Bile reflux due to disturbed gastric movement is a cause of spontaneous gastric ulcer in W/Wv mice

Gastroparesis Worsens Indomethacin-Induced Gastric Antral Ulcers by Bile Reflux via Activation of 5-HT3 and Dopamine D2 Receptors in Mice

BACKGROUND/AIMS

We examined the contributions of gastric emptying and duodenogastric bile reflux in the formation of gastric antral ulcers induced by NSAIDs in mice.

METHODS

We used the murine re-fed indomethacin (IND) experimental ulcer model. Outcome measures included the appearance of gastric lesions 24 h after IND treatment and the assessment of gastric contents and the concentration of bile acids 1.5 h after re-feeding. The effects of atropine, dopamine, SR57227 (5-HT3 receptor agonist), apomorphine, ondansetron, haloperidol, and dietary taurocholate and cholestyramine were also examined.

RESULTS

IND (10 mg/kg, s.c.) induced severe lesions only in the gastric antrum in the re-fed model. The antral lesion index and the amount of food intake during the 2-h refeeding period were positively correlated. Atropine and dopamine delayed gastric emptying, increased bile reflux, and worsened IND-induced antral lesions. SR57227 and apomorphine worsened antral lesions with increased bile reflux. These effects were prevented by the anti-emetic drugs ondansetron and haloperidol, respectively. The anti-emetic drugs markedly decreased the severity of antral lesions and the increase of bile reflux induced by atropine or dopamine without affecting delayed gastric emptying. Antral lesions induced by IND were increased by dietary taurocholate but decreased by the addition of the bile acid sequestrant cholestyramine.

CONCLUSIONS

These results suggest that gastroparesis induced by atropine or dopamine worsens NSAID-induced gastric antral ulcers by increasing duodenogastric bile reflux via activation of 5-HT3 and dopamine D2 receptors.

Xiaotan Tongfu granules contribute to the prevention of stress ulcers

AIM: To investigate the efficacy and potential mechanism of Xiaotan Tongfu granules (XTTF) in stress ulcers.

METHODS: One hundred sixty rats were randomly divided into 4 groups (n = 10) as follows: the model group (MP group), the control group (CP group), the ranitidine group (RP group) and the XTTF granule group (XP group). Rats in the MP group received no drugs, rats in the CP group received 0.2 mL of a 0.9% sodium chloride solution via oral gavage, and rats in the RP and XP groups received the same volume of ranitidine (50 mg/kg) or XTTF granule (4.9 g/kg). The cold-restraint stress model was applied to induce stress ulcers after 7 consecutive days of drug administration. Afterwards, rats were sacrificed at 0, 3, 6 and 24 h. Gastric pH was measured by a precise pH meter; gastric emptying rate (GER) was measured by using a methylcellulose test meal; myeloperoxidase activity (MPO), macrophage migration inhibitory factor (MIF), proliferating cell nuclear antigen (PCNA), and heat shock protein 70 (HSP70) were measured by immunohistochemical staining; and mucosal cell apoptosis was measured by transferase dUTP nick end labeling.

RESULTS: In the cold-restraint stress model, the development of stress ulcers peaked at 3 h and basically regressed after 24 h. Gastric lesions were significantly different in the RP and XP groups at each time point. Interestingly, although this index was much lower in the RP group than in the XP group immediately following stress induction (7.00 ± 1.10 vs 10.00 ± 1.79, P < 0.05. Concerning gastric pH, between the RP and XP groups, we detected a statistically significant difference immediately after stress induction (0 h: 4.56 ± 0.47 vs 3.34 ± 0.28, P < 0.05) but not at any of the subsequent time points. For GER, compared to the RP group, GER was remarkably elevated in the XP group because a statistically significant difference was detected (3 h: 46.84 ± 2.70 vs 61.16 ± 5.12, P < 0.05; 6 h: 60.96 ± 6.71 vs 73.41 ± 6.16, P < 0.05; 24 h: 77.47 ± 3.17 vs 91.31 ± 4.34, P < 0.05). With respect to MPO and MIF, comparisons between the RP and XP groups revealed statistically significant differences at 3 h (MPO: 18.94 ± 1.20 vs 13.51 ± 0.89, P < 0.05; MIF: 150.67 ± 9.85 vs 122.17 ± 5.67, P < 0.05) and 6 h (MPO: 13.22 ± 1.54 vs 8.83 ± 0.65, P < 0.05; MIF: 135.50 ± 9.46 vs 109.83 ± 6.40, P < 0.05). With regard to HSP70, HSP70 expression was significantly increased in the RP and XP groups at 3 and 6 h compared to the MP and CP groups. In addition, comparing the RP and XP groups also showed statistically significant differences at 3 and 6 h. The expression of PCNA was higher in the RP and XP groups 3 h after stress induction. Between these two groups, small but statistically significant differences were observed at all of the time points (3 h: 69.50 ± 21.52 vs 79.33 ± 15.68, P < 0.05; 6 h: 107.83 ± 4.40 vs 121.33 ± 5.71, P < 0.05; 24 h: 125.33 ± 5.65 vs 128.50 ± 14.49, P < 0.05) except 0 h. With regard to apoptosis, the apoptotic activity in the RP and XP groups was significantly different from that in the MP and CP groups. The XP group exhibited a higher inhibition of cell apoptosis than the RP group at 3 h (232.58 ± 24.51 vs 174.46 ± 10.35, P < 0.05) and 6 h (164.74 ± 18.31 vs 117.71 ± 12.08, P < 0.05).

CONCLUSION: The Xiaotan Tongfu granule was demonstrated to be similar to ranitidine in preventing stress ulcers. It exhibited multiple underlying mechanisms and deserves further study.

Mast cells are critical for protection against peptic ulcers induced by the NSAID piroxicam

Many commonly used non-steroidal anti-inflammatory drugs (NSAIDs) also cause gastrointestinal toxicity, including the development of life-threatening peptic ulcers. We report that mast cell-deficient mice have an extremely high incidence of severe peptic ulceration when exposed to the NSAID piroxicam. This enhanced ulcer susceptibility can be reversed by reconstitution with mast cells. Furthermore, wild type mice treated with diphenhydramine hydrochloride, a commonly used antihistamine that blocks histamine H1 receptors, develop a similarly high incidence of peptic ulcers following piroxicam exposure. The protective effect of mast cells is independent of TNF, blockade of H2 receptors, or acid secretion. These data indicate a critical role for mast cells and the histamine that they produce in prevention and/or repair of piroxicam-induced gastric mucosal injury. Additional studies will be required to determine whether this represents a NSAID class effect that can be exploited to develop novel therapeutic strategies to limit the incidence of NSAID-induced side effects in humans.

Pyloric sphincter dysfunction in nNOS-/- and W/Wv mutant mice: animal models of gastroparesis and duodenogastric reflux

BACKGROUND & AIMS

Nitrergic nerves and interstitial cells of Cajal (ICC) have been implicated in the regulation of pyloric motility. The purpose of these studies was to define their roles in pyloric function in vivo.

METHODS

Pyloric sphincter manometry was performed in wild-type controls, neuronal nitric oxide synthase-deficient (nNOS(-/-)) mice, and ICC-deficient W/W(v) mice, and the effect of deafferented cervical vagal stimulation was examined.

RESULTS

Mice showed a distinct approximately 0.6-mm-wide zone of high pressure at the antroduodenal junction, representing the pyloric sphincter. In wild-type controls, the pylorus exhibited tonic active pressure of 12.4 +/- 1.6 mm Hg with superimposed phasic contractions. The motility indices, minute motility index, and total myogenic activity were reduced by vagal stimulation, and the reduction was antagonized by the nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME). In nNOS(-/-) mice, pyloric basal tone, minute motility index, and total myogenic activity were not significantly different from those in controls, but vagal stimulation paradoxically increased pyloric motility. In contrast, the W/W(v) mice had significantly reduced resting pyloric pressure that was suppressed by vagal stimulation in an L-NAME-sensitive manner. The stomachs of fasted nNOS(-/-) mice showed solid food residue and bezoar formation, while W/W(v) mice showed bile reflux.

CONCLUSIONS

In nNOS(-/-) mice, loss of nitrergic pyloric inhibition leads to gastric stasis and bezoars. In contrast, basal pyloric hypotension with normal nitrergic inhibition predisposes W/W(v) mice to duodenogastric bile reflux.

Mechanisms of action of leptin in preventing gastric ulcer

AIM: To investigate the effects of leptin (1-20 μg/kg) on acidified ethanol (AE)- and indomethacin (Indo)-induced gastric lesions in rats and compare it with ranitidine, lanso-prazole, and omeprazole and to determine its mechanisms of actions.

METHODS: Gastric ulcers, which were approximately 1 mm in width, formed in the glandular portion of the gastric mucosa produced by oral administration of either AE or Indo were taken as ulcer index. The inhibitory effect of subcutaneous administration of leptin, two proton pump inhibitors (PPIs) lansoprazole and omeprazole, or H₂-receptor antagonist ranitidine 30 min before AE or Indo was evaluated. A radioimmunoassay was used to determine the PGE₂ concentration in the homogenate of the glandular portion of the stomach. We performed histological study of the glandular stomach for the evaluation of total, acidic, and sulfated mucus content.

RESULTS: Subcutaneous administration of leptin, two PPIs lansoprazole and omeprazole or H₂-receptor antagonist ranitidine 30 min before AE or Indo produced a dose-dependent and reproducible inhibition of gastric ulcers (GUs). This inhibition was found to be more potent than other antagonists used. In N^G-nitro L-arginine methyl ester (L-NAME)-pretreated animals, the ulcer prevention ability of leptin in AE-induced ulcer was significantly reduced, compared to rats without L-NAME pretreatment. However, the ulcer prevention ability of leptin was not altered by L-NAME treatment in Indo-induced ulcers. Leptin produced a dose-dependent increase in PGE₂ level in the gastric glandular tissues. Leptin also increased mucus secretion.

CONCLUSION: The results of the present study show that leptin inhibits GU formation by AE or Indo in a dose-dependent and reproducible manner in rats. The results also suggest that leptin prevents ulcer formation by increasing the activities of the cyclo-oxygenase and/or nitric oxide pathways and by increasing mucus secretion.

Bile acids in gastric fluids from llamas and alpacas with and without ulcers

To investigate the relationship between duodenogastric reflux and ulceration, gastric fluid was collected from the 1st (n = 26) and 3rd (n = 45) gastric compartments of llamas and alpacas during postmortem examination. Gastric fluids were analyzed for the presence of bile acids. Additionally, the 3rd compartment was examined grossly for the presence of erosions or ulcers, and the intestines were examined for evidence of fluid distention. Detectable bile acids were found in the 3rd compartment fluid of 1 of 28 camelids without ulcers, 7 of 14 camelids with ulcers, and 3 of 3 camelids with intestinal distention. Third compartment bile content was significantly higher in camelids with ulcers (median = 2.9 micromol/L) or intestinal distention (median = 371.5 micromol/L) than those with neither (median = 0 micromol/L). Bile acids were detected in the 1st gastric compartment in only 2 camelids. These findings suggest a reflux of duodenal contents, including bile acids, into the 3rd compartment in camelids with ulcers, similar to what is seen in camelids with poor intestinal emptying. Whether bile reflux was the cause of the ulcers or occurred after or concurrent to their development remains unknown.

Ulceration as a possible link between duodenogastric reflux and neoplasms in the stomach of rats

BACKGROUND

Duodenogastric reflux predisposes to gastric cancer. This study investigates whether ulceration induced by duodenogastric reflux is associated with the development of neoplasms in the stomach.

MATERIALS AND METHODS

In a rat experiment, duodenal fluid was directed into the corpus (jejunal reflux) or through the pylorus into the antrum (pyloric reflux). Sham-operated animals served as controls. The animals were sacrificed after 24, 36, or 52 weeks.

RESULTS

Ulcerations and neoplasms occurred more frequently in the corpus than in the antrum. In the corpus, ulceration was observed significantly more often in animals with jejunal reflux (62, 55, and 53% at 24, 36, and 52 weeks, respectively) than in animals with pyloric reflux (15, 21, and 30%). The incidence of neoplasm in the corpus increased significantly with time from 38% at 24 weeks to 89% at 52 weeks in animals with jejunal reflux and from 12 to 33% in animals with pyloric reflux. Ulceration and neoplasms shared location in the corpus adjacent to the gastrojejunostomy and by 24 weeks, all but one neoplasm in the jejunal reflux and one in pyloric reflux groups occurred adjacent to ulceration. In the antrum, 37% of the animals had a prepyloric ulceration after 24 weeks of pyloric reflux and only one of these animals had a neoplasm. By 52 weeks 20% of animals with pyloric reflux had a neoplasm that appeared in the prepyloric area.

CONCLUSIONS

Ulceration and neoplasm occurred at the same sites in the stomach, and ulcerations preceded the development of neoplasms in the antrum and very likely in the corpus. The results suggest that ulceration plays an important role in the genesis of neoplasms in the stomach and that the vulnerability to duodenogastric reflux is more pronounced in the corpus than in the antrum mucosa.