L-365,260 inhibits in vitro acid secretion by interacting with a PKA pathway

Gastrin attenuates ischemia-reperfusion-induced intestinal injury in rats

Intestinal ischemia-reperfusion (I/R) injury is a devastating complication when the blood supply is reflowed in ischemic organs. Gastrin has critical function in regulating acid secretion, proliferation, and differentiation in the gastric mucosa. We aimed to determine whether gastrin has an effect on intestinal I/R damage. Intestinal I/R injury was induced by 60-min occlusion of the superior mesenteric artery followed by 60-min reperfusion, and the rats were induced to be hypergastrinemic by pretreated with omeprazole or directly injected with gastrin. Some hypergastrinemic rats were injected with cholecystokinin-2 (CCK-2) receptor antagonist prior to I/R operation. After the animal surgery, the intestine was collected for histological analysis. Isolated intestinal epithelial cells or crypts were harvested for RNA and protein analysis. CCK-2 receptor expression, intestinal mucosal damage, cell apoptosis, and apoptotic protein caspase-3 activity were measured. We found that high gastrin in serum significantly reduced intestinal hemorrhage, alleviated extensive epithelial disruption, decreased disintegration of lamina propria, downregulated myeloperoxidase activity, tumor necrosis factor-α, and caspase-3 activity, and lead to low mortality in response to I/R injury. On the contrary, CCK-2 receptor antagonist L365260 could markedly impair intestinal protection by gastrin on intestinal I/R. Severe edema of mucosal villi with severe intestinal crypt injury and numerous intestinal villi disintegrated were observed again in the hypergastrinemic rats with L365260. The survival in the hypergastrinemic rats after intestinal I/R injury was shortened by L365260. Finally, gastrin could remarkably upregulated intestinal CCK-2 receptor expression. Our data suggest that gastrin by omeprazole remarkably attenuated I/R induced intestinal injury by enhancing CCK-2 receptor expression and gastrin could be a potential mitigator for intestinal I/R damage in the clinical setting.

Mechanism(s) of action involved in the gastroprotective activity of Muntingia calabura

ETHNOPHARMACOLOGICAL RELEVANCE

Muntingia calabura L. (Muntingiaceae) is locally known as kerukup siam. Its leaves, flowers, barks and roots have been used traditionally in East Asia and South America to treat various diseases including ulcer-related diseases. The present study aimed to investigate the mechanism(s) of gastroprotective effect of methanol extract of Muntingia calabura leaves (MEMC) using the pylorus ligation induced gastric ulceration in rats.

MATERIALS AND METHODS

Five groups of rats (n=6) were administered orally once daily for 7 days with 8% Tween 80 (negative control), 100 mg/kg ranitidine (positive control), or MEMC (100, 250 or 500 mg/kg), followed by the ulcer induction via ligation of the pyloric part of the rat's stomach. This was followed by the macroscopic analysis of the stomach, evaluation of gastric content parameters, and quantification of mucus content. The antioxidant (measured using the superoxide anion and 2,2-diphenyl-1-picrylhydrazyl (DPPH)-radical scavenging, oxygen radical absorbance capacity (ORAC) and total phenolic content (TPC) assays), anti-inflammatory (evaluated using the in vitro lipoxygenase and xanthine oxidase assays), phytoconstituents and HPLC analysis of MEMC were also carried out.

RESULTS

The MEMC significantly (p<0.05) reduced gastric lesion in this model. Furthermore, the extract also significantly (p<0.01) reduced the volume of gastric content whereas the total acidity was significantly (p<0.05) reduced in the doses of 100 and 500 mg/kg MEMC. Moreover, the mucus content increased significantly (p<0.01) in MEMC-treated rats. The extract also showed high antioxidant and anti-inflammatory activities in all assays tested, and demonstrated the presence of high tannins and saponins followed by flavonoids.

CONCLUSION

The MEMC exerted gastroprotective effect via several mechanisms including the anti-secretory, antioxidant and anti-inflammatory activities. These activities could be attributed to the presence of tannins, saponins and flavonoids (e.g. rutin, quercitrin, fisetin and dihydroquercetin).

C-terminal heptapeptide of gastrin inhibits astrocytomas motility by interacting with a new gastrin binding site

It is well known that the amidated C-terminal part of gastrin is crucial for its interaction with the classical seven transmembrane domain receptors CCK-1 or CCK-2. Nevertheless, over the past 10 years, several groups have characterized new binding sites using peptides related to gastrin (particularly glycine-extended forms of gastrin) on various tumoral and nontumoral cell lines. In the present study, we focused on the human astrocytic tumoral cell line U373. Although it has been described that gastrin was able to inhibit the motility of these cells, we were unable to detect any classical CCK/gastrin receptor. On the other hand, by using the radiolabeled C-terminal heptapeptide of gastrin ((125)I-G-7), we evidenced a new binding site that possessed a pharmacological profile different from the classical CCK/gastrin receptors. This new gastrin binding site seemed to be coupled to G proteins and be implicated in c-Fos transcription gene. Moreover, we showed that G-7 was able to induce a strong inhibition of U373 cell migration, a crucial biological effect when we know that astrocytoma cells' migration in brain parenchyma constitutes a major feature of malignancy in astrocytic tumors.