Protection of the gastroduodenal mucosa by prostaglandins

Fatty acid abnormalities in cystic fibrosis-the missing link for a cure?

The care for cystic fibrosis (CF) has dramatically changed with the development of modulators, correctors, and potentiators of the CFTR molecule, which lead to improved clinical status of most people with CF (pwCF). The modulators influence phospholipids and ceramides, but not linoleic acid (LA) deficiency, associated with more severe phenotypes of CF. The LA deficiency is associated with upregulation of its transfer to arachidonic acid (AA). The AA release from membranes is increased and associated with increase of pro-inflammatory prostanoids and the characteristic inflammation is present before birth and bacterial infections. Docosahexaenoic acid is often decreased, especially in associated liver disease Some endogenously synthesized fatty acids are increased. Cholesterol and ceramide metabolisms are disturbed. The lipid abnormalities are present at birth, and before feeding in transgenic pigs and ferrets. This review focus on the lipid abnormalities and their associations to clinical symptoms in CF, based on clinical studies and experimental research.

Protective Effects of Melatonin and Misoprostol against Experimentally Induced Increases in Intestinal Permeability in Rats

Intestinal mucosal barrier dysfunction caused by disease and/or chemotherapy lacks an effective treatment, which highlights a strong medical need. Our group has previously demonstrated the potential of melatonin and misoprostol to treat increases in intestinal mucosal permeability induced by 15-min luminal exposure to a surfactant, sodium dodecyl sulfate (SDS). However, it is not known which luminal melatonin and misoprostol concentrations are effective, and whether they are effective for a longer SDS exposure time. The objective of this single-pass intestinal perfusion study in rats was to investigate the concentration-dependent effect of melatonin and misoprostol on an increase in intestinal permeability induced by 60-min luminal SDS exposure. The cytoprotective effect was investigated by evaluating the intestinal clearance of ⁵¹Cr-labeled EDTA in response to luminal SDS as well as a histological evaluation of the exposed tissue. Melatonin at both 10 and 100 µM reduced SDS-induced increase in permeability by 50%. Misoprostol at 1 and 10 µM reduced the permeability by 50 and 75%, respectively. Combination of the two drugs at their respective highest concentrations had no additive protective effect. These in vivo results support further investigations of melatonin and misoprostol for oral treatments of a dysfunctional intestinal barrier.

Use of Cyclo-Oxygenase Inhibitors Is Not Associated with Clinical Relapse in Inflammatory Bowel Disease: A Case-Control Study

Patients with inflammatory bowel disease (IBD) often have associated conditions, for which anti-inflammatory medication with cyclo-oxygenase (COX) inhibitors may be helpful. The current evidence is conflicting regarding the role of COX-inhibitors in causing relapse in IBD. This case-control study examined the association between the use of COX inhibitors and relapse of IBD. Logistic regression was used to analyse the relationship between COX-inhibitors and IBD relapse. Overall COX inhibitor use (combined non-steroidal anti-inflammatory drugs (NSAIDs) and selective COX-2 agents) had a negative association with relapse of IBD (adjusted OR 0.26, 95% CI 0.09–0.80). This negative association was confined to ulcerative colitis (UC) (adjusted OR = 0.06, 95% CI 0.01–0.50) and no association was found in Crohn’s disease (CD) patients (adjusted OR 1.25, 95% CI 0.18–7.46). The significant negative association between UC relapse and medication use was also seen with non-specific NSAIDs. Selective COX-2 inhibitor use was rare but non-significantly more common in stable patients. There was no association between low-dose aspirin or paracetamol use and relapse of CD or UC. We conclude that COX-inhibitor use was not associated with an increased risk of relapse in UC or CD, and may be protective in UC. Where indicated, NSAIDs should not be withheld from IBD patients.

Gastrointestinal lesions and complications of low-dose aspirin in the gastrointestinal tract

Low dose aspirin (ASA) use has been associated with a wide range of adverse side effects in the upper gastrointestinal (GI) tract, which range from troublesome symptoms without mucosal lesions to more serious toxicity, including ulcers, GI bleeding, perforation and even death. Upper GI symptoms in low dose ASA users are common but often careless or misinterpreted and they are not always related to the presence of mucosal injury. Usually, low dose ASA related ulcers are reasonably small and asymptomatic, and probably heal over a period of weeks to a few months. But, the real clinical problem occurs when the ulcer results in a GI complication (mostly bleeding). The estimated average excess risk of symptomatic or complicated ulcer related to low dose ASA is five cases per 1000 ASA users per year. Death is the worst outcome of GI complications in low dose ASA users, but data about this aspect are scarce. Current evidence indicates that low dose ASA can damage the lower GI tract also, but the real size of the problem is still unknown.

Gastrointestinal effects of aspirin

Aspirin is being used as an effective analgesic and anti-inflammatory agent at doses >325 mg daily. At low doses (75-325 mg daily), aspirin is the key antiplatelet drug in the pharmacological prevention of cardiovascular diseases. Topical and systemic effects of aspirin in the gastrointestinal mucosa are associated with mucosal damage in the upper and lower gastrointestinal tract. The risk of upper gastrointestinal bleeding with aspirin is increased with old age, male sex, ulcer history and concomitant medication with NSAIDs, cyclooxygenase 2 selective inhibitors, corticosteroids or other antithrombotic agents. In some patients, the cardiovascular benefits of low-dose aspirin might be overcome by the risk of gastrointestinal complications, but withdrawal of aspirin therapy can precipitate a cardiovascular event. These patients will need concomitant therapy with antisecretory agents, especially PPIs, to reduce the gastrointestinal risk. Eradication of Helicobacter pylori infection might be an additional option in patients with a history of ulcer. Furthermore, there is growing evidence that long-term use of aspirin decreases the risk of colorectal cancer, even at low doses. As aspirin is one of the most prescribed drugs worldwide and its clinical impact is huge, physicians need to consider the benefits and harms for each individual patient in order to maximize the benefits of aspirin.

Gastroduodenal toxicity of low-dose acetylsalicylic acid: a comparison with non-steroidal anti-inflammatory drugs

BACKGROUND

Low-dose acetylsalicylic acid (ASA; aspirin; 75-325 mg/day) is effective for the prevention of cardiovascular events, and its use in this indication is rapidly increasing. However, the use of ASA and, indeed, other non-steroidal anti-inflammatory drugs (NSAIDs) is limited by the incidence of adverse gastroduodenal events. OBJECTIVES AND SCOPE: To review the clinical evidence for, and the pharmacodynamic basis of, ASA-induced gastroduodenal toxicity in comparison with NSAIDs, and address the question of whether low-dose ASA is 'safe' from a gastroduodenal perspective. This was a narrative, descriptive review, rather than a formal systematic review.

FINDINGS

Adverse gastroduodenal effects, which are well known to occur with NSAIDs, are also prevalent in patients receiving low-dose ASA for cardiovascular protection even at doses as low as 75 mg/day. The risk of gastroduodenal toxicity is particularly high among 'at-risk' low-dose ASA patients (aged >70 years, previous ulcer or upper gastrointestinal bleeding and users of antiplatelets or NSAIDs). There are important differences in the mechanism of ASA-induced gastroduodenal toxicity, relative to NSAIDs. These differences include the effects on the cyclooxygenase (COX)-1 isoenzyme, local effects on the gastroduodenal mucosa specific to ASA and a reduction in platelet aggregation.

CONCLUSION

Data suggest that ASA causes significant gastroduodenal damage even at the low doses used for cardiovascular protection. These effects (both systemic and possibly local) may be pharmacodynamically distinct from the gastroduodenal toxicity seen with NSAIDs. Studies are required to establish strategies for improving the tolerability of low-dose ASA, allowing patients to continue to benefit from the cardiovascular protection associated with such therapy.

Who's Winning the War? Molecular Mechanisms of Antibiotic Resistance in Helicobacter pylori

The ability of clinicians to wage an effective war against many bacterial infections is increasingly being hampered by skyrocketing rates of antibiotic resistance. Indeed, antibiotic resistance is a significant problem for treatment of diseases caused by virtually all known infectious bacteria. The gastric pathogen Helicobacter pylori is no exception to this rule. With more than 50% of the world's population infected, H. pylori exacts a tremendous medical burden and represents an interesting paradigm for cancer development; it is the only bacterium that is currently recognized as a carcinogen. It is now firmly established that H. pylori infection is associated with diseases such as gastritis, peptic and duodenal ulceration and two forms of gastric cancer, gastric adenocarcinoma and mucosa-associated lymphoid tissue (MALT) lymphoma. With such a large percentage of the population infected, increasing rates of antibiotic resistance are particularly vexing for a treatment regime that is already fairly complicated; treatment consists of two antibiotics and a proton pump inhibitor. To date, resistance has been found to all primary and secondary lines of antibiotic treatment as well as to drugs used for rescue therapy.

Effect of nitric oxide synthase inhibition on the gastric mucosal barrier in rats

The aim of this study was to investigate the effect of N-G-nitro-L-arginine-methyl ester (L-NAME), a nitric oxide synthase inhibitor, on the gastric mucosal barrier in rats. A group of Swiss albino rats received L-NAME (60 mg/kg/d) in their drinking water daily for 21 d. The mucin and prostaglandin E2 (PGE2) contents of the gastric mucosa were measured in gastric tissue samples. L-NAME intake did not affect gastric mucin, but it significantly reduced PGE2, a component of the gastric mucosal barrier. The results of this study imply that nitric oxide plays an important mediatory role in maintaining the gastric mucosal barrier. The inhibition of nitric oxide may be involved in the increased vulnerability of the gastric mucosa to injurious stimuli in rats.

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.

A correlative study on the mechanism of adaptive cytoprotection against ethanol-induced gastric lesion formation in rats

The protective effect of mild irritants against the subsequent gastric injury induced by necrotizing agents has been termed 'adaptive cytoprotection'. In this study, the possible pathway and mechanisms of adaptive cytoprotection induced by 20% ethanol were investigated. An ex-vivo gastric chamber preparation was used. The gastric mucosa was exposed to 20% ethanol before subsequent administration of 100% ethanol 15 min later. Subdiaphragmatic vagotomy or drug pretreatment was carried out in order to elucidate the mechanisms of adaptive cytoprotection by 20% ethanol. The results showed that 20% ethanol pre-exposure significantly protected the gastric mucosa against damage caused by 100% ethanol. This protective action was completely abolished by atropine or lidocaine pretreatment, whereas vagotomy and hexamethonium failed to have a significant influence. The cytoprotective effect, however, was independent of the gastric secretory volume, titratable acid content, luminal soluble mucus level and gastric mucosal blood flow. Exposure of only half the gastric mucosa to the mild irritant resulted in the protection of both sides of the mucosa. All these findings indicate that the adaptive cytoprotection of 20% ethanol involves the participation of chemoreceptors and muscarinic receptors in the gastric mucosa. An internal enteric reflex arc, with transmission of signals within the gastric mucosa, may also contribute to the cytoprotective process of the mild irritant.

The role of luminal factors in prostaglandin protection against ethanol-induced gastric mucosal injury

Prostaglandins (PG) protect the gastric mucosa against damage by several irritants, but the mechanisms remain unclear. A standard rat model of gastric injury induced by 50% ethanol was used to test the hypothesis that PG protection occurs either by increasing luminal fluid volume and hence diluting the irritant, or by production of protective factors within this fluid. Quantitative histology was used to assess microscopic mucosal damage. The increase in luminal fluid volume in prostaglandin E2 (PGE2)-treated animals was measured, and the ability of this increased fluid to protect saline-treated animals via dilution of the irritant was assessed. The transfer of protection by exchange of luminal fluid from PG to non-PG treated animals was also tested. Results showed that PGE2 induced a specific increase in luminal fluid volume of 45.6%. When given together with ethanol treatment the extra fluid volume was not protective. Removal of luminal fluid after PG and before ethanol treatment did not abolish protection and no protective factor was transferred with the luminal fluid. In conclusion, this study has shown that neither dilution of ethanol by accumulation of luminal fluid nor the presence of luminal factors is responsible for PG protection.

Probable role of both sulfhydryls and prostaglandins in gastric mucosal protection induced by S-adenosylmethionine

The role of both sulfhydryl groups and endogenous prostaglandins in the protective effect of S-adenosylmethionine against ethanol-induced gastric mucosal damage was studied in rats. Drugs were administered subcutaneously or intragastrically to fasted rats 30 or 60 min before 100% ethanol (1 ml/rat), and mucosal lesions were measured planimetrically 1 h later. The gastric mucosal protection given by S-adenosylmethionine or by 20% ethanol (adaptive protection) was significantly diminished by pretreatment of rats with the sulfhydryl blocker iodoacetamide or with the cyclooxygenase inhibitor indomethacin. The protective effect of S-adenosylmethionine could be totally abolished only by pretreatment with the combination of iodoacetamide and indomethacin. Our present data suggest that endogenous release of prostaglandins and sulfhydryl groups may play a role in the protective actions of both S-adenosylmethionine and 20% ethanol (adaptive protection) against ethanol-induced gastric mucosal damage.

Effect of mifentidine on mepirizole-induced duodenal ulcer in the rat

The H2-receptor antagonists mifentidine, famotidine, cimetidine and ranitidine were examined for their ability to prevent the duodenal ulcer caused by mepirizole (250 mg/kg p.o.), a non-steroidal anti-inflammatory agent, in the conscious rat. All the compounds exerted a dose-related protective effect and on the basis of their ED50s, the following rank order of potency was found: mifentidine = famotidine greater than ranitidine greater than cimetidine. The antiulcer activity displayed by the H2-receptor antagonists evaluated in this model reflects their potency in inhibiting basal and stimulated gastric acid secretion in rat. The results of these studies indicate mifentidine as a potent anti-ulcer agent.

Enprostil and ranitidine: comparative efficacy and safety in patients with duodenal ulcer

This randomised, double-blind, double-dummy, multiclinic study of duodenal ulcer healing compared the efficacy and safety of enprostil with ranitidine. The six week trial admitted 164 patients with endoscopically demonstrated duodenal ulcer. Ratings of symptoms and adverse events were collated from patients' daily diaries, and endoscopy was repeated to verify healing after four weeks and, if appropriate, after six weeks. Medication used was enprostil (35 micrograms capsule) or ranitidine hydrochloride (150 mg tablet) with matching placebos twice daily. After six weeks, 81% of patients treated with enprostil and 95% of those treated with ranitidine had healed ulcers, a statistically significant difference (p = 0.007). There were no differences between treatment groups for the number of days until the daytime ulcer pain completely ceased. Night-time ulcer pain ceased significantly earlier in the group receiving ranitidine (p = 0.019) and was less severe during the week before the last visit (p = 0.001); daytime pain for ranitidine users was also less severe (p = 0.020) during this week. Mild to moderate adverse experiences were reported by 44% of enprostil and 35% of ranitidine patients. There were no severe adverse events. In conclusion, both enprostil and ranitidine were found to be safe and effective in the treatment of duodenal ulcer. However, the ranitidine regimen used in this trial produced better results than the enprostil regimen.

Enprostil and cimetidine: comparative efficacy and safety in patients with duodenal ulcer

The safety and efficacy of enprostil, 35 micrograms twice daily, and of cimetidine, 400 mg twice daily, in the treatment of duodenal ulcers were compared in a randomized, double-blind, parallel, multiclinic study. Endoscopy was performed before treatment and at 2-week intervals for 6 weeks or until the ulcer healed. Patients recorded their drug compliance, antacid use, ulcer symptoms, and adverse experiences daily. One hundred and six patients entered the trial, of which 104 were eligible for the initial endoscopy analysis. Base-line characteristics were similar in the two treatment groups. The cumulative healing rates in the enprostil group were 56%, 86%, and 92% at 2, 4, and 6 weeks, respectively, and those in the cimetidine group were 53%, 84%, and 90% (NS). The healing rates for nonsmokers at 6 weeks were 96% in the enprostil group and 97% in the cimetidine group, which were significantly greater than those for smokers--88% and 81%, respectively. There were no significant differences in the duration, severity, or frequency of daytime or nighttime pain between the groups. Seventeen of the enprostil patients (32%) reported 21 adverse experiences during the trial, and 20 of the cimetidine patients (39%) reported 23 adverse experiences. No patients withdrew because of adverse experiences. The two drugs were similarly safe and effective in the treatment of duodenal ulcer.

Failure of a cytoprotective dose of arbaprostil to heal acute duodenal ulcers. Results of a multiclinic trial

Previous therapeutic trials with prostaglandins have shown them to be effective in healing duodenal ulcers when used at doses that are highly effective suppressors of gastric acid secretion. We undertook this trial to determine if a cytoprotective dose of arbaprostil (10 micrograms q.i.d. for 4 wk) would also be efficacious in this disease state. Eighty-two patients between the ages of 19 and 72 yr with endoscopically documented duodenal ulcers were entered into this randomized double-blind placebo-controlled trial. The patients were monitored with biweekly endoscopies and laboratory examinations, weekly interviews during the period when drug was administered, and a follow-up interview plus laboratory examinations 1 wk after drug administration was completed. No statistically significant differences between the arbaprostil and placebo treatment groups were found for ulcer healing rates, pain relief, antacid consumption, side effects, or laboratory examinations. It is presumed that this prostaglandin may not have sufficient duodenal cytoprotective capacity to effectively heal duodenal ulcers, or that some suppression of gastric acid secretion may be required to achieve significant clinical efficacy.