Phagocytosis of latex beads by a human monocytic Mono Mac 6 cell line and effects of low-frequency electromagnetic field interaction.

Some studies have shown that electromagnetic fields (EMFs) may impact immune response cells and their functions. The first stage of the defense from pathogens is innate immunity encompassing phagocytosis and phagocytosis-related intracellular effects. Our work aimed to determine the influence of a low-frequency electromagnetic field (7 Hz, 30 mTrms) on the phagocytosis process of latex beads (LBs), the production of reactive oxygen species (ROS), and viability changes in a human monocytic Mono Mac 6 (MM6) cell line as an experimental model of the phagocytosing cells in in vitro cell culture conditions. For these purposes, cells were firstly activated with infectious agents such as lipopolysaccharide (LPS), Staphylococcal enterotoxin B (SEB), or the proliferatory agent phytohaemagglutinin (PHA), and then a phagocytosis test was performed. Cell viability and range of phagocytosis of latex beads by MM6 cells were measured by flow cytometry, and the level of ROS was evaluated with the use of a cytochrome C reduction test. The obtained results revealed that applied EMF exposure mainly increased the necrosis parameter of cell death when they were pre-stimulated with SEB as an infectious factor and subsequently phagocytosed LBs (P=0.001). Prestimulation with other agents like LPS or PHA preceding phagocytosis resulted in no statistically significant changes in cell death parameters. The level of ROS depended on the used stimulatory agent, phagocytosis, and/or EMF exposure. The obtained effects for EMF exposure indicated only a slight decrease in the ROS level for cells phagocytosing latex beads and being treated with SEB or PHA, while the opposite effect was observed for LPS pre-stimulated cells (data not statistically significant). The results concerning the viability of phagocytosing cells, the effectiveness of the phagocytosis process, and the level of radical forms might result from applied EMF parameters like signal waveform, frequency, flux density, and especially single EMF exposure.

Short-chain fatty acids in the saliva of patients with gastroesophageal reflux disease.

Gastroesophageal reflux disease (GERD) is a condition characterized by persistent symptoms and complications resulting from reflux of gastric contents into the esophagus. Short-chain fatty acids (SCFAs) are fermentation products of dietary fibres by the gut microbiota and are often studied for their anti-inflammatory and anticancer effects. The presence of SCFAs in the upper gastrointestinal tract, including in patients with GERD, has not been previously studied. The aim of this study was to investigate the relationship between the concentrations of SCFAs in the saliva of different age groups of patients with GERD. The study included 86 patients diagnosed with GERD, divided into two groups according to age: under and over 60 years of age, treated in the Gastroenterology and Hepatology Outpatient Clinic of the University Hospital in Cracow and 39 patients without gastrointestinal tract diseases. After clinical examination, blood was drawn to determine complete blood count, haemoglobin, and CRP. The oral cavity was examined, and unstimulated mixed saliva was collected. The SCFAs analysis was made by liquid chromatography-tandem mass spectrometry after facile derivatization coupled with liquid-liquid extraction. Of the six SCAFs studied, the highest median concentrations of acetic acid and propionic acid were observed in the saliva of patients with GERD and in the control group, in both the younger and older groups of patients. The concentrations of acetic acid and propionic acid were also higher compared with the four other fatty acids in the saliva of patients with GERD and in the control subjects. There were no correlations between salivary SCFAs levels and selected clinical and endoscopic parameters, including chronic inflammatory changes of the esophagus and stomach. In conclusions: SCFAs are present in the saliva of patients with GERD and in the control healthy persons. With the exception of valeric and isovaleric acids, salivary levels of SCFAs were significantly higher in patients with GERD compared to the control group. The highest concentrations of acetic acid and propionic acid were observed in patients with GERD and in both the younger and older patient groups. There were no differences in the concentrations of SCFAs in the saliva of female and male groups. We found no correlations between salivary SCFAs levels and selected clinical, laboratory and endoscopic changes of the oesophagus and stomach.

Determination of the effect of selected diseases on the level of zinc and magnesium in teeth extracted from patients for clinical reasons.

As in other human tissues, determination of the content of elements in dentition may be of significance in disease diagnostics. Zinc and magnesium are bioelements that play an important role in humans. The tissue and serum concentrations of these elements may be linked to numerous diseases; thus, they may be useful biomarkers in the early detection of diseases. The objective of this study was to compare the content of zinc and magnesium in teeth extracted for clinical reasons from patients of both genders in different age groups, who were diagnosed with the following medical conditions: cardiovascular diseases, digestive diseases, infectious disorders, other chronic diseases, and hereditary diseases. Furthermore, the study attempted to determine the effect of the drugs used by the patients on the content of zinc and magnesium in their teeth. After cleaning and fragmenting, the extracted teeth were mineralized, and subsequently the content of the investigated elements was determined by flame atomic absorption spectrometry. In patients with chronic diseases, who continuously received drugs, a statistically significantly higher level of zinc (p < 0.001) and magnesium (p < 0.001) was observed as compared with the patients who did not take those medicines. People without chronic diseases but having cardiovascular diseases also exhibited a higher level of zinc. The highest zinc level in teeth was determined in people aged above 50 (p = 0.11). Furthermore, the levels of zinc and magnesium in the teeth of the study group were related and an increase in zinc concentration was observed with an increase in the concentration of magnesium (p < 0.001). Moreover, a statistically significant correlation was observed between the age of the examined people and the level of zinc (p > 0.04). The older patient had the higher the level of zinc in teeth. The level of magnesium was statistically significantly higher in the teeth of persons with other chronic diseases (p = 0.01) and those who were on medication (p < 0.001). The accumulation of zinc and magnesium in the teeth of patients is partially a result of the physiological and pathological processes occurring in aged humans. For this reason, determination of the content of these elements in teeth, which are intended for disposal according to standards, could offer diagnostic information and enable restricting the effect of pathological environmental factors on the patient's health status.

Low-frequency electromagnetic field influences human oral mucosa keratinocyte viability in response to lipopolysaccharide or minocycline treatment in cell culture conditions.

The aim of the current study was to investigate the influence of low-frequency electromagnetic field (LF-EMF) exposure on viability parameters of oral mucosa keratinocytes cultured in in vitro conditions. The effect of LF-EMF stimulation on cell viability was also specified in the simultaneous presence of lipopolysaccharide (LPS) infectious agent or minocycline (Mino) anti-inflammatory agent. Viability parameters such as early-, late apoptosis and necrosis of keratinocytes were analysed by the flow cytometry method (FCM). The exposure of human oral keratinocyte cell cultures to LF-EMF acting alone or combined with LPS/minocycline agents caused changes in the percentage of cells that undergo programmed or incidental cell death. The overall obtained results are compiled in a graphical form presented in Fig. 1.

Artificial saliva and its use in biological experiments.

Examination of dental materials and their properties at the initial stage of the digestive process requires the development of conditions that mimic the environment of the oral cavity. One of the main components of this area is saliva, where many reactions occur under natural conditions. Human saliva is an important physiological fluid that is essential for the maintenance of good oral health and of the entire human body; it is the place where digestion begins and thus contributes to the supply of those nutrients and health-promoting substances that are essential to the body but may also cause release of potential toxins. Thereby, the main aim of the study was to review the use of artificial saliva models in the context of stomatological and biological research. Biological studies have shown that the amount of biologically active substances in biological material is not the same as their quantity released under the conditions of the human digestive system and thus bioavailable to it. These results show that tables of active ingredients in drugs and food stuffs do not present their actual usefulness and availability to the human body.

Alterations in glutathione peroxidase and superoxide dismutase activities in plasma and saliva in relation to disease activity in patients with Crohn's disease.

Crohn's disease (CD) is a chronic inflammatory condition with uncertain aetiology. Dysfunction of immunoregulatory factors and overproduction of reactive oxygen species (ROS) may contribute to the damage of the gastrointestinal tract. Superoxide dismutase (SOD) and glutathione peroxidase (GPx) are involved in protection of cells from the damaging effects of ROS. The aim of the study was to assess activity of antioxidative stress enzymes, GPx and SOD, in plasma and saliva of patients with active and inactive forms of CD. Forty-seven patients with CD were prospectively enrolled in the study. The control group comprised 25 healthy volunteers. Patients' demographics, clinical features, localization of inflammatory changes, CD history, and treatment were recorded. SOD and GPx were assayed in plasma and saliva samples by ELISA method. CD activity index (CDAI) scores correlated inversely with SOD in plasma (r = - 0.46; P = 0.0012), but not in saliva. No correlations were observed in respect to GPx activities in both plasma and saliva and CDAI. Higher activity of plasma SOD was observed in patients with inactive CD in comparison with active CD (P = 0.004). No significant differences in SOD and GPx activity both in plasma and saliva were found between CD remission group and the control group. We concluded that in active CD the antioxidant defence system was diminished and returned to normal values in remission. Results of SOD and GPx assays in saliva are not conclusive, suggesting that saliva seems to be not an appropriate material for further similar studies.

Only live Helicobacter pylori is capable of caspase-3 dependent apoptosis induction in gastric mucosa epithelial cells.

Physiological process of cell death, apoptosis, plays a beneficial role in organism survival, but in some pathologies, like gastric Helicobacter pylori (Hp) infection, this process may turn against the host organism causing tissue damage. Knowledge of the mechanisms controlling apoptosis may have potential significance in treatment of these pathologic states. Therefore, we sought to determine whether apoptosis induced in the gastric epithelial cells exposed to live Hp involves the alteration in heat shock protein 70 (HSP70) expression and activation of caspase-3 in peroxisome proliferator-activated receptors (PPARgamma dependent manner). Experiments were performed with KATO III, gastric epithelial cells, exposed to CagA and Vac A positive live Hp, water Hp extracts or Hp culture supernatant over different time periods. Total cellular RNA and proteins were isolated for PCR, western-blot and EMSA studies. Genomic DNA was isolated to analyze apoptosis status. We propose new model of Hp induced HSP70 dependent, caspase-3 executed apoptosis in human gastric epithelium. KATO III cells exposed to Hp, showed an increase in caspase-3 activity accompanied and preceeded by activation of nuclear translocation of PPARg peaking at 48 h of culture. Moreover, heat shock factor 1 (HSF-1) bound up with phosphorylated STAT-3 was unable to activate HSP70 protein synthesis in KATO III exposed to Hp. Lack of protective effect of HSP70, activation of caspase-3--dependent apoptosis pathway caused by Hp and alteration of the bax/bcl-2 cellular equilibrium led to gastric epithelial cell death. The observed phenomenon might be helpful in understanding of the mechanism of Hp related gastrointestinal tract diseasess, especially gastric cancer.

Helicobacter pylori and its eradication in rosacea.

Rosacea is a common condition of unknown etiology usually accompanied by gastrointestinal symptoms and favorably responding to the treatment with antibiotics. This study was designed to examine the prevalence of gastric Helicobacter pylori (Hp) infection verified by 13C-UTB-test, CLO, Hp culture and serology (IgG) in patients with rosacea. Gastroduodenoscopy was combined with pentagastrin secretory test and antral and fundic biopsy samples were taken for histological evaluation (the Sydney system). Blood samples were also taken for the determination of plasma gastrin using RIA and plasma interleukin (IL)-8 and tumor necrosis factor alpha (TNFalpha) using ELISA. This study was performed in 60 patients, 31-72 year old, with visible papules and pustules associated with erythema and flushing on the face and on 60 age- and gender-matched patients without any skin diseases but with similar as in rosacea gastrointestinal symptoms but without endoscopic changes in gastroduodenal mucosa (non-ulcer dyspepsia - NUD). The Hp prevalence in rosacea patients was about 88 % as compared to 65% in control NUD patients. Among rosacea patients, 67% were cytotoxin associated gene A (CagA) positive, while in NUD patients only 32% were CagA positive. Rosacea patients showed gastritis with activity of about 2.1 in antrum and 0.9 in the corpus of the stomach while those with NUD only mild gastritis with activity of approximately 1.0) confined to the antrum only. Following initial examination, typical 1 wk anti-Hp therapy including omeprazole (20 mg bd.), clarithromycin (500 mg bd.) and metronidazol (500 mg bd.) was carried out. After eradication, 51 out of 53 treated rosacea patients became Hp negative. Within 2-4 weeks, the symptoms of rosacea disappeared in 51 patients, markedly declined in 1 and remained unchanged in 1 other subject. A dramatic reduction in activity of gastritis (to 0.3 in antrum and to 0.1 in corpus) was observed. Basal plasma gastrin decreased from 48 +/- 5 pM before to 17+/-3 pM after eradication, while pentagastrin-induced maximal (MAO) declined, respectively, from about 16.6 +/- 4.2 to 8.5 +/- 1.8 mmol/h. Plasma TNFalpha and IL-8 were reduced after the therapy by 72% and 65%, respectively. We conclude that: 1) Rosacea is a disorder with various gastrointestinal symptoms closely related to gastritis, especially involving the antrum mucosa, with Hp expressing cagA in the majority of cases and elevated plasma levels of TNFalpha and IL-8; 2) The eradication of Hp leads to a dramatic improvement of symptoms of rosacea and reduction in related gastrointestinal symptoms, gastritis, hypergastrinemia and gastric acid secretion; and 3) Rosacea could be considered as one of the major extragastric symptoms of Hp infection probably mediated by Hp-related cytotoxins and cytokines.

Role of capsaicin-sensitive sensory nerves in gastroprotection against acid-independent and acid-dependent ulcerogens.

Treatment with small doses of topical capsaicin protects the gastric mucosa from the damage by strong irritants but functional ablation of sensory nerves by pretreatment with larger dose of parenteral capsaicin augments the formation of gastric lesions via unknown mechanism. This study was designed to determine the role of gastric acid secretion, mucosal blood flow (GBF) and prostaglandins (PG) generation in the gastroprotection induced by small doses of topical or parenteral capsaicin in rats with intact or capsaicin-deactivated sensory nerves. Gastric lesions were produced in rats with intact sensory nerves (series A) or capsaicin-deactivated nerves (series B) using intragastric (i.g.) application of 100% ethanol, acidified aspirin (ASA) or water immersion and restraint stress (WRS). Pretreatment with i.g. capsaicin (0.12-1.0 mg/kg) in rats with intact sensory nerves (series A) reduced dose-dependently the mucosal damage caused by ethanol, ASA or WRS, the dose inhibiting the lesion area by 50% (ID50) being 0.3, 0.5 and 0.7 mg/kg, respectively. This protection was accompanied by a significant rise in gastric mucosal blood flow (GBF). Parenteral application of capsaicin (1.2-10 mg/kg s.c.) that in intact rats dose-dependently increased GBF, also dose-dependently reduced gastric damage induced by ASA or WRS (but not by ethanol), the ID50 being 5 and 3 mg/kg, respectively. The reduction by i.g. capsaicin of ethanol-or WRS-induced mucosal lesions was accompanied by a rise in GBF and this effect was reversed by indomethacin at a dose that suppressed endogenous PG biosynthesis by about 90%, indicating that PG are involved in the protective activities of topical capsaicin. Furthermore, topical and to a lesser extent parenteral capsaicin given to rats with intact or deactivated sensory nerves inhibited gastric acid and pepsin outputs, suggesting that this inhibition could contribute to the capsaicin-induced gastroprotection against acid-dependent mucosal lesions (ASA or WRS). Capsaicin deactivation of sensory nerves aggravated mucosal lesions induced by all three ulcerogens and this effects was accompanied by a marked decrease in GBF. In such capsaicin-deactivated rats, topical capsaicin also reduced ethanol-, ASA- or WRS-induced lesions, while parenteral capsaicin was effective only in the protection against the damage induced by acidified ASA and WRS but not by ethanol. The protection against WRS lesions and accompanying rise in GBF by parenteral capsaicin were also reversed by the pretreatment with indomethacin applied in a dose suppressing the generation of PG. We conclude that capsaicin is capable of protecting gastric mucosa in rats with both intact and capsaicin-deactivated rats and that this protective activity depends, at least in part, upon its hyperemic and antisecretory effects that may be mediated, at least in part, by endogenous release of PG.

Oral cavity as permanent reservoir of Helicobacter pylori and potential source of reinfection.

Recent studies in developed countries showed that neither dental plaques nor dentures are important reservoir for Helicobacter pylori (Hp), whereas studies in developing countries revealed a high prevalence of Hp in dental plaques, though elsewhere the culture of bacterium or its DNA analysis by polymerase chain reaction in the material obtained from oral cavity were not successful. This study was designed to compare the incidence of Hp in oral cavity (saliva, dental plaques and gingival pockets) using Campylobacter-like organism (CLO) test and culture and in the presence of Hp in the stomach using 14C-urea breath test (UBT), CLO-test and culture (antral biopsy specimens). Hundred dyspeptic subjects with endoscopically normal gastro-duodenal mucosa and 55 symptomatic patients with active duodenal peptic ulcer (DU) were tested for the presence of Hp. Thirty of these DU patients were also examined for presence of Hp in oral cavity and the stomach just before the start and 4 weeks after the termination of one week triple therapy (Omeprazole 20 mg bd, Clarithromycin 500 mg bd and Tinidazole 500 mg bd) when the DU was found endoscopically healed. In the group of 100 dyspeptic subjects, the Hp was detected by CLO-test in saliva, dental plaques and gingival pockets in 84%, 100% and 100% of cases and by the culture in 55%, 88% and 100%, respectively. The presence of Hp, as determined by UBT in the stomach in these subjects was 60%. Using CLO-test and culture, all (100%) out of 55 DU patients, were found to be Hp positive in the oral cavity and in 95% in the stomach. Following one week triple therapy in 30 DU patients, the Hp was still detected in oral cavity by CLO-test in all patients (100%) and by culture in 27 patients (90%), whereas in the stomach, the Hp was found by UTB and culture only in one of these patients (97% Hp eradicated). We conclude that the Polish population including dyspeptic and DU patients, the mouth is permanent reservoir of Hp and that the successful Hp eradication from the stomach by systemic therapy fails the Hp status in the oral cavity that might be a potential source of gastric reinfection in these patients.

Microdose 14C-urea breath test in detection of Helicobacter pylori.

Etiologic role for Helicobacter pylori (Hp) seems to be well established in gastric pathology. The high urease activity of Hp can be used to detect this bacterium by non-invasive urea breath tests (UBT). We validated the microdose version of the test in which 37 kBq 14C-urea is given orally in capsule. With the cut off value > 100 DPM as positive, UBT results correlated highly significant with combined results for invasive methods i.e. CLOtest + histology score. The reproducibility of the test was 100%. The results obtained for the breath test performed locally were almost identical with that read at remote laboratory. The data found for fasting and fed states of subjects agreed in 87%. When 14C-urea was confined in the mouth of both Hp positive and Hp negative patients UBT showed the presence of urease activity in the mouth cavity. 14C-urea capsule based breath test is highly reliable, safe, and reproducible for detection of Hp in the stomach. Results can be obtained within 15 min if a scintilation counter is nearby, or breath samples can be mailed to a testing laboratory for analysis.

Comparison of cholecystokinin, pentagastrin, and duodenal oleate in gastroprotection in rats.

BACKGROUND: Cholecystokinin (CCK) and gastrin show a potent influence on gastric secretion and motility, but their role in mucosal integrity has been little studied. METHODS: In this study the effects of CCK-8, pentagastrin, and duodenal oleate on acute gastric lesions induced by 100% ethanol were studied in rats. RESULTS: CCK-8 was about 13 times more potent than pentagastrin in protecting the gastric mucosa against ethanol damage. CCK released by duodenal oleate also protected gastric mucosa against this damage. The protective effects of CCK-8 were almost completely abolished by the blockage of CCK-A receptors with loxiglumide, whereas the protective effect of pentagastrin was completely abolished by L-365,260. The protective effects of CCK, pentagastrin, or duodenal oleate against ethanol injury were accompanied by a marked increase in luminal content of somatostatin, suggesting that this peptide is implicated in this protection. The protective activity of CCK and pentagastrin against ethanol injury was accompanied by a significant increase in gastric blood flow. Inhibition of nitric oxide (NO) synthase with NG-nitro-L-arginine methyl ester abolished almost completely both gastric protection and hyperemia induced by CCK and pentagastrin. Addition of L-arginine, but not D-arginine, restored the protective and hyperemic effects of CCK and pentagastrin. Pretreatment with the sulfhydryl blocking agent N-ethylmaleimide also abolished the protective and hyperemic effects of CCK and pentagastrin. The hyperemia, but not the protection, afforded by CCK and pentagastrin was reduced after sensory nerve deactivation with capsaicin. CONCLUSIONS: Both exogenous and endogenous CCK and pentagastrin exert protective activity against ethanol damage, and this effect is mediated through separate receptors, NO, and sulfhydryl-sensitive pathway.

Exogenous and endogenous cholecystokinin protects gastric mucosa against the damage caused by ethanol in rats.

Cholecystokinin (CCK) shows a potent influence on gastric secretion and motility but its role in gastric mucosal integrity has been little examined. In this study we found that exogenous CCK octapeptide protected gastric mucosa against ethanol-induced gastric injury but was ineffective against aspirin-induced damage. The protective effects of CCK were dose-dependent and almost completely reversed by pretreatment with the specific CCKA receptor antagonist, loxiglumide, while the CCKB receptor antagonist, L-365,260, was not effective. The CCK-induced protection against ethanol injury was accompanied by a significant increase in gastric blood flow. The inhibition of nitric oxide (NO) synthase by NG-nitro-L-arginine methyl ester attenuated the gastroprotection and gastric hyperemia induced by CCK while the concurrent treatment with L-arginine, but not D-arginine restored the protective activity of CCK and the accompanying increase in gastric blood flow. Endogenous CCK released by intraduodenal instillation of oleate prevented the formation of acute gastric lesions induced by both ethanol and aspirin and the protective effects were abolished by pretreatment with loxiglumide. We conclude that CCK exerts protective activity against ethanol-induced damage and that this effect is mediated through specific CCKA receptors and hyperemia involving NO.

Gastric adaptation to stress: role of sensory nerves, salivary glands, and adrenal glands.

BACKGROUND: Single exposure to water immersion and restraint stress (WRS) in rats produces acute gastric mucosal damage, but repetitive WRS insults lead to gastric adaptation to stress ulcerogenesis. This study was designed to assess the mechanism of this adaptation, particularly the role of sensory nerves, salivary glands, adrenal glands, and gastric acid secretion. METHODS: WRS was applied for a standard period of 3.5 h, either once or repeated every other day for up to 8 days in intact rats and in animals with capsaicin-induced deactivation of sensory nerves, vagotomy, salivectomy, adrenalectomy, and inhibition of gastric acid secretion by H2-blocker. RESULTS: WRS applied once produced multiple gastric erosions accompanied by a significant increase in gastric acid secretion and a decrease in gastric blood flow (GBF) and DNA synthesis. Repeated WRS insults resulted in a significant decrease in the number of gastric lesions, reaching a maximum after four consecutive exposures to WRS. This adaptation to stress ulcerogenesis was accompanied by a decrease in gastric acid secretion and an increase in GBF and mucosal generation of DNA synthesis. Salivectomy, which decreased the luminal content of epidermal growth factor (EGF) (by about 80%), markedly attenuated this adaptation, and this was reversed by the addition of exogenous EGF. Capsaicin-induced ablation of sensory nerves eliminated gastric adaptation to WRS, and this was accompanied by a significant decrease in the GBF, but pretreatment with calcitonin gene-related peptide restored gastric adaptation to stress in capsaicin-denervated rats. Selective vagotomy and adrenalectomy failed to affect gastric adaptation to WRS, whereas gastric acid inhibition by ranitidine enhanced this adaptation. CONCLUSIONS: The stomach is able to adapt to repeated stress insults by enhancing GBF and DNA synthesis, and this adaptation is mediated, at least in part, by sensory nerves and EGF.

Nitric oxide in gastroprotective and ulcer healing effects of sucralfate.

BACKGROUND: Sucralfate is known to protect gastric mucosa against the damaging action of strong irritants and to accelerate healing of chronic ulcers, but the mechanisms underlying these effects have not been elucidated. Similar gastroprotective and healing effects can be obtained with exogenous donors of nitric oxide (NO) and prostaglandins (PG). METHODS: The area of gastric lesions was measured by planimetry. Gastric blood flow was determined using laser Doppler flowmetry. The role of NO in the prevention of ethanol-induced gastric damage and in the healing of gastric ulcerations by sucralfate and nocloprost, a stable PGE2 analog, was therefore assessed. RESULTS: Pretreatment with NG-nitro-L-arginine (L-NNA), an inhibitor of NO synthase, enhanced ethanol-induced mucosal damage and reduced dose-dependently the gastroprotective and hyperemic effects of sucralfate. The doses of L-NNA attenuating significantly the protective effects of sucralfate were 25-50 mg/kg. The effects of L-NNA were reversed by the addition of L-arginine but not D-arginine. For comparison, the gastroprotective (but not hyperemic) effects of nocloprost were not affected by the pretreatment with L-NNA and/or arginine. Daily treatment with L-NNA (50 mg/kg per day) prolonged the healing of chronic gastric ulcers and significantly reduced the acceleration of healing by sucralfate. CONCLUSIONS: We conclude that (i) the gastroprotective and hyperemic effects of sucralfate involve, at least in part, the NO-arginine pathway, (ii) the ulcer healing effects of sucralfate may also involve NO, probably through the hyperemia around the ulcer, and (iii) NO is not essential for the mucosal protection of PGE2 analog, but may account for the gastric vasodilatory effect of this PG.

Inhibition of nitric oxide synthase delays healing of chronic gastric ulcers.

We investigated the influence of inhibition of nitric oxide (NO) synthase, using NG-nitro-L-arginine (L-NNA) or NG-mono-methyl-L-arginine (L-NMMA), and the effects of exogenous donor of NO, such as glyceryl trinitrate (GTN), on the healing of chronic gastric ulcers induced by acetic acid, on gastric blood flow around the ulcer and on the number of capillaries in the granulation tissue at the ulcer bed. The inhibition of NO synthase resulted in a delay in ulcer healing and in a reduction in blood flow at the ulcer margin and in the number of capillaries in the granulation tissue at the ulcer bed. These effects of inhibition of NO synthase were antagonized, in part, by the administration of GTN or L-arginine but not D-arginine. We conclude that endogenous NO plays an important role in the maintenance of blood flow around the ulcer, in the angiogenesis in the granulation tissue and, thus, in the healing of gastric ulcers.

Role of nitric oxide and prostaglandins in gastroprotection induced by capsaicin and papaverine.

Capsaicin and papaverine are potent vasorelaxants with strong gastroprotective activity against damage induced by absolute ethanol. This protection was originally attributed to the increase in gastric mucosal blood flow (GBF) and the present study was designed to determine the possible role of nitric oxide (NO) and prostaglandins (PG) in the protective and hyperemic effects of capsaicin and papaverine on rat gastric mucosa. We found that the pretreatment with capsaicin (0.1-0.5 mg/kg i.g.) or papaverine (0.1-2 mg/kg i.g.) reduced dose dependently the area of ethanol-induced lesions, the ED50 being 0.3 and 1 mg/kg, respectively. This protection was accompanied by a gradual increase in the GBF. Intravenous injection of N omega-nitro-L-arginine (L-NNA; 1.2-5 mg/kg), a selective blocker of NO synthase, which by itself caused only a small increase in ethanol lesions, reversed dose dependently the protective and hyperemic effects of capsaicin and papaverine against ethanol-induced damage and attenuated the increase in GBF induced by each of these agents alone. This deleterious effect of L-NNA on the gastric mucosa and the GBF was fully antagonized by L-arginine (200 mg/kg i.v.) but not by D-arginine. L-arginine partly restored the decrease in GBF induced by L-NNA. Pretreatment with indomethacin (5 mg/kg i.p.), which suppressed the generation of PG by 85%, slightly enhanced the mucosal lesions induced by ethanol but failed to affect the fall in GBF induced by this irritant. Gastroprotective and hyperemic effects of capsaicin and papaverine were partly reversed by indomethacin suggesting that endogenous PG are also implicated in these effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Implications of nitric oxide in the action of cytoprotective drugs on gastric mucosa.

Cytoprotective drugs, including sucralfate, colloidal bismuth (De-Nol), aluminium-containing antacids (Maalox), carbenoxolone-like agents (sofalcone), and stable PGE2 analogues (nocloprost), are known to prevent acute gastric mucosal damage induced by topical irritants. This effect is usually accompanied by an elevation in mucosal blood flow. Recently, nitric oxide (NO), a potent vasorelaxant, has been implicated in gastroprotection by carbenoxolone, the prototype of cytoprotective drugs. In this study we assessed the involvement of NO in acute gastric damage induced by ethanol and in the prevention of this damage by sucralfate, Maalox, De-Nol, sofalcone, and nocloprost. Each of these drugs dose-dependently reduced the formation of ethanol-induced gastric lesions. The optimal gastroprotective dose was used in further studies to check the possible contribution of NO in this protection. Pretreatment with NG-nitro-L-arginine (L-NNA) (12.5-50 mg/kg i.v.), an inhibitor of NO synthase, dose-dependently enhanced the mucosal damage by ethanol itself and reduced the protective effects of sucralfate and Maalox but not those of sofalcone, De-Nol or nocloprost against the ethanol injury. Reduction by L-NNA of the mucosa-protective action of sucralfate or Maalox was accompanied by a decrease in gastric blood flow, which was antagonized by L-arginine (a substrate of NO synthase) but not by D-arginine. This study suggest that gastroprotective agents such sucralfate and Maalox, but not sofalcone or De-Nol, activate the NO system that may contribute to mucosal integrity and preservation of mucosal microcirculation.

Role of acid milieu in the gastroprotective and ulcer-healing activity of sucralfate.

Sucralfate prevents the formation of acute gastric lesions induced by various ulcerogens and enhances the healing of chronic gastroduodenal ulcerations, but the mechanism of these effects has not been fully explained. This study was designed to determine the importance of intragastric pH in the sucralfate-induced gastroprotection against 100% ethanol, acidified aspirin, taurocholate, or stress, and in the healing of chronic gastroduodenal ulcerations induced by acetic acid. Sucralfate acidified to pH 2.0 showed significantly stronger protective activity against all four irritants, its protective potency against 100% ethanol being about eight times greater and the duration of the protection about four times longer than those obtained with sucralfate at its pH of 5.0. Pretreatment with indomethacin to suppress mucosal generation of prostaglandin or the removal of salivary glands to eliminate the endogenous source of epidermal growth factor failed to affect sucralfate-induced gastroprotection. In contrast, the rate of healing of chronic gastric ulcerations was significantly delayed by indomethacin or sialoadenectomy; but sucralfate enhanced the healing, and a marked inhibition of gastric acid secretion by ranitidine did not eliminate this enhancement. We conclude that the protective activity of sucralfate depends on the presence of acid milieu in the stomach, but that the ulcer-healing effects of this drug occur even after a marked inhibition of gastric acid secretion.

Solcoseryl in prevention of stress-induced gastric lesions and healing of chronic ulcers.

Solcoseryl, a deproteinized extract of calf blood, protects the gastric mucosa against various topical irritants and enhances the healing of chronic gastric ulcerations but the mechanisms of these effects have been little studied. This study was designed to elucidate the active principle in Solcoseryl and to determine the role of prostaglandins (PG) and polyamines in the antiulcer properties of this agent. Using both, the radioimmunoassay and radioreceptor assay, EGF-like material was detected in Solcoseryl preparation. Solcoseryl given s.c. prevented the formation of stress-induced gastric lesions and this was accompanied by an increase in the generation of PGE2 in the gastric mucosa. Similar effects were obtained with EGF. Pretreatment with indomethacin, to suppress mucosal generation of prostaglandins (PG), greatly augmented stress-induced gastric ulcerations and antagonized the protection exerted by both Solcoseryl and EGF. Solcoseryl, like EGF, enhanced the healing of chronic gastro-duodenal ulcerations. This effect was abolished by the pretreatment with difluoromethylornithine, an inhibitor of ornithine decarboxylase, the key enzyme in the biosynthesis of polyamines. The healing effects of Solcoseryl and EGF was also reduced by prednisolone which decreased the angiogenesis in the granulation tissue in the ulcer area. These results indicate that Solcoseryl 1. contains EGF-like material, 2. displays the protective and ulcer healing effects similar to those of EGF and involving both PG and polyamines and 3. acts via similar mechanism as does EGF.