Gastrin, somatostatin, G and D cells of gastric ulcer in rats

Enhanced Therapeutic Efficacy of Omeprazole Nanosuspension in Ethanol-Induced Gastric Ulcer: A Focus on Oxidative Stress and Inflammatory Pathways

Gastric ulcer is a concerning condition that affects numerous individuals globally. Omeprazole (OMP), a well-known drug for treating stomach ulcers, has been associated with several adverse effects and limited solubility. The study aimed to create an omeprazole nanosuspension (OMP-NS) with improved solubility and bioavailability. Additionally, the study investigated the potential therapeutic effects of OMP-NS on ethanol-induced gastric injury in rats, comparing it to traditional OMP therapy to identify novel therapeutic alternatives. The characterization of the OMP-NS was assessed using DLS, TEM, XRD, FTIR, UV spectrophotometric analysis, in vitro release studies, and entrapment efficiency (EE) assays. A total of 24 male Wistar albino rats (weighing 150-200 g, aged 8-10 weeks) were randomly divided into four groups (six rats/group). Gastric injury was induced using absolute ethanol (5 mL/kg), followed by oral administration of either OMP or OMP-NS (20 mg/kg) for 7 days. Data were analyzed using one-way ANOVA accompanied by the Bonferroni post hoc test or the Kruskal-Wallis test, based on data distribution, with significance set at p < 0.05. The OMP-NS demonstrated a Z-average diameter of 216.1 nm, a polydispersity index of 0.2, and a zeta potential of -19.6 mV. The particles were predominantly spherical with an average size of 67.28 nm. In vitro release studies showed 97.78% release at 8 h, with an EE% of 96.97%. Ethanol-induced gastric ulcers were associated with oxidative stress, characterized by elevated levels of NADPH, ROS, MDA, and NO, while the level of SOD was reduced. It was accompanied by increased inflammatory markers HMGB1, which subsequently increased TLR-2, MyD88, NF-κBp56, NLRP3, TNF-α, IL-1β, and IL-6 levels; conversely, a significant decrease in Nrf2/PPAR-γ/SIRT1 levels was observed. In contrast, OMP-NS administration significantly reduced oxidative stress and inflammatory markers, restored SOD activity, and upregulated protective pathways Nrf2/PPAR-γ/SIRT1 more effectively than conventional OMP therapy. In conclusion, OMP-NS represents a promising therapeutic strategy with notable anti-inflammatory and anti-ulcerogenic effects in ethanol-induced gastric ulcers.

Somatostatin Mitigates Gastric Mucosal Damage Induced by LPS in a Male Wistar Rat Model of Sepsis

Upper gastrointestinal bleeding from erosive gastritis remains associated with high mortality in septic or postoperative patients. While stress ulcer bleeding has declined, it still occurs in septic patients and is considered a manifestation of intestinal failure within multi-organ failure syndrome. The integrity of the gastric mucosal barrier plays a crucial role in protection against this condition. Somatostatin (SS) appears as a biomolecule with cytoprotective properties. We aimed to investigate whether SS treatment protected the gastric mucosa in a rat model of lipopolysaccharide (LPS)-induced sepsis. Rats received LPS (10 mg/kg) intraperitoneally, followed by saline or SS (200 μg/kg; 5 mL/kg) treatment after 30 min (early treatment group) or 120 min (late treatment group). Control rats received only saline. Two hours after saline or SS administration (total procedure duration of 150 or 240 min), gastric lavage, gastric mucosa, and plasma samples were collected for analysis. SS treatment mitigated the LPS-induced gastric mucosal barrier disruption preserving phosphatidylcholine (PC) levels, as well as decreasing leukocyte infiltration marker myeloperoxidase (MPO), inflammation-related enzyme phospholipase A2 (PLA2), and lipid peroxidation indicator malondialdehyde (MDA). SS also reduced arachidonic acid-related metabolites thromboxane B2 (TXB2) and leukotriene B4 (LTB4) while increasing prostaglandin I2 (PGI2). SS treatment effectively maintained gastric mucosal integrity, reducing inflammation, and modulating arachidonic acid metabolites. These findings suggest that SS may serve as a therapeutic agent for preserving gastric mucosal integrity and reducing inflammation in LPS-induced gastric injury.

Evaluation of a Comprehensive Profile of Salivary Analytes for the Diagnosis of the Equine Gastric Ulcer Syndrome

In this report, the measurement of salivary biomarkers as an aid for diagnosis of equine gastric ulcer syndrome (EGUS) was studied. A comprehensive panel of 23 salivary analytes was measured in the saliva of horses affected by EGUS and compared to healthy animals and horses with other diseases clinically similar to EGUS but with a negative diagnosis at gastroscopic examination. A total of 147 horses were included in the study and divided into heathy population (n = 12), the EGUS group (n = 110), and the group of horses with other diseases (n = 25). From the 23 analytes studied, 17 showed increased values in EGUS horses when compared to healthy ones, and uric acid, triglycerides, and calcium were significantly increased in horses with EGUS compared to the group of other diseases. The receiver operating characteristic curve analyses showed a modest but significant discriminatory power of those three analytes to identify EGUS from other diseases with similar symptoms. The discriminatory power enhanced when the results of the three analytes were combined. In conclusion, the results showed that selected salivary analytes could have potential use as biomarkers in horses with EGUS.

Chronic Stress-Related Gastroenteric Pathology in Cheetah: Relation between Intrinsic and Extrinsic Factors

Simple Summary

The cheetah is the fastest land mammal. Habitat destruction, high mortality due to other predators, and illegal wildlife trade has led to a decrease in the wild population. Currently, the global adult population present in their natural habitat is estimated to be 7100 individuals. In captivity, the population suffers from limited reproduction and disease. Both the wild and captive populations have reduced genetic diversity from a historic bottleneck, leading to increased ecological and environmental vulnerability. Over the years, conservation programs have been developed for habitat protection, management of human–animal conflict, and the study of disease and genetics. Among these, the one with the greatest prevalence in captivity is chronic gastritis. This review analyzes the scientific literature on gastric pathology in cheetah, with the potential causes divided into “extrinsic factors”, such as living conditions and diet, and “intrinsic factors”, including the presence of Helicobacter-like organisms and the genetic predisposition.

Abstract

The rapid decline of cheetah (Acinonyx jubatus) throughout their range and long-term studies of captive breeding has increased conservation action for this species including the study of chronic diseases. Gastritis is one of the captive diseases that leads to high mortality presented with symptoms including vomiting, diarrhea, anorexia, and weight loss. The disease presents different histological lesions in the gastrointestinal tract that are characterized by inconstant and different clinical appearance in captive and free-range cheetahs. The aim of this review is to summarize the causes of chronic gastritis in the cheetah. Factors including diet, living conditions, infections with gastric Helicobacter-like organisms (GHLOs), the lack of genetic polymorphism and the cheetah’s specific-immunocompetence are analyzed. All studies on gastroenteric cheetah pathologies, conducted between 1991 (to the best of our knowledge, the first report on online databases) and 2021, are included in this review, highlighting the possible correlation between stress-related captive conditions and chronic gastric pathology.

Qingke β-glucan synergizes with a β-glucan-utilizing Lactobacillus strain to relieve capsaicin-induced gastrointestinal injury in mice

Capsaicin (CAP) is the main pungent component in capsicum fruits. Eating too much CAP leads to gastrointestinal injury. Previously, Qingke β-glucan combined with β-glucan-utilizing Lactobacillus plantarum S58 (LP.S58) ameliorated high fat-diet-induced obesity, but their effects on CAP-induced gastrointestinal injury have not been investigated. Our results showed that Qingke β-glucan reduced the CAP-induced gastrointestinal injury in Kunming mice. The serum levels of inflammatory cytokines and gastrointestinal hormones, and the localized inflammation and the expression of EGF, EGFR, VEGF, and ZO-1 in the gastrointestinal tissues in CAP-treated mice were partly restored by Qingke β-glucan. The CAP-induced increase in the abundances of proinflammatory intestinal bacteria was also reduced by Qingke β-glucan. More importantly, we found that these beneficial effects of Qingke β-glucan were markedly enhanced by β-glucan-utilizing LP.S58 supplementation. Our study indicated that Qingke β-glucan coupled with β-glucan-utilizing LP.S58 relieved CAP-induced gastrointestinal injury.

Protective effect of silkworm pupa oil on hydrochloric acid/ethanol-induced gastric ulcers

BACKGROUND

Silkworm pupae are a traditional Chinese food, rich in various saturated and unsaturated fatty acids. Unsaturated fatty acids have a certain protective effect against oxidative damage. The present study used an animal model to determine the protective effect of silkworm pupa oil on hydrochloric acid / ethanol-induced gastric ulcer.

RESULTS

Silkworm pupa oil is rich in unsaturated fatty acids, including palmitoleic acid 63.4 g kg^-1 , oleic acid 249.1 g kg^-1 , linoleic acid 47.0 g kg^-1 , and linolenic acid 337.8 g kg^-1 , whereas its unsaturated fatty acid content is 700 g kg^-1 . Compared to a gastric ulcer control group, high and low doses of pupa oil reduced gastric ulcer area and gastric secretion, whereas gastric pH increased. It also increased serum antioxidant superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) levels, somatostatin (SST), and vasoactive intestinal peptide (VIP) levels, and reduced serum interleukin-6 (IL-6), interleukin-12 (IL-12), tumor necrosis factor (TNF-α), and interferon-γ (IFN-γ), motilin (MTL), and gastrin (GT) levels. RT-qPCR and western blot analyses indicated that silkworm pupa oil significantly increased CAT, GSH-Px, epidermal growth factor (EGF), Epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF), endothelial nitric oxide synthase (eNOS), Cu/Zn-SOD, Mn-SOD, and NF-kappa-B inhibitor-α (IκB-α) expression and lowered nuclear factor-kappa B (NF-κB), B-cell lymphoma-2 (Bcl-2), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) expression.

CONCLUSION

Silkworm pupa oil treatment reduced oxidative damage and inflammation in mice, and high-dose silkworm pupa oil was superior to low-dose silkworm pupa oil, following ranitidine. © 2018 Society of Chemical Industry.

Effects of Short-Distance Recreational Mushing on Oxytocin, Gastrin, and Creatinine Kinase in Sled Dogs

A considerable increase in creatinine kinase (CK) activity and gastrin hormone due to exercise has been observed in sled dogs during endurance mushing races; however, there have been no studies on sled dogs during recreational mushing. Although oxytocin hormone is involved in social behaviors and empathy, it has not been studied in sled dogs. This study aimed to assess changes in plasma CK activity, and gastrin and oxytocin concentrations in adult sled dogs used in touristic mushing in North Patagonia, Argentina. Blood samples were collected before, during, and after the winter season of 2017. Creatinine kinase activity measurement was done using an enzymatic assay. Hormone analyses were performed using commercial Enzyme-Linked InmunoSorbent Assay kits. Results showed an expected two-fold increase in CK activity during the winter, with recovering basal values after winter (< 400 UI/L), low and stable levels of gastrin (9.4 ± 8.8 pg/mL), and a slight increase in oxytocin (23%) after mushing activities. No evidence indicated gastrin alterations or muscular damage from touristic mushing, but an oxytocin increase would indicate a stimulation of the brain reward system.

Ulcer healing and mechanism(s) of action involved in the gastroprotective activity of fractions obtained from Syngonanthus arthrotrichus and Syngonanthus bisulcatus

Background

Syngonanthus arthrotrichus and Syngonanthus bisulcatus, currently known for Comanthera aciphylla (Bong.) L.R.Parra & Giul. and Comanthera bisulcata (Koern.) L.R. Parra & Giul, popularly known in Brazil as “sempre-vivas,” are plants from the family Eriocaulaceae. They are found in the states of Minas Gerais and Bahia. The species are known to be rich in flavonoids to which their gastroprotective activity has been attributed. In this research, experimental protocols were performed to elucidate the associated mechanisms of action.

Methods

The activity was evaluated using induced gastric ulcer models (acetic acid and ethanol-induced gastric lesions in NEM or L-NAME pre-treated mice, and by ischemia/reperfusion). Antioxidant enzymes, serum somatostatin, and gastrin were also evaluated.

Results

In chronic gastric ulcers, a single daily oral dose of Sa-FRF or Sb-FRF (100 mg/kg body wt.) for 14 consecutive days accelerated ulcer healing to an extent similar to that seen with an equal dose of cimetidine. The pre-treatment of mice with NEM (N-ethylmaleimide) or L-NAME (N-nitro-L-arginine) abolished the protective activity of Sa-FRF, Sa-FDF, Sb-FDF and Sb-FRF or Sa-FRF and Sb-FRF, respectively, which indicates that antioxidant compounds and nitric oxide synthase activity are involved in the gastroprotective. Sa-FRF and Sb-FRF (100 mg/kg p.o) protected the gastric mucosa against ulceration that was induced by ischemia/reperfusion (72 and 76 %, respectively). It also decreased lipid peroxidation and restored total thiols in the gastric wall of mice that had been treated with ethanol. When administered to rats submitted to ethanol-induced gastric lesions, Sa-FRF and Sb-FRF (100 mg/kg, p.o.) increased the somatostatin serum levels, while the gastrin serum levels were proportionally decreased.

Conclusions

The results indicate significant healing effects and gastroprotective activity for the Sa-FRF and Sb-FRF, which probably involves the participation of SH groups, nitric oxide (NO), the antioxidant system, somatostatin, and gastrin. All are integral parts of the gastrointestinal mucosa’s cytoprotective mechanisms against aggressive factors.

Gastrointestinal Safety Pharmacology in Drug Discovery and Development

Although the basic structure of the gastrointestinal tract (GIT) is similar across species, there are significant differences in the anatomy, physiology, and biochemistry between humans and laboratory animals, which should be taken into account when conducting a gastrointestinal (GI) assessment. Historically, the percentage of cases of drug attrition associated with GI-related adverse effects is small; however, this incidence has increased over the last few years. Drug-related GI effects are very diverse, usually functional in nature, and not limited to a single pharmacological class. The most common GI signs are nausea and vomiting, diarrhea, constipation, and gastric ulceration. Despite being generally not life-threatening, they can greatly affect patient compliance and quality of life. There is therefore a real need for improved and/or more extensive GI screening of candidate drugs in preclinical development, which may help to better predict clinical effects. Models to identify drug effects on GI function cover GI motility, nausea and emesis liability, secretory function (mainly gastric secretion), and absorption aspects. Both in vitro and in vivo assessments are described in this chapter. Drug-induced effects on GI function can be assessed in stand-alone safety pharmacology studies or as endpoints integrated into toxicology studies. In silico approaches are also being developed, such as the gut-on-a-chip model, but await further optimization and validation before routine use in drug development. GI injuries are still in their infancy with regard to biomarkers, probably due to their greater diversity. Nevertheless, several potential blood, stool, and breath biomarkers have been investigated. However, additional validation studies are necessary to assess the relevance of these biomarkers and their predictive value for GI injuries.

The mechanism through which octreotide inhibits hepatic stellate cell activity

Hepatic stellate cells (HSCs) are important in the development of liver fibrosis and in the pathogenesis of portal hypertension. Octreotide, an analogue of somatostatin, has been demonstrated to effectively treat fibrosis and portal hypertension; however, its relative mechanism in HSCs remains unknown. LX‑2, the immortalized HSC line, was used to study the mechanism whereby octreotide functions at different concentrations. Real‑time polymerase chain reaction (PCR) and western blot analysis were used to analyze the expression of fibrosis markers and transcription factors following treatment with octreotide. Soluble secreted endothelin‑1 (ET‑1), collagen I and vascular endothelial growth factor (VEGF) were assessed in the supernatants of cultured cells by enzyme-linked immunosorbent assay (ELISA). In the present study, it was shown that octreotide was able to inhibit the proliferative ability of the LX‑2 cells and decrease the expression of transforming growth factor β (TGF‑β), α‑smooth muscle actin (α‑SMA) and smad‑4a. The transcription factors, including c‑Jun and sp‑1, were downregulated in a dose‑dependent manner following treatment with octreotide. The levels of ET‑1 and collagen I in the supernatant decreased significantly in contrast with the normal levels, whereas the levels of VEGF in the LX‑2 cells and the supernatant increased at a high octreotide concentration (10‑5 nM). Octreotide may exert its effects on ET‑1 or other targeting genes in HSCs through the downregulation of c‑Jun and specificity protein 1 (sp‑1), and the increased levels of VEGF may be the reason for the side effects observed at high concentrations of octreotide.

Cannabinoid HU210 protects isolated rat stomach against impairment caused by serum of rats with experimental acute pancreatitis

Acute pancreatitis (AP), especially severe acute pancreatitis often causes extra-pancreatic complications, such as acute gastrointestinal mucosal lesion (AGML) which is accompanied by a considerably high mortality, yet the pathogenesis of AP-induced AGML is still not fully understood. In this report, we investigated the alterations of serum components and gastric endocrine and exocrine functions in rats with experimental acute pancreatitis, and studied the possible contributions of these alterations in the pathogenesis of AGML. In addition, we explored the intervention effects of cannabinoid receptor agonist HU210 and antagonist AM251 on isolated and serum-perfused rat stomach. Our results showed that the AGML occurred after 5 h of AP replication, and the body homeostasis was disturbed in AP rat, with increased levels of pancreatic enzymes, lipopolysaccharide (LPS), proinflammtory cytokines and chemokines in the blood, and an imbalance of the gastric secretion function. Perfusing the isolated rat stomach with the AP rat serum caused morphological changes in the stomach, accompanied with a significant increment of pepsin and [H⁺] release, and increased gastrin and decreased somatostatin secretion. HU210 reversed the AP-serum-induced rat pathological alterations, including the reversal of transformation of the gastric morphology to certain degree. The results from this study prove that the inflammatory responses and the imbalance of the gastric secretion during the development of AP are responsible for the pathogenesis of AGML, and suggest the therapeutic potential of HU210 for AGML associated with acute pancreatitis.

Octreotide ameliorates gastric lesions in chronically mild stressed rats

AIM: To evaluate the effect of chronic mild stress (CMS) on the emergence of gastric ulcers and possible modulation by octreotide, a synthetic somatostatin analogue.

METHODS: Adult male Wistar rats were subjected to nine different unpredictable random stress procedures for 21 d, a multifactorial interactional animal model for CMS. Octreotide was administered daily for 21 d at two dose levels (50 and 90 μg/kg) before exposure to stress procedure. Macro- and microscopical assessments were made, in addition to quantification of plasma corticosterone and gastric mucosal inflammatory, oxidative stress, and apoptotic biomarkers.

RESULTS: Exposure to CMS elevated plasma corticosterone (28.3 ± 0.6 μg/dL, P = 0.002), an event that was accompanied by gastric lesions (6.4 ± 0.16 mm, P = 0.01) and confirmed histopathologically. Moreover, the insult elevated gastric mucosal lipid peroxides (13 ± 0.5 nmol/g tissue, P = 0.001), tumor necrosis factor-α (3008.6 ± 78.18 pg/g tissue, P < 0.001), prostaglandin E2 (117.1 ± 4.31 pg/g tissue, P = 0.002), and caspase-3 activity (2.4 ± 0.14 OD/mg protein, P = 0.002). Conversely, CMS mitigated interleukin-10 (627.9 ± 12.82 pg/g tissue, P = 0.001). Furthermore, in animals exposed to CMS, octreotide restored plasma corticosterone (61% and 71% from CMS, P = 0.002) at both dose levels. These beneficial effects were associated with a remarkable suppression of gastric lesions (38% and 9% from CMS, P = 0.01) and reversal of derangements in gastric mucosa.

CONCLUSION: The current investigation provides evidence that exposure to CMS induces gastric ulceration, which was alleviated by administration of octreotide possibly possessing antioxidant, anti-inflammatory, and anti-apoptotic actions.

Loss of RegI in conjunction with gastrin deficiency in mice facilitates efficient gastric ulcer healing but is dispensable for hyperplasia and tumourigenesis

RegI (Regenerating islet derived-1) was originally characterized as a growth factor involved in pancreatic islet cell regeneration. It is also considered a gastrointestinal mitogen as its expression is increased during pathologies involving aberrant cell proliferation that can lead to neoplasia. However, the absolute requirement for RegI to directly stimulate gastric mucosal cell proliferation in vivo requires further investigation. We used RegI-deficient mice to determine the requirement for RegI in normal gastric mucosal development, wound healing, hyperplasia and tumourigenesis. We found that epithelial repair of acetic acid ulcers in compound mutant RegI/gastrin-deficient mice was significantly reduced compared to wild type, RegI-deficient or gastrin-deficient mice. In contrast, RegI was dispensable for normal gastric mucosal development, hyperplasia in HKbeta-deficient mice and tumourigenesis in gp130(F/F) mice. Although RegI was not required for proliferation in these pathological models, expression of multiple Reg family members were increased during gp130(F/F) tumourigenesis. Interestingly, loss of RegI in gp130(F/F) mice resulted in decreased expression of other Reg family members. Our results indicate that RegI and gastrin may synergistically regulate gastric mucosal proliferation during certain pathological settings like wound healing while gastric epithelial proliferation in other pathologies may require coordinated expression of multiple Reg genes.

The anti-ulcerogenic effects of Curatella americana L

ETHNOPHARMACOLOGICAL RELEVANCE

Curatella americana L. (Dilleneaceae) is a medicinal plant very frequently cited as acting against gastrointestinal disorders in ethnopharmacological inventories of the Cerrado region of Brazil.

AIM OF THE STUDY

The ethanolic extract (CEB) and infusion (BI) of Curatella americana bark were investigated for their ability to prevent and heal ulceration of the gastric mucosa.

MATERIALS AND METHODS

The preventive and healing actions of Curatella americana were evaluated in experimental in vivo models in rodents that simulated this disease in human gastric mucosa.

RESULTS

CEB significantly decreased the severity of gastric damage formation induced by the combination of several gastroprotective models (HCl/ethanol, indomethacin/bethanecol, absolute ethanol, stress and pylorus ligature). But, unlike CEB, the BI did not exert gastroprotective effect. The gastroprotective action of CEB involved antisecretory action, augmentation of gastric mucus (48%) and participation of endogenous sulfhydryl compounds that increase efficacy of barrier mucosa against injurious agents. CEB also presents effective healing action in chronic gastric disease (1.90+/-0.55 vs. 6.86+/-0.46 mm2)in the control) and its action mechanisms consisted of increasing the PGE2 (40%) and somatostatin levels (269%) while decreasing the gastrin level in rat plasma (79%).

CONCLUSIONS

The gastroprotective effect and healing action of Curatella americana involved modulation of PGE2, somatostatin and gastrin levels, probably due to the presence of oligomeric and polymeric proanthocyanidins in the bark.

Effects of hypoxia on glucose, insulin, glucagon, and modulation by corticotropin-releasing factor receptor type 1 in the rat

To determine the influence of continuous hypoxia on body weight, food intake, hepatic glycogen, circulatory glucose, insulin, glucagon, leptin, and corticosterone, and the involvement of the corticotropin-releasing factor receptor type 1 (CRFR1) in modulation of these hormones, rats were exposed to a simulated altitude of 5 km (approximately 10.8% O2) in a hypobaric chamber for 1, 2, 5, 10, and 15 d. Potential involvement of CRFR1 was assessed through five daily sc injections of a CRFR1 antagonist (CP-154,526) prior to hypoxia. Results showed that the levels of body weight, food intake, blood glucose, and plasma insulin were significantly reduced; the content of hepatic glycogen initially and transiently declined, whereas the early plasma glucagon and leptin remarkably increased; plasma corticosterone was markedly increased throughout the hypoxic exposure of 1-15 d. Compared with hypoxia alone, CRFR1 antagonist pretreatment in the hypoxic groups prevented the rise in corticosterone, whereas the levels of body weight and food intake were unchanged. At the same time, the reduction in blood glucose was greater and the pancreatic glucose was increased, plasma insulin reverted toward control, and plasma glucagon decreased. In summary, prolonged hypoxia reduced body weight, food intake, blood glucose, and plasma insulin but transiently enhanced plasma glucagon and leptin. In conclusion, CRFR1 is potentially involved in the plasma insulin reduction and transient glucagon increase in hypoxic rats.

Gastric protection by α-melanocyte-stimulating hormone against ethanol in rats: Involvement of somatostatin

The proopiomelanocortin-derived tridecapeptide alpha-melanocyte-stimulating hormone (alpha-MSH) is a neuropeptide that exerts broad anti-inflammatory actions in mammals. This study aimed to investigate the effect of alpha-MSH on ethanol-induced gastric ulcer in rats and to evaluate the involvement of endogenous somatostatin in the actions of the peptide. The rats received 1 mL 75% ethanol or saline orally. alpha-MSH was given (25 micro g/rat; i.p.) alone or following the somatostatin antagonist cyclo-(7-aminoheptanoyl-PH-E-d-Trp-Lys-THR) (10 microM/kg; i.p.) administration. Gastric lesions were scored macroscopically and microscopically following decapitation at 30 min after ethanol challenge. Gastric malondialdehyde (MDA) level, myeloperoxidase (MPO) activity and mast cell counts were assessed. Ethanol-induced gastric hemorrhagic lesions were characterized by increased gastric MDA level, MPO activity and mast cell counts. alpha-MSH treatment decreased the extent of tissue injury and reversed tissue MDA level, MPO activity and mast cell counts. The effect of the peptide on the severity of gastric lesions, MDA level and MPO activity was reversed by the somatostatin antagonist. In conclusion, alpha-MSH is beneficial in a rat model of gastric ulcer via mechanisms which partly involve the endogenous somatostatin.

Antiulcerogenic activity of Alchornea castaneaefolia: effects on somatostatin, gastrin and prostaglandin

The hydroethanolic extract of the leaves (HEL) and bark (HEB) obtained from Alchornea castaneaefolia (Euphorbiaceae) were investigated for their ability to prevent ulceration of the gastric mucosa in animal models. HEL (500 and 1000 mg/kg) and HEB (1000 mg/kg) significantly reduced the gastric injuries induced by the combination of HCl/ethanol and lowered the severity of gastric damage formation induced by indomethacin/bethanechol in mice. Further investigation showed that HEL also inhibited formation of ulcers in mice submitted to stress and pylorus ligature, but HEL did not modify gastric juice parameters in Shay mice. HEL was also effective in promoting the healing process in chronic gastric ulcer induced by acetic acid in rats. An enriched flavonoidic fraction (EFF at dose of 100mg/kg) obtained from HEL reduced gastric lesions induced by HCl/ethanol and indomethacin/bethanechol in mice. Although EFF did not modify the amount of free mucus production by gastric mucosa, it was able to increase prostaglandin production. When administered to rats submitted to ethanol-induced gastric lesions, EFF increased the somatostatin serum levels, while the gastrin serum levels were proportionally decreased. Phytochemical investigation on HEL and EFF led to the isolation of flavonoids glycosides as the main compounds, thus suggesting that these substances may be involved in the observed antiulcer activity.

An overview of acetic acid ulcer models--the history and state of the art of peptic ulcer research

Four types of experimental chronic ulcer models, named acetic acid ulcer models, have been developed to examine the healing process of peptic ulcers, screen anti-ulcer drugs, and better evaluate the adverse effects of various anti-inflammatory drugs on the gastrointestinal mucosa. The model easily and reliably produces round, deep ulcers in the stomach and duodenum, allowing acetic acid ulcer production in mice, rats, Mongolian gerbils, guinea pigs, cats, dogs, miniature pigs, and monkeys. These ulcer models highly resemble human ulcers in terms of both pathological features and healing process. The models have been established over the past 35 years and are now used throughout the world by basic and clinical scientists. One of the characteristic features of acetic acid ulcers in rats is the spontaneous relapse of healed ulcers >100 d after ulceration, an endoscopically confirmed phenomenon. Indomethacin significantly delays the healing of acetic acid ulcers, probably by reducing endogenous prostaglandins and inhibiting angiogenesis in ulcerated tissue. Helicobacter pylori significantly delays healing of acetic acid ulcers and causes relapse of healed ulcers at a high incidence in Mongolian gerbils. Anti-secretory drugs (e.g. omeprazole), prostaglandin analogs, mucosal defense agents (e.g. sucralfate), and various growth factors all significantly enhance healing of acetic acid ulcers. Gene therapy with epidermal growth factor and vascular endothelial growth factor applied to the base of acetic acid ulcers in rats is effective in enhancing ulcer healing. Since an inhibitor of nitric oxide syntase prevents ulcer healing, nitric oxide might be involved in the mechanism underlying ulcer healing. We conclude that acetic acid ulcer models are quite useful for various studies related to peptic ulcers.

Effects of duodenogastric reflux on gastrin cells, somatostatin cells and serotonin cells in human antral gastric mucosa

Duodenogastric reflux (DGR) has been found to give rise to a hypochlorhydria secondary to alkaline reflux. We investigated whether there is a link between DGR and the gastrin, somatostatin, and serotonin cell numbers and the granular content of gastrin, somatostatin, and serotonin in endocrine cells in human antral mucosa. We investigated 38 selected Helicobacter pylori-negative patients with visual primary excessive DGR in upper endoscopy and symptoms of epigastric pain and bile vomiting. Ten control patients were included in this study. None of the patients had peptic ulcer or had received any medication. Antrum (10 biopsies from five different zones: the lesser and major curvature, the anterior and posterior wall, and the pylorus) and corpus (two biopsies from major curvature about 10 cm below the cardia) biopsy specimens were collected for routine histology, as well as for light and electron immunohistochemistry. In patients without atrophy or intestinal metaplasia and in patients with mild atrophy or mild intestinal metaplasia, the number of gastrin and somatostatin cells was not different from that in controls. In moderate atrophy or moderate intestinal metaplasia, however, the number of gastrin and somatostatin cells decreased. Serotonin cell number was significantly higher in all patients with DGR as compared with controls. The mean somatostatin granular content was increased (3.6+/-0.2 vs. 3.2+/-0.1). In addition, lysosomes with engulfed somatostatin granules were found. The mean serotonin granular content was decreased (2.3+/-0.3 vs. 2.9+/-0.3), while the mean gastrin granular content remained unchanged (2.5+/-0.3 vs. 2.4+/-0.2). Ultrastructurally, the granules in serotonin-positive cells corresponded to the gastric variant or to the intestinal variant of serotonin cells. The endocrine cells were found to have few granules positive for serotonin. It is concluded that DGR inhibits somatostatin granular release, but stimulates both serotonin granular release and serotonin cell growth.

Preventive activity of pyrrolizidine alkaloids from Seneciobrasiliensis (Asteraceae) on gastric and duodenal induced ulcer on mice and rats

The alkaloid extract of Senecio brasiliensis inflorescences contain a mixture of the pyrrolizidine alkaloids (PA) senecionine, integerrimine, retrorsine, usaramine and seneciphylline. We evaluated this PA mixture on preventive antiulcerogenic effects on standard rodent models of induced gastric and duodenal ulcers. In the HCl/ethanol, indomethacin-bethanechol and hypothermic-restraint-induced gastric ulcer, the lesion was significantly inhibited by PA (p.o.) (p < 0.001). In the pylorus-ligature, PA (i.d.), significantly increased the gastric juice content and the pH values and decreased the acid output. In the cysteamine induced duodenal ulcers, PA (p.o.) showed significant inhibition (p < 0.001) of the duodenal lesions when compared to the respective control. The levels of the somatostatin hormone in the blood samples of animals pre-treated with the PA (12.5 mg/kg) and the free mucus and prostaglandin synthesis also increased (p < 0.001) after administration of PA extract (p.o.). The results suggested that the PA extract from Senecio brasiliensis inflorescences presents a significant anti-ulcer effect in the selected ulcer models. The mechanism involved with the action of the PA extract is the cytoprotection. Additional studies are in progress to determine other possible mechanisms involved with effect of the PA as anti-ulcer agents.

G and D cells in rat antral mucosa: An immunoelectron microscopic study

AIM: To investigate the gastrin secreting cells (G cells) and the somatostatin secreting cells (D cells) of antral mucosa in rats at the ultrastructural level.

METHODS: Revised immunoelectron microscopic technique was used to detect the G cells and D cells in rat antral mucosa through gastrin and somatostatin antibodies labeled by colloidal gold. Also the relevant quantitative analysis regarding the granular number of colloidal gold in G cells and in D cells was conducted.

RESULTS: Immunological granules of colloidal gold were distributed in G cells and D cells. Gastrin labeled golden granules or somatostatin labeled ones presented mainly as lobation-like or island-like congeries. Most of the golden congeries were observed dissociated in cytoplasms of G cells or D cells, near the basement membrane. A few golden congeries were located in nuclei. The number of golden granules in one G cell was around 107.04 ± 19.68 and was 83.36 ± 17.58 in one D cell.

CONCLUSION: Gastrin secreting granules are located in cytoplasms and nuclei of G cells, and somatostatin secreting granules both in cytoplasms and in nuclei of D cells. The number of golden granules can be quantitatively analyzed to determine the relative amount of gastrin secreting granules or somatostatin secreting granules.

Inhibitory effect of octreotide on gastric cancer growth via MAPK pathway

AIM: Somatostatin and its analogues may suppress the growth of various tumor cells. However, the effect of octreotide on growth of gastric adenocarcinoma is still largely unknown. This study was to explore if octreotide could inhibit the growth of gastric adenocarcinoma and its probable mechanisms.

METHODS: Proliferation of gastric cancer cell line affected by octreotide was determined by ³H-thymidine incorporation. After xenografts of human gastric cancer were implanted orthotopically in stomach, nude mice were administrated octreotide for 8 weeks. The mRNA of somatostatin receptor in the SGC-7901 cells was detected by reverse transcription polymerase chain reaction technique. Extracellular signal-regulated protein kinase and c-Fos in gastric cancer tissues were measured by immunohistochemistry and Western blot. Activator protein-1 binding activity was examined by electrophoretic mobility sift assay.

RESULTS: ³H-thymidine incorporation into SGC-7901 cells was significantly decreased by octreotide in a concentration dependent manner. Either size or weight of tumors treated with octreotide was significantly reduced in vivo. The inhibition rate for tumor was 62.3% in octreotide group. The genes of somatostatin receptors 2 and 3 were expressed in SGC-7901 gastric cancer cell lines. Extracellular signal-regulated protein kinase and c-Fos protein level were decreased in gastric adenocarcinoma treated with octreotide. Moreover, fetal calf serum stimulated activator protein-1 binding activity could be suppressed by octreotide potentially.

CONCLUSION: Inhibition of sequential molecular events in MAPK pathway may interpret the mechanisms underlying the effect of octreotide on the growth of gastric adenocarcinoma.