Effects of nitric oxide on gastric ulceration induced by nicotine and cold-restraint stress

Effects of the probiotic, Lactobacillus rhamnosus GG, on ulcer pathogenesis, HSP70 stress protein and nitric oxide levels in stress induced ulcer

Peptic ulcer is a gastric or duodenal mucosal injury; psychological stress may participate in development of the lesions. Heat shock protein-70 (HSP70) is a molecular chaperone that is responsible for cellular healing; it is an early biomarker of cellular damage. Nitric oxide (NO) is an intra- and intercellular messenger in the gastrointestinal system that protects mucosal integrity. Lactobacillus rhamnosus is among the microflora of the intestinal tract; it is resistant to gastric acidity. We investigated the efficacy of L. rhamnosus administration on ulcer pathogenesis, stress protein HSP70 and NO levels in experimental stress induced ulcer. The proton pump inhibitor, pantoprazole, was used for comparison with the gastroprotective effect of the probiotic. We administered 10 mg/kg pantoprazole and L. rhamnosus at doses of 3 × 10⁸ cfu/ml (M1), 15 × 10⁸ cfu/ml (M5), 30 × 10⁸ cfu/ml (M10) to rats according to McFarland-1, McFarland-5, McFarland-10 standards, respectively. Rats were stressed by immobilization at 4 °C, then sacrificed. The pH, amounts of gastric mucus, NO and HSP70 levels were measured and the histological structure of stomach was assessed. We found increased NO levels in the M5 group and increased HSP70 expression in the pantoprazole group. Significant epithelial damage was observed in the stressed groups and minimal epithelial damage was observed in M5 group compared to controls. The probiotic, L. rhamnosus, may be useful for preventing stress induced ulcers.

Chronic mild stress paradigm as a rat model of depression: facts, artifacts, and future perspectives

RATIONALE

The chronic mild stress (CMS) paradigm was first described almost 40 years ago and has become a widely used model in the search for antidepressant drugs for major depression disorder (MDD). It has resulted in the publication of almost 1700 studies in rats alone. Under the original CMS procedure, the expression of an anhedonic response, a key symptom of depression, was seen as an essential feature of both the model and a depressive state. The prolonged exposure of rodents to unpredictable/uncontrollable mild stressors leads to a reduction in the intake of palatable liquids, behavioral despair, locomotor inhibition, anxiety-like changes, and vegetative (somatic) abnormalities. Many of the CMS studies do not report these patterns of behaviors, and they often fail to include consistent molecular, neuroanatomical, and physiological phenotypes of CMS-exposed animals.

OBJECTIVES

To critically review the CMS studies in rats so that conceptual and methodological flaws can be avoided in future studies.

RESULTS

Analysis of the literature supports the validity of the CMS model and its impact on the field. However, further improvements could be achieved by (i) the stratification of animals into 'resilient' and 'susceptible' cohorts within the CMS animals, (ii) the use of more refined protocols in the sucrose test to mitigate physiological and physical artifacts, and (iii) the systematic evaluation of the non-specific effects of CMS and implementation of appropriate adjustments within the behavioral tests.

CONCLUSIONS

We propose methodological revisions and the use of more advanced behavioral tests to refine the rat CMS paradigm, which offers a valuable tool for developing new antidepressant medications.

Recent advances on endogenous gasotransmitters in inflammatory dermatological disorders

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Endogenous gasotransmitters nitric oxide (NO), carbon monoxide (CO), hydrogen sulfide (H₂S), and potential candidates sulfur dioxide (SO₂), methane (CH₄), hydrogen gas (H₂), ammonia (NH₃) and carbon dioxide (CO₂), are generated within the human body.

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Endogenous and potential gasotransmitters regulate inflammation, vasodilation, and oxidation in inflammatory dermatological disorders.

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Endogenous and potential gasotransmitters play potential roles in psoriasis, atopic dermatitis, acne, and chronic skin ulcers.

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Further research should explore the function of these gases and gas donors and inhibitors in inflammatory dermatological disorders.

Background

Endogenous gasotransmitters are small gaseous mediators that can be generated endogenously by mammalian organisms. The dysregulation of the gasotransmitter system is associated with numerous disorders ranging from inflammatory diseases to cancers. However, the relevance of these endogenous gasotransmitters, prodrug donors and inhibitors in inflammatory dermatological disorders has not yet been thoroughly reviewed and discussed.

Aim of review

This review discusses the recent progress and will provide perspectives on endogenous gasotransmitters in the context of inflammatory dermatological disorders.

Key scientific concepts of review

Endogenous gasotransmitters nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H₂S) are signaling molecules that regulate several physiological and pathological processes. In addition, sulfur dioxide (SO₂), methane (CH₄), hydrogen gas (H₂), ammonia (NH₃), and carbon dioxide (CO₂) can also be generated endogenously and may take part in physiological and pathological processes. These signaling molecules regulate inflammation, vasodilation, and oxidative stress, offering therapeutic potential and attracting interest in the field of inflammatory dermatological disorders including psoriasis, atopic dermatitis, acne, rosacea, and chronic skin ulcers. The development of effective gas donors and inhibitors is a promising alternative to treat inflammatory dermatological disorders with controllable and precise delivery in the future.

Gastroprotective Effects of Paeonia Extract Mixture HT074 against Experimental Gastric Ulcers in Rats

Background

Paeonia extract mixture HT074 is a standardized multiherbal mixture comprising extracts from Inula britannica flowers and Paeonia lactiflora roots, which are used to treat digestive disorders in traditional Korean medicine. This study was focused on elucidating the underlying mechanisms of the gastroprotective effects of HT074 in different gastric ulcer models.

Methods

Gastric lesions were induced in rats by an HCl/EtOH solution, water immersion-restraint stress (WIRS), and indomethacin. Gastric secretions were studied in pylorus-ligated rats, while mucus secretions were assessed by measuring alcian blue-binding capacity of mucus in the rat model of HCl/EtOH-induced gastric ulcer. Additionally, the involvement of nitric oxide (NO) and sulfhydryl compounds in HT074-mediated mucosal protection was elucidated using their inhibitors, i.e., N^G-nitro- _L-arginine methyl ester hydrochloride (L-NAME) and N-ethylmaleimide (NEM), respectively. Furthermore, the effects on indomethacin-induced cell death and prostaglandin E₂ (PGE₂) levels were assessed in AGS cells.

Results

Oral administration of HT074 significantly decreased gastric lesions induced by HCl/EtOH, WIRS, and indomethacin. Furthermore, it significantly decreased the volume, acidity, and total acidity of gastric juice in pylorus-ligated rats and increased the alcian blue-stained gastric mucus in HCl/EtOH-induced gastric ulcer in rats. Pretreatment with NEM abolished the gastroprotective effects of HT074, while L-NAME did not. In AGS cells, HT074 significantly reduced indomethacin-induced cell death and increased the PGE₂ levels.

Conclusions

These findings suggest that HT074 has gastroprotective effects against various ulcerogens, including HCl/EtOH, immersion stress, and NSAIDs. These effects are attributed to the inhibition of gastric secretions and preservation of the gastric mucosal barrier by increased mucus production, which is partially mediated through endogenous sulfhydryl compounds and PGE₂. Based on these findings, we propose that HT074 may be a promising therapeutic agent for gastritis and gastric ulcer.

Mechanisms of Antiulcer Effect of an Active Ingredient Group of Modified Xiao Chaihu Decoction

The present study aimed to investigate the antiulcer activities and mechanisms of action of an active ingredient group (AIG) of Modified Xiao Chaihu Decoction (MXCD). The gastroprotective action of the AIG was studied in ethanol-induced, pylorus ligature-induced, and acetic acid-induced in vivo gastric ulcer models. The enzyme-linked immunoadsorbent assay (tumor necrosis factor-α (TNF-α), prostaglandin E₂ (PGE₂), and epidermal growth factor (EGF)), nitrate reductase assay (nitric oxide (NO)), western blot analysis (Bax, Bcl-2, cleaved-caspase-3, and cleaved-PARP (poly (ADP-Ribose) polymerase)), histological analysis (HE), and immunohistochemical analysis (HSP-70, p-AKT, and PCNA) were used to evaluate the anti-inflammatory, antiapoptotic, and healing properties of AIG. Numerous mechanisms are involved in the antiulcer activity of AIG, including the increase of PGE₂, NO, and EGF content and a reduction in TNF-α levels. The upregulation of HSP-70, p-AKT, and PCNA seems to be directly linked to the healing effect of AIG. Bax, Bcl-2, cleaved-caspase-3, and cleaved-PARP also play a key role in this process. The AIG exerted gastroprotective effects by reducing antisecretory, anti-inflammatory, and antiapoptotic mechanisms. In addition, it promotes cell proliferation. Therefore, activation of the PI3K/AKT signaling pathway may play an important role in cell proliferation.

Chronic stress impacts the cardiovascular system: animal models and clinical outcomes

Psychological stresses are associated with cardiovascular diseases to the extent that cardiovascular diseases are among the most important group of psychosomatic diseases. The longstanding association between stress and cardiovascular disease exists despite a large ambiguity about the underlying mechanisms. An array of possibilities have been proposed including overactivity of the autonomic nervous system and humoral changes, which then converge on endothelial dysfunction that initiates unwanted cardiovascular consequences. We review some of the features of the two most important stress-activated systems, i.e., the humoral and nervous systems, and focus on alterations in endothelial function that could ensue as a result of these changes. Cardiac and hematologic consequences of stress are also addressed briefly. It is likely that activation of the inflammatory cascade in association with oxidative imbalance represents key pathophysiological components of stress-induced cardiovascular changes. We also review some of the commonly used animal models of stress and discuss the cardiovascular outcomes reported in these models of stress. The unique ability of animals for adaptation under stressful conditions lessens the extrapolation of laboratory findings to conditions of human stress. An animal model of unpredictable chronic stress, which applies various stress modules in a random fashion, might be a useful solution to this predicament. The use of stress markers as indicators of stress intensity is also discussed in various models of animal stress and in clinical studies.

Biochanin a gastroprotective effects in ethanol-induced gastric mucosal ulceration in rats

BACKGROUND

Biochanin A notable bioactive compound which is found in so many traditional medicinal plant. In vivo study was conducted to assess the protective effect of biochanin A on the gastric wall of Spraguedawley rats` stomachs.

METHODOLOGY

The experimental set included different animal groups. Specifically, four groups with gastric mucosal lesions were receiving either a) Ulcer control group treated with absolute ethanol (5 ml/kg), b) 20 mg/kg of omeprazole as reference group, c) 25 of biochanin A, d) 50 mg/kg of biochanin A. Histopathological sectioning followed by immunohistochemistry staining were undertaken to evaluate the influence of the different treatments on gastric wall mucosal layer. The gastric secretions were collected in the form of homogenate and exposed to superoxide dismutase (SOD) and nitric oxide enzyme (NO) and the level of malondialdehyde (MDA) and protein content were measured. Ulceration and patchy haemorrhage were clearly observed by light microscopy. The morphology of the gastric wall as confirmed by immunohistochemistry and fluorescent microscopic observations, exhibited sever deformity with notable thickness, oedematous and complete loss of the mucosal coverage however the biochanin-pretreated animals, similar to the omeprazole-pretreated animals, showed less damage compared to the ulcer control group. Moreover, up-regulation of Hsp70 protein and down-regulation of Bax protein were detected in the biochanin A pre-treated groups and the gastric glandular mucosa was positively stained with Periodic Acid Schiff (PAS) staining and the Leucocytes infiltration was commonly seen. Biochanin A displayed a great increase in SOD and NO levels and decreased the release of MDA.

CONCLUSIONS

This gastroprotective effect of biochanin A could be attributed to the enhancement of cellular metabolic cycles perceived as an increase in the SOD, NO activity, and decrease in the level of MDA, and also decrease in level of Bax expression and increase the Hsp70 expression level.

Antinociceptive effect and gastroprotective mechanisms of 3,5-diprenyl-4-hydroxyacetophenone from Ageratina pichinchensis

The present study aimed to evaluate the antinociceptive activity (in inflammatory and neuropathic pain models) and gastroprotective effect of the 3,5-diprenyl-4-hydroxyacetophenone (HYDP), isolated from Ageratina pichinchensis. The gastroprotective activity of this plant was previously reported by our workgroup, finding encesanescin to be one active compound. The present results show that HYDP reduced nociception in a dose-dependent manner in carrageenan and L5/L6 spinal nerve ligation, with efficacies of 72.6 and 57.1%, respectively, at doses of 100 and 562 mg/kg. HYDP also showed gastroprotective activity in the model of ethanol-induced gastric lesion, with a 75.59% maximum inhibition of ulcers at a dose of 100mg/kg. This gastroprotective effect was attenuated by N(G)-nitro-L-arginine methyl ester, indomethacin and N-ethylmaleimide, indicating that NO, prostaglandins and sulfhydryl groups are involved in the mechanisms of action. This is the first evidence, to our knowledge, of the antinociceptive and gastroprotective activities of HYDP.

Preventive effects of curcumin against drug- and starvation-induced gastric erosions in rats

The present study was designed to investigate the gastroprotective, analgesic, and antipyretic effects of curcumin (Cur), the major constituent of turmeric. Acetylsalicylic acid (ASA) was used in this study as a standard drug for comparison. The analgesic activity was measured using the Hot-Plate Test. The antipyretic and antiulcer effects were assessed using yeast-induced pyrexia and gastric ulceration, respectively. Curcumin (100 mg/kg) injected intra-peritoneally 1 hr prior to the Hot-Plate Test showed significant analgesic activity expressed by both parameters: an increase in latency time and a reduction in paw licking as compared to the controls. In the animal model of pyrexia, curcumin (100 mg/kg injected intra-peritoneally) exhibited a significant reduction in the rectal temperature after 1 hr, 2 hrs, 4 hrs, and 5 hrs of treatment, indicating the antipyretic effect of curcumin. Rats with orally administered curcumin (200 mg/kg) did not show any lesions on the inner lining of the stomach after a 16 hr fast, indicating the gastroprotective effects of curcumin as compared to saline- and acetylsalicylic acid-administered rats. The significantly low ulcer index in curcumin-treated rats following starvation highlights the gastroprotective characteristics of curcumin.

Hadi AH, Mohd Ali H, Majid N, Abdulla MA. Acute toxicity and gastroprotection studies of a new schiff base derived copper (II) complex against ethanol-induced acute gastric lesions in rats

BACKGROUND

Copper is an essential element in various metabolisms. The investigation was carried out to evaluate acute gastroprotective effects of the Copper (II) complex against ethanol-induced superficial hemorrhagic mucosal lesions in rats.

METHODOLOGY/PRINCIPAL FINDINGS

Rats were divided into 7 groups. Groups 1 and 2 were orally administered with Tween 20 (10% v/v). Group 3 was orally administered with 20 mg/kg omeprazole (10% Tween 20). Groups 4-7 received 10, 20, 40, and 80 mg/kg of the complex (10% Tween 20), respectively. Tween 20 (10% v/v) was given orally to group 1 and absolute ethanol was given orally to groups 2-7, respectively. Rats were sacrificed after 1 h. Group 2 exhibited severe superficial hemorrhagic mucosal lesions. Gastric wall mucus was significantly preserved by the pre-treatment complex. The results showed a significant increase in glutathione (GSH), superoxide dismutase (SOD), nitric oxide (NO), and Prostaglandin E2 (PGE(2)) activities and a decrease in malondialdehyde (MDA) level. Histology showed marked reduction of hemorrhagic mucosal lesions in groups 4-7. Immunohistochemical staining showed up-regulation of Hsp70 and down-regulation of Bax proteins. PAS staining of groups 4-7 showed intense stain uptake of gastric mucosa. The acute toxicity revealed the non-toxic nature of the compound.

CONCLUSIONS/SIGNIFICANCE

The gastroprotective effect of the Copper (II) complex may possibly be due to preservation of gastric wall mucus; increase in PGE(2) synthesis; GSH, SOD, and NO up-regulation of Hsp70 protein; decrease in MDA level; and down-regulation of Bax protein.

A review on animal models for screening potential anti-stress agents

Stress is a state of threatened homeostasis that produces different physiological as well as pathological changes depending on severity, type and duration of stress. The animal models are pivotal for understanding the pathophysiology of stress-induced behavioral alterations and development of effective therapy for its optimal management. A battery of models has been developed to simulate the clinical pain conditions with diverse etiology. An ideal animal model should be able to reproduce each of the aspects of stress response and should be able to mimic the natural progression of the disease. The present review describes the different types of acute and chronic stress models including immersion in cold water with no escape, cold environment isolation, immobilization/restraint-induced stress, cold-water restraint stress, electric foot shock-induced stress, forced swimming-induced stress, food-deprived activity stress, neonatal isolation-induced stress, predatory stress, day-night light change-induced stress, noise-induced stress, model of post-traumatic stress disorder and chronic unpredictable stress models.

Asymmetric dimethylarginine: A novel biomarker of gastric mucosal injury?

Nitric oxide (NO), a multifunctional endogenous gas molecule, is metabolized from L-arginine by enzymatic reaction in the presence of nitric oxide synthase. NO, an important gas signaling molecule, is a gastric mucosa protective factor that contributes significantly to maintain normal gastric mucosa integrity. NO increases gastric mucosa blood flow, regulates the secretion of mucus and bicarbonate, and inhibits the secretion of gastric juice. Asymmetric dimethylarginine (ADMA) has been identified as the major endogenous inhibitor of nitric oxide synthase. The function of ADMA is to decrease NO production via inhibiting nitric oxide synthase activity. Besides inhibiting NO synthesis, ADMA also directly induces oxidative stress and cell apoptosis, and participates in inflammation reaction. Its systemic accumulation was observed in conjunction with several cardiovascular and metabolic diseases. ADMA also mediates gastric ulcer injury induced by ethanol, stress, helicobacter pylori and indomethacin. The mechanism of ADMA directly producing adverse effect in gastric mucosa is incompletely understood. It is widely accepted that NO bioavailability decrease is the majority reason. Promotion of apoptosis and aggravation of inflammation may be other important mechanisms of ADMA-induced gastric injury. ADMA might be a novel clinical and experimental biomarker related to gastric mucosa disorder. Although therapeutic tool targeting to ADMA is available in multiple cardiovascular diseases, it is unknown in gastrointestinal disease. The strategy to inhibit ADMA is beneficial to gastric ulcer induced by ethanol in rats. Thus, ADMA might be a candidate of therapeutic target in gastric mucosa damage.

Mechanisms of the gastric antiulcerogenic activity of Anacardium humile St. Hil on ethanol-induced acute gastric mucosal injury in rats

Leaves and bark infusions Anacardium humile St. Hil. (Anacardiaceae), known as in Brazil as "cajuzinho do cerrado", have been used in folk medicine as an alternative treatment for ulcers and gastritis. This study evaluated the gastroprotective activity of an ethyl acetate extract of the leaves of A. humile (AcF) and the mechanism involved in this gastroprotection. Pretreatment concentrations (50, 100, 200 mg x kg⁻¹) were administered by gavage. Following a 60 min. period, all the rats were orally administered 1 mL of absolute ethanol. One hour after the administration of ethanol, all groups were sacrificed, and the gastric ulcer index was calculated. Prostaglandin PGE₂ concentration, gastric adherent mucous, and the participation of nitric oxide (NO) and sulfhydryl compounds in the gastroprotection process were also analyzed using the most effective tested dose (50 mg x kg⁻¹). A histological study of the glandular stomach for the evaluation of the epithelial damage and mucus content was also performed. AcF significantly reduced the gastric damage produced by ethanol. This effect was statistically significant for the 50 mg x kg⁻¹ group compared to control. Also, it significantly increased the PGE₂ (by 10-fold) and mucous production, while pretreatment with NG-nitro-L-arginine methyl ester (L-NAME) or N-ethylmaleimide (NEM) completely abolished the gastroprotection. AcF has a protective effect against ethanol, and this effect, might be due to the augmentation of the protective mechanisms of mucosa.

Detrimental effects of nicotine on the acute gastric mucosal injury induced by ethanol: role of asymmetric dimethylarginine

The aim of this study was to determine whether asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase (NOS), is responsible for the detrimental effects of nicotine on ethanol-induced gastric mucosal injury and its underlying mechanisms. Gastric mucosal injury was induced by an injection of ethanol in the stomach in rats. Animals were pretreated with nicotine for 28 days before ethanol injection. The gastric mucosal ulcer index (UI) and the levels of ADMA and NO in gastric juice were determined. In vitro, the cultured mucosal epithelial cells were treated with nicotine in the presence or absence of ethanol. The concentration of ADMA in the culture medium and the ratio of cell apoptosis were measured, and the effect of nicotine or ADMA alone on cell apoptosis was also examined. In rats treated with ethanol, the UI and ADMA levels were increased and the NO level was decreased, and these effects of ethanol were augmented by pretreatment with nicotine. Administration of nicotine alone did not show significant impact on UI, ADMA level, or NO level. In vitro, incubation of human epithelial cells with ethanol induced cell injury accompanied by increased ADMA levels in the culture medium, an effect which was amplified in the presence of nicotine. Similarly, ethanol was able to induce epithelial cell apoptosis that was exacerbated by nicotine. Incubation of epithelial cells with nicotine alone did not induce cell apoptosis, but administration of ADMA alone did induce cell apoptosis. The results suggest that the gastric mucosal injury induced by ethanol is augmented by nicotine, which is related to the increased ADMA level.

The aggravatory effect of nicotine on Helicobacter pylori-induced gastric mucosa injury: role of asymmetric dimethylarginine

BACKGROUND AND GOAL

Nitric oxide (NO) is a well-known gastric mucosa protection factor. Recently, it has been reported that methylated arginine compound such as asymmetric dimethylarginine (ADMA), which inhibits nitric oxide synthesis, may be related to the development of gastric mucosa injury in patients with Helicobacter pylori infection. In the present study, we tested the relationship between endogenous ADMA and gastric mucosa injury in H. pylor- infected patients and cultured gastric epithelial cells.

METHODS

One hundred and fifty subjects with gastric diseases were entered in this study. The levels of ADMA in gastric juice and plasma were measured in both H. pylori+ and H. pylori- patients. We analyzed independent risk factors that contribute to ADMA levels by multiple linear regression analyses. Mucosal epithelium cells were treated with nicotine (10 microM) for 24 hours in the presence or absence of H. pylori. The concentrations of ADMA in the culture medium and the rate of cell apoptosis were determined.

RESULTS

The ADMA level in gastric juice was significantly increased in H. pylori+ patients (P<0.05), whereas there were no differences in the content of ADMA in the plasma between H. pylori+ patients and H. pylori- patients. Smoking and H. pylori infection were 2 independent risk factors contributing to ADMA levels, and in the population of H. pylori+ patients, the level of ADMA in smokers was higher compared with nonsmokers. Incubation of nicotine (10 microM) with epithelial cells for 24 hours further increased the elevated level of ADMA and the rate of cell apoptosis owing to H. pylori infection.

CONCLUSIONS

H. pylori infection caused an increase of ADMA levels in gastric juice, which was aggravated by smoking. Endogenous ADMA may be an important factor contributing to gastric mucosa injury.

Nicotine withdrawal alleviates acetic acid-induced gastric injury in rats

Epidemiological and experimental studies have demonstrated that cigarette smoking intensifies gastric ulceration. Although nicotine can act as an anxiolytic and antidepressant, its withdrawal may also lead to increased anxiety and depression. In order to associate the toxic actions of nicotine on gastric mucosa with alterations of anxiety level and to evaluate the impact of nicotine withdrawal on the anxiety level and the severity of ulcer, an acetic acid-induced ulcer model was used. Male Sprague-Dawley rats were given either tap water or nicotine bitartarate (50μg/ml in drinking water) for 15 days, while another group of rats had 5 days of withdrawal following 10 days of nicotine treatment. Ulcer was induced by acetic acid on the 15th day of the treatments, and the rats were followed for 3 days until they were decapitated and the gastric tissues were obtained. Using the hole-board test, basal anxiety levels measured on the first day of the treatments were compared with the measurements made at the early and late phases of ulcer induction. Chronic administration of nicotine did not have a potentiating effect on acetic acid-induced gastric ulcer, since the gastric injury, as assessed by both macroscopic and microscopic evaluation and increased gastric myeloperoxidase activity indicating neutrophil recruitment, was not exaggerated or attenuated by nicotine intake. On the other hand, nicotine withdrawal attenuated gastric mucosal injury, despite an increased level of anxiety. Smoking cessation, which triggers the onset of depressive symptoms with nicotine withdrawal, still has a worthwhile positive effect on the gastric mucosa.

Reduction of asymmetric dimethylarginine in the protective effects of rutaecarpine on gastric mucosal injury

Our recent study has shown that asymmetric dimethylarginine (ADMA) plays an important role in facilitating gastric mucosal injury by multiple factors. To explore whether the protection of rutaecarpine against gastric mucosal injury is related to reduction of ADMA content, a model of ethanol-induced gastric mucosal injury in rats was selected for this study. The ulcer index, the content of ADMA and NO, and the activity of dimethylarginine dimethylaminohydrolase (DDAH) in gastric tissues were measured in vivo after pretreatment with rutaecarpine. The in vitro effect of rutaecarpine on the release of calcitonin gene-related peptide (CGRP) and NO from isolated gastric tissues was also determined. The results showed that ethanol significantly increased the ulcer index, decreased the DDAH activity and the NO level, and elevated the ADMA level, which was attenuated by pretreatment with rutaecarpine (0.6 mg/kg or 1.2 mg/kg). In the isolated gastric tissues, rutaecarpine significantly increased the release of both CGRP and NO; the release of NO, but not CGRP, was abolished in the presence of l-NAME (10(-4) mol/L). The present results suggest that rutaecarpine protects the gastric mucosa against injury induced by ethanol and that the gastroprotection of rutaecarpine is related to reduction of ADMA levels through stimulating the release of CGRP.

Role of endogenous nitric oxide synthase inhibitor in gastric mucosal injury

To explore the role of the endogenous nitric oxide synthase (NOS) inhibitor asymmetric dimethylarginine (ADMA) in gastric mucosal injury, 3 models of gastric mucosal injury induced by ethanol, indomethacin, or cold stress were used in rats. The cultured human gastric mucosal epithelial cell line GES-1 infected by Helicobacter pylori (Hp) was selected to mimic human gastric mucosal injury. Gastric mucosal ulcer index (UI), levels of ADMA and NO, and activity of dimethylarginine dimethylaminohydrolase (DDAH) were determined in the mucosal injury models; in Hp-infected or ADMA-treated GES-1 cells, levels of ADMA, NO, and TNF-alpha and activity of DDAH were measured. The results showed that UI and levels of ADMA were markedly increased and accompanied by significantly decreased DDAH activity in the mucosal injury models. Incubation of GES-1 cells with Hp increased levels of TNF-alpha and ADMA and decreased activity of DDAH. Administration of ADMA also increased levels of TNF-alpha. The results suggest that ADMA plays an important role in facilitating gastric mucosal injury, an effect which is associated with inhibiting NO synthesis and inducing inflammatory reaction.

Selective effects of citalopram in a mouse model of stress-induced anhedonia with a control for chronic stress

A stress-induced decrease in sucrose preference in rodents is regarded as an analog of anhedonia, a key symptom of depression. We investigated the effects of citalopram, administrated via drinking water (15 mg/kg/day), in a mouse model of stress-induced anhedonia. In this model, chronic stress induces anhedonia in a subset of C57BL/6N mice, while the remaining animals do not show a hedonic deficit or other depressive-like behaviors, although they are exposed to the same stressors as the anhedonic mice. Pre-stress and post-stress treatment with citalopram counteracted the development and maintenance of anhedonia and rescued normal floating in the forced swim test, demonstrating an antidepressant-like action. During the post-stress treatment, citalopram selectively increased sucrose preference and intake on the fourth week of treatment in anhedonic mice without affecting non-anhedonic animals. Citalopram also decreased elevated water consumption in the anhedonic group. Citalopram, administered 1 week before and during a 4-week stress procedure, decreased the percentage of anhedonic mice and reduced the increase of water intake in stressed mice. This study suggests that our chronic stress paradigm can serve as a model of anhedonia, in which antidepressant treatment is selectively effective in animals with a hedonic deficit.

PROSTAGLANDINS, CAPSAICIN-SENSITIVE SENSORY NERVES AND NEUTROPHIL INFILTRATION, BUT NOT NITRIC OXIDE, CONTRIBUTE TO COLD RESTRAINT STRESS-INDUCED GASTRIC ADAPTATION IN RATS

The aim of the present study was to determine the role of prostaglandins (PG), nitric oxide (NO) and capsaicin-sensitive sensory nerves in neutrophil infiltration in gastric adaptation to cold restraint stress in rats. Wistar rats were exposed to single or repeated cold restraint stress for 3.5 h every other day for up to 4 days. Prior to repeated stress, rats were pretreated with NG-nitro-L-arginine methyl ester (L-NAME; 10 mg/kg, s.c.), indomethacin (10 mg/kg, s.c.) or capsaicin (125 mg/kg, s.c.). The extent of gastric mucosal lesions was evaluated histologically and myeloproxidase (MPO) activity, PGE2, NO and calcitonin gene-related peptide (CGRP) levels were measured in gastric tissue. Cold restraint stress produced haemorrhagic lesions and reduced PGE2 and CGRP levels in the stomach, with an increase in MPO activity and NO levels. Repeated stress insults reduced stress-induced gastric damage, NO production and MPO activity, with an increase in PGE2 and CGRP levels compared with rats exposed to single cold restraint stress. Adaptation to cold restraint stress was prevented by indomethacin and capsaicin pretreatment, but not by L-NAME. We conclude that the stomach has the ability to adapt to repeated exposure to cold restraint stress and that the adaptation, via inhibition of neutrophil infiltration, is mediated, at least in part, by endogenous PG and CGRP.

Dynamic functional and ultrastructural changes of gastric parietal cells induced by water immersion-restraint stress in rats

AIM: To investigate the dynamic functional and ultrastructural changes of gastric parietal cells induced by water immersion-restraint stress (WRS) in rats.

METHODS: WRS model of Sprague-Dawley (SD) rats was established. Fifty-six male SD rats were randomly divided into control group, stress group and post-stress group. The stress group was divided into 1, 2 and 4 h stress subgroups. The post-stress group was divided into 24, 48 and 72 h subgroups. The pH value of gastric juice, ulcer index (UI) of gastric mucosa and H⁺, K⁺-ATPase activity of gastric parietal cells were measured. Ultrastructural change of parietal cells was observed under transmission electron microscope (TEM).

RESULTS: The pH value of gastric juice decreased time-dependently in stress group and increased in post-stress group. The H⁺, K⁺-ATPase activity of gastric parietal cells and the UI of gastric mucosa increased time-dependently in stress group and decreased in post-stress group. Compared to control group, the pH value decreased remarkably (P = 0.0001), the UI and H⁺, K⁺-ATPase activity increased significantly (P = 0.0001, P = 0.0174) in 4 h stress subgroup. UI was positively related with stress time (r = 0.9876, P < 0.01) but negatively with pH value (r = -0.8724, P < 0.05). The parietal cells became active in stress group, especially in 4 h stress subgroup, in which plenty of intracellular canalicular and mitochondria were observed under TEM. In post-stress group, the parietal cells recovered to resting state.

CONCOUSION: The acid secretion of parietal cells is consistent with their ultrastructural changes during the development and healing of stress ulcer induced by WRS and the degree of gastric mucosal lesions, suggesting gastric acid play an important role in the development of stress ulcer and is closely related with the recovery of gastric mucosal lesions induced by WRS.

Effects and mechanism of changes of local neurotransmitters in rats' pylorus and bile reflux to the stomach with stress ulcer

Stress ulcer occurs primarily in severe conditions, with a high incidence and mortality in intensive care units. However, studies on the association between stress ulcer and bile reflux to the stomach with stress ulcer are still inconclusive. Therefore, our research aimed to determine whether or not bile reflux exists during stress ulcer and then to investigate the effects and mechanism of changes of pyloric local neurotransmitters on bile reflux in such circumstances so as to provide a new pathway for clinical intervention. Cold water immersion was used to copy the stress ulcer model of rats. Sixty-five adult Sprague-Dawley rats of either sex were randomly divided into three groups: the normal control group (n = 10), the stress group (n = 30), and the antagonist group (n = 25). The gastric ulcer index, pH, and bile acid of gastric juice were measured before and after stress. Radio Immunoassay Detection Kit and Biochemic Detection Kit were used to measure local contents of CGRP (calcitonin gene-related peptide) and nitric oxide, respectively, in rats' pylorus. The local contents of nitric oxide in rats' pylorus reached a maximum at 1 hr after stress. The bile acid and pH of gastric juice peaked at 2 hr after stress and the ulcer index peaked at 4 hr after stress. But the local contents of CGRP in rats' pylorus decreased to the minimum at 4 hr after stress. The bile acid and ulcer index in the L-NAME group were significantly lower than in the antagonist control group. However, the bile acid in the hCGRP8-37 group was less than in the antagonist control group. Compared with hCGRP8-37 group, there was a significant reduction in bile acid in the L-NAME group. There was a significant reduction in the ulcer index of the hCGRP8-37 group compared with the L-NAME group and the antagonist control group. There was a certain kind of positive correlation between nitric oxide in rats' pylorus and bile acid to the stomach, for nitric oxide could loosen the pyloric sphincter and increase the bile acid to the stomach. L-NAME might reduce the local nitric oxide contents in rats' pylorus so that bile acid to the stomach might be decreased, obviously with a looser tight pyloric sphincter. Meanwhile, the CGRP in rats' pylorus was negatively associated with the ulcer index, hence CGRP might protect gastric mucosa under stress conditions.

Effects of pyloric local CGRP and NO on bile reflux in rat stomach with stress ulcer

AIM: To investigate the effects of pyloric local CGRP and NO on bile reflux in rat stomach with stress ulcer.

METHODS: Rats stress ulcer model was established by cold water soaking. Sixty-five rats were divided into three groups: normal control group, the stress group and the antagonist group. The gastric ulcer index, pH and bile acid of gastric juice were measured before and after stress. The pyloric local CGRP was measured by a radioimmunoassay detection kit. The pyloric local nitric oxide was measured by a biochemic detection kit.

RESULTS: The pyloric local nitric oxide reached the climax at 1 hour after stress. The bile acid and pH of gastric juice reached the maximum at 2 hours after stress. The ulcer index did it at 4 hours after stress. But the pyloric local CGRP decreased to the minimum at 4 hours after stress. The bile acid and ulcer index in L-NAME group decreased significantly compared with those of h-CGRP8-37 group. However, the bile acid of hCGRP837 group was less than that of antagonist control group, which was weaker than that in L-NAME group.

CONCLUSION: There is a correlation between the pyloric local NO and bile acid in the stomach. L-NAME might reduce the pyloric local NO so that the bile acid in the stomach could be decreased obviously with less slacker pyloric sphincter. Meanwhile, the pyloric local CGRP has the negative correlation with ulcer index, for CGRP might protect gastric mucosa with stress ulcer.

Effects of transections of cervical sympathetic trunk on gastric mucosal blood flow and ET-1 in water immersion restrain rats

AIM: To investigate the effect of transections of the cervical sympathetic trunk (TCST) on the gastric mucosal blood flow (GMBF) in water immersion restrain rats.

METHODS: A total of 30 male Sprague-Dawleys rats were randomly allocated into three groups: control group (Group I), water immersion restrain group (Group II) and TCST followed by water immersion restrain (Group III). Superior cervical ganglion were exposed and splited, but not cut off in Group I and Group II. In Group III, we cut off and ligated the cervical sympathetic nerve trunk below 3 mm of superior cervical ganglion. Then the rats of Group II and Group III were vertically immersed into water (23±1 ℃). Six hours later, GMBF were measured by laser Doppler blood stream meter. And we evaluated the gastric mucosal ulcer index (UI) according to Guth score.

RESULTS: There was mucosal bleeding and erosion in Group II, Group III was obviously relived as compared with Group II. The GMBF was 68.9±12.7; 130.0±14.5 (PU) in Group II and Group III respectively, while the UI was 50.1±12.3; 26.6±9.4.(P<0.01). The GMBF and UI was significant negative correlation (= -0.847, P<0.01). ET-1 in plasma and gastric mucosa in Group II were higher than those in Group I. ET-1 in plasma in Group III were higher than that in Group I, while they were lower than that in Group II. ET-1 in plasma had a moderate negative-correlation with GMBF.

CONCLUSION: Increased the GMBF due to TCST may contribute to attenuation in the lesion of gastric muscoa in water immersion restrain rats, and it may have something to do with ET-1 in plasma and gastric mucosa.