastatin (SIM) is a commonly prescribed statin with anti-inflammatory and antioxidant properties. Excessive generation of oxygen-derived free radicals (ODFR) and proinflammatory mediators has been implicated in the pathogenesis of gastric ulcers. This investigation aimed to study the effect of SIM on experimentally induced gastric acid secretion and ulcer formation.

METHODS

Adult Wistar rats were divided into experimental groups containing six animals. Acid secretion studies were undertaken using pylorus-ligated rats pretreated with SIM (20, 40, and 60 mg/kg). The effect of orally administered SIM was also studied on indomethacin- and ethanol-induced gastric ulcers. The levels of myeloperoxidase (MPO), non-protein sulfhydryls (NP-SH), nitric oxide (NO), antioxidant enzymes, and gastric wall mucus were measured in the glandular stomach of rats following ethanol-induced gastric lesions.

RESULTS

Administration of SIM significantly and dose-dependently inhibited the volume of gastric secretion and the acidity. Pretreatment with SIM significantly reduced the formation of indomethacin- and ethanol-induced gastric lesions. The antiulcer activity of SIM was associated with significant attenuation of adverse effects of ethanol on gastric wall mucus, NP-SH and MPO. SIM modified the gastric NO levels and reversed the ethanol-induced decrease in glutathione-S-transferase and increase in superoxide dismutase and catalase.

CONCLUSIONS

These findings clearly suggest the involvement of proinflammatory agents and ODFR in the pathogenesis of gastric lesions. The gastroprotective effects of SIM are mediated by inhibition of neutrophils activity, reduction of oxidative stress, and maintenance of vascular integrity. This study was conducted in rats; its relevance to human gastric ulcers is not known and warrants further study.

Gastroduodenal defense

PURPOSE OF REVIEW

The gastroduodenum resists mucosal injury despite continuous exposure to concentrated gastric acid. The mucosal barrier consists of a preepithelial mucus HCO3- layer, intercellular tight junctions connecting the epithelial cells, and submucosal acid sensors, prostaglandins, cytokines, enteric nerves and blood flow. In the past year, study of these defensive mechanisms has revealed new insight into the observed sex differences in ulcer prevalence, the protective role of transforming growth factor, the role of serotonin in regulating HCO3- secretion, the role of mechanisms in ulcer healing, the interaction of trefoil factors with the mucus gel, the interaction of glucocorticoids with cyclooxygenase and the characterization of novel, mucosal sparing antiinflammatory agents.

RECENT FINDINGS

Transforming growth factor, melatonin, serotonin, trefoil factors and H2S all enhance mucosal barrier function or accelerate ulcer healing. Newer coxibs may have safety and advantages over existing compounds. Existing nonsteroidal antiinflammatory drugs may be safer than originally thought.

SUMMARY

The continued elucidation of basic defense mechanisms has led to the development of several new compounds designed to enhance barrier function and repair mechanisms.

Gastrin regulates the TFF2 promoter through gastrin-responsive cis-acting elements and multiple signaling pathways

Trefoil family factor 2 (TFF2) is expressed in gastrointestinal epithelial cells where it serves to maintain mucosal integrity and promote epithelial repair. The peptide hormone, gastrin, stimulates acid secretion but also induces proliferation of the acid-secreting mucosa. Because the relationship between these peptides of overlapping function is not understood, we chose to investigate the regulatory effect of gastrin on TFF2 expression. The expression of mRNA and protein of TFF2 was determined by RT-PCR and immunohistochemical staining, respectively. A series of truncated and mutant murine TFF2 promoter constructs was generated. Promoter activity was assessed using dual luciferase reporter assays. Gastrin-responsive DNA-binding sites in the TFF2 promoter were evaluated by electrophoretic mobility shift assay. Gastrin significantly increased the level of endogenous mRNA of TFF2 in the gastrin receptor-expressing AGS-E gastric cancer cell line in a time- and dose-dependent manner. TFF2 protein expression in the gastric fundus was elevated in hypergastrinemic (INS-GAS) transgenic mice and reduced in gastrin-deficient mice. Gastrin treatment increased TFF2 promoter activity through cis-acting regions, containing CCAATA- and GC-rich enhancers. Pretreatment with Y-F476, a gastrin/CCK(B) receptor antagonist, abolished gastrin-dependent promoter activity. Inhibitors of protein kinase C (PKC), mitogen/extracellular signal-regulated kinase (MEK1), and phosphatidylinositol 3-kinase (PI 3-kinase) reduced gastrin-dependent TFF2 promoter activity, whereas an epithelial growth factor receptor (EGFR) inhibitor had no effect. We found that gastrin regulates TFF2 transcription through a GC-rich DNA-binding site and a PKC-, MEK1- and PI 3-kinase-dependent but EGFR-independent pathway. Regulation of TFF2 by gastrin may play a role in the maintenance and repair of the gastrointestinal mucosa.