Cyclooxygenase 2, pS2, inducible nitric oxide synthase and transforming growth factor alpha in gastric adaptation to stress

The Apelin-Apela Receptor APJ is Necessary for Formation and Healing of Ischemia Reperfusion-Induced Gastric Ulcer in Rats

The apelinergic system, widely expressed and regulates hormone-enzyme secretion, motility, and protective mechanisms of the stomach. This system consists of the apelin receptor (APJ) and two peptides known as apela and apelin. The IR-induced experimental gastric ulcer model, is a well-known and commonly used one that induces hypoxia and causes the release of proinflammatory cytokines. Expressions of apelin and its receptor APJ are induced by hypoxia and inflammation in the gastrointestinal tract. Apelin has been shown to affect angiogenesis positively, considered the most critical component of the healing process. Although it is known that apelin and AJP expressions are induced by inflammatory stimuli and hypoxia, stimulate endothelial cell proliferation and have a role in regenerative angiogenesis, no information or has been found in the literature regarding the role of APJ in the formation and healing of gastric mucosal lesions induced by I/R. So, we conducted a study to clarify the role of APJ in formation and healing mechanisms of IR-induced gastric lesions. Male Wistar rats were divided into five groups; control, sham-operated, IR, APJ antagonist treated-IR group (F13A+IR), and the healing groups. F13A was intravenously given to the animals. Gastric lesion index, mucosal blood flow, PGE₂, NOx, 4-HNE-MDA, HO activity, and protein expressions of VEGF and HO-1 were measured. F13A application before the IR increased the mucosal injury, F13A application following the ischemia delayed the mucosal healing during the reperfusion period. Consequently, blocking apelin receptors may worsen gastric injury due to the IR and delay mucosal healing.

Effect of the IGF-1/PTEN/Akt/FoxO signaling pathway on the development and healing of water immersion and restraint stress-induced gastric ulcers in rats

Insulin-like growth factor 1 (IGF-1) and Akt [also known as protein kinase B (PKB)] proteins have been reported to exhibit gastroprotective effects by reducing water immersion and restraint stress (WRS)-induced gastric mucosal cellular apoptosis. To confirm whether the IGF-1/PTEN/Akt/FoxO signaling pathway is effective in protecting against gastric ulcers, our current study was conducted to examine the expression and localization of IGF-1, phosphatase and tensin homologue deleted on chromosome 10 (PTEN), Akt and O subfamily of forkhead box (FoxO) proteins, caspase-3 activity and the number of apoptotic cells in gastric mucosa of rats subjected to WRS. Our results demonstrated that WRS induced gastric ulcers by enhancing cell apoptosis in rat gastric mucosa. In addition, in normal rat gastric mucosa, PTEN, total Akt and FoxO1 were found mainly in the cell cytoplasm of fundic glands in the lamina propria close to the muscularis mucosa. In addition, strong staining of IGF-1, FoxO3a and FoxO4 in the gastric mucosa was primarily concentrated in the cell cytoplasm of the fundic glands in whole lamina propria. However, in rat gastric ulcers, IGF-1, total Akt, FoxO3a and FoxO4 were localized in proximity to the base of the ulcer margin and were also present in the granulation tissues of the gastric ulcers. Moreover, in the rat gastric ulcers, the mRNA transcript levels of IGF-1, PTEN, Akt-1, Akt-2, FoxO3 and FoxO4 were upregulated in the gastric ulcer margin, with a peak between Days 4 and 8 following 7 h of WRS. In conclusion, our results imply that the IGF-1/PTEN/Akt/FoxO signaling pathway plays a certain role(s) in the protection against ulceration through the regulation of cellular apoptosis as observed in the development and healing of rat gastric ulcers.

The effect of nitric oxide, growth factors, and estrogen on gastric cell migration

BACKGROUND

To study gastric epithelial cell migration during nitric oxide (NO) and growth factor treatment, simulating inflammation and infection. Also, the effects of estrogen on migration of different malignant and nonmalignant gastric epithelial cell lines were explored.

MATERIAL AND METHODS

Isolated primary cultured rabbit gastric epithelial cells, rat gastric mucosal cells, human gastric adenocarcinoma cells, and human colon adenocarcinoma cells (WiDr) were cultured to confluency in appropriate media (5% CO2, 37 degrees C). The cells were treated by hepatocyte growth factor (HGF), transforming growth factor-alpha (TGF-alpha) and keratinocyte growth factor (KGF), with and without sodium nitroprusside (SNP, NO donor) or 17beta-estradiol. Caspase-3 activity and cell viability and migration speed after wounding were measured.

RESULTS

HGF was the most potent growth factor to stimulate migration. SNP dose-dependently decreased the speed of migration. HGF and TGF-alpha were able to overcome the SNP-induced inhibition of migration, whereas KGF was not. SNP also induced caspase-3 activity, which was inhibited by HGF and TGF-alpha. 17beta-estradiol decreased migration in all epithelial cells, but the decrease was more profound in malignant cell lines. HGF could overcome the estrogen retarded migration.

CONCLUSIONS

Growth factors can overcome NO-induced retardation of cell migration and inhibit NO-induced caspase-3 activity, which altogether might also have physiological significance in in vivo inflammation and in gastric cancer. The more profound decrease in migration speed of gastric adenocarcinoma cell line may suggest that estrogen might be one of the protective factor against female gastric adenocarcinoma before menopausal age.

PROSTAGLANDINS, CAPSAICIN-SENSITIVE SENSORY NERVES AND NEUTROPHIL INFILTRATION, BUT NOT NITRIC OXIDE, CONTRIBUTE TO COLD RESTRAINT STRESS-INDUCED GASTRIC ADAPTATION IN RATS

The aim of the present study was to determine the role of prostaglandins (PG), nitric oxide (NO) and capsaicin-sensitive sensory nerves in neutrophil infiltration in gastric adaptation to cold restraint stress in rats. Wistar rats were exposed to single or repeated cold restraint stress for 3.5 h every other day for up to 4 days. Prior to repeated stress, rats were pretreated with NG-nitro-L-arginine methyl ester (L-NAME; 10 mg/kg, s.c.), indomethacin (10 mg/kg, s.c.) or capsaicin (125 mg/kg, s.c.). The extent of gastric mucosal lesions was evaluated histologically and myeloproxidase (MPO) activity, PGE2, NO and calcitonin gene-related peptide (CGRP) levels were measured in gastric tissue. Cold restraint stress produced haemorrhagic lesions and reduced PGE2 and CGRP levels in the stomach, with an increase in MPO activity and NO levels. Repeated stress insults reduced stress-induced gastric damage, NO production and MPO activity, with an increase in PGE2 and CGRP levels compared with rats exposed to single cold restraint stress. Adaptation to cold restraint stress was prevented by indomethacin and capsaicin pretreatment, but not by L-NAME. We conclude that the stomach has the ability to adapt to repeated exposure to cold restraint stress and that the adaptation, via inhibition of neutrophil infiltration, is mediated, at least in part, by endogenous PG and CGRP.