Changes of nitric oxide and growth factors during gastric ulcer healing

The Influence of Prolonged Acetylsalicylic Acid Supplementation-Induced Gastritis on the Neurochemistry of the Sympathetic Neurons Supplying Prepyloric Region of the Porcine Stomach

This experiment was designed to establish the localization and neurochemical phenotyping of sympathetic neurons supplying prepyloric area of the porcine stomach in a physiological state and during acetylsalicylic acid (ASA) induced gastritis. In order to localize the sympathetic perikarya the stomachs of both control and acetylsalicylic acid treated (ASA group) animals were injected with neuronal retrograde tracer Fast Blue (FB). Seven days post FB injection, animals were divided into a control and ASA supplementation group. The ASA group was given 100 mg/kg of b.w. ASA orally for 21 days. On the 28^th day all pigs were euthanized with gradual overdose of anesthetic. Then fourteen-micrometer-thick cryostat sections were processed for routine double-labeling immunofluorescence, using primary antisera directed towards tyrosine hydroxylase (TH), dopamine β-hydroxylase (DβH), neuropeptide Y (NPY), galanin (GAL), neuronal nitric oxide synthase (nNOS), leu 5-enkephalin (LENK), cocaine- and amphetamine- regulated transcript peptide (CART), calcitonin gene-related peptide (CGRP), substance P (SP) and vasoactive intestinal peptide (VIP). The data obtained in this study indicate that postganglionic sympathetic nerve fibers supplying prepyloric area of the porcine stomach originate from the coeliac-cranial mesenteric ganglion complex (CCMG). In control animals, the FB-labelled neurons expressed TH (94.85 ± 1.01%), DβH (97.10 ± 0.97%), NPY (46.88 ± 2.53%) and GAL (8.40 ± 0.53%). In ASA group, TH- and DβH- positive nerve cells were reduced (85.78 ± 2.65% and 88.82 ± 1.63% respectively). Moreover, ASA- induced gastritis resulted in increased expression of NPY (76.59 ± 3.02%) and GAL (26.45 ± 2.75%) as well as the novo-synthesis of nNOS (6.13 ± 1.11%) and LENK (4.77 ± 0.42%) in traced CCMG neurons. Additionally, a network of CART-, CGRP-, SP-, VIP-, LENK-, nNOS- immunoreactive (IR) nerve fibers encircling the FB-positive perikarya were observed in both intact and ASA-treated animals. The results of this study indicate involvement of these neuropeptides in the development or presumably counteraction of gastric inflammation.

Inflammatory changes of the gastric mucosa and serum concentration of chosen growth factors in children

PURPOSE

To assess whether there is a correlation between the severity of gastritis and concentration of chosen growth factors in the serum of children infected with H. pylori.

MATERIAL AND METHODS

The study included 64 children of whom 50% (Group I) were infected with H. pylori and had gastritis; 18.7% (Group II) of the examined children had a positive titre of IgG against H. pylori and normal gastric mucosa. Controls (Group III) comprised 31.3%. The gastric mucosa was evaluated histopathologically according to the Sydney System. The serum concentrations of growth factors: EGF, TGF-alpha, VEGF, were determined using ELISA.

RESULTS

Mean concentrations of the growth factors were also the highest in Group I compared to Group II and Group III (EGF - 137.3+/-10.4 pg/mL, TGF-alpha - 0.4+/-1.2 pg/mL, VEGF - 146.8 pg/mL). Analysis of correlations between growth factors and the severity of gastritis as well as the activity of antral gastric mucosa inflammation proved that mean EGF concentration in H. pylori infected children was the highest (149.5+/-84.8 pg/mL) in severe gastritis, whereas mean concentrations of TGF-alpha (2.0+/-4.3 pg/mL) and of VEGF (148.1+/-92.6 pg/mL) were the highest in moderate gastritis. Mean concentrations of EGF (155.1+/-116.4 pg/mL) and of VEGF (156.0+/-118.9 pg/mL) were the highest in high activity antral gastritis, whereas the mean concentration of TGF-alpha was the highest (2.0+/-4.2 pg/ml) in moderate activity gastritis.

CONCLUSIONS

In the children with H. pylori infection, serum concentrations of EGF, TGF-alpha, VEGF were the highest in moderate and severe antral gastritis.

Day/night differences in stress-induced gastric lesions in rats with an intact pineal gland or after pinealectomy

The formation of acute gastric lesions depends upon the balance between the aggressive factors promoting mucosal damage and the natural defense mechanisms. Previous studies have shown that melatonin inhibits gastric acid secretion, enhances the release of gastrin, augments gastric blood flow (GBF), increases the cyclooxygenase-2 (COX-2)-prostaglandin (PG) system and scavenges free radicals, resulting in the prevention of stress-induced gastric lesions. Besides the pineal gland, melatonin is also generated in large amounts in the gastrointestinal tract and due to its antioxidant and anti-inflammatory properties; this indole might serve as local protective endogen preventing the development of acute gastric damage. The results of the present study indicate that stress-induced gastric lesions show circadian variations with an increase in the day time and a decline at night. These changes are inversely related to plasma melatonin levels. Following pinealectomy, stress-induced gastric mucosal lesions were more pronounced both during the day and at night, and were accompanied by markedly reduced plasma melatonin levels with a pronounced reduction in mucosal generation of prostaglandin E(2) (PGE(2)), GBF and increased free radical formation and by small rise in plasma melatonin during the dark phase. We conclude that stress-induced gastric ulcerations exhibit a circadian variation with an increase in the day and attenuation at night and that these fluctuations of gastric stress ulcerogenesis occur also after pinealectomy, depending upon the interaction of COX-PG and free radicals, probably mediated by the changes in local gastric melatonin.

Low-energy laser irradiation increases endothelial cell proliferation, migration, and eNOS gene expression possibly via PI3K signal pathway

BACKGROUND AND OBJECTIVES

The purpose of this study, therefore, was to determine the mechanisms by which low-energy laser irradiation (LELI) may exert some of its angiogenic effects via the PI3 kinase/eNOS signaling pathway and induce endothelial cell migration and neovascularization, an important and necessary part of wound healing.

STUDY DESIGN/MATERIALS AND METHODS

The possible molecular mechanism of helium-neon (He-Ne) laser irradiation on endothelial cells was proposed. He-Ne laser at 632.5 nm was used to stimulate human umbilical vein endothelial cell (HUVEC), and its effect on cell proliferation, nitric oxide secretion, and cell migration was determined.

RESULTS

Irradiation enhanced endothelial nitric oxidase synthase (eNOS) protein expression, and irradiation of less than 0.26 J/cm(2) enhanced eNOS gene expression in HUVEC. The cell migration ability was promoted for HUVEC irradiated with 0.26 J/cm(2). This agreed with the vinculin protein expression induced by irradiation. In addition, the angiogenesis was promoted. The induced eNOS expression was inhibited by LY294002, indicating that the effect of laser on EC could be attributed to the up-regulation of eNOS expression through PI3K pathway at the cellular and molecular levels as a result of the He-Ne laser.

CONCLUSIONS

The study has shown that LELI increased endothelial cell proliferation, migration, NO secretion, and identified that activation of PI3K/Akt pathway was a critical step for the elevated for eNOS expression upon LELI.

Evaluation of malignant and benign gastric biopsy specimens by mRNA expression profile and multivariate statistical methods

BACKGROUND

mRNA expression array and multivariate statistical analysis of gastric biopsies can yield insight into the molecular biology basis of local alterations, supporting expression-based identification of morphological alterations.

METHODS

From 11 patients with erosive gastritis(EG), 5 with adenocarcinoma (GC), 11 with atrophic gastritis (AG) gastric biopsies were collected, total RNA isolated, T7 amplification and expression analysis of 1047 mRNAs was performed using commercial glass arrays (Clontech, USA). After microarray quality control, applicable data were available from 7 EG, 4 GC, and 5 AG. Multivariate statistical and cell functional analysis were performed. Real-time RT-PCR and immunohistochemistry were used for validation.

RESULTS

GC was characterized by overregulated v-raf, v-erb-a, BCL2-associated- athanogene, immediate-early-response-3, Polo-like kinase, CDK-2, cyclin-C, Pin1 genes, and downregulated ADP-ribosyltransferase, sialophorin and DCC. AG cases had increased PDGF-receptor, TGF-beta-receptor-3, and decreased death-associated-protein-3, beta-1-catenin, topoisomerase-1 levels. In EG upregulation of IGF-receptor-1, CD9, transferrin receptor, integrins, and underexpression of keratin-5, caspase-4 was found. Discriminant analysis could reclassify all samples correctly using four parameters.

CONCLUSIONS

mRNA expression array analysis of gastric biopsies yields previously known and new data in the evaluation of local gastric alterations.

Endothelin-1, an ulcer inducer, promotes gastric ulcer healing via mobilizing gastric myofibroblasts and stimulates production of stroma-derived factors

Endothelin (ET)-1 is a potent inducer of peptic ulcers. The roles of ET-1 in ulcer healing, however, have remained unclear, and these were investigated in mice. Gastric ulcers were induced in mice by serosal application of acetic acid. Three days later, mice were given a neutralizing ET-1 antibody or nonimmunized serum. The ulcer size, amount of fibrosis and myofibroblasts, and localization of ET-1 and ET(A/B) receptors were analyzed. To elucidate the mechanisms underlying the effects of ET-1, we examined the proliferation, migration, and release of growth and angiogenic factors in gastric myofibroblasts with or without ET-1. The expression of prepro-ET-1 (an ET-1 precursor) and ET-converting enzyme-1 was examined in gastric myofibroblasts using RT-PCR. Immunoneutralization of ET-1 delayed gastric ulcer healing. The areas of fibrosis and myofibroblasts were smaller in the anti-ET-1 antibody group than in the control. ET-1 was expressed in the gastric epithelium, myofibroblasts, and other cell types. ET(A) receptors, but not ET(B) receptors, were present in myofibroblasts. ET-1 increased proliferation and migration of gastric myofibroblasts. ET-1 stimulated the release of hepatocyte growth factor, VEGF, PGE(2), and IL-6 from gastric myofibroblasts. mRNA for prepro-ET-1 and ET-converting enzyme-1 was also expressed. ET-1 promotes the accumulation of gastric myofibroblasts and collagen fibrils at gastric ulcers. ET-1 also stimulates migration and proliferation of gastric myofibroblasts and enhances the release of growth factors, angiogenic factors, and PGE(2). Thus ET-1 has important roles not only in ulcer formation but also in ulcer healing via mobilizing myofibroblasts and inducing production of stroma-derived factors.

Effect of Helicobacter pylori infection on gastric mucosal pathologic change and level of nitric oxide and nitric oxide synthase

AIM

To investigate the level of nitric oxide (NO) and nitrous oxide synthase (NOS) enzyme and its effect on gastric mucosal pathologic change in patients infected with Helicobacter pylori (H pylori), and to study the pathogenic mechanism of H pylori.

METHODS

The mucosal tissues of gastric antrum were taken by endoscopy, then their pathology, H pylori and anti-CagA-IgG were determined. Fifty H pylori positive cases and 35 H pylori negative cases were randomly chosen. Serum level of NO and NOS was detected.

RESULTS

One hundred and seven cases (71.33%) were anti-CagA-IgG positive in 150 H pylori positive cases. The positive rate was higher especially in those with pre-neoplastic diseases, such as atrophy, intestinal metaplasia and dysplasia. The level of NO and NOS in positive group was higher than that in negative group, and apparently lower in active gastritis than in pre-neoplastic diseases such as atrophy, intestinal metaplasia and dysplasia.

CONCLUSION

H pylori is closely related with chronic gastric diseases, and type I H pylori may be the real factor for H pylori-related gastric diseases. Infection with H pylori can induce elevation of NOS, which produces NO.

Melatonin as an organoprotector in the stomach and the pancreas

Melatonin was thought to originate primarily from the pineal gland and to be secreted during the night, but recent studies revealed that gastrointestinal (GI) tract presents another, many times larger, source of melatonin that contributes significantly to the circulating concentration of this indole. Melatonin may exert a direct effect on GI tissues but its major influence on GI organs seems to occur indirectly, via the brain-gut axis including peripheral receptors, sensory afferent (vagal or sympathetic) pathways and central nervous system (CNS) acting on these organs via autonomic efferents and neuromediators. This article reviews and updates our experience with the fascinating molecule, as related to GI organs, with special focus on secretory activity of the stomach and pancreas and the maintenance of their tissue integrity. In addition to being released into the circulation, melatonin is also discharged into the gut lumen and this appears to be implicated in the postprandial stimulation of pancreatic enzyme secretion, mediated by melatonin-induced release of cholecystokinin, acting through entero-gastro-pancreatic reflexes. Although exerting certain differences in the mechanism of action on gastric and pancreatic secretory activities, melatonin derived from its precursor L-tryptophan, exhibits similar highly protective actions against the damage of both the stomach and the pancreas and accelerates the healing of chronic gastric ulcerations by stimulating the microcirculation and cooperating with arachidonate metabolites such as prostaglandins, with nitric oxide released from vascular endothelium, and/or sensory nerves and with their neuropeptides such as calcitonin gene related peptide. The beneficial effects of melatonin results in gastro- and pancreato-protection, prevents various forms of gastritis and pancreatitis through the activation of specific MT2-receptors and scavenges reactive oxygen species (ROS). Melatonin counteracts the increase in the ROS-induced lipid peroxidation and preserves, at least in part, the activity of key anti-oxidizing enzymes such as superoxide dismutase. It is proposed that melatonin should be considered as the agent exerting an important role in prevention of gastric and pancreatic damage and in accelerating healing of gastric ulcers.

Endogenous myocardial angiogenesis and revascularization using a gastric submucosal patch

BACKGROUND

The gastrointestinal submucosa physiologically produces angiogenic proteins. We examined whether these properties could lead to endogenous myocardial angiogenesis in a swine model of chronic ischemia.

METHODS

Fifteen Yorkshire swine underwent ameroid constrictor placement around the circumflex artery and either lateral epicardial abrasion, creation of a gastroepiploic artery (GEA) based gastric patch, mucosal avulsion, transdiaphragmatic transfer, and apposition of the patch against the circumflex myocardial territory (number = 8; test animals), or lateral epicardial abrasion alone (number = 7; controls). Seven weeks later, lateral myocardial perfusion, endothelial cell density, and expression of VEGFR-1 and VE-cadherin were determined using isotope-labeled microsphere assays, immunohistochemistry, and immunoblotting, respectively.

RESULTS

Microsphere assays showed equivalent lateral/anterior myocardial perfusion indices at rest (1.10 +/- 0.49 vs 0.95 +/- 0.23, test vs control animals; p = 0.54), but higher perfusion in test animals versus controls during pacing (1.05 +/- 0.29 vs 0.69 +/- 0.09, test vs controls; p = 0.02). Increased myocardial endothelial cell density (42.6 +/- 8.5 vs 26.1 +/- 11.6 cells per 3850 microm2, test vs controls; p = 0.02) and expression of VE-cadherin (3.10 +/- 0.60-fold change, test vs controls; p = 0.001) were also observed in the lateral territory of test animals versus controls. Reconstitution of the proximally occluded circumflex artery from patch collaterals was demonstrated on gastroepiploic arteriography in a subset of test animals.

CONCLUSIONS

This model results in an angiogenic process of significantly greater magnitude than that resulting from chronic myocardial ischemia alone, without the need for exogenous angiogenic agents.

A novel antioxidant and antiapoptotic role of omeprazole to block gastric ulcer through scavenging of hydroxyl radical

The mechanism of the antiulcer effect of omeprazole was studied placing emphasis on its role to block oxidative damage and apoptosis during ulceration. Dose-response studies on gastroprotection in stress and indomethacin-induced ulcer and inhibition of pylorus ligation-induced acid secretion indicate that omeprazole significantly blocks gastric lesions at lower dose (2.5 mg/kg) without inhibiting acid secretion, suggesting an independent mechanism for its antiulcer effect. Time course studies on gastroprotection and acid reduction also indicate that omeprazole almost completely blocks lesions at 1 h when acid inhibition is partial. The severity of lesions correlates well with the increased level of endogenous hydroxyl radical (*OH), which when scavenged by dimethyl sulfoxide causes around 90% reduction of the lesions, indicating that *OH plays a major role in gastric damage. Omeprazole blocks stress-induced increased generation of *OH and associated lipid peroxidation and protein oxidation, indicating that its antioxidant role plays a major part in preventing oxidative damage. Omeprazole also prevents stress-induced DNA fragmentation, suggesting its antiapoptotic role to block cell death during ulceration. The oxidative damage of DNA by *OH generated in vitro is also protected by omeprazole or its analogue, lansoprazole. Lansoprazole when incubated in a *OH-generating system scavenges *OH to produce four oxidation products of which the major one in mass spectroscopy shows a molecular ion peak at m/z 385, which is 16 mass units higher than that of lansoprazole (m/z 369). The product shows no additional aromatic proton signal for aromatic hydroxylation in (1)H NMR. The product absorbing at 278 nm shows no alkaline shift for phenols, thereby excluding the formation of hydroxylansoprazole. The product is assigned to lansoprazole sulfone formed by the addition of one oxygen atom at the sulfur center following attack by the *OH. Thus, omeprazole plays a significant role in gastroprotection by acting as a potent antioxidant and antiapoptotic molecule.

Role of prostaglandins, nitric oxide, sensory nerves and gastrin in acceleration of ulcer healing by melatonin and its precursor, L-tryptophan

Melatonin, a major hormone of pineal gland, was recently shown to attenuate acute gastric lesions induced by strong irritants because of the scavenging of free radicals but its role in ulcer healing has been little investigated. In this study we compared the effects of intragastric (i.g.) administration of melatonin and its precursor, L-tryptophan, with or without concurrent treatment with luzindole, a selective antagonist of melatonin MT2 receptors, on healing of chronic gastric ulcers induced by serosal application of acetic acid (ulcer area 28 mm2). The involvement of endogenous prostaglandins (PG), nitric oxide (NO) and sensory nerves in ulcer healing action of melatonin and L-tryptophan was studied in rats treated with indomethacin and NG-nitro-L-arginine (L-NNA) to suppress, respectively, cyclo-oxygenases (COX) and NO synthases or in those with functionally deactivated sensory nerves with capsaicin. The influence of melatonin on gastric secretion during ulcer healing was tested in separate group of rats with gastric ulcer equipped with gastric fistulas (GF). At day 8 and 15 upon the ulcer induction, the area of gastric ulcers was measured by planimetry, the mucosal blood flow (GBF) was determined by H2-gas clearance technique and gastric luminal NO2-/NO3- levels was assessed by Griess reaction. Plasma melatonin and gastrin levels were measured by specific radioimmunoassay (RIA). Biopsy mucosal samples were taken for expression of constitutive NO-synthase (cNOS) and inducible NOS (iNOS) by reverse transcriptase-polymerase chain reaction (RT-PCR). Melatonin (2.5-20 mg/kg-d i.g.) and L-tryptophan (25-100 mg/kg-d i.g.) dose-dependently accelerated ulcer healing, the dose inhibiting by 50% (ED50) of ulcer area being 10 and 115 mg/kg, respectively. This inhibitory effect of melatonin (10 mg/kg-d i.g.) and L-tryptophan (100 mg/kg-d i.g.) on ulcer healing was accompanied by a significant rise in the GBF at ulcer margin and an increase of plasma melatonin. luminal NO2-/NO3- and plasma gastrin levels. Gastric acid and pepsin outputs were significantly inhibited during the ulcer healing in melatonin-treated gastric mucosa as compared with those in vehicle-treated animals. Luzindole abolished completely the healing effects of melatonin and L-tryptophan and attenuated significantly the rise in plasma gastrin evoked by the hormone and its precursor. Indomethacin (5 mg/kg-d i.p). that blocked PG biosynthesis by 90% or L-NAME (20 mg/kg i.v), inhibitor of NOS. that suppressed luminal NO release, attenuated significantly melatonin and L-tryptophan-induced acceleration of ulcer healing and accompanying rise in GBF at ulcer margin and luminal NO release. The melatonin-induced acceleration of ulcer healing, hyperemia at ulcer margin and increase in the release of NO were enhanced when L-arginine but not D-arginine was added to L-NAME. The ulcer healing and the GBF effects of melatonin and L-tryptophan were significantly impaired in rats with capsaicin-induced denervation of sensory nerves and both, ulcer healing and the hyperemia at ulcer margin were restored in these rats by addition of exogenous CGRP to melatonin and L-tryptophan. Expression of cNOS mRNA was detected by RT-PCR in the intact gastric mucosa as well as at the edge of gastric ulcers treated with both, vehicle and melatonin, while iNOS mRNA that was undetectable in the intact gastric mucosa, appeared during ulcer healing and especially this was strongly up-regulated in the melatonin-treated gastric mucosa. We conclude that (1) exogenous melatonin and that derived from its precursor, L-tryptophan, accelerate ulcer healing probably via interaction with MT2 receptors; (2) this ulcer healing action is caused by an enhancement by melatonin of the microcirculation at the ulcer margin possibly mediated by COX-derived PG and NO because of overexpression of iNOS and (3) gastrin, which exhibits trophic activity in the gastric mucosa and calcitonin gene related peptide (CGRP), released from sensory nerves, may also contribute to the ulcer healing action of melatonin.