Neutrophil infiltration does not contribute to the ulcerogenic effects of indomethacin in the rat gastric antrum

We have previously suggested (Trevethick et al., Gut34, 156–160) that indomethacin-induced ulceration of the rat gastric antrum may be a neutrophil-dependent process. Accordingly, in this study we have used an anti-neutrophil serum (ANS) to investigate the effects of neutrophil depletion on this pathology. In animals pretreated with the ANS to induce a nearly total neutropaenia, indomethacin-induced increases in blood neutrophilia and cell infiltration into the gastric antrum (assessed as LTB₄ releaseex vivo) were eliminated. In marked contrast, however, ANS pretreatment affected neither the area of mucosa damaged nor the microscopic characteristics or distribution of the lesions. These results suggest that, in contrast to the published reports examining indomethacin-induced ulceration of the gastric fundus, neutrophil infiltration is not involved in the pathogenesis of indomethacin-induced ulceration of the rat gastric antrum.     

Neutrophil depletion does not prevent indomethacin-induced ulceration of the rat gastric antrum

Indomethacin-induced ulceration of the rat gastric antrum is paralleled by an increase in blood neutrophil numbers and of neutrophil infiltration into the antrum. Thus, in this study, neutrophil depletion has been employed to study the potential role of neutrophils in the pathogenesis of indomethacin-induced ulceration of the rat gastric antrum. Pretreatment with an anti-neutrophil serum (ANS) induced a near complete neutropaenia and inhibition of neutrophil infiltration into the gastric antrum (as assessed by antral LTB₄ release). In contrast, ANS pretreatment did not alter the area of indomethacin-induced mucosal damage detected microscopically.

Our results suggest that, in contrast to published reports examining fundic ulceration, neutrophil infiltration does not contribute to the ulcerogenic effects of indomethacin in the rat gastric antrum.

     

The effect of osmolality changes on gastric mucosal endogenous prostacyclin levels in drug-induced experimental ulcer model of rat

Osmolality changes evoked with intragastric administration of natural honey or mannitol, significantly decreased the gastric ulceration of rats induced by indomethacin. Together with this effect, a parallel increase was detectable in the mucosal level of endogenous prostacyclin. Although many processes may be involved in this phenomenon, the authors explain their data with a stimulating effect on gastric mucosal microcirculation due to osmolality changes.     

Role of neutrophils in indomethacin-induced gastric mucosal lesions in rats

Nonsteroidal anti-inflammatory drugs (NSAIDs) cause clinically important gastric damage by several mechanisms. In order to evaluate the role of neutrophil infiltration in lesion formation, tissue myeloperoxidase activities were assessed in different gastric layers of the stomach both in rats with normal neutrophil levels and in neutropenic rats. Sprague-Dawley rats were treated either with indomethacin (Indo; 25 mg/kg, s.c.) or the vehicle. A group of rats were made neutropenic by administration of methotrexate (MTX; 2.5 mg/kg i.p.) once a day for 3 days. The stomachs were removed for the determination of lesion index, glutathione, lipid peroxide levels, protein oxidation and tissue myeloperoxidase activities. MTX treatment appeared to reduce neutrophil infiltration significantly while producing insignificant effects on eosinophils and macrophages. Indo administration caused multiple gastric lesions and treatment with MTX significantly reduced lesion index. In rats treated with Indo, neither glutathione nor LP levels showed any significant changes but the protein oxidation was significantly higher than that of other groups. The MPO level of gastric mucosa was increased in Indo-treated rats and reversed by MTX pretreatment. The results of the present study indicate that neutrophil infiltration in the gastric mucosa of rats may be involved in the pathogenesis of NSAID-induced gastric mucosal injury, but no correlation was found between lesion formation and protein oxidation in the gastric mucosa.     

Analysis of the cold-water restraint procedure in gastric ulceration and body temperature

Gastric mucosal injury induced by body restraint can be enhanced when combined with cold-water immersion. Based on this fact, the present study had two main purposes: (i) to examine the contribution of each of these two forms of stress on the development of gastric ulceration and regulation of body temperature and (ii) to investigate the importance of the animal's consciousness on gastric ulceration induced by the cold-water restraint. Independent groups of animals were exposed for 3 h to one of the following stressful treatments: body restraint plus cold-water (20+1 degrees C) immersion, body restraint alone or cold-water immersion alone. Control animals were not exposed to any form of stress. Half of the animals submitted to each of the four treatments were anesthetized with thionembutal (35 mg/kg), whereas the other half was injected with saline. Results indicated that body restraint alone was not sufficient to induce gastric ulceration or changes in body temperature. On the other hand, cold-water exposure, either alone or in conjunction with body restraint, induced the same amount of stomach erosions and hypothermia. Therefore, it appears that body restraint does not play an important role on gastric ulceration induced by the cold-water restraint procedure. Present results also indicated that conscious and anesthetized animals immersed in cold water presented robust gastric ulceration and a marked drop in body temperature. However, conscious animals developed more severe gastric damage in comparison to anesthetized animals although both groups presented the same degree of hypothermia. These findings suggest that hypothermia resulting from cold-water exposure has a deleterious effect on gastric ulceration but the animal's conscious activity during the cold-water immersion increases the severity of gastric mucosal damage. It is concluded that cold-water restraint is a useful procedure for the study of the underlying mechanisms involved in stress-induced ulceration.     

Enhancement of indomethacin-induced gastric damage by mouth breathing in rabbits

Previous studies have reported that mouth breathing is associated with respiratory acidosis. Regarding to the reports that renal elimination of weak acids such as indomethacin is pH dependent, this study was carried out to evaluate the role of mouth breathing on plasma level of indomethacin and indomethacin-induced gastric damage in rabbits. Mouth breathing was induced by surgical ligation of nostrils under general anesthesia. One day after the operation, arterial blood samples were collected for acid–base balance analysis and indomethacin was administered intraperitoneally in a single dose of 40 mg/kg. The animals were killed 4 h after indomethacin administration and blood samples were collected for spectrofluorometric determination of indomethacin in plasma. The results showed that indomethacin induces more severe gastric damage in nose obstructed rabbits compared with sham and unoperated (UNOP) animals. Acid–base analysis revealed a respiratory acidosis in nose obstructed rabbits and indomethacin level of plasma was significantly higher in nose obstructed animals in comparison with control rabbits. The study shows that mouth breathing can increase the potentiation of indomethacin-induced gastric mucosal damage that may be due to higher level of indomethacin in plasma of nose obstructed animals.     

Use of cold-restraint to examine psychological factors in gastric ulceration

The influence of prior classical conditioning and predictability of shock on stress-induced gastric ulceration produced by cold-restraint was examined. Optimal durations of cold-restraint treatment were first determined. Secondly, the ulcerogenic effect of reserpine and the ulcer-inhibiting influence of atropine were demonstrated using cold-restraint. Next, it was found that neither prior classical conditioning nor the psychological manipulation of predictability of shock affected gastric ulceration produced by cold-restraint. The final study suggests the hypothesis that hypothermia produced by cold-restraint inhibits the influence of the psychological factors on stress ulceration. Cold-restraint is viewed as an inappropriate technique to use in the further examination of the influence of specific psychological factors on stress-induced ulceration.     

Leukotrienes in the pathogenesis of NSAID-induced gastric and intestinal mucosal damage

Studies in pigs and rats were undertaken to explore further the role of leukotrienes following administration of NSAIDs on the development of gastrointestinal damage. Increased leukotriene C₄ production occurred in the gastric circulation in the early stages after administration of a single dose of indomethacin (10 mg/kg i.g.) to pigs. Gastric and intestinal mucosal lesions by NSAIDs were prevented by both prior (2–5 h)+0.25 or 0 h oral dosing of the 5-lipoxygenase inhibitor, MK-886, but not when only one of these doses was given. These results show the importance of enhanced peptidoleukotriene production in relation to microvascular damage from cyclooxygenase inhibition by NSAIDs.     

Leukotrienes in the pathogenesis of NSAID-induced gastric and intestinal mucosal damage

Studies in pigs and rats were undertaken to explore further the role of leukotrienes following administration of NSAIDs on the development of gastrointestinal damage. Increased leukotriene C₄ production occurred in the gastric circulation in the early stages after administration of a single dose of indomethacin (10 mg/kg i.g.) to pigs. Gastric and intestinal mucosal lesions by NSAIDs were prevented by both prior (2–5 h)+0.25 or 0 h oral dosing of the 5-lipoxygenase inhibitor, MK-886, but not when only one of these doses was given. These results show the importance of enhanced peptidoleukotriene production in relation to microvascular damage from cyclooxygenase inhibition by NSAIDs.     

Changes in cyclic nucleotide levels and lysosomal enzyme activity in the gastric mucosa of rats with experimental ulceration

Central Research Institute of Gastroenterology, Moscow. Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 106, No. 8, pp. 149–151, August, 1988.     

Escherichia coli S fimbriae do not contribute to intestinal colonization or translocation in the gnotobiotic rat.

Escherichia coli S fimbriae, which bind to sialic acid residues, are a virulence factor for extraintestinal infection, but also promote binding to intestinal epithelial cells. In this study, we investigated whether S fimbriae would enhance intestinal colonization by E. coli or promote translocation to extraintestinal sites. A mixture of two E. coli isogenic strains both expressing type-1 fimbriae but differing in the carriage of S fimbriae (Sfim+ and Sfim-) were given perorally to germfree neonatal, infant or adult rats. The Sfim+ bound better to rat intestinal mucus and epithelial cells. However, both strains colonized equally well in both the small and large intestine and their rate of translocation to the mesenteric lymph nodes was similar. Infant rats had higher E. coli levels in the small intestine than adult rats, but their translocation rates were lower. This was at least partly due to their milk diet, since weaned infant rats had more translocating bacteria than infant rats that continued suckling their mother. The results suggest that S fimbriae, despite binding to intestinal epithelial cells and mucus, do not contribute to either colonization or translocation in the gnotobiotic rat.     

Histological evidence that vascular damage and mucosal ulceration caused by indomethacin precede neutrophil infiltration in the rat gastric antrum

The use of non-steroidal antiinflammatory drugs (NSAIDs) to treat chronic inflammatory conditions is often limited by drug-induced ulceration of the GI tract. Effective protection of this mucosa is highly desirable. A model of indomethacin (IND)-induced ulceration of the antrum in starved-refed rats was used to investigate the sequence of events leading to mucosal damage, by examining tissues microscopically. Venous congestion was seen to precede mucosal damage in starved rats, and to occur even in non-starved rats that did not ulcerate in response to IND. Mucosal death was coagulative and spread from the luminal surface. Neutrophils (PMNs) arrived after mucosal necrosis had appeared, and formed a band beneath the dead tissue but did not enter it. The results suggest that extra vascular PMNs do not contribute to mucosal damage in this model.

     

Role of nitric oxide in indomethacin-induced gastric mucosal dysfunction in the rat

The present study was undertaken to explore the role of nitric oxide (NO) in the pathogenesis of experimental non-steroidal anti-inflammatory drug (NSAID)-induced gastropathy. We assessed the role of NO inhibition and donation in indomethacin-induced gastric mucosal dysfunction. The stomach was perfused with vehicle (control) for 20 min, followed by indomethacin (10 mg ml-1 in 1 25 % sodium bicarbonate, pH 8 4) for 120 min. NG-nitro-L-arginine methyl ester (L-NAME, 5 and 10 mg kg-1, I.V. bolus), L-arginine, D-arginine (100 mg kg-1 I.V. bolus, 10 mg kg-1 h-1, 2 h infusion) and the NO donor glyceryl trinitrate (GTN) were given at the same time (20, 40 and 80 microg kg-1 min-1, 15 min infusion) as perfusion with indomethacin was started. Epithelial permeability was quantified by measuring blood-to-lumen clearance of 51Cr-labelled EDTA. Indomethacin caused a 20-fold increase in 51Cr-EDTA leakage compared with that of the control group. Treatment with L-NAME or L-arginine did not affect the indomethacin-induced alterations in mucosal permeability. Administration of GTN (20 microg kg-1 min-1) significantly reduced the indomethacin-induced mucosal dysfunction. By contrast, higher doses of GTN (80 microg kg-1 min-1) exacerbated epithelial dysfunction induced by indomethacin. Elevated levels of carbonyls and myeloperoxidase (MPO) observed after indomethacin administration were significantly reduced, to the control values, when GTN (20 microg kg-1 min-1) was administered along with indomethacin. These data suggest that NO from exogenous sources can exert a dual action on the integrity of the gastric mucosa challenged by indomethacin. Low doses of GTN can prevent mucosal dysfunction induced by indomethacin, while higher doses of GTN may exacerbate the increases in epithelial permeability.     

Variants in EMX2 and PTEN do not contribute to risk of endometriosis

Endometriosis has a genetic component, and significant linkagehas been found to a region on chromosome 10q. Two candidategenes, EMX2 and PTEN, implicated in both endometriosis and endometrialcancer, lie on chromosome 10q. We hypothesized that variationin EMX2 and/or PTEN could contribute to the risk of endometriosisand may account for some of the linkage signal on 10q. We genotypedsingle nucleotide polymorphisms (SNPs) in a case–controldesign to evaluate association between endometriosis and commonvariations in these two genes. The genotyping and statisticalanalysis were based on samples collected from Australian volunteers.The cases were 768 unrelated women with surgically confirmedendometriosis selected from affected sister pair (ASP) familiesparticipating in the Australian Genes behind Endometriosis Study.The controls were 768 female participants in twin studies who,based on screening questions, did not have a diagnosis of endometriosis.Genotypes of 22 SNPs in the EMX2 gene and 15 SNPs in the PTENgene were the main outcome measures. Statistical analysis providedmeasures of linkage disequilibrium and association. Permutationtesting showed no globally significant association between anySNPs or haplotypes and endometriosis for either gene. It isunlikely that the EMX2 or PTEN gene variants investigated contributeto risk for initiation and/or development of endometriosis.     

Effect of Aronia melanocarpa fruit juice on indomethacin-induced gastric mucosal damage and oxidative stress in rats

Aronia melanocarpa fruits are rich in phenolic substances—mainly flavonoids from the anthocyanin subclass. The anthocyanins are water-soluble plant pigments with antioxidant, anti-inflammatory, antimicrobial, hepatoprotective, gastroprotective and other activities. We studied the effect of A. melanocarpa fruit juice (AMFJ) on indomethacin-induced gastric mucosal damage in rats and its possible relation to the oxidative status. AMFJ (5, 10 and 20 ml kg⁻¹) was applied orally as a pretreatment 1 h before the subcutaneous administration of indomethacin (30 mg kg⁻¹). Gastric ulcer formation was estimated morphometrically and histopathologically 4 h after the indomethacin administration. Malondialdehyde (MDA) in rat plasma and gastric mucosa and also reduced glutathione (GSH) and oxidized glutathione (GSSG) in gastric mucosa were determined and used as biochemical markers of the oxidative status.

AMFJ-pretreatment diminished the number and area of indomethacin-induced gastric lesions. Histopathological examination of rat stomachs demonstrated that AMFJ induced an increase in gastric mucus production and a reduction of the depth and severity of indomethacin-induced mucosal lesions. AMFJ dose-dependently reduced the elevated indomethacin plasma and gastric MDA levels and at the doses of 10 and 20 ml kg⁻¹ they were not significantly different from the control values. Neither indomethacin-treatment, nor AMFJ-pretreatment had a significant influence on GSH and GSSG gastric mucosal levels.

These results demonstrated that indomethacin-induced gastric mucosal damage was accompanied by the development of oxidative stress, evidenced by the accumulation of MDA. AMFJ-pretreatment decreased the gastric lesions caused by indomethacin. It could be suggested that this effect of AMFJ was probably due to the increased mucus production and interference with oxidative stress development as evidenced by the decreased plasma and gastric mucosal MDA.     

Role of gastric acid in restraint-induced ulceration in the rat.

Gastric hyperacidity in response to starvation and to restraint stress was selectively blocked during either or both of these periods in order to assess the relative contributions of these treatments to ulcer formation. The results clearly showed that when the antacid drug (aluminum hydroxide) was administered during food deprivation, regardless of subsequent treatment, both rumenal and glandular ulcer incidence and severity were markedly reduced. It was suggested that food deprivation produces increased stomach acidity which, if prevented, reduces ulceration ultimately resulting from a subsequent stressor. If such acidity increases are unaltered, stress-induced gastric pathology is accentuated.     

Enhanced pyridoxal 5′-phosphate synthetic enzyme immunoreactivities do not contribute to GABAergic inhibition in the rat hippocampus following pilocarpine-induced status epilepticus

To comprehend the role of pyridoxal 5′-phosphate (PLP) in epilepsy or seizure, we investigated whether the expressions of two PLP synthetic enzymes (pyridoxal kinase, PLK; pyridoxine-5′-phosphate oxidase, PNPO) are altered in the hippocampus and whether changes in paired-pulse responses in the hippocampus are associated with altered PLP synthetic enzyme expressions following status epilepticus (SE). PLK and PNPO immunoreactivities were significantly increased in the rat hippocampus accompanied by reductions in paired-pulse inhibition at 1 day and 1 week after SE. Four weeks after SE, PLK and PNPO immunoreactivities in dentate granule cells were similar to those in control animals, while their immunoreactivities were markedly reduced in Cornu Ammonis 1 (CA1) pyramidal cells due to neuronal loss. Linear regression analysis identified a direct proportional relationship between PLK/PNPO immunoreactivity and normalized population spike amplitude ratio in the dentate gyrus and the CA1 region as excluded the data obtained from 4 weeks after SE. These findings indicate that the upregulation of PLK and PNPO immunoreactivities in principal neurons may not be involved in γ-aminobutyric acid (GABA)ergic inhibition, but rather in enhanced excitability during epileptogenic periods.