Gastric secretion

Activation of the TRPML1 Ion Channel Induces Proton Secretion in the Human Gastric Parietal Cell Line HGT-1

The lysosomal Ca2+ channel TRPML1 was found to be responsible for gastric acid secretion in murine gastric parietal cells by inducing the trafficking of H+/K+-ATPase containing tubulovesicles to the apical membrane. Therefore, we hypothesized a similar role of TRPML1 in regulating proton secretion in the immortalized human parietal cell line HGT-1. The primary focus was to investigate the involvement of TRPML1 in proton secretion using the known synthetic agonists ML-SA1 and ML-SA5 and the antagonist ML-SI3 and, furthermore, to identify food-derived compounds that target the channel. Proton secretion stimulated by ML-SA1 was reduced by 122.2 ± 22.7% by the antagonist ML-SI3. The steroid hormone 17β-estradiol, present in animal-derived foods, diminished the proton secretory effect of ML-SA1 by 63.4 ± 14.5%. We also demonstrated a reduction in the proton secretory effects of ML-SA1 and ML-SA5 on TRPML1 knock-down cells. The food-derived compounds sulforaphane and trehalose promoted proton secretion in HGT-1 cells but may act independently of TRPML1. Also, histamine- and caffeine-induced proton secretion were affected by neither the TRPML1 antagonist ML-SI3 nor the TRPML1 knock-down. In summary, the results obtained suggest that the activation of TRPML1 promotes proton secretion in HGT-1 cells, but the channel may not participate in canonical signaling pathways.

Evaluation of the gastroprotective and ulcer healing properties by Fridericia chica (Bonpl.) L.G. Lohmann hydroethanolic extract of leaves

ETHNOPHARMACOLOGICAL RELEVANCE

Fridericia chica (Bonpl.) L.G. Lohmann (Bignoniaceae), is a climber native to Brazil, found in all Brazilian biomes. It is mostly known in Brazil as "carajiru," and home medicines made from the leaves have been used to cure disorders including stomach ulcers and other gastrointestinal disorders.

AIM OF THE STUDY

The objective of the study was to investigate the F. chica hydroethanolic extract of leaves (HEFc) preventative and curative antiulcer gastrointestinal efficacy as well as the mechanisms of action using in vivo rodent models.

MATERIALS AND METHODS

F. chica was collected in the municipality of Juína, Mato Grosso, and its leaves were used to prepare the extract by maceration technique (70% hydroethanol in the 1:10 ratio, w/v) to obtain the HEFc. The chromatographic analysis of HEFc was carried out by High Performance Liquid Chromatography-Photo Diode Array-Electrospray Ionization-Mass Spectrometry (HPLC-PDA-ESI-MS)- LCQ Fleet™ system. To determine the potential antiulcer potential of HEFc (1, 5 and 20 mg/kg, p.o.), the gastroprotective activity was assessed in various animal models of stomach ulcers caused by acidified ethanol, water constraint stress, indomethacin, (acute), and acid acetic (chronic). Additionally, the prokinetic properties of the HEFC were assessed in mice. The gastroprotective underlying mechanisms were evaluated by the histopathological analysis and determination of gastric secretion (volume, free and total acidity), gastric barrier mucus, activation of PGs, NO, K ⁺_ATP channels, α₂-adrenoceptor, antioxidant activity (GSH, MPO and MDA), NO and mucosal cytokines (TNF-α, IL-1β, and IL-10) levels.

RESULTS

The chemical composition of HEFc was analyzed and apigenin, scutellarin, and carajurone were identified. HEFc (1, 5 and 20 mg/kg) showed effect against acute ulcers induced by HCl/EtOH with a reduction in the ulcerated area of 64.41% (p < 0.001), 54.23% (p < 0.01), 38.71% (p < 0.01), respectively. In the indomethacin experiment, there was no change in the doses tested, whereas in the water immersion restraint stress ulcer there was a reduction of lesions at doses of 1, 5, and 20 mg/kg by 80.34% (p < 0.001), 68.46% (p < 0.01) and 52.04% (p < 0.01). HEFc increased the mucus production at doses of 1 and 20 mg/kg in 28.14% (p < 0.05) and 38.36% (p < 0.01), respectively. In the pyloric ligation-induced model of gastric ulceration, the HEFc decreased the total acidity in all doses by 54.23%, 65.08%, and 44.40% (p < 0.05) and gastric secretory volume in 38.47% at dose of 1 mg/kg (p < 0,05) and increased the free acidity at the dose of 5 mg/kg by 11.86% (p < 0.05). The administration of EHFc (1 mg/kg) showed a gastroprotective effect possibly by stimulating the release of prostaglandins and activating K⁺_ATP channels and α_2-adrenoreceptors. Also, the gastroprotective effect of HEFc involved an increase in CAT and GSH activities, and a reduction in MPO activity and MDA levels. In the chronic gastric ulcer model, the HEFc (1, 5 and 20 mg/kg) decreased the ulcerated area significantly (p < 0.001) at all doses by 71.37%, 91.00%, and 93.46%, respectively. In the histological analysis, HEFc promoted the healing of gastric lesions by stimulating the formation of granulation tissue and consequently epithelialization. On the other hand, regarding the effect of HEFc on gastric emptying and intestinal transit, it was observed that the extract did not alter gastric emptying, but there was an increase in intestinal transit at the dose of 1 mg/kg (p < 0.01).

CONCLUSION

These outcomes confirmed the advantages of Fridericia chica leaves for the treatment of stomach ulcers, which are well-known. HEFc was discovered to have antiulcer characteristics through multitarget pathways, which might be related to an increase in stomach defense mechanisms and a decrease in defensive factor. HEFc can be regarded as a potential new antiulcer herbal remedy because of its antiulcer properties, which may be attributed to the mixture of flavonoids, apigenin, scutellarin and carajurone.

Pathophysiological role of ion channels and transporters in gastrointestinal mucosal diseases

The incidence of gastrointestinal (GI) mucosal diseases, including various types of gastritis, ulcers, inflammatory bowel disease and GI cancer, is increasing. Therefore, it is necessary to identify new therapeutic targets. Ion channels/transporters are located on cell membranes, and tight junctions (TJs) affect acid–base balance, the mucus layer, permeability, the microbiota and mucosal blood flow, which are essential for maintaining GI mucosal integrity. As ion channel/transporter dysfunction results in various GI mucosal diseases, this review focuses on understanding the contribution of ion channels/transporters to protecting the GI mucosal barrier and the relationship between GI mucosal disease and ion channels/transporters, including Cl⁻/HCO₃⁻ exchangers, Cl⁻ channels, aquaporins, Na⁺/H⁺ exchangers, and K⁺ channels. Here, we provide novel prospects for the treatment of GI mucosal diseases.

Gastric Peptides-Gastrin and Somatostatin

Gastric acid secretion (i) facilitates digestion of protein as well as absorption of micronutrients and certain medications, (ii) kills ingested microorganisms, including Helicobacter pylori, and (iii) prevents bacterial overgrowth and enteric infection. The principal regulators of acid secretion are the gastric peptides gastrin and somatostatin. Gastrin, the major hormonal stimulant for acid secretion, is synthesized in pyloric mucosal G cells as a 101-amino acid precursor (preprogastrin) that is processed to yield biologically active amidated gastrin-17 and gastrin-34. The C-terminal active site of gastrin (Trp-Met-Asp-Phe-NH₂ ) binds to gastrin/CCK₂ receptors on parietal and, more importantly, histamine-containing enterochromaffin-like (ECL) cells, located in oxyntic mucosa, to induce acid secretion. Histamine diffuses to the neighboring parietal cells where it binds to histamine H₂ -receptors coupled to hydrochloric acid secretion. Gastrin is also a trophic hormone that maintains the integrity of gastric mucosa, induces proliferation of parietal and ECL cells, and is thought to play a role in carcinogenesis. Somatostatin, present in D cells of the gastric pyloric and oxyntic mucosa, is the main inhibitor of acid secretion, particularly during the interdigestive period. Somatostatin exerts a tonic paracrine restraint on gastrin secretion from G cells, histamine secretion from ECL cells, and acid secretion from parietal cells. Removal of this restraint, for example by activation of cholinergic neurons during ingestion of food, initiates and maximizes acid secretion. Knowledge regarding the structure and function of gastrin, somatostatin, and their respective receptors is providing novel avenues to better diagnose and manage acid-peptic disorders and certain cancers. Published 2020. Compr Physiol 10:197-228, 2020.

Specific and Non-Specific Biomarkers in Neuroendocrine Gastroenteropancreatic Tumors

The diagnosis of neuroendocrine tumors (NETs) is a challenging task: Symptoms are rarely specific, and clinical manifestations are often evident only when metastases are already present. However, several bioactive substances secreted by NETs can be included for diagnostic, prognostic, and predictive purposes. Expression of these substances differs between different NETs according to the tumor hormone production. Gastroenteropancreatic (GEP) NETs originate from the diffuse neuroendocrine system of the gastrointestinal tract and pancreatic islets cells: These tumors may produce many non-specific and specific substances, such as chromogranin A, insulin, gastrin, glucagon, and serotonin, which shape the clinical manifestations of the NETs. To provide an up-to-date reference concerning the different biomarkers, as well as their main limitations, we reviewed and summarized existing literature.

Gastroprotective effect of ethyl acetate extract from Avicennia schaueriana Stapf & Leechman and underlying mechanisms

OBJECTIVE

Avicennia schaueriana Stapf is an endemic mangrove species widely used by traditional Brazilian communities as a folk remedy for the treatment of rheumatism, ulcers, and skin wounds. The aim of the present study was to evaluate the gastroprotective potential of the ethyl acetate extract from the leaves of A. schaueriana (As-AcOEt).

METHODS

Ultra-performance liquid chromatography coupled with diode-array detection and quadrupole time-of-flight mass spectrometry (UPLC-DAD-QTOF-MS/MS) was performed to identify chemical constituents of the ethyl acetate extract from the leaves ofA. schaueriana. Total phenols, flavonoids and tannins were determined and antioxidant activity was evaluated using the DPPH and ABTS methods. The acute toxicity of As-AcOEt and gastroprotective activity on HCl/ethanol-induced gastric ulcers were assessed and mechanisms of action involving the role of nitric oxide, sulfhydryl compounds, and prostaglandins were investigated.

RESULTS

Terpenes, flavonoids and tannins were detected in the extract. As-AcOEt exhibited antioxidant activity, with an EC₅₀ of 42.2 ± 4.4 μg/mL (DPPH) and 73.2% inhibition of ABTS radicals. UPLC-DAD-QTOF-MS/MS analysis identified gallic acid, gallic acid derivative, ellagic acid, myricetin pentoside, myricetin deoxyhexose, quercetin pentoside, quercetin deoxyhexose, and other compounds. Gallic acid was isolated in this species for the first time. During the acute toxicity test, no deaths or changes occurred in the variables evaluated. In the ethanol-induced ulcer model, As-AcOEt reduced the ulcerative lesion index, with 50, 100 and 200 mg/kg achieving 83.8, 88.5 and 86.9% inhibition, respectively. MPO levels decreased and the gastric mucosa of the animals treated with the extract was preserved. Pre-treatment with N-omega-nitro-l-arginine methyl ester (L-NAME; NO blocker) or carbenoxolone (CBXN; NP-SH blocker) reversed the gastroprotective effect of As-AcOEt, but this effect was not reversed with the previous administration of indomethacin.

CONCLUSION

The present findings reveal that the extract from the leaves ofA. schaueriana has gastroprotective effects, suggesting the involvement of nitric oxide and nonprotein sulfhydryl compounds, but not prostaglandin. Therefore, the use of A. schaueriana in Brazilian folk medicine for the treatment of gastric disorders has a scientific basis.

Identification of Bitter-Taste Intensity and Molecular Weight as Amino Acid Determinants for the Stimulating Mechanisms of Gastric Acid Secretion in Human Parietal Cells in Culture

Secretion of gastric acid, aimed at preventing bacterial growth and aiding the digestion of foods in the stomach, is chiefly stimulated by dietary intake of protein and amino acids (AAs). However, AAs' key structural determinants responsible for their effects on mechanisms regulating gastric acid secretion (GAS) have not been identified yet. In this study, AAs have been tested in the parietal cell model HGT-1 on GAS and on mRNA expression of genes regulating GAS. AAs' taste intensities from 0 (not bitter at all) to 10 (very bitter) were assessed in a sensory study, in which ARG (l: 6.42 ± 0.41; d: 4.62 ± 0.59) and ILE (l: 4.21 ± 0.43; d: 2.28 ± 0.33) were identified as bitter-tasting candidates in both isomeric forms. Pearson correlation showed that GAS in HGT-1 cells is directly associated with the bitter taste quality ( r: -0.654) in combination with the molecular weight of l-AA ( r: -0.685).

Acid-gastric antisecretory effect of the ethanolic extract from Arctium lappa L. root: role of H+, K+-ATPase, Ca2+ influx and the cholinergic pathway

BACKGROUND

Arctium lappa L., popularly known as burdock, is a medicinal plant used worldwide. The antiulcer and gastric-acid antisecretory effects of ethanolic extract from roots of Arctium lappa (EET) were already demonstrated. However, the mechanism by which the extract reduces the gastric acid secretion remains unclear. Therefore, this study was designed to evaluate the antisecretory mode of action of EET.

MATERIALS AND METHODS

The effects of EET on H⁺, K⁺-ATPase activity were verified in vitro, whereas the effects of the extract on cholinergic-, histaminergic- or gastrinergic-acid gastric stimulation were assessed in vivo on stimulated pylorus ligated rats. Moreover, ex vivo contractility studies on gastric muscle strips from rats were also employed.

RESULTS

The incubation with EET (1000 µg/ml) partially inhibited H⁺, K⁺-ATPase activity, and the intraduodenal administration of EET (10 mg/kg) decreased the volume and acidity of gastric secretion stimulated by bethanechol, histamine, and pentagastrin. EET (100-1000 µg/ml) did not alter the gastric relaxation induced by histamine but decreased acetylcholine-induced contraction in gastric fundus strips. Interestingly, EET also reduced the increase in the gastric muscle tone induced by 40 mM KCl depolarizing solution, as well as the maximum contractile responses evoked by CaCl₂ in Ca²⁺-free depolarizing solution, without impairing the effect of acetylcholine on fundus strips maintained in Ca²⁺ -free nutritive solution.

CONCLUSION

Our results reinforce the gastric antisecretory properties of preparations obtained from Arctium lappa, and indicate that the mechanisms involved in EET antisecretory effects include a moderate reduction of the H⁺, K⁺-ATPase activity associated with inhibitory effects on calcium influx and of cholinergic pathways in the stomach muscle.

Gastrin and Gastric Cancer

Gastric cancer is the third leading cause of cancer-related mortality worldwide. Despite progress in understanding its development, challenges with treatment remain. Gastrin, a peptide hormone, is trophic for normal gastrointestinal epithelium. Gastrin also has been shown to play an important role in the stimulation of growth of several gastrointestinal cancers including gastric cancer. We sought to review the role of gastrin and its pathway in gastric cancer and its potential as a therapeutic target in the management of gastric cancer. In the normal adult stomach, gastrin is synthesized in the G cells of the antrum; however, gastrin expression also is found in many gastric adenocarcinomas of the stomach corpus. Gastrin's actions are mediated through the G-protein-coupled receptor cholecystokinin-B (CCK-B) on parietal and enterochromaffin cells of the gastric body. Gastrin blood levels are increased in subjects with type A atrophic gastritis and in those taking high doses of daily proton pump inhibitors for acid reflux disease. In experimental models, proton pump inhibitor-induced hypergastrinemia and infection with Helicobacter pylori increase the risk of gastric cancer. Understanding the gastrin:CCK-B signaling pathway has led to therapeutic strategies to treat gastric cancer by either targeting the CCK-B receptor with small-molecule antagonists or targeting the peptide with immune-based therapies. In this review, we discuss the role of gastrin in gastric adenocarcinoma, and strategies to block its effects to treat those with unresectable gastric cancer.

Gastroprotective and anti-secretory mechanisms of 2-phenylquinoline, an alkaloid isolated from Galipea longiflora

BACKGROUND

We previously described the gastroprotective effect of 2-phenylquinoline (2-PQ), the main alkaloid isolated from the bark of Galipea longiflora (Rutaceae). However, despite the significant and promising results, the pharmacological mechanisms of the gastroprotection induced by 2-PQ have not been investigated.

PURPOSE

To evaluate the mechanisms underlying the gastroprotective effects of 2-PQ.

STUDY DESIGN

We used an in vivo mouse ulcer model and in vitro methodologies involving H⁺/K⁺-ATPase and L929 murine fibroblasts.

METHODS

The gastroprotective activity of 2-PQ (10-100 mg/kg, orally, p.o) was assessed against gastric ulcer induced by 60% ethanol/0.03 M hydrochloric acid (HCl) in mice or that induced by indomethacin (80 mg/kg, p.o) in rats. The cytotoxicity was assessed in L929 murine fibroblasts. Ulcerated tissues were analyzed histologically, histochemically, and biochemically. The antisecretory activity of 2-PQ was evaluated in vivo and in vitro.

RESULTS

2-PQ showed no cytotoxicity, reduced the lesion area induced by ethanol/HCl (log half-maximal effective dose, ED₅₀ = 1.507), and the histological evaluation supported these results. Furthermore, 2-PQ reduced indomethacin-induced gastric ulceration. The gastroprotection was accompanied by normalization of superoxide dismutase (SOD) and glutathione-S-transferase (GST) activity, an intense increase in reduced glutathione (GSH) levels, and reduction in lipid peroxide (LPO) and tumor necrosis factor (TNF)-α levels in the gastric mucosa. The antisecretory properties of 2-PQ were confirmed by the decreased volume and total acidity of the gastric juice, and it reduced histamine- or pentagastrin-stimulated gastric acid secretion. However, 2-PQ did not change the in vitro H⁺/K⁺-ATPase activity or the content of gastric-adhered mucous in mice. In addition, pretreatment with N-ethylmaleimide, NG-nitro-l-arginine methyl esters, yohimbine, or indomethacin reversed the gastroprotective effect of 2-PQ, suggesting nitric oxide, nonprotein sulfhydryl compounds, α-2-receptors, and prostaglandin were involved.

CONCLUSION

2-PQ provides gastroprotection by reducing oxidative damage and inhibiting acid secretion mediated by histaminergic and gastrinergic regulatory pathways.

Inhibiting the proton pump: mechanisms, benefits, harms, and questions

Inhibition of the H⁺/K⁺-adenosine triphosphatase (the proton pump) is the final common mechanistic pathway in reducing gastric acid secretion pharmacologically. Proton pump inhibitors are widely used in upper gastrointestinal diseases, including gastric and duodenal ulcers, eradication of Helicobacter pylori in combination with antibiotics, gastroesophageal reflux disease, Zollinger-Ellison syndrome, eosinophilic esophagitis, and prevention of non-steroidal anti-inflammatory drug-induced peptic ulceration. Reviewing their benefits and harms in BMC Medicine, Scarpignato et al. report effectiveness in these conditions, and harms that are generally mild and uncommon (1-3 %). Serious adverse reactions, such as tubulointerstitial nephritis, are rare. However, the risks of gastric and pancreatic cancer are unclear. Drug-drug interactions can occur through effects on P glycoprotein and cytochrome P450 (CYP) isoenzymes. Several questions remain. Do all proton pump inhibitors carry the same risks of serious adverse reactions? Which individuals are most susceptible? What are the time courses of individual reactions? What monitoring strategies are best? New drugs for the same indications continue to emerge, including potassium-competitive acid blockers, inhibitors of transient lower esophageal sphincter relaxation, serotonergic agents/prokinetics, mucosal protectants, histamine H₃ receptor agonists, anti-gastrin agents, and esophageal pain modulators. Their benefit to harm balance remains to be discovered.Please see related article: https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-016-0718-z.

The effects of baicalein on gastric mucosal ulcerations in mice: Protective pathways and anti-secretory mechanisms

Many flavonoids have been shown to present good results for the treatment of gastric ulcers. Baicalein, a bioactive flavonoid derived from the Scutellaria baicalensis Georgi root, possesses several biological effects, such as anti-inflammatory and antioxidant. This study was conducted to assess the gastroprotective properties of baicalein. Anti-ulcerogenic assay was performed using the protocol of ulcer induced by ethanol/HCl in mice; then, the role of presynaptic α₂-receptors, sulfhydryl (SH) compounds, nitric oxide (NO), prostaglandin (PG) and ATP-sensitive K⁺ (K_ATP) channels in gastroprotection of baicalein was investigated. The levels of reduced glutathione (GSH) and the myeloperoxidase (MPO) activity were measured in the gastric mucosa. Parameters of gastric secretion (volume, [H⁺] and pH) were determined with or without the presence of the secretagogue agent histamine, as well as mucus in gastric contents, by the pylorus ligation model. In vitro H⁺,K⁺-ATPase activity was also determined. Baicalein (10, 30 and 100 mg/kg) exhibited a dose related gastroprotective effect (P < 0.001) against acidified ethanol-induced lesions. The intraperitoneal treatment of mice with a α₂-adrenoreceptor antagonist (yohimbine; 2 mg/kg), a SH compounds blocker (N-ethylmaleimide, NEM; 10 mg/kg), a non-selective inhibitor of NO synthase (N_w-nitro-L-arginine methyl ester hydrochloride, L-NAME; 10 mg/kg), a non-selective inhibitor of cyclo-oxygenase (indomethacin; 10 mg/kg) or a K_ATP channel blocker (glibenclamide; 10 mg/kg) was able to reverse (P < 0.001) the gastroprotective response caused by baicalein (30 mg/kg). Baicalein (30 mg/kg; P < 0.05) was able to increase GSH levels and decreasing MPO activity. The intraduodenal treatment with baicalein (30 and 100 mg/kg) significantly increased (P < 0.05) the gastric mucus secretion. Additionally, the treatment with baicalein reduced (30 and 100 mg/kg; P < 0.05) the secretion volume and total acid secretion, and also increased (10, 30 and 100 mg/kg; P < 0.001) the pH value, after pylorus ligature. Baicalein (30 mg/kg) was also effective in inhibiting the effects of histamine on gastric secretion (volume, [H⁺] and pH; P < 0.001). Baicalein at 10 and 30 μg/mL showed anti-H⁺,K⁺-ATPase activity. In conclusion, the present results provide convincing evidence that baicalein could be used as a cytoprotective (preventive effect) and anti-ulcerogenic (anti-secretory effect) agent in the gastric ulcers.

Antiulcer mechanisms of Vernonia condensata Baker: A medicinal plant used in the treatment of gastritis and gastric ulcer

ETHNOPHARMACOLOGICAL RELEVANCE

The leaves from Vernonia condensata Baker are broadly used in folk medicine for the treatment of gastric ulcers and dyspepsia. The Brazilian Public Health System (SUS) describes this species as having the potential to serve as a new herbal product with therapeutic benefits.

AIM OF THE STUDY

The purpose of the study was to evaluate the gastroprotective activity and gastric healing properties of a crude ethanolic extract from leaves of V. condensata (CEEV) in different animal models.

MATERIALS AND METHODS

In order to assess the gastroprotective potential of CEEV, ulcer models were established using ethanol and indomethacin. The gastric healing effect was then evaluated in the acetic acid-induced ulcer model, where the tissue was used to assess oxidative levels (reduced glutathione and lipid hydroperoxide levels, as well as superoxide dismutase and catalase activity), inflammatory [myeloperoxidase (MPO)] parameters, and mucin content. Furthermore, the ligature pylorus model, with and without secretagogue stimuli, was employed to investigate the mechanism of action of CEEV. In addition, H(+)K(+)-ATPase activity, MPO activity, and antioxidant activity through the DPPH assay were examined through in vitro trials. Phytochemical analyses were also performed. The ethanol/HCl-induced gastric ulcer method was employed to verify the gastroprotective effect of the main compound in CEEV.

RESULTS

CEEV (30 and 300mg/kg, p.o) exhibited gastroprotective activity and prevented both gastric lesions induced by ethanol or indomethacin in rats. The gastric healing effect of CEEV (300mg/kg, p.o. taken twice a day for a duration of seven days) was confirmed by examining the macroscopic and microscopic appearance of chronic gastric ulcers induced by acetic acid in rats. The restorative effect of CEEV was accompanied by a significant increase in mucin content (PAS staining) and by a reduction in oxidative stress and inflammatory parameters at the site of the ulcer. Moreover, CEEV (300mg/kg), administered via an intraduodenal route, significantly reduced the volume, pH, total acidity and pepsin activity of gastric content in the pylorus ligature model in rats. The gastric acid antisecretory effect of CEEV was maintained even in the presence of cholinergic and gastrinergic, but not histaminergic, stimuli. In vitro, CEEV (1-10µg/ml) was able to scavenge free radical DPPH, but did not promote inhibitory effects on MPO or H(+),K(+)-ATPAse activity. Phytochemical analysis of CEEV indicated that luteolin is the main compound present in the extract. However, luteolin (1, 3 and 10mg/kg, p.o or 1mg/kg, i.p.) did not promote gastroprotection against ethanol/HCl in mice. It is also important to mention that oral administration of CEEV did not produce any sign of acute toxicity in animals.

CONCLUSIONS

V. condensata extract demonstrates gastroprotective effects through the inhibition of gastric secretion via cholinergic and gastrinergic pathways. Furthermore, it exhibits cytoprotective effects, involving antioxidant activity, an increase in mucin content and inhibition of neutrophil migration. Thus, this medicinal plant may be a suitable natural source for the prevention and treatment of gastric lesions.

Potassium channel KCNJ15 is required for histamine-stimulated gastric acid secretion

Gastric acid secretion is mediated by the K+-dependent proton pump (H+,K+-ATPase), which requires a continuous supply of K+ at the luminal side of the apical membrane. Several K+ channels are implicated in gastric acid secretion. However, the identity of the K+ channel(s) responsible for apical K+ supply is still elusive. Our previous studies have shown the translocation of KCNJ15 from cytoplasmic vesicles to the apical membrane on stimulation, indicating its involvement in gastric acid secretion. In this study, the stimulation associated trafficking of KCNJ15 was observed in a more native context with a live cell imaging system. KCNJ15 molecules in resting live cells were scattered in cytoplasm but exhibited apical localization after stimulation. Furthermore, knocking down KCNJ15 expression with a short hairpin RNA adenoviral construct abolished histamine-stimulated acid secretion in rabbit primary parietal cells. Moreover, KCNJ15, like H+,K+-ATPase, was detected in all of the parietal cells by immunofluorescence staining, whereas only about half of the parietal cells were positive for KCNQ1 under the same condition. Consistently, the endogenous protein levels of KCNJ15, analyzed by Western blotting, were higher than those of KCNQ1 in the gastric mucosa of human, mouse, and rabbit. These results provide evidence for a major role of KCNJ15 in apical K+ supply during stimulated acid secretion.

Gastroprotective Effect of Geopropolis from Melipona scutellaris Is Dependent on Production of Nitric Oxide and Prostaglandin

The aim of this study was to evaluate the gastroprotective activity of ethanolic extract of geopropolis (EEGP) from Melipona scutellaris and to investigate the possible mechanisms of action. The gastroprotective activity of the EEGP was evaluated using model ulcer induced by ethanol. To elucidate the possible mechanisms of action, we investigated the involvement of the nonprotein sulfhydryl (NP-SH) groups, nitric oxide and prostaglandins. In addition, the antisecretory activity of EEGP was also evaluated by pylorus ligated model. The EEGP orally administrated (300 mg/kg) reduced the ulcerative lesions induced by the ethanol (P < 0.05). Regarding the mechanism of action, the prior administration of nitric oxide and prostaglandins antagonists suppressed the activity of gastroprotective EEGP (P < 0.05). On the other hand the gastroprotective activity of EEGP was kept in the group pretreated with the antagonist of the NP-SH groups; furthermore the antisecretory activity was not significant (P > 0.05). These results support the alternative medicine use of geopropolis as gastroprotective and the activities observed show to be related to nitric oxide and prostaglandins production.

Gastric neuropeptide W is regulated by meal-related nutrients

Neuropeptide W (NPW) is secreted from gastrin (G) cells in the stomach in response to food intake. The mechanisms underlying food intake-induced regulation of gastric NPW is largely unknown. We hypothesized that specific macronutrients were responsible for food-induced NPW secretion. We evaluated the acute effects of fat, carbohydrate and protein on plasma NPW concentrations in humans and mice. The effect of different nutrients on expression of NPW in the antral stomach was also determined in mice. Primary cell cultures of mouse gastric antral mucosal cells were used to investigate the signaling pathway of NPW expression. Plasma NPW concentrations did not change after nutrient ingestion in either humans or mice. NPW mRNA expression and the number of NPW positive cells in the mouse antrum were increased in mice gavage fed with protein or glucose, but not lipid. In primary antral mucosal cell culture, NPW mRNA expression was stimulated by l-phenylalanine, but not glucose. Calcium-sensing receptor (CaSR) positive cells were largely co-localized with NPW in mouse gastric antral mucosal cells, and NPW mRNA expression was inhibited by a selective antagonist of CaSR NPS2143. However, the l-phenylalanine-induced increase in NPW expression was not affected by NPS2143. In conclusion, these studies indicated an inconsistency between plasma and gastric NPW expression in response to nutrient ingestion, suggesting food induced gastric NPW expression may play a more important role locally. Moreover, glucose and especially protein are potent regulators of gastric NPW, via distinct mechanisms.

Stomach antral endocrine cells in patients with irritable bowel syndrome

To the best of our knowledge, stomach antral endocrine cells have not previously been investigated in patients with irritable bowel syndrome (IBS). Thus, in the present study, 76 patients with IBS were examined (designated as IBS-total). Diarrhoea was the predominant symptom in 26 of these patients (IBS-D), while in 21 patients, the predominant symptoms were both diarrhoea and constipation (IBS-M) and in 29 patients the predominant symptom was constipation (IBS-C). Forty-three healthy subjects were enrolled as the controls. Stomach antral biopsy samples obtained from all of the subjects were immunostained using the avidin-biotin-complex method for serotonin, gastrin, somatostatin and serotonin transporter (SERT). The immunopositive cell densities and immunoreactivity intensities were determined by computer-aided image analysis. The density of the serotonin-immunoreactive cells was significantly decreased in the IBS-M patients and increased in the IBS-C patients relative to the controls. The immunoreactivity intensity did not differ significantly between the controls and IBS-total. The density of the gastrin-immunoreactive cells was significantly greater in the IBS-D, IBS-M and IBS-C patients than in the controls. The immunoreactivity intensity of gastrin was significantly greater in the IBS-D patients than in the controls. The density of the somatostatin-immunoreactive cells cells was significantly lower in the IBS-total, IBS-D, IBS-M and IBS-C patients than in the controls. The immunoreactivity intensities of both somatostatin and SERT did not differ significantly between the controls and IBS-total. The increase in gastrin cell density and the decrease in somatostatin cell density in all IBS subtypes may cause high levels of gastric secretion, which may in turn contribute to the high incidence of dyspepsia and gastro-oesophageal reflux observed in patients with IBS.

Effect of dietary management on the gastric endocrine cells in patients with irritable bowel syndrome

Background/objectives:

The gastric endocrine cells in patients with irritable bowel syndrome (IBS) tend to normalize following dietary guidance. The aim of the present study was to identify the gastric endocrine cell types that are changed following such dietary guidance.

Subjects/methods:

Fourteen IBS patients and 14 healthy subjects were included in the study. Patients received three sessions of individual dietary management guidance. Gastroscopy was performed on both the controls and the patients at baseline and then again for the patients at 3–9 months after dietary guidance. Biopsy samples from the corpus and antrum were immunostained for all gastric endocrine cell types. Endocrine cells were quantified by computerized image analysis.

Results:

The densities of the ghrelin cells for the controls and IBS patients before and after dietary guidance were 149.6±36.2 (mean±s.e.m.; 95% confidence interval (CI) 71.3–227.8), 114.5±32.7 and 161.8±37.8 cells/mm², respectively. The densities of the gastrin cells in these groups were 155.8±21.0 (95% CI 110.3–201.2), 159.4±24.3 and 211.6±28.0 cells/mm², respectively; the corresponding densities of serotonin cells in the corpus were 18.2±3.9 (95% CI 9.8–26.6), 10.6±3.4 and 14±2.0 cells/mm² and in the antrum were 44.6±12.2 (95% CI 18.1–71.1), 1.7±0.5 and 14.7±6.3 cells/mm². The densities of the somatostatin cells in the corpus were 40.0±7.7 (95% CI 23.5–56.5), 23.0±3.0 and 37.3±4.2 cells/mm², respectively, and in the antrum were 138.9±22.0 (95% CI 91.4–186.3), 95.6±15.9 and 86.0±16.9 cells/mm², respectively.

Conclusions:

The densities of all of the gastric endocrine cell types changed towards the healthy control values in the IBS patients following a change in food intake.

Antiulcer and gastric antisecretory effects of dichloromethane fraction and piplartine obtained from fruits of Piper tuberculatum Jacq. in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Piper tuberculatum Jacq. (Piperaceae) is medicinally used as an analgesic and as a treatment for gastric complaints. Thus, the current study aimed to investigate the gastroprotective and antisecretory properties of the dichloromethane fraction of the fruit of Piper tuberculatum (DFPT) and piplartine, a compound isolated from the DFPT, in rats.

MATERIALS AND METHODS

Gastric ulcers were induced in fasted rats by oral administration of absolute ethanol and then mucus content and glutathione (GSH) levels were measured. Mechanisms underlying the antisecretory action were studied through gastric H(+),K(+)-ATPase activity of highly purified rabbit gastric microsomes and pylorus ligature method in rats.

RESULTS

In the acute toxicity test the values of estimated LD50 for oral and intraperitoneal administration of DFPT were 1.6266 and 0.2684g/kg, respectively. The DFPT (ED50=29mg/kg, p.o.) and piplartine (4.5mg/kg, p.o.) promoted gastroprotection against acute lesions induced by ethanol, effect that could be related with the maintenance of GSH levels in the gastric mucosa. However, only DFPT stimulated gastric mucus secretion. In vitro, the DFPT and piplartine inhibited the H(+),K(+)-ATPase activity and, in vivo DFPT and piplartine also reduced basal gastric acid secretion, as well as that stimulated by pentagastrin.

CONCLUSIONS

These results demonstrate that DFPT and piplatine cause marked gastroprotective effects accompanied by the increase and maintenance of gastric mucus and GSH levels, as well as a reduction in gastric acid secretion through the gastrinergic pathway.

Gastric antisecretory and antiulcer activity of bovine hemoglobin

AIM: To investigate gastric antisecretory and gastroprotective activity of bovine hemoglobin (B-Hb) in rats.

METHODS: Adult Albino-Wistar rats were divided into groups of 6 animals each. B-Hb in doses of 100, 300 and 900 mg/kg body weight was tested for gastric acid secretion and antiulcer activity. Gastric secretions were measured 6 h after pylorus ligation in rats pretreated with B-Hb. The acidity was measured by titrating gastric contents against 0.01 mol/L NaOH to pH 7. Indomethacin ulcers were produced by oral administration of 30 mg/kg bw in the rats pretreated with B-Hb one hour before indomethacin. Six hours after indomethacin stomach removed and ulcer index was recorded. Ethanol ulcer were produced by 1 mL of ethanol in the rats pretreated with B-Hb 30 min before the ethanol. One hour after ethanol stomach were cut open to score ulcers. Histological examination and analysis of gastric wall mucus, non-protein sulfhydryl groups (NP-SH), and myeloperoxidase (MPO) were carried in gastric tissue following ethanol administration.

RESULTS: In control rats pylorus ligation for 6 h resulted in the accumulation of 8.1 ± 0.61 mL of gastric secretion. The treatment of the rats with 100, 300 and 900 mg/kg of B-Hb produced a significant decrease in the volume of gastric secretion 5.6 ± 0.63, 5.5 ± 0.75 and 4.7 ± 0.58 mL respectively as compared to the control group [analysis of variance (ANOVA) F = 4.77, P < 0.05]. The lesion area in the control group was found to be 22.4 ± 3.2 mm² six hours after the administration of indomethacin. Treatment of rats with B-Hb at doses of 100 mg/kg (24.3 ± 3.29 mm²), 300 mg/kg (16.2 ± 1.45 mm²) and 900 mg/kg (12.6 ± 1.85 mm²) produced a dose dependent decreased the lesion scores (ANOVA F = 4.50, P < 0.05). The ulcer index following one hour after 1 mL ethanol was 7.1 ± 0.31. Pretreatment of rats with B-Hb at the doses of 100 mg/kg (2.5 ± 0.42), 300 mg/kg (2.1 ± 0.4) and 900 mg/kg (0.7 ± 0.21) significantly inhibited the formation of gastric lesions (ANOVA F = 63.26, P < 0.0001). Histological examination of gastric mucosa following ethanol showed significant lesions in the form of gastric pits with detachment of the surface epithelium; vacuolation of epithelial cells and elongation of microvessels. The changes were dose-dependently attenuated by B-Hb. The treatment of rats with ethanol significantly decreased the Alcian blue binding capacity of gastric wall mucus (480 ± 25.6 μg Alcian blue/g of tissue) as compared to control rats (667 ± 25.8 μg). Pretreatment of rats with B-Hb at the doses of 100 mg/kg (516 ± 31.6 μg/g), 300 mg/kg (558 ± 28.8 μg/g) and 900 mg/kg (654 ± 33.8 μg/g) significantly attenuated ethanol induced depletion of gastric wall mucus (ANOVA F = 8.05, P < 0.005). A significant and dose dependent increase of gastric mucosal NP-SH (ANOVA F = 19.62, P < 0.001) and decrease in MPO activity (ANOVA F = 3.1, P < 0.05) was observed in B-Hb treated rats.

CONCLUSION: B-Hb possesses significant gastric antisecretory and gastroprotective activity against experimentally induced gastric lesion. The gastroprotective effects of B-Hb are accompanied by inhibition of neutrophils activity, reduction of oxidative stress and maintenance of mucosal integrity.

High dietary salt intake exacerbates Helicobacter pylori-induced gastric carcinogenesis

Persistent colonization of the human stomach with Helicobacter pylori is a risk factor for gastric adenocarcinoma, and H. pylori-induced carcinogenesis is dependent on the actions of a bacterial oncoprotein known as CagA. Epidemiological studies have shown that high dietary salt intake is also a risk factor for gastric cancer. To investigate the effects of a high-salt diet, we infected Mongolian gerbils with a wild-type (WT) cagA(+) H. pylori strain or an isogenic cagA mutant strain and maintained the animals on a regular diet or a high-salt diet. At 4 months postinfection, gastric adenocarcinoma was detected in 100% of the WT-infected/high-salt-diet animals, 58% of WT-infected/regular-diet animals, and none of the animals infected with the cagA mutant strain (P < 0.0001). Among animals infected with the WT strain, those fed a high-salt diet had more severe gastric inflammation, higher gastric pH, increased parietal cell loss, increased gastric expression of interleukin 1β (IL-1β), and decreased gastric expression of hepcidin and hydrogen potassium ATPase (H,K-ATPase) compared to those on a regular diet. Previous studies have detected upregulation of CagA synthesis in response to increased salt concentrations in the bacterial culture medium, and, concordant with the in vitro results, we detected increased cagA transcription in vivo in animals fed a high-salt diet compared to those on a regular diet. Animals infected with the cagA mutant strain had low levels of gastric inflammation and did not develop hypochlorhydria. These results indicate that a high-salt diet potentiates the carcinogenic effects of cagA(+) H. pylori strains.

The guggulsterone derivative GG-52 inhibits NF-κB signaling in gastric epithelial cells and ameliorates ethanol-induced gastric mucosal lesions in mice

Gastric mucosal inflammation can develop after challenge with noxious stimuli such as alcohol. Specially, alcohol stimulates the release of inflammatory cytokines but does not increase gastric acid secretion, leading to gastric mucosal damage. The plant sterol guggulsterone and its novel derivative GG-52 have been reported to inhibit nuclear factor-κB (NF-κB) signaling in intestinal epithelial cells and experimental colitis. In the present study, we investigated the anti-inflammatory effects of GG-52 on gastric epithelial cells and on ethanol-induced gastric mucosal inflammation in mice. GG-52 inhibited the expression of interleukin-8 (IL-8) in gastric epithelial AGS and MKN-45 cell lines stimulated with tumor necrosis factor (TNF)-α in a dose-dependent manner. Pretreatment with GG-52 suppressed TNF-α-induced activation of IκB kinase (IKK) and NF-κB signaling in MKN-45 cells. In contrast, the inactive analog GG-46 did not produce significant changes in IL-8 expression or NF-κB activation. In a model of ethanol-induced murine gastritis, administration of GG-52 significantly reduced the severity of gastritis, as assessed by macroscopic and histological evaluation of gastric mucosal damage. In addition, the ethanol-induced upregulation of chemokine KC, a mouse homolog of IL-8, and phosphorylated p65 NF-κB signals were significantly inhibited in murine gastric mucosa pretreated with GG-52. These results indicate that GG-52 suppresses NF-κB activation in gastric epithelial cells and ameliorates ethanol-induced gastric mucosal lesions in mice, suggesting that GG-52 may be a potential gastroprotective agent.

Recent developments in gastroesophageal reflux disease and Barrett's esophagus: ANNO 2012

The incidence of gastroesophageal reflux disease (GERD) and esophageal columnar metaplasia is rising worldwide. Both mechanical and functional factors perturb the double sphincter barrier at the esophagogastric junction (EGJ). Discovery of the acid pocket is fundamental in understanding postprandial acid reflux. Adding impedencemetry to pH measurements allows detection of non-acid or weakly acidic reflux. Histologic and endoscopic injury of the squamous mucosa rises from dilation of the intercellular spaces, papillary extension, accentuated intrapapillary looping, red streaks, erosive tissue loss, etc., graded with the Los Angeles system. Seventy percent of patients have no recognizable abnormalities (non-erosive or neGERD). Treatment of GERD mainly relates to the control of acid secretion but a revival of alginate/antacid obliterating the acid pocket is to be expected. Weaker heartburn control in neGERD is a misnomer because most studies included patients with no evidence of reflux disease. Traditional (delayed-release) proton pump inhibitors (PPIs) are powerful suppressors of acid secretion but do have limitations such as gradual build up of acid control, weak control of nocturnal acid recovery, possibility of rebound, occasional need for dose escalation, etc. Barrett's esophagus (BE) is endoscopically diagnosed also in the absence of intestinal metaplasia. A prerequisite is the precise location of the EGJ (proximal end of gastric folds, esophageal sphincter pinch, distal extent of palisade vessels). BE is graded with the Prague C & M system. Barrett's cancer develops usually via low-grade and high-grade dysplasia. Endoscopic examination may indicate suspicious areas, amenable for targeted biopsy. Otherwise, four quadrant biopsies are obtained when searching for neoplasia. Low-grade dysplasia, especially when it is multifocal and p53 positive, high-grade dysplasia and mucosal cancer should be treated with endoscopic resection of the target area, followed by radiofrequency ablation of the adjacent non-neoplastic columnar mucosa, followed with powerful acid suppressant therapy. The long-term results of the combination of resection and ablation are exiting and at least comparable to surgical resection.

Cellular localization of dopamine receptors in the gastric mucosa of rats

Dopamine (DA) plays a critical role in the protection of gastric mucosa and is mediated through corresponding receptors. However, the details of the expression of DA receptors (D1-D5) in the gastric mucosa are lacking. The present study investigated the expression and cellular localization of DA receptors in rat gastric mucosa by means of real-time PCR and immunofluorescent techniques. The results indicated that the mRNA expressions of all five subtypes of DA receptors were found in the gastric mucosa, among which the D2 level was the highest. The immunopositive cells of D1-D3 and D5 were primarily localized to the basilar gland of the epithelial layer in gastric corpus, but D4 immunoreactivity (IR) was only observed in the enteric nerve plexus. The D1, D2, and D5 IR were found in pepsin C-IR cells except D3. No IR of any DA receptor was detected in the H(+)/K(+)-ATPase- or mucin 6-IR cells. In conclusion, for the first time, this study demonstrates the predominant distribution of DA receptors in the chief cells, not the parietal and mucous neck cells, in rat gastric mucosa, thus suggesting that DA may not directly regulate the function of parietal cells or mucous neck cells, but it may modulate the function of chief cells through the D1, D2, and D5 receptors.