L-Arginine protects and exacerbates ethanol-induced rat gastric mucosal injury

A Mixture of Kaempferol-3-O-sambubioside and Kaempferol-3-O-sophoroside from Malvaviscus arboreus Prevents Ethanol-Induced Gastric Inflammation, Oxidative Stress, and Histologic Changes

Malvaviscus arboreus is used in traditional Mexican medicine to treat gastrointestinal diseases. Therefore, a mixture of Kaempferol-O-sambubioside and Kaempferol-O-sophoroside (MaSS) isolated from flowers of this species was tested as a preventive treatment on gastric lesions induced with ethanol in rats. MaSS was obtained by chromatographic methods and administered by oral pathway to male Sprague Dawley rats with ethanol-induced gastric lesions. Pretreatment with MaSS at doses of 30, 90, 120, and 180 mg/kg significantly prevents gastric lesions, inhibits the increment in relative stomach weight (%) in gastric IL-6, and also provokes an increment of IL-10 concentration and catalase activity. Finally, MaSS prevented edema in the mucosa and submucosa and diminished microscopic gastric lesions provoked by ethanol.

Gastroprotective effects of N-acylarylhydrazone derivatives on ethanol-induced gastric lesions in mice are dependent on the NO/cGMP/KATP pathway

The gastroprotective effects of N-acylarylhydrazone derivatives on ethanol-induced gastric lesions in mice were investigated with respect to the NO/cGMP/K_ATP pathway. To investigate our hypothesis, the mice were intraperitoneally pretreated with glibenclamide, L-NAME, or ODQ 30 min before treatment with DMSO, LASSBio-294 (1, 2, and 4 mg/kg, p.o.), LASSBio-897 (0.5, 1, and 2 mg/kg, p.o.), or omeprazole. After 1 h, the mice received absolute ethanol (4 ml/kg) by gavage to induce gastric mucosal lesions, and the microscopic and macroscopic parameters were evaluated. GSH (non-protein sulfhydryl groups) and MDA (malondialdehyde) concentrations, hemoglobin levels, nitric oxide production, myeloperoxidase (MPO) activity, and TNF-α and IL-1β levels were also analyzed in the stomach after absolute ethanol administration. Pretreatment with LASSBio-294 or LASSBio-897 significantly reduced the microscopic and macroscopic lesion area. The compounds restored the GSH, MDA, and hemoglobin levels and reduced MPO activity. Moreover, the compounds significantly reduced nitrate and nitrite concentrations in the stomach samples after ethanol administration. Molecular docking studies revealed that LASSBio-294 and LASSBio-897 interact with active sites of the eNOS (endothelial nitric oxide synthase) enzymes through hydrogen bonds. LASSBio-294 and LASSBio-897 also reduced TNF-α and IL-1β levels. It was observed that a NO synthase inhibitor, an ATP-sensitive potassium channel blocker, and a guanylate cyclase inhibitor significantly reversed the gastroprotective effects of these compounds. Thus, the gastroprotective effect of LASSBio-294 and LASSBio-897 against gastric lesions is mediated through the NO/cGMP cascade, followed by blocking of the K_ATP channels.

alpha-Amino acid derivatives as proton pump inhibitors and potent anti-ulcer agents

In a program to identify new anti-ulcer compounds, a series of N-acyl derivatives of alpha-amino acids were screened for their in vitro H(+)/K(+) ATPase inhibitory activity, and in vivo efficacy in Pylorus ligation model. 3D-QSAR studies were carried out and a representative compound 13 was studied for the nature of its proton pump inhibition.

Role of nitric oxide in the protective effect of rabeprazole on gastric mucosal lesions in rats

AIM: To explore the role of nitric oxide (NO) in the protective effect of rabeprazole on the gastric mucosal lesions in rats.

METHODS: Before gastric mucosal lesion was made in rats by pure alcohol, rabeprazole (20 mg/kg) was administered into the gastric chamber and Nw-nitro-l-arginine methyl ester (l-NAME, 4 mg/kg), l-arginine (250 mg/kg) and d-arginine (250 mg/kg) were injected into the vein. Gastric mucosal blood flow (GMBF) was assessed with laser Doppler flowmetry (LDF); gastric mucosal and serum NO^-₂/NO^-₃ were measured by cadmium granulation reduction and colorimetric method; and the changes of ulcer index and the severity of tissue necrosis as well as neutrophil infiltration were observed.

RESULTS: The Ulcer index of the rabeprazole group was markedly lower than that in the controls (5.5 ± 0.5 vs 25.2 ± 2.3, P < 0.01), and the degrees of tissue necrosis and neutrophil infiltration were significantly milder (necrosis ++ - +++/≤+: 1/9 vs 8/2, P < 0.01; infiltration ++ - +++/≤+: 3/7 vs 9/1, P < 0.01). The protective effect of rabeprazole was significantly decreased by prior administration of l-NAME. The inhibitory effect of l-NAME was antagonized by prior administration of l-arginine, but not d-arginine. Rabeprazole administered into the gastric chamber obviously increased GMBF, gastric mucosal and serum NO^-₂/NO^-₃, which was prevented by pretreatment with l-NAME, but the antisecretory effect of rabeprazole was not affected by l-NAME.

CONCLUSION: Rabeprazole can exert important protection against gastric mucosal lesions in rats mediated by nitric oxide, and the action of rabeprazole against gastric acid secretion contributes little to the protective effect.

Protective effect of pantoprazole on gastric mucosal lesions in rats and its mechanism

AIM: To explore the protective effect of pantoprazole on the gastric mucosal lesions in rats and its related mechanism.

METHODS: Before the gastric mucosal lesion was in-duced by pure alcohol, the rats were intravenously injected with pantoprazole (20 mg/kg), Nω-nitro-L-arginine methyl ester (L-NAME, 4 mg/kg), and L-arginine (250 mg/kg). The gastric mucosal blood flow (GMBF) was detected by laser Doppler flowmetry (LDF), and the level of NO^-₂/NO^-₃ in the gastric mucosa and serum was measured by cadmium granulation reduction and colorimetric method. The ulcer index (UI), the severity of tissue necrosis, and neutrophils infiltration were observed.

RESULTS: Compared with that in the control group, the UI was significantly decreased (5.7±2.1 vs 25.4±2.5, P <0.01), and the degrees of tissue necrosis and neutrophils infiltration were markedly lightened. The protective effect of pantoprazole was significantly decreased by L-NAME. The inhibitory effect of L-NAME was antagonized by prior administration of L-arginine. The GMBF and the content of NO^-₂/NO^-₃ in gastric mucosa and serum were increased by the intravenous administration of pantoprazole. This effect was prevented by the pretreatment of L-NAME, but the antisecretion effect of pantoprazole was not affected by L-NAME.

CONCLUSION: Pantoprazole can protect gastric muc-osa against the lesions in rats by the mediation of nitric oxide (NO), and the protective effect has no relation with its antisecretory action of gastric acid.

Gastroduodenal mucosal defense: coordination by a network of messengers and mediators

Gastroduodenal mucosal defense is composed of structural features of the mucosa, cellular monitors of pending or actual injury, and a web of effector cells that protect the mucosa from damage and govern its recovery from injury. By virtue of these systems, the gastroduodenal mucosa can cope with the harmful ingredients of ingested food and the potentially deleterious effects of gastric acid and pepsin. It is increasingly appreciated that a network of chemical messengers coordinates the alarm, defensive, and healing mechanisms. This article highlights some of the advances from the past year that have furthered our understanding of the regulatory systems that govern gastroduodenal mucosal homeostasis. Particular emphasis is given to control of the mucous and epithelial phospholipid barriers, the mucosal microcirculation, and the epithelial, neural, immune, and inflammatory mediators of the mucosal repair mechanisms.

Protective effect of L-arginine against stress-induced gastric mucosal lesions in rats and its relation to nitric oxide-mediated inhibition of neutrophil infiltration

Pretreatment with l -arginine (150-600 mg kg(-1), i.p.), but not d -arginine (600 mg kg(-1), i.p.), protected against gastric mucosal lesions in rats with water immersion restraint stress over a 6-h period. This protective effect occurred in a dose-dependent manner. Increases in the activities of inducible nitric oxide synthase (iNOS) and myeloperoxidase (MPO), an index of tissue neutrophil infiltration, and the concentration of nitrite/nitrate, breakdown products of nitric oxide, and a decrease in the activity of constitutive nitric oxide synthase (cNOS) occurred in the gastric mucosal tissue with the development of gastric mucosal lesions. The l -arginine pretreatment attenuated the increases in iNOS and MPO activities and nitrite/nitrate concentration and the decrease in cNOS activity in the gastric mucosal tissue in a dose-dependent manner, while the d -arginine pretreatment did not. Both the protective effect of l -arginine (300 mg kg(-1)) against stress-induced gastric mucosal lesions and the attenuating effect of the amino acid on the increases in gastric mucosal iNOS and MPO activities and the decrease in gastric mucosal cNOS activity with the lesion development were counteracted by pretreatment with N(G)-monomethyl- l -arginine (100 mg kg(-1), s.c.), a nitric oxide synthase inhibitor, but not its d -isomer (100 mg kg(-1), s.c.). These results suggest that the protective effect of exogenously administered l -arginine against stress-induced gastric mucosal lesions in rats is, at least in part, due to nitric oxide-mediated inhibition of neutrophil infiltration into the gastric mucosal tissue.