Elevation of histidine decarboxylase activity in the stomach of mice by ulcerogenic drugs

Protective Effects of Methanol Extract of Vernonia amygdalina (del.) Leaf on Aspirin-Induced Gastric Ulceration and Oxidative Mucosal Damage in a Rat Model of Gastric Injury

This study investigated the quantitative polyphenolic constituents and gastroprotective effects of methanol extract of Vernonia amygdalina leaf (MEVA) against aspirin-induced gastric ulcer in rats. Ulceration was induced by 3 days’ oral administration of aspirin (150 mg/kg body weight). Wistar rats were pretreated with cimetidine (reference drug) at a dose of 100 mg/kg body weight and MEVA at 200, 300, and 400 mg/kg body weight once daily for 28 days prior to ulcer induction. At the end of the experiment, gastric secretions, antioxidant status, and histopathological alteration were evaluated. We observed that the significantly increased ulcer index, gastric volume, free and total acidity, malondialdehyde level, and pepsin activity were effectively reduced following treatment with 200 and 300 mg/kg MEVA. The extract also markedly attenuated the reduced activity of superoxide dismutase and reduced glutathione level as well as pH and mucin content in the ulcerated rats. Administration of the extract also significantly attenuates necrosis of the stomach tissue of the ulcerated rats. The results suggested that the MEVA leaf, preferably at 200 and 300 mg/kg body weight, ameliorated aspirin-induced gastric ulceration via antioxidative and H₂ receptor antagonist.

Gastro-protective effect of methanol extract of Vernonia amygdalina (del.) leaf on aspirin-induced gastric ulcer in Wistar rats

This study investigated the protective effects of methanol extract of Vernonia amygdalina leaf (MEVA) on aspirin induced gastric ulcer in rats. Thirty Wistar rats, 150-200 g were divided into six groups as follows: Group 1 (control) rats received 2 mL/kg of propylene glycol for 28 consecutive days. Group 2 (Ulcer Control) received 150 mg/kg/day of aspirin suspended in 3 mL of 1% carboxymethylcellulose in water orally for 3 consecutive days during which the rats were fasted for the induction of ulcer. Group 3 received cimetidine at 100 mg/kg/day orally for 28 consecutive days and thereafter treated as group 2. Groups 4, 5 and 6 received MEVA orally at 200, 300 and 400 mg/kg/day respectively for 28 consecutive days and thereafter were treated with aspirin as group 2. All the animals were sacrifice at the end of the study to determine the gastric pH, gastric acidity, gastric ulcer score, haematological indices, superoxide dismutase (SOD) activity, reduced glutathione (GSH) and Lipid peroxidation (LPO) levels. The result showed that aspirin significantly (p < 0.05) increased gastric ulcer score and index, decreased gastric pH, gastric acidity, SOD activity, GSH level as well as increased LPO level. It induced significant necrosis of the stomach tissue. Administration of MEVA significantly (p < 0.05) increased gastric pH, but decreased gastric acid secretion and reversed alteration of haematological parameters. It also significantly (p < 0.05) increased SOD activity, GSH level and decreased LPO level. The results suggest that Vernonia amygdalina possesses gastro-protective properties against aspirin-induced gastric ulcer.

Anti-ulcer effect and potential mechanism of licoflavone by regulating inflammation mediators and amino acid metabolism

ETHNOPHARMACOLOGICAL RELEVANCE

Glycyrrhiza is the dry root and rhizome of the leguminous plant, Glycyrrhiza uralensis Fisch., Glycyrrhiza inflata Bat. or Glycyrrhiza glabra L., which was firstly cited in Shennong's Herbal Classic in Han dynasty and was officially listed in the Chinese Pharmacopoeia, has been widely used in China during the past millennia. Licoflavone is the major component of Glycyrrhiza with anti-ulcer activity. The present study is based on clarifying the anti-ulcer effect of licoflavone, aiming at elucidating the possible molecule mechanisms of its action for treating gastric ulcer rats induced by acetic acid.

MATERIALS AND METHODS

Rats were divided into 7 groups, and drugs were administered from on the day after the onset of gastric ulcer (day 3) until day 11 of the experiment once daily continuously. The plasma were analyzed by high-performance liquid chromatography combined with time-of-flight mass spectrometry (HPLC/ESI-TOF-MS), significant different metabolites were investigated to explain its therapeutic mechanism. Furthermore, quantitative real time polymerase chain reaction (RT-PCR) analysis was performed to detect the expression of RNA in stomach tissue for verifying the above results.

RESULTS

Licoflavone can effectively cure the gastric ulcer, particularly the middle dose group. According to the statistical analysis of the plasma different metabolites from each groups and the expression of genes in tissues, sixteen significant different metabolites, including histamine, tryptophan, arachidonic acid, phingosine-1-phosphate etc., contributing to the treatment of gastric ulcer were discovered and identified. In RT-PCR analysis, the results of the expression of RNA were corresponded with what we discovered.

CONCLUSIONS

Our study indicated licoflavone plays the role of treating gastric ulcer by regulating inflammation mediators and amino acid metabolism. We demonstrated that metabolomics technology combined with gene technology is a useful tool to search different metabolites and to dissect the potential mechanisms of traditional Chinese medicine (TCM) in treating gastric ulcer.

Comparative appraisal of clodronate, aspirin and dexamethasone as agents reducing alendronate-induced inflammation in a murine model

Among the bisphosphonates, the nitrogen-containing bisphosphonates have much stronger anti-bone-resorptive activities than bisphosphonates containing no nitrogen, but nitrogen-containing bisphosphonates mostly have inflammatory side effects. Our previous murine-model experiments with a single intraperitoneal bisphosphonate injection demonstrated that (i) nitrogen-containing bisphosphonates induce various inflammatory reactions via an IL-1-dependent mechanism, (ii) alendronate (an nitrogen-containing bisphosphonate) produces a clear sclerotic line in the tibia that is easily detectable by radiography a few weeks later (tentatively called the bisphosphonate line, a useful marker for the anti-bone-resorptive activities of bisphosphonates), and (iii) clodronate (a non-nitrogen-containing bisphosphonate) reduces the inflammatory reactions induced by alendronate but does not reduce the bisphosphonate line formation induced by alendronate. We compared the effects of clodronate, aspirin and dexamethasone on the inflammatory reactions induced by alendronate (40 micromol/kg) (induction of the histamine-forming enzyme, accumulation of pleural exudate and splenomegaly) and on the bisphosphonate line formation induced by alendronate (0.1 micromol/kg). The effects of aspirin (833 micromol/kg) were weak. However, like clodronate, dexamethasone (10 micromol/kg, injected 5 min. after alendronate), strongly inhibited the alendronate-induced inflammatory reactions but did not reduce the alendronate-induced bisphosphonate line formation. Alendronate produced normal bisphosphonate lines in IL-1-deficient mice, too. These results suggest that clodronate and/or dexamethasone may be suitable for preventing or reducing the inflammatory side effects of nitrogen-containing bisphosphonates while preserving their powerful anti-bone-resorptive activities (although in practice the known side effects of dexamethasone may limit its use), and that the anti-bone resorptive activities of nitrogen-containing bisphosphonates are not influenced by IL-1.

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.

Neuroendocrinology of gastric H+ and duodenal HCO3- secretion: the role of brain-gut axis

Gastric H+ and duodenal HCO3- secretions are precisely regulated by neuro-hormonal mechanisms at central and peripheral levels to match the rate of these secretions with the type of stimulation of sensory receptors in the head area (sight, smell, taste, etc.) and in the gastro-intestinal system. Two-way communication pathways operate between the brain and the gut, each comprising afferent fibers signaling sensory information from the gut to the brain and efferent fibers transmitting signals in opposite direction. Short intramural and long extramural reflexes are triggered as well as various gut hormones are released by feeding that "cooperate" with the "brain-gut axis" in the alteration of exocrine and endocrine gastro-duodenal secretion, motility and blood circulation. The malfunction of gastric or duodenal secretory mechanisms may lead to disturbances of gastric H+-pepsin or duodenal mucus-HCO3- secretion and to gastro-duodenal disorders and diseases. This review presents recent advances in pathophysiological mechanisms underlying gastro-duodenal secretory disorders.

Gastric secretion

PURPOSE OF REVIEW

Gastric acid facilitates the digestion of protein and the absorption of iron, calcium, and vitamin B12. It also protects against bacterial overgrowth and enteric infection, including prion disease. When homeostatic mechanisms malfunction, the volume and concentration of acid may overwhelm mucosal defense mechanisms, leading to duodenal ulcer, gastric ulcer, and gastroesophageal reflux disease. This article reviews recent knowledge contributing to understanding of the regulation of gastric acid secretion at the central, peripheral, and intracellular levels.

RECENT FINDINGS

The vagus nerve contains afferent fibers that transmit sensory information from the stomach to the nucleus of the solitary tract. Input from the nucleus of the solitary tract is relayed to vagal efferent neurons that originate from two brain stem nuclei: the nucleus ambiguus and the dorsal motor nucleus of the vagus. The latter is also influenced by thyrotropin-releasing hormone neurons that act centrally to stimulate acid secretion. The main peripheral stimulants of acid secretion are the hormone gastrin and the paracrine amine histamine. Gastrin stimulates acid secretion directly and, more importantly, indirectly by releasing histamine from fundic enterochromaffin-like cells. Gastrin also exerts trophic effects on various tissues, including the gastric and intestinal mucosa. The main inhibitor of acid secretion is somatostatin. Somatostatin, acting via ssTR2 receptors, exerts a tonic paracrine inhibitory influence on the secretion of gastrin, histamine, and acid secretion. Calcitonin gene-related peptide, adrenomedullin, amylin, atrial natriuretic peptide, and pituitary adenylate cyclase-activating polypeptide all stimulate somatostatin secretion and thus inhibit acid secretion. HK-ATPase, the proton pump of the parietal cell, is stored within cytoplasmic tubulovesicles during the resting state, but during stimulation, it is shuttled to the canalicular membrane by a poorly understood mechanism that probably involves soluble N-ethylmaleimide-sensitive factor attachment protein receptor proteins. The proton pump inhibitor, pantoprazole, is unique in that it binds cysteine 822, located deep within the membrane domain of the alpha-subunit. The difficulty that reducing agents, such as glutathione, have in reaching cysteine 822 may be responsible for the longer half-time for acid recovery observed with pantoprazole. Hypergastrinemia, induced by proton pump inhibitors, enhances expression of cyclooxygenase-2 and hence prostaglandins within parietal cells, a feedback pathway that may protect the stomach against acid-induced damage.

SUMMARY

In the past year, significant advances have been made in understanding of the regulation of gastric acid secretion. Ultimately, these advances should lead to improved therapies to prevent and treat acid-related disorders. Gastric acid secretion must be precisely controlled at a variety of levels to prevent disease caused by hyperchlorhydria and hypochlorhydria. The mechanisms include neural (central and peripheral), hormonal, paracrine, and intracellular pathways that operate in concert to switch acid secretion on during ingestion of a meal and off during the interdigestive period. A better understanding of the physiology of acid secretion in health and disease should eventually lead to improved therapies to prevent and treat acid-related disorders.