Involvement of sensory afferent fibers and lipid peroxidation in the pathogenesis of stress-induced gastric mucosa damage.

Ablation of sensory nerves impairs healing of gastric ulcers, but the role of free radicals in the healing process has been little studied. The aim of our present investigations was to determine the participation of reactive oxygen species (ROS) in sensory nerve activity during WRS. Experiments were carried out on male Wistar rats and the number of gastric lesions was measured by planimetry. Colorimetric assays were used to determine gastric mucosal levels of malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE), as well as superoxide dismutase (SOD) activity. We found that capsaicin-inactivation of sensory nerves resulted in magnification of gastric mucosal damage induced by the WRS. In this process, oxidative stress occurs, as reflected by an increase of MDA and 4-HNE tissue concentrations (an index of lipid peroxidation), and a decrease of SOD activity, could play an important role. Pentoxyfilline-induced gastroprotection and hyperemia depends upon attenuation of the oxidative stress. This protection and hyperemia were, at least in part, attenuated by ASA. Afferent sensory fibers participate in the pathogenesis of ulcers. Lipid peroxidation plays an important role in this process.

Immunoneutralization of circulating pancreatic polypeptide and pancreatic secretion.

To determine the role of endogenous pancreatic polypeptide (PP) as a physiological inhibitor of pancreatic secretion, normal rabbit serum (control) or rabbit PP-antiserum was administered intravenously to dogs with chronic esophageal, gastric, and pancreatic fistulas. In all dogs tested, sham-feeding and ordinary feed with a meat meal resulted in a marked rise in the plasma level of immunoreactive PP that coincided with an increase in the exocrine pancreatic secretion of HCO3- and protein. After intravenous administration of PP antiserum, endogenous plasma PP was almost completely bound by infused antibodies to PP, whereas no such binding was detected after infusion of normal rabbit serum. In contrast, plasma gastrin remained unchanged both under basal and stimulated conditions. Immunoneutralization of PP, released endogenously, failed significantly to affect gastric acid and pancreatic protein responses to sham-feeding and the pancreatic HCO3- and protein responses to feeding a meat meal in chronic pancreatic fistula dogs. However, the PP antiserum abolished, in part, the inhibitory effect of exogenous PP on pancreatic secretion stimulated by exogenous hormones. We conclude that endogenous PP is not a physiological inhibitor of exocrine pancreatic secretion, as has been suggested previously.

Luminal Nalpha-methyl histamine stimulates gastric acid secretion in duodenal ulcer patients via releasing gastrin.

Nalpha-methyl histamine is an unusual histamine metabolite which is produced in the stomach infected by Helicobacter pylori and which was shown in animals to stimulate gastric acid secretion and to release gastrin in vitro isolated G-cells, but no information is available regarding its influence on gastric secretion and gastrin release in duodenal ulcer patients before and after H. pylori eradication. In this study, we compared the effects of intragastric administration of single or graded doses of Nalpha-methyl histamine on gastric acid secretion and plasma gastrin levels in 16 male duodenal ulcer patients (aging from 35 to 48 years and weighing 65-82 kg) before and after the eradication of H. pylori. Furthermore, the gastric luminal histamine and gastrin contents were determined before and after H. pylori eradication. In H. pylori-infected duodenal ulcer patients, the intragastric application of Nalpha-methyl histamine failed to affect gastric acid secretion or plasma gastrin levels. Following eradication of H. pylori, gastric luminal histamine and gastrin, and both basal gastric acid secretion and plasma gastrin levels, were significantly reduced. Nalpha-methyl histamine given intragastrically in graded doses to such H. pylori-eradicated duodenal ulcer patients was found to increase dose-dependently gastric acid output reaching at a dose of 5 mg, about 80% of histamine maximum induced by i.v. infusion of 25 microg/kg h of histamine dihydrochloride. We conclude that Nalpha-methyl histamine is a potent luminally active stimulant of gastrin release and gastric acid secretion in H. pylori-eradicated patients when luminal histamine is low but is not effective in H. pylori infected patients when luminal histamine is enhanced, possibly due to desensitization of gastrin (G-cells) and acid-producing (parietal) cells by Nalpha-methyl histamine produced excessively in H. pylori-infected stomach.

Helicobacter pylori and impaired gastric secretory functions associated with duodenal ulcer and atrophic gastritis.

Previous study showed that duodenal ulcer (DU) patients infected with Helicobacter pylori (H. pylori) have increased basal and pentagastrin- or GRP-induced gastric acid secretion and that these disturbances reversed fully after eradication of H. pylori. This study was designed to compare the gastric acid secretory profile, plasma gastrin levels and growth factors (EGF and TGF alpha) expression in gastric mucosa in DU patients with those in atrophic gastritis patients before and six months after verified eradication of H. pylori. In DU patients, basal and stimulated (GRP and pentagastrin) gastric acid secretion was significantly higher than in healthy controls. Six months following the eradication of H. pylori with triple therapy (omeprazole+clarithromycin+amoxicillin), this secretion returned to normal value. In contrast, in patients with atrophic gastritis, such eradication of H. pylori resulted in a significant increase in basal and pentagastrin- and GRP-stimulated acid secretion. Mucosal expression of immunoreactive EGF and TGF alpha was significantly enhanced in H. pylori positive DU and atrophic gastritis patients but this elevation disappeared or was markedly decreased 6 months upon the eradication of H. pylori. We conclude that 1) H. pylori infection is accompanied both in DU and atrophic gastritis patients by an enhanced plasma gastrin and increased mucosal expression of EGF and TGF alpha, 2) basal and GRP-induced acid secretion is significantly elevated in DU, whereas that in atrophic gastritis patients is greatly reduced, and 3) the H. pylori eradication restores gastric acid and plasma gastrin release as well as the mucosal expression of growth factors in DU and atrophic gastritis.

The role of reactive oxygen species and capsaicin-sensitive sensory nerves in the pathomechanisms of gastric ulcers induced by stress.

Gastric microcirculation plays an important role in the maintenance of the gastric mucosal barrier and mucosal integrity. Sensory nerves are involved in the regulation of mucosal blood circulation and mucosal defense. Therefore, the ablation of these nerves by neurotoxic doses of capsaicin provides the possibility of determination of their role in gastric mucosal integrity. Stress ulceration represents a serious gastric lesions. Results of our previous experiments have indicated that water immersion and restraint stress (WRS) led to increased oxidative metabolism. Ablation of sensory nerves by high doses of capsaicin retards healing of gastric ulcers, but the role of reactive oxygen species (ROS) in the healing process has been little studied. Therefore, the aim of our present investigations was to determine the participation of ROS in sensory nerve activity during WRS. Experiments were carried out on 90 male Wistar rats and the area of gastric lesions was measured by planimetry. Colorimetric assays were used to determine gastric mucosal levels of malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE), as well as superoxide dismutase (SOD) activity. We demonstrated that inactivation of sensory nerves resulted in magnification of gastric mucosal damage induced by the WRS. In this process, oxidative stress, as reflected by an increase of MDA and 4-HNE tissue concentrations (an index of lipid peroxidation), as well as decrease of SOD activity, could play an important role. Aspirin, applied in a low dose, exerts a protective activity, possibly due to its metabolites, which possess the anti-oxidant and ROS scavanging properties. Pentoxyfilline-induced gastroprotection and hyperemia depends upon attenuation of the oxidative stress. This protection and hyperemia were, at least in part, attenuated by ASA.

Gastroprotection by pentoxyfilline against stress-induced gastric damage. Role of lipid peroxidation, antioxidizing enzymes and proinflammatory cytokines.

Impairment of blood perfusion in gastric mucosa results in the formation of erosions and ulcers. Nitric oxide (NO), produced via activity of NO-synthase (NOS), appears to be a one of major factors, involved in the regulation of the gastric blood flow (GBF). Inhibition of this enzyme by N-nitro-L-arginine (L-NNA) results in local decrease of NO production, reduces GBF and impairs gastric mucosal integrity, the effects that can be reversed by the pretreatment with L-arginine, the NOS substrate. However, little information is available regarding the contribution of reactive oxygen species (ROS)-induced lipid peroxidation and NO to the mechanism of gastric mucosal integrity. Therefore, the aim of our present study was to determine the action of pentoxyfilline (PTX), an inhibitor of tumor necrosis factor alpha (TNFalpha) with or without NOS inhibition by L-NNA administration in rats with water immersion and restraint stress (WRS)-induced gastric lesions. Experiments were carried out on 100 male Wistar rats. The gastric blood flow (GBF) was measured using laser Doppler flowmeter. The area of gastric lesions was determined by planimetry and the levels of proinflammatory cytokines (IL-1beta and TNFalpha) were measured by ELISA. Colorimetric assays were employed to determine gastric mucosal levels of lipid peroxidation products, such as malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE) and antioxidant enzymes including superoxide dismutase (SOD) activity, as well as tissue concentration of reduced glutathione (GSH). Administration of PTX significantly attenuated the gastric lesions, induced by 3.5 h of WRS and this was accompanied by the rise in the GBF and a significant decrease in plasma proinflammatory cytokines (IL-1beta and TNFalpha) levels, as well as the reduction of lipid peroxidation. Exposure of rats to WRS suppressed the SOD and GSH activities and these effects were reversed by PTX. The protective and hyperemic effects of PTX, as well as an increase in mucosal SOD activity and GSH concentration were counteracted by pretreatment with L-NNA, but restored by the pretreatment with L-arginine, a NOS substrate. We conclude that PTX exerts beneficial, gastroprotective effect against WRS-induced gastric lesions due to enhancement in gastric microcirculation, possibly mediated by the enhanced NOS activity as well as local action of NO and by the attenuation of oxidative metabolism and generation proinflammatory cytokines.

Salivary and gastric luminal release of epidermal growth factor under basal conditions and after pentagastrin stimulation in healthy subjects and in duodenal ulcer patients before and after eradication of Helicobacter pylori.

Epidermal growth factor (EGF) is secreted by salivary and Brunner's glands and shows a potent inhibitory effect on gastric acid and stimulatory influence on mucosal growth and protection but little is known about the effect of the Helicobacter pylori (Hp) infection on the release of EGF. In this study the salivary and gastric concentrations of EGF have been measured and gastric mucosal expression of EGF has been determined in 25 Hp positive duodenal ulcer (DU) patients before and after the eradication of Hp (using triple therapy with omeprazole, 20 mg bd, amoxycillin, 500 mg qd and metronidazole, 500 mg bd for 2 weeks) and in 10 healthy controls under basal conditions and following pentagastrin (2 micrograms/kg-h) stimulation. Basal salivary and gastric concentrations of EGF were similar and no significant difference was found between DU patients and healthy controls. Pentagastrin infusion (2 micrograms/kg-h) caused a significant increase in EGF release into saliva and gastric juice both in healthy controls and DU patients but in DU patients the Hp eradication resulted in several folds higher basal and pentagastrin-induced gastric EGF content than that before the anti-Hp therapy, whereas such Hp eradication had no significant influence on basal and pentagastrin-induced salivary EGF. Antral mucosal expression of EGF in Hp-positive DU patients was significantly higher than that in healthy Hp-negative controls and this elevation persisted after eradication of Hp. Basal and pentagastrin-induced gastric acid outputs in Hp-positive DU patients were significantly higher than in healthy controls and they were slightly reduced after the triple therapy. In all DU patients, 4 weeks after termination of anti-Hp therapy, a complete ulcer healing occurred. We conclude that (1) the stomach is capable of secreting large amounts of EGF and pentagastrin appears to be a potent stimulus of salivary and gastric EGF release; (2) the Hp infection reduces the release of gastric EGF and the eradication of Hp results in the augmentation of basal and pentagastrin-induced EGF release into the stomach but not into the saliva and (3) since the eradication of Hp infection in DU patients resulted in DU healing and this was accompanied by an increase in EGF release, we conclude that EGF plays a crucial role in the DU healing process.

One week treatment with omeprazole, clarithromycin and tinidazole or lansoprazole, amoxicillin and metronidazole for cure of Helicobacter pylori infection in duodenal ulcer patients.

We defined optimal Helicobacter pylori (Hp) treatment as Hp eradication rate about 90%, well-tolerated with few side-effects. Two centers carried out randomized trials including 90 patients (74% men, 26% women, ages ranging from 18 to 65, mean age 42 +/- 8) with active duodenal ulcers (DU). Patients were treated with the combination of Omeprazole (O) 20 mg bd + Clarithromycin (C) 250 mg bd + Tinidazole (T) (500 mg bd) or with Lansoprazole (L) 15 mg bd + Amoxicillin (A) 750 mg bd + Metronidazole (M) 500 mg bd administered for one week. The DU healing rate was evaluated by endoscopy and the Hp status by rapid urease CLO-test and 14C-urea breath test (UBT). The healing rate of the DU in a group treated with the combination of O + C + T was 91% and in group treated with L + A + M was 93%. The eradication of Hp in group O + C + T and L + A + M averaged 91% and 87%, respectively. There was no statistically significant difference in the DU healing rate and the Hp eradication rate between these two groups. Both treatments were accompanied by a marked rise in the basal and postprandial plasma gastrin levels and the rise in the intragastric pH but these alterations returned to the pre-treatment values 4 weeks after the termination of the therapy. Both treatments were well tolerated and the only side effect was the taste disturbance observed in few patents treated with O + C + T. None of patients discontinued the treatment because of the adverse events. We conclude that one week treatment using O + C + T or L + A + M are highly and equally effective in the healing of DU and in the eradication of Hp.

Gastric acid inhibitory profile of ebrotidine, a novel H2-receptor antagonist in humans.

This study was designed to assess the gastric secretory effects of ebrotidine, a novel H2 receptor antagonist, in humans. Three groups (A, B and C) of male subjects with normal gastric mucosa were used. Group A (6 subjects) was used to determine the dose-dependency of gastric inhibitory effect of ebrotidine on basal and pentagastrin-induced maximal acid output. Group B (8 subjects) was employed to examine the duration of the inhibitory effect of ebrotidine on basal and pentagastrin-induced acid secretion. In group C (6 subjects), the 24h pH-metry was assessed using intraluminal pH-electrode placed in the gastric corpus and connected to a portable recording unit. Single oral dose of ebrotidine (200, 400 or 800 mg) caused a dose-dependent reduction in basal and pentagastrin-induced acid secretion that at a dose of 800 mg amounted to about 89% and 93%, respectively. This inhibition was still observed after 6h and averaged 72% and 50%, respectively. After 12 and 24h upon the drug intake, both basal and pentagastrin-induced acid secretion returned to the control values. Single oral dose of ebrotidine (800 mg) caused a significant reduction in circadian acidity and resulted in a marked and significant reduction of intragastric acidity for about 6h upon the administration. This inhibition was accompanied by a transient increase in basal and postprandial gastrin levels. We conclude that ebrotidine is highly effective inhibitor of basal, pentagastrin-induced and circadian gastric acid secretion in humans.

Effect of carprofen and indomethacin on gastric function, mucosal integrity and generation of prostaglandins in men.

The effects of indomethacin and carprofen on gastric secretion, serum gastrin level, electropotential difference, gastric microbleeding, DNA loss, mucosal blood flow and the production of mucosal prostaglandins (PGs) were investigated in a double-blind cross-over study in 18 healthy volunteers after one week of treatment. We did not observe any significant changes in basal and pentagastrin-stimulated gastric secretory parameters, serum gastrin level and electro-potential difference before and after treatment with these drugs. Mucosal blood flow was significantly reduced following indomethacin treatment. The most pronounced differences were found in endoscopic score studies of gastric mucosa. After indomethacin all subjects developed multiple erosions, submucosal haemorrhages, and half of them showed diffuse antral erythema. These effects were accompanied by a significant increase in both gastric microbleeding and DNA loss, and significant decrease in the production of PGE2. We concluded that carprofen, in contrast to indomethacin, did not alter gastric mucosal integrity and production of PGE2. This study indicates that the gastric mucosal damage by non-steroid anti-inflammatory compounds (NOSAC) depends upon the suppression of PGE2 biosynthesis, and that endogenous PGE2 is involved in the control of mucosal blood flow and mucosal integrity.

The use of carprofen, a non-steroidal antiinflammatory agent, in peptic ulcer diseases.

The effects of carprofen (Roche), a nonsteroid antiinflammatory agent, on gastric secretion, serum gastrin level, electropotential difference (PD), gastric microbleeding, DNA loss, and the generation of mucosal prostaglandins (PGs) were examined in 20 duodenal ulcer patients with active ulcer (15 patients) or in remission (5 patients). Carprofen administered for one-week period at a therapeutic dose (300 mg/day) was well tolerated by all ulcer patients and no adverse effects were observed during or after treatment. Endoscopy performed after carprofen treatment showed complete ulcer healing in 9 out of 15 patients and no exacerbations were observed in the rest of patients. No significant changes were observed in basal or pentagastrin-induced secretion, PD, gastric microbleeding and DNA loss. The generation of PGE2, 6-keto-PGF1 alpha and thromboxane B2 was not affected by the treatment with carprofen. This study indicates that carprofen shows excellent gastrointestinal tolerance in ulcer patients, and it might be useful in the treatment of arthritic patients with peptic ulcer disease.

Gastroprotection by sucralfate against acetylsalicylic acid in humans. Role of endogenous prostaglandins.

Sucralfate has been shown to prevent the formation of acute gastric lesions induced by nonsteroidal antiinflammatory drugs such as aspirin (ASA) in animals, but little is known about the prevention by this agent of ASA-induced gastric damage in humans. This report describes the effects of sucralfate on mucosal formation of prostaglandins (PG), gastric microbleeding and DNA loss in intact and ASA-challenged stomach. Two groups of 12 healthy volunteers were used in a double-blind, placebo controlled trial to assess the effects of sucralfate 1.0g qid on the stomach in subjects without (group A) and with administration of 2.5g ASA during 2 days (group B). Sucralfate treatment during 4 days significantly reduced spontaneous gastric bleeding and DNA loss in group A and prevented blood loss caused by ASA in group B. The protective effects of sucralfate on spontaneous gastric blood loss were accompanied by increased mucosal biosynthesis and luminal release of PGE2 and 6-keto-PGF1 alpha with decreased release of TXB2. In ASA-treated subjects mucosal generation and luminal release of PG and TXB2 were greatly suppressed and sucralfate treatment did not influence these PGs in spite of the decreased mucosal damage. It is concluded that sucralfate has a potent protective action on spontaneous and ASA-treated gastric bleeding in man and that this protection may be partly due to the increased mucosal biosynthesis of prostaglandins.

Generation of prostaglandins in gastric mucosa of patients with peptic ulcer disease: effect of nonsteroidal antiinflammatory compounds.

Human fundic mucosa generates various prostaglandins (PGs), particularly PGE2, and tromboxanes. This generation appears to be significantly lower in gastric ulcer patients than in duodenal ulcer patients or normal subjects. Nonsteroidal antiinflammatory compounds (NOSAC), such as aspirin or indomethacin, greatly reduce the PG biosynthesis and cause mucosal damage, including mucosal erosions and hemorrhages observed at endoscopy, increased gastric microbleeding and DNA loss. In contrast, paracetamol or carprofen, a novel NOSAC, fails to affect mucosal generation of PGs and does not influence gastric mucosal integrity. This study indicates that endogenous PGs may be involved in the pathogenesis of gastric ulcer and that normal generation of mucosal PGs is essential for the mucosal integrity.

Kinetics and duration of action of ranitidine on gastric secretion and its effect on pancreatic secretion in duodenal ulcer patients.

Inhibitory effects of ranitidine, a new H2-receptor antagonist, and cimetidine on histamine and pentagastrin-induced gastric secretion have been compared in duodenal ulcer patients. Compared with cimetidine, ranitidine was found to be about 6-8 times a more potent inhibitor of gastric acid secretion, the inhibition of histamine-induced secretion being competitive, whereas that of pentagastrin-induced secretion not competitive. Ranitidine was an effective inhibitor of pentagastrin-induced secretion 8-12 h after administration. When given in a dose inhibiting gastric secretion by over 90%, it did not affect pancreatic secretion induced by secretin and pancreozymin. The availability of ranitidine, a more powerful inhibitor of gastric secretion, provides an opportunity of a treatment alternative to cimetidine, for peptic ulcer and related diseases.

Prostaglandins in peptic ulcer disease: effect of nonsteroidal anti-inflammatory compounds (NOSAC).

This study shows that human fundic mucosa generates various PGs, particularly PGE2, and thromboxanes and this generation appears to be significantly lower in gastric ulcer than in duodenal ulcer patients or normal subjects. Non-steroidal antiinflammatory compounds (NOSAC), such as aspirin and indomethacin, greatly reduce the PG biosynthesis and cause mucosal damage including mucosal erosions and haemorrhages observed at endoscopy, increased gastric microbleeding and DNA loss. In contrast, carprofen, a novel NOSAC with good antiinflammatory properties and gastric tolerance, failed to affect mucosal generation of PGs and did not influence gastric mucosal integrity. This study indicates that the deficiency of endogenous PGs may play a role in the pathogenesis ulcer and that the degree of gastric mucosal damage by NOSAC is closely related to the alteration in the capability of the mucosa to generate PGs.

Effects of pirenzepine and atropine on gastric secretory and plasma hormonal responses to sham-feeding in patients with duodenal ulcer.

The effects of atropine and pirenzepine on sham-feeding stimulated gastric secretion and serum gastrin and pancreatic polypeptide levels have been studied in 12 patients with duodenal ulcer. Both atropine and pirenzepine caused a dose-dependent decrease in acid and pepsin secretion induced by sham-feeding. Serum gastrin response to sham-feeding was negative and it was enhanced by atropine but suppressed by pirenzepine. Plasma pancreatic polypeptide level, which was markedly increased by sham-feeding, was abolished both by atropine and pirenzepine. This study shows that pirenzepine is a more selective inhibitor of gastric secretory and serum hormonal responses to sham-feeding than atropine and that it may be a useful tool for studying the cholinergic innervation of the oxyntic glands and the G-cells in man.

[Role of antral gastrin in regulating gastric secretion and bile flow]. / Rol' antral'nogo gastrina v reguliatsii zheludochnoi sekretsii i zhelchevydelenii.

In chronic experiments on dogs with removed mucosa of the antral portion of the stomach, administration of the liver extract into the stomach or intestine decreased the output of hydrochloric acid as compared with intract animals. The liver extract administration caused no raise of gastrin level in the blood serum of the operated animals.

Gastric acid response to topical or intravenous histamine and topical H2-receptor blockade in dogs.

This study was undertaken to determine gastric acid surface and to examine the local effect f ranitidine, a histamine H2-receptor antagonist, on the gastric acid response to histamine. Histamine applied to the Heidenhain pouch (HP) mucosa resulted in a slight and dose-dependent stimulation of acid secretion without affecting acid secretion from the main stomach. Ranitidine given into the HP caused dose-dependent inhibition of the HP response to topical or intravenous histamine without affecting the acid response of the main stomach and without any significant change in the serum ranitidine level. Ranitidine applied to the main stomach with the pylorus occluded inhibited histamine-induced acid secretion also without any increase in the serum ranitidine level. This inhibition was about 30% of that obtained with the same dose of ranitidine given into the stomach with the pylorus left open during the experiment. This study provides evidence that topical histamine is a weak stimulant of gastric secretion and that topical ranitidine is capable of local inhibition of the acid response to both topical and intravenous histamine.