Gastroprotective Efficacy of Coenzyme Q10 in Indomethacin-Induced Gastropathy: Other Potential Mechanisms

Though recently the mitochondrial bioenergetic coenzyme (Co)Q10 has been shown to protect against indomethacin-induced gastric ulceration, yet the full mechanistic cassettes have not been investigated. Therefore, the current investigation assessed further gastroprotective mechanisms of CoQ10 using the indomethacin-induced gastropathy model. While CoQ10 was administered at 3 dose levels to male Wistar rats, the proton pump inhibitor, pantoprazole, was given at 4 dose levels ahead of pyloric ligation and indomethacin administration. Indomethacin evoked gastric ulcerations that were associated by decreased gastric mucosal nitric oxide and glutathione levels. The NSAID reduced gastric volume and mucin content, but increased titratable acidity, acid output, and peptic activity. CoQ10, especially at the higher dose levels, as well as pantoprazole pretreatments reverted almost all diversions induced by the NSAID to different extends. Moreover, preadministration with the nonselective nitric oxide synthase inhibitor, L-NAME, boosted ulcer formation that was associated by suppression of gastric mucosal nitric oxide in CoQ10 and pantoprazole-treated groups. The current investigation shows that CoQ10 guards against gastric ulceration via its partial inhibition of titratable acidity and peptic activity, as well as enhancement of mucin secretion due to both gastric mucosal nitric oxide and glutathione replenishment, especially at the higher dose levels.

Pepsin in Nonacidic Refluxate Can Damage Hypopharyngeal Epithelial Cells

Objectives: Studies using combined multichannel intraluminal impedance with pH monitoring reveal a role for nonacidic reflux in laryngopharyngeal symptoms and injury. We have discovered that pepsin is taken up by laryngeal epithelial cells by receptor-mediated endocytosis. This finding reveals a novel mechanism by which pepsin could cause cell damage, potentially even in nonacidic refluxate. The objective of this study was to determine whether pepsin, at pH 7.4 and thus in nonacidic refluxate, causes cell damage. Methods: Cultured hypopharyngeal epithelial (FaDu) cells were exposed to human pepsin (0.1 mg/mL) at pH 7.4 for either 1 hour or 12 hours at 37°C and analyzed by electron microscopy, cytotoxicity assay, and SuperArray. Results: We report mitochondrial and Golgi complex damage in cells exposed to pepsin at neutral pH, observed by electron microscopy. We also report cell toxicity of pepsin at pH 7.4, measured by a cytotoxicity assay. Furthermore, using SuperArray, we found that pepsin at pH 7.4 significantly alters the expression levels of multiple genes implicated in stress and toxicity. Conclusions: These findings are perhaps the first to explain why many patients have symptoms and injury associated with nonacidic reflux, and could have important implications for the development of new therapies for reflux, such as pepsin receptor antagonists and/or irreversible inhibitors of peptic activity.

Ligation of the abdominal esophagus decreases scorpion toxin-induced gastric secretion in rats

PURPOSE: Scorpion toxin purified from Tityus serrulatus venom (Tx) induces an increase in volume, acidity and pepsin secretion in the gastric juice of rats. Ligation of oesophagus has been shown to reduce the acid gastric secretion in rats. The aim of this paper was to determine the influence of the esophageal ligation on gastric secretion induced by Tx in rats METHODS: Forty-four male albino rats were given water ad libitum, but no food for 20 to 24 hours, anesthetized with urethane and the trachea and jugular vein cannulated. Cervical or abdominal esophageal ligation or sham-operations were performed before and after the injection of 0.25 mg/kg of scorpion toxin (fraction T1) into the jugular vein. One hour later, the volume, acidity, pH and peptic activity of gastric juice were determined. RESULTS: The scorpion toxin induced an increase in gastric juice volume, acidity and pepsin output and a decrease in pH when injected into the vein of intact animals or in sham-operated animals. Cervical esophagus ligation did not interfere with the effects of toxin, however, ligation of the abdominal esophageal decreased the toxin effect on the rat stomach. CONCLUSION: Ligation of the abdominal esophagus decreases the gastric secretion induced by scorpion toxin.

Nonparallel secretion of pepsinogen and acid by gastric oxyntopeptic cells of the toad (Bufo marinus)

Pepsinogen and HCl secretion in the amphibian stomach are performed by a single cell type, the oxyntopeptic cell. These functions were studied in gastric mucosae of toads (Bufo marinus) mounted in Ussing-type chambers. HCl and peptic activity of luminal fluid were measured by titration and proteolysis of albumin, respectively. Distribution of pepsinogen in the gastric mucosa was heterogeneous, activity being highest in the proximal part of the stomach. Zymogen granules in the oxyntopeptic cell were more abundant in the deeper cells of the glands and in the fundus. On stimulation, the granules were released into the lumen of the glands by exocytosis. Histamine, forskolin, or carbachol alone each induced an increase in HCl and pepsinogen secretion. Carbachol after maximal histamine or forskolin stimulation produced an extra increase in both secretions that was greater for pepsinogen response. Similarly, joint addition of carbachol and histamine was more potent than histamine alone for both parameters; however, the effect was greater on pepsinogen release. Pretreatment with cimetidine blocked HCl and pepsinogen responses to carbachol but did not affect responses to forskolin. Addition of omeprazole to forskolin-stimulated mucosae uncoupled the two secretions, inducing a total inhibition of HCl secretion with a slight reduction in pepsinogen secretion. Thus pepsinogen release, similar to HCl secretion, is sensitive to cAMP and Ca(2+)-dependent secretagogues. However, the action of Ca2+ would require the previous elevation of cAMP induced by the different secretagogues. In such a case, the increase in intracellular Ca2+ would result in a nonparallel activation of the two secretions.