Involvement of the xanthine-xanthine oxidase system and neutrophils in the development of acute gastric mucosal lesions in rats with water immersion restraint stress

Neurons and Astrocytes in Ventrolateral Periaqueductal Gray Contribute to Restraint Water Immersion Stress-Induced Gastric Mucosal Damage via the ERK1/2 Signaling Pathway

BACKGROUND

The restraint water immersion stress (RWIS) model includes both psychological and physical stimulation, which may lead to gastrointestinal disorders and cause gastric mucosal damage. The ventrolateral periaqueductal gray (VLPAG) contributes to gastrointestinal function, but whether it is involved in RWIS-induced gastric mucosal damage has not yet been reported.

METHODS

The expression of glial fibrillary acidic protein, neuronal c-Fos, and phosphorylated extracellular signal regulated kinase 1/2 in the VLPAG after RWIS was assessed using western blotting and immunocytochemical staining methods. Lateral ventricle injection of astrocytic toxin L-a-aminoadipate and treatment with extracellular signal-regulated kinase (ERK)1/2 signaling pathway inhibitor PD98059 were further used to study protein expression and distribution in the VLPAG after RWIS.

RESULTS

The expression of c-Fos, glial fibrillary acidic protein, and phosphorylated extracellular signal regulated kinase 1/2 in the VLPAG significantly increased following RWIS and peaked at 1 hour after RWIS. Lateral ventricle injection of the astrocytic toxin L-a-aminoadipate significantly alleviated gastric mucosal injury and decreased the activation of neurons and astrocytes. Treatment with the ERK1/2 signaling pathway inhibitor PD98059 obviously suppressed gastric mucosal damage as well as the RWIS-induced activation of neurons and astrocytes in the VLPAG.

CONCLUSIONS

These results suggested that activation of VLPAG neurons and astrocytes induced by RWIS through the ERK1/2 signaling pathway may play a critical role in RWIS-induced gastric mucosa damage.

Sphaeranthus senegalensis DC: Evaluation of chemical constituents, oral safety, gastroprotective activity, and mechanism of action of its hydroethanolic extract

ETHNOPHARMACOLOGICAL RELEVANCE

Sphaeranthus senegalensis DC is a seasonal herb with a spicy smell that grows wild in wet grounds of tropical Africa and Asia. The plant is used in folk medicine for the treatment of various diseases; that includes its use to treat gastric ulcers.

AIM OF THE STUDY

This study aimed to investigate the chemical constituents of the hydroethanolic extract of Sphaeranthus senegalensis DC and evaluate its oral safety, gastroprotective activity, and mechanisms of action using laboratory models in rats and mice.

MATERIALS AND METHODS

Hydroethanolic extract (70%) of the powdered whole dried material was prepared, and chemical constituents of the resultant extract (denoted HESs) standardized using the high-performance liquid chromatography (HPLC) method. The safety profile of HESs was assessed using 2000 mg/kg, oral (p.o.) for Hippocratic screening in mice, and 800 mg/kg, p.o. for 28 days subchronic toxicity assay in rats. The gastroprotective effect of HESs (25, 100, and 400 mg/kg, p.o.) was investigated using acidified ethanol, piroxicam, water immobilization stress, and acetic acid-induced ulcer models. The gastroprotective mechanisms of HESs were evaluated using its effect on gastric mucus protection, nitric oxide modulation, gastric juice secretory parameters, catalase and myeloperoxidase activities. Histological analysis of the stomach tissues was also carried out.

RESULTS

The HPLC analysis indicated the presence of 25.94% phenolics (gallic acid, caffeic acid, and ferulic acid) and 14.53% flavonoids (rutin, morin, luteolin, quercetin, and apigenin). Hippocratic screening and the 28 days subchronic study indicated that HESs is generally safe. Result shows that oral administration of HESs (25, 100 and 400 mg/kg) alleviated the severity of the gastric ulcers induced by acidified ethanol by 35.65% (p < 0.05), 48.70% (p < 0.05) and 78.02% (p < 0.001) respectively; exhibited gastroprotective effect against the gastric lesions induced by piroxicam by 37.97% (p < 0.05), 53.27% (p < 0.05) and 76.23% (p < 0.001) respectively; and decreased the severity of the water immobilization stress-induced gastric ulcers by 32.43% (p < 0.05), 55.26% (p < 0.01) and 74.05% (p < 0.001) respectively, when compared to the vehicle control group. The mechanisms of action assays indicated that the gastroprotective activity was mediated mainly through gastroprotection, antisecretory, and antioxidant activities. Histological analysis showed it inhibited epithelial cell loss, vascular damage, and leucocyte infiltration.

CONCLUSION

HESs contains useful phytochemicals, is safe, and exhibited significant gastroprotective action. The results provided justification for its claim in the treatment of gastric ulcers and its evaluation for potential application as a gastroprotective agent.

Role of nucleotide binding oligomerization domain-like receptor protein 3 inflammasome in stress-induced gastric injury

BACKGROUND AND AIM

The inflammasomes promote pro-caspase-1 cleavage, leading to processing of pro-interleukin (IL)-1β into its mature form. We investigated the role of the IL-1β and nucleotide binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome in gastric injury in mice receiving water-immersion restraint stress (WIRS), focusing on the cyclooxygenase (COX)-2/prostaglandin (PG) E₂ axis.

METHODS

To induce gastric injury, the mice were placed in a restraint cage and immersed in the water bath to the level of the xiphoid process. Protein levels of mature caspase-1 and IL-1β were assessed by western blotting.

RESULTS

Water-immersion restraint stress induced gastric injury with increase in IL-1β expression by activation of NLRP3 inflammasome. Exogenous IL-1β attenuated the injury, whereas anti-IL-1β neutralizing antibody and IL-1β receptor antibody aggravated it. NLRP3^-/- and caspase-1^-/- mice enhanced the injury with reducing of mature IL-1β, and this aggravation was reduced by exogenous IL-1β supplementation. Toll-like receptor 4^-/- mice were hyporesponsive to WIRS in terms of mature IL-1β production. Rabeprazole attenuated the injury with preventing inflammasome activation. WIRS injured the stomach with promotion of COX-2 mRNA and PGE₂ production, and exogenous IL-1β enhanced these molecules, while IL-1β immunoneutralization exerted opposite effect. PGE₂ supplementation abolished the hypersensitivity in NLRP3^-/- and caspase-1^-/- mice through negative regulation of inflammatory cytokines.

CONCLUSION

These results suggest that NLRP3 inflammasome-derived IL-1β plays a protective role in stress-induced gastric injury via activation of the COX-2/PGE₂ axis. Toll-like receptor 4 signaling and gastric acid may be involved in NLRP3 inflammasome activation.

Nervous mechanisms of restraint water-immersion stress-induced gastric mucosal lesion

Stress-induced gastric mucosal lesion (SGML) is one of the most common visceral complications after trauma. Exploring the nervous mechanisms of SGML has become a research hotspot. Restraint water-immersion stress (RWIS) can induce GML and has been widely used to elucidate the nervous mechanisms of SGML. It is believed that RWIS-induced GML is mainly caused by the enhanced activity of vagal parasympathetic nerves. Many central nuclei, such as the dorsal motor nucleus of the vagus, nucleus of the solitary tract, supraoptic nucleus and paraventricular nucleus of the hypothalamus, mediodorsal nucleus of the thalamus, central nucleus of the amygdala and medial prefrontal cortex, are involved in the formation of SGML in varying degrees. Neurotransmitters/neuromodulators, such as nitric oxide, hydrogen sulfide, vasoactive intestinal peptide, calcitonin gene-related peptide, substance P, enkephalin, 5-hydroxytryptamine, acetylcholine, catecholamine, glutamate, γ-aminobutyric acid, oxytocin and arginine vasopressin, can participate in the regulation of stress. However, inconsistent and even contradictory results have been obtained regarding the actual roles of each nucleus in the nervous mechanism of RWIS-induced GML, such as the involvement of different nuclei with the time of RWIS, the different levels of involvement of the sub-regions of the same nucleus, and the diverse signalling molecules, remain to be further elucidated.

Can the gastric healing effect of Eugenia punicifolia be the same in male and female rats?

ETHNOPHARMACOLOGICAL RELEVANCE

Eugenia punicifolia (Kunth) DC. (Myrtaceae), an Amazonian medicinal plant known as "pedra-ume-caá," is popularly used as a natural remedy for inflammation, wounds, infections, diabetes, fever, and flu. Its anti-inflammatory, antinociceptive, and gastroprotective effects have already been characterized. We evaluated the gastric healing effect of the hydroalcoholic extract of the leaves of E. punicifolia (HEEP) in male and female Wistar rats against nonsteroidal anti-inflammatory drugs (NSAIDs) and ethanol.

MATERIALS AND METHODS

The healing effect of HEEP on the gastric mucosa of adult male and female Wistar rats was measured after the chronic application of aggressive factors such as NSAIDs or 80% ethanol. Male, and intact and ovariectomized (OVZ) female rats were treated with HEEP for two days (NSAIDs) or one, two, four, and six days (80% ethanol). The stomachs were analyzed macroscopically for ulcerative lesions (mm²), and the healing process was measured using biochemical analysis with anti-inflammatory and antioxidant parameters.

RESULTS

Macroscopic evaluation of the gastric mucosa showed that gastric lesions induced by NSAIDs were significantly healed (66%) and pro-inflammatory interleukin 5 cytokine level was decreased after two-day oral treatment with HEEP compared with those in the negative control group (p < 0.05). However, the gastric lesions induced by NSAIDs did not heal in HEEP-treated female rats (p > 0.05). In addition, four-day treatment with HEEP significantly healed the gastric lesions induced by ethanol in male and female rats (63% and 78%, respectively) compared to those of the negative control group (p < 0.05). However, the OVZ group required six days of HEEP treatment to heal gastric ulcers (67% compared to the control group). HEEP exerts the healing effect against ethanol by significantly reducing neutrophil infiltration into the gastric mucosa by decreasing myeloperoxidase activity in male and OVZ rats after four and six days of treatment, respectively (p < 0.05). Four-day treatment with HEEP also increased the level of a non-enzymatic antioxidant, reduced glutathione in intact females compared to that of the negative control group (p < 0.05).

CONCLUSION

These findings indicated that HEEP was effective in promoting the healing of gastric ulcers induced by NSAIDs or ethanol. The gastric healing effects of this extract could be affected by female sex hormone interference; in future, comprehensive studies should be performed by considering sex differences.

Dietary red raspberries attenuate dextran sulfate sodium-induced acute colitis

Persistent intestinal inflammation severely impairs intestinal integrity resulting in inflammatory bowel disease. Red raspberries (RB) are a rich source of bioactive compounds; their beneficial effect on the colitis protection was evaluated in the current study using a dextran sulfate sodium (DSS)-induced acute colitis mouse model. Six-week-old mice were fed a standard rodent research diet supplemented with RB (0 or 5% w/w, n=20 each group) for 6 weeks. At the 4th week of dietary treatment, approximately half of mice in each dietary group (n=12 each group) were subjected to 2.5% DSS induction for 6 days, followed by 6 days of recovery, to induce colitis. RB supplementation decreased body weight loss (P≤.01), disease activity index (P≤.01), and colon shortening (P≤.05) in DSS-treated mice. In addition, RB supplementation protected the colonic structure (P≤.01), associated with suppressed NF-κB signaling and reduced expression of inflammatory interleukin (IL)-1β, IL-6, IL-17, cyclooxegenase-2, and tumor necrosis factor-α in DSS-treated mice. RB supplementation reduced neutrophil infiltration, monocyte chemoattractant protein-1 mRNA expression, and xanthine oxidase content, but enhanced catalase content in DSS-treated mice. Consistently, RB supplementation reduced pore forming tight junction protein claudin-2, increased barrier strengthening claudin-3, zonula occluden-1 protein content and mucin (MUC)-2 mRNA level, and activated AMP-activated protein kinase (AMPK) in DSS-treated mice. In conclusion, dietary RB protected against inflammation and colitis symptoms induced by DSS, providing a promising dietary approach for the management of colitis.

Anxiolytic, antidepressant, and antistress activities of the aqueous extract of Cinnamomum tamala Nees and Eberm in rats

OBJECTIVE

The current study was designed to explore anxiolytic, antidepressant, and antistress actions of Cinnamomum tamala (CT) leaves (aqueous extract) in rats.

MATERIALS AND METHODS

Behavioral procedures of anxiety, depression, and stress were assessed in rats. CT (100, 200, and 400 mg/kg) was given once a daily for 7 days via oral route and the efficacy was matched by those elicited by lorazepam (1 mg/kg, p.o.), imipramine (10 mg/kg, p.o.), and Withania somnifera (100 mg/kg, p.o.) for anxiolytic, antidepressant, and antistress studies, respectively. Standard drugs were given 1 time, 30 min preceding the behavioral trials.

RESULTS

One-way analysis of variance followed by Newman-Keuls multiple comparison test was employed to analyze the results. P < 0.05 was considered statistically significant as compared to control. CT at 400 mg/kg produced an antianxiety effect equivalent to lorazepam, in the elevated plus maze, open field, and social interaction tests among selected doses of the CT. CT at 400 mg/kg also induced an antidepressant activity similar to imipramine, in the behavioral despair, learned helplessness test, and tail suspension among selected doses of the CT. Moreover, CT at 400 mg/kg produced a significant antistress effect comparable to W. somnifera in water immersion-restraint stress by decreasing ulcer index, adrenal gland weight, and by normalizing the plasma levels of corticosterone, glucose, cholesterol, and triglyceride levels when related to stress control.

CONCLUSION

The study shows that among the different CT doses, CT at 400 mg/kg possesses significant anxiolytic, antidepressant, and anti-stress effects and has therapeutic beneficial for the management of psychological ailments.

Effect of water-immersion restraint stress on tryptophan catabolism through the kynurenine pathway in rat tissues

The aim of this study was to clarify the effect of water-immersion restraint stress (WIRS) on tryptophan (Trp) catabolism through the kynurenine (Kyn) pathway in rat tissues. The tissues of rats subjected to 6 h of WIRS (+WIRS) had increased tryptophan 2,3-dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO) activities and increased TDO and IDO1 (one of two IDO isozymes in mammals) mRNA expression levels, with decreased Trp and increased Kyn contents in the liver. +WIRS rats had unchanged TDO and IDO activities in the kidney, decreased TDO activity and unchanged IDO activity in the brain, and unchanged IDO activity in the lung and spleen, with increased Kyn content in all of these tissues. Pretreatment of stressed rats with RU486, a glucocorticoid antagonist, attenuated the increased TOD activity, but not the increased IDO activity, with partial recoveries of the decreased Trp and increased Kyn contents in the liver. These results indicate that WIRS enhances hepatic Trp catabolism by inducing both IDO1 and TDO in rats.

Effect of Dietary Vitamin E Supplementation on Liver Oxidative Damage in Rats with Water-Immersion Restraint Stress

We examined how dietary supplementation of vitamin E protects against liver oxidative damage in rats with water-immersion restraint stress (WIRS). Before WIRS exposure, rats received a normal diet (ND) or vitamin E-supplemented diet (VESD) (500 IU α-tocopherol/kg diet) at a mean dose of 15 g/animal/d for 4 wk. The two diet groups had serum transaminases and lactate dehydrogenase activities and adrenocorticotropic hormone, corticosterone, and glucose levels to a similar extent. VESD-fed rats had higher liver α-tocopherol concentrations and lower liver ascorbic acid, total coenzyme Q9 (CoQ9), reduced CoQ9, reduced CoQ10, and lipid peroxide (LPO) concentrations than ND-fed rats. When the two diet groups were exposed to 6 h of WIRS, the serum liver cell damage index enzyme activities increased more greatly in ND-fed rats than in VESD-fed rats but the serum stress marker levels increased to a similar extent. The WIRS exposure caused no change in liver LPO concentration with the further increase in liver α-tocopherol concentration in VESD-fed rats but increased liver LPO concentration without changing liver α-tocopherol concentration in ND-fed rats. Upon the WIRS exposure, liver reduced glutathione concentration decreased with the further decrease in liver ascorbic acid concentration in VESD-fed rats and those concentrations decreased in ND-fed rats. The WIRS exposure recovered the decreased liver total CoQ9 and reduced CoQ9 concentrations in VESD-fed rats but decreased liver total CoQ9, reduced CoQ9, and reduced CoQ10 concentrations in ND-fed rats. These results indicate that dietary vitamin E supplementation protects against liver oxidative damage without affecting the stress response in rats with WIRS.

Ginsenoside Rg3 attenuated omethoate-induced lung injury in rats

Organophosphorus exposure affects different organs such as the lung, gastrointestinal tract, liver, and brain. The present experiment aimed to evaluate the effect of ginsenoside Rg3 on lung injury induced by acute omethoate poisoning. Rats were administered with omethoate subcutaneously at a single dose of 60 mg/kg, followed by ginsenoside Rg3 (5, 10, or 20 mg/kg) treatment. Histopathological examination of the lung was performed at 24 h after the omethoate exposure. The antioxidative parameters in the lung were also assayed. Moreover, the activities of acetylcholinesterase, myeloperoxidase, and the content of tumor necrosis factor α (TNF-α) in the lung were determined. The results showed that ginsenoside Rg3 attenuated omethoate-induced lung injury. Ginsenoside Rg3 increased the level of glutathione in the lung ( p < 0.05 or p < 0.01). The altered activities of superoxide dismutase and catalase in the lung were also ameliorated by ginsenoside Rg3 treatment ( p < 0.05 or p < 0.01). Ginsenoside Rg3 caused significant reductions in the contents of malondialdehyde, TNF-α, and the activity of myeloperoxidase ( p < 0.05 or p < 0.01). The present study demonstrated that ginsenoside Rg3 had a protective effect against omethoate-induced lung injury in rats, and the mechanisms were related to its antioxidant potential and anti-inflammatory effect.

Morin protects gastric mucosa from nonsteroidal anti-inflammatory drug, indomethacin induced inflammatory damage and apoptosis by modulating NF-κB pathway

BACKGROUND

Deregulation in prostaglandin (PG) biosynthesis, severe oxidative stress, inflammation and apoptosis contribute to the pathogenesis of nonsteroidal anti-inflammatory drug (NSAID)-induced gastropathy. Unfortunately, most of the prescribed anti-ulcer drugs generate various side effects. In this scenario, we could consider morin as a safe herbal potential agent against IND-gastropathy and rationalize its action systematically.

METHODS

Rats were pretreated with morin for 30 min followed by IND (48 mgkg(-1)) administration for 4 h. The anti-ulcerogenic nature of morin was assessed by morphological and histological analysis. Its effects on the inflammatory (MPO, cytokines, adhesion molecules), ulcer-healing (COXs, PGE(2)), and signaling parameters (NF-κB and apoptotic signaling) were assessed by biochemical, RP-HPLC, immunoblots, IHC, RT-PCR, and ELISA at the time points of their maximal changes due to IND administration.

RESULTS

IND induced NF-κB and apoptotic signaling in rat's gastric mucosa. These increased proinflammatory responses, but reduced the antioxidant enzymes and other protective factors. Morin reversed all the adverse effects to prevent IND-induced gastric ulceration in a PGE2 independent manner. Also, it did not affect the absorption and/or primary pharmacological activity of IND.

CONCLUSIONS

The gastroprotective action of morin is primarily attributed to its potent antioxidant nature that also helps in controlling several IND-induced inflammatory responses.

GENERAL SIGNIFICANCE

For the first time, the study reveals a mechanistic basis of morin mediated protective action against IND-induced gastropathy. As morin is a naturally abundant safe antioxidant, future detailed pharmacokinetic and pharmacodynamic studies are expected to establish it as a gastroprotective agent.

Efficacy and safety of herbal medicines in treating gastric ulcer: A review

Gastric ulcer is a common disorder of the digestive system. Current therapeutic regimens largely rely on Western medicine. However, numerous studies have demonstrated that herbal medicines can effectively treat gastric ulcer in humans and various animal models via divergent mechanisms. This review updates the efficacy and safety of herbal medicines in treating gastric ulcer, and the mechanisms of their action in humans and animal models. Studies have demonstrated that the efficacy of herbal medicines is comparable or superior to that of drugs such as omeprazole or cimetidine in humans and animal models, and herbal medicines display fewer adverse effects. The mechanisms by which herbal medicines benefit gastric ulcer include stimulation of mucous cell proliferation, anti-oxidation, and inhibition of gastric acid secretion and H(+)/K(+)-ATPase activity. Some herbal medicines also exhibit antimicrobial properties. Utilization of herbal medicines could be a valuable alternative to treat gastric ulcer in humans effectively, with few adverse effects.

The protective effect of apelin against water-immersion and restraint stress-induced gastric damage

The aim of the present study was to investigate the gastroprotective effect of apelin on water-immersion and restraint stress (WIRS)-induced gastric lesions. Male Wistar rats were divided into four groups: control, WIRS, F13A + WIRS and F13A. APJ receptor antagonist F13A was administered to rats to determine the influence of apelin on stress-induced gastric injury. WIRS administered for 6 h resulted in the development of gastric mucosal lesions accompanied by a significant increase in plasma corticosterone. WIRS increased the concentration of 4-hydroxynonenol (4-HNE) + malondialdehyde (MDA) and the expression of apelin and hypoxia inducible factor-1α (HIF-1α) in gastric mucosa. In addition, WIRS reduced the mucosal blood flow and gastric prostaglandin E(2) (PGE(2)) concentration. Plasma corticosterone, which was increased due to stress, was significantly decreased in the F13A + WIRS group. Gastric lesions and the 4-HNE + MDA concentration were also higher in the F13A + WIRS compared to the WIRS group. We conclude that apelin has a gastroprotective effect against stress-induced lesions possibly by reducing lipid peroxidation in gastric mucosa.

Gastroprotective Effects of Glutinous Rice Extract against Ethanol-, Indomethacin-, and Stress-induced Ulcers in Rats

This study was designed to evaluate the efficacy of an orally administered aqueous extract of glutinous rice (GRE) to protect against acute gastric mucosal lesions induced by ethanol, indomethacin, and water immersion restraint stress in rats and to characterize the active substances responsible for the protection. GRE was shown to dose-dependently prevent the gastric lesions induced by the above ulcerogenic treatments at doses of 30 to 300 mg/kg. GRE treatment increased the gastric mucin content and partially blocked the ethanol-induced depletion of the gastric mucus layer. Also, it increased the nonprotein sulfhydryl concentration in the gastric mucosa. The gastroprotective action of GRE was markedly enhanced by co-treatment with 4-8 mg/kg tea extracts. The activity of GRE was completely lost by heat treatment at 80℃ for 3 min or treatment with 0.01% pepsin at 37℃ for 1 h. Protein extraction studies indicated that prolamins are involved in the gastroprotective activity of GRE. Our results suggest that glutinous rice proteins are useful for the prevention and treatment of gastritis and peptic ulcer.

Protective Effect of Repeatedly Preadministered Brazilian Propolis Ethanol Extract against Stress-Induced Gastric Mucosal Lesions in Rats

The present study was conducted to clarify the protective effect of Brazilian propolis ethanol extract (BPEE) against stress-induced gastric mucosal lesions in rats. The protective effect of BPEE against gastric mucosal lesions in male Wistar rats exposed to water-immersion restraint stress (WIRS) for 6 h was compared between its repeated preadministration (50 mg/kg/day, 7 days) and its single preadministration (50 mg/kg). The repeated BPEE preadministration attenuated WIRS-induced gastric mucosal lesions and gastric mucosal oxidative stress more largely than the single BPEE preadministration. In addition, the repeated BPEE preadministration attenuated neutrophil infiltration in the gastric mucosa of rats exposed to WIRS. The protective effect of the repeated preadministration of BPEE against WIRS-induced gastric mucosal lesions was similar to that of a single preadministration of vitamin E (250 mg/kg) in terms of the extent and manner of protection. From these findings, it is concluded that BPEE preadministered in a repeated manner protects against gastric mucosal lesions in rats exposed to WIRS more effectively than BPEE preadministered in a single manner possibly through its antioxidant and anti-inflammatory actions.

Nonsteroidal anti-inflammatory drug induces proinflammatory damage in gastric mucosa through NF-κB activation and neutrophil infiltration: anti-inflammatory role of heme oxygenase-1 against nonsteroidal anti-inflammatory drug

Nonsteroidal anti-inflammatory drug (NSAID)-induced mitochondrial oxidative stress (MOS) is an important prostaglandin (PG)-independent pathway of the induction of gastric mucosal injury. However, the molecular mechanism behind MOS-mediated gastric pathology is still obscure. In various pathological conditions of tissue injury oxidative stress is often linked with inflammation. Here we report that MOS induced by indomethacin (an NSAID) induces gastric mucosal inflammation leading to proinflammatory damage. Indomethacin, time dependently stimulated the expression of proinflammatory molecules such as intercellular adhesion molecule 1(ICAM-1), vascular cell adhesion molecule 1(VCAM-1), interleukin1β (IL-1β), and monocyte chemotactic protein-1 (MCP-1) in gastric mucosa in parallel with the increase of neutrophil infiltration and injury of gastric mucosa in rat. Western immunoblotting and confocal microscopic studies revealed that indomethacin induced nuclear translocation of nuclear factor kappa-B (NF-κB) in gastric mucosal cells, which resulted in proinflammatory signaling. The prevention of MOS by antioxidant tryptamine-gallic acid hybrid (SEGA) inhibited indomethacin-induced expression of ICAM-1, VCAM-1, IL-1β, and MCP-1. SEGA also prevented indomethacin-induced NF-κB activation and neutrophil infiltration as documented by chromatin immunoprecipitation studies and neutrophil migration assay, respectively. Heme oxygenase-1 (HO-1), a cytoprotective enzyme associated with tissue repair mechanisms is stimulated in response to oxidative stress. We have investigated the role of HO-1 against MOS and MOS-mediated inflammation in recovering from gastropathy. Indomethacin stimulated the expression of HO-1 and indomethacin-stimulated HO-1 expression was reduced by SEGA, an antioxidant, which could prevent MOS. Thus, the data suggested that the induction of HO-1 was a protective response against MOS developed by indomethacin. Moreover, the induction of HO-1 by cobalt protoporphyrin inhibited inflammation and chemical silencing of HO-1 by zinc protoporphyrin aggravated the inflammation by indomethacin. Thus, NSAID by promoting MOS-induced proinflammatory response damaged gastric mucosa and HO-1 protected NSAID-induced gastric mucosal damage by preventing NF-κB activation and proinflammatory activity.

Development of oxidative stress and cell damage in the liver of rats with water-immersion restraint stress

We examined how oxidative stress and cell damage develop in the liver of rats subjected to water-immersion stress (WIRS). In rats subjected to WIRS for 1.5, 3 or 6 h, serum alanine aminotransferase and aspartate aminotransferase activities increased time-dependently. In the liver tissue, vacuolization and apoptosis occurred at 1.5 h of WIRS and vacuolization further developed without further appearance of apoptosis at 3 h or 6 h. Serum lipid peroxide (LPO) and NOx (nitrite/nitrate) concentrations increased at 3 h of WIRS and these increases were enhanced at 6 h. In liver tissue, increases in LPO and NOx concentrations and myeloperoxidase activity and decreases in ascorbic acid and reduced glutathione concentrations and superoxide dismutase activity occurred at 3 h of WIRS and these changes were enhanced at 6 h, although vitamin E concentration and xanthine oxidase activity were unchanged. These results indicate that oxidative stress in the liver of rats with WIRS develops after the appearance of cell damage in the tissue, and suggests that oxidative stress is caused through disruption of the antioxidant defense system and increases in NO generation and neutrophil infiltration in the liver, which may contribute to the progression of cell damage in the tissue.

Protective effects of Ankaferd blood stopper on aspirin-induced oxidative mucosal damage in a rat model of gastric injury

The exposure of gastric mucosa to damaging factors, such as ethanol and some therapeutic drugs, produces pathological changes: inflammatory process, hemorrhagic erosions and even acute ulcers. Ankaferd blood stopper (ABS) comprises a standardized mixture of five different plant extracts. The purpose of our present investigations is to explain the participation of reactive oxygen species in acute gastric mucosal damage by acetylsalicylic acid (ASA) and the effects of new hemostatic agent ABS. Experiments were carried out on 23 male Wistar rats. To assess gastric mucosal damage, biochemical and histopathological data were used. The colorimetric assays were used to determine the malondialdehyde (MDA) and superoxide dismutase (SOD) activity. The level of myeloperoxidase (MPO) activity, the level of nitric oxide (NO) and the proinflammatory cytokine tumor necrosis factor-α (TNF-α) were measured by enzyme-linked immunosorbent assay technique. We demonstrated that the biological effects of ROS were estimated by measuring the tissue and plasma levels of MDA, the products of lipid peroxidation, as well as the activity of SOD and the scavenger of ROS produced by ASA in the experiment group. Moreover, it was found that MPO activity as well as NO and TNF-α levels also demonstrated significant improvement by ABS treatment. The pathogenesis of experimental ASA-induced mucosal damage in rat stomach includes the generation of ROS that seems to play an important role, due to the generation of lipid peroxides, accompanied by the impairment of antioxidative enzyme activity of cells. ABS appeared to attenuate the oxidative and inflammatory changes caused by ASA-induced gastric mucosal damage in rats.

Disruption of non-enzymatic antioxidant defense systems in the brain of rats with water-immersion restraint stress

We examined whether non-enzymatic antioxidant defense systems are disrupted in the brain of rats with water-immersion restraint stress. When rats were exposed to water-immersion restraint stress for 1.5, 3 or 6 h, the brain had decreased ascorbic acid and reduced glutathione contents and increased lipid peroxide and nitric oxide metabolites contents at 3 h and showed further changes in these components with a reduction of vitamin E content at 6 h. Increased serum levels of stress markers were found at 1.5, 3 or 6 h of WIRS. Oral pre-administration of L-ascorbic acid (1.5 mmol/kg) or vitamin E (0.5 mmol/kg) to rats with 6 h of water-immersion restraint stress attenuated the increases in lipid peroxide and nitric oxide metabolites contents and the decrease in vitamin E content in the brain. Pre-administered L-ascorbic acid attenuated the decreases in brain ascorbic acid and reduced glutathione contents at 6 h of water-immersion restraint stress, while pre-administered vitamin E enhanced the decreases in those contents. Pre-administered L-ascorbic acid or vitamin E did not affect the increased serum levels of stress markers in rats with 6 h of water-immersion restraint stress. These results indicate that water-immersion restraint stress causes disruption of non-enzymatic antioxidant defense systems through enhanced lipid peroxidation and nitric oxide generation in the brain of rats with water-immersion restraint stress.

Palm vitamin E reduces catecholamines, xanthine oxidase activity and gastric lesions in rats exposed to water-immersion restraint stress

Background

This study examined the effects of Palm vitamin E (PVE) and α-tocopherol (α-TF) supplementations on adrenalin, noradrenalin, xanthine oxidase plus dehydrogenase (XO + XD) activities and gastric lesions in rats exposed to water-immersion restraint stress (WIRS).

Methods

Sixty male Sprague–Dawley rats (200-250 g) were randomly divided into three equal sized groups. The control group was given a normal diet, while the treated groups received the same diet with oral supplementation of PVE or α-TF at 60 mg/kg body weight. After the treatment period of 28 days, each group was further subdivided into two groups with 10 rats without exposing them to stress and the other 10 rats were subjected to WIRS for 3.5 hours. Blood samples were taken to measure the adrenalin and noradrenalin levels. The rats were then sacrificed following which the stomach was excised and opened along the greater curvature and examined for lesions and XO + XD activities.

Results

The rats exposed to WIRS had lesions in their stomach mucosa. Our findings showed that dietary supplementations of PVE and α-TF were able to reduce gastric lesions significantly in comparison to the stressed control group. WIRS increased plasma adrenalin and noradrenalin significantly. PVE and α-TF treatments reduced these parameters significantly compared to the stressed control.

Conclusions

Supplementations with either PVE or α-TF reduce the formation of gastric lesions. Their protective effect was related to their abilities to inhibit stress induced elevation of adrenalin and noradrenalin levels as well as through reduction in xanthine oxidase and dehydrogenase activities.

The protective of hydrogen on stress-induced gastric ulceration

Stress ulceration frequently occurs as a result of major stressful events and hydroxyl radical (⋅OH) is one of the major causative factors for it. Recently, it has been proved that hydrogen, a potent selectively ⋅OH scavenger, can effectively protect animals against ROS-induced tissue damage. In like manner, we hypothesize that hydrogen may have a protective effect against stress ulceration. Gastric ulceration was induced by the method of cold restraint stress. Rats in the hydrogen treatment group received hydrogen-rich saline (10 mL/kg body weight) 5 min before the stress. At 6h post-stress, gastric corpus mucosa was harvested for the measurement of malondialdehyde, protein carbonyl, 8-hydroxy-desoxyguanosine, glutathione, superoxide dismutase, myeloperoxidase, TNF-α, IL-1β and cytokine-induced neutrophils chemoattractant-1. In addition, western blotting was used to determine the expression of p38 MAPK, P-p38 MAPK, P-JNk, JNK, Bcl-xl, Bax and cleaved caspase-3. Nuclear translocation of NF-κB was assessed by electrophoretic mobility shift assay. Gastric mucosa structure and mucosal epithelial cells apoptosis were measured at 12h post-stress. Our present study showed that hydrogen treatment lessened the stress-induced lipid peroxidation, protein carbonyl and DNA oxidant and improved tissue antioxidant potential. In addition, hydrogen mitigated inflammatory response and neutrophils infiltration with suppressing the activity of P-p38 MAPK, P-JNk and NF-κB. Importantly, hydrogen ameliorated gastric mucosa damage with preventing cell apoptosis. Furthermore, the up-regulation of cleaved caspase-3, Bax and down-regulation of Bcl-xl expression were blocked by hydrogen treatment. In conclusion, hydrogen treatment effectively ameliorated stress-associated gastric mucosa damage via its anti-oxidant, anti-inflammatory and anti-apoptotic effects.

Molecular mechanism of indomethacin-induced gastropathy

The probable cross talk among large numbers of inflammatory and angiogenic parameters in indomethacin (IND)-induced gastropathy and the associated signaling mechanism were studied in a mouse model. A single dose of IND (18 mg/kg, po) produced robust gastric ulceration in mice without any mortality, which peaked on the third day, but started healing from the fifth day onward. The ulceration was associated with increased myeloperoxidase activity and expression of proinflammatory (TNF-α, adhesion molecules, COX-2) and antiangiogenic (endostatin) parameters. The levels of proangiogenic factors such as COX-1, prostaglandin E, VEGF, and von Willebrand factor VIII were downregulated by IND. Our results revealed that although the maximal and minimal levels of these parameters were attained sequentially at different time points, TNF-α upregulation was the primary event to initiate and induce gastric ulceration. IND also activated NF-κB and all the MAP kinases, but only the inhibitors of TNF-α, NF-κB, and JNK MAP kinase could abrogate the IND-induced damages. Further TNF-α inhibition also reduced the IND-mediated activation of NF-κB and JNK MAP kinase. All this evidence strongly suggests that mitigation of TNF-α may offer a potential solution to IND-mediated gastropathy.

The effects of palm vitamin E on stress hormone levels and gastric lesions in stress-induced rats

INTRODUCTION

This study examines the effects of palm vitamin E (PVE) or α-tocopherol (α-TF) supplementation on adrenocorticotropin hormone (ACTH), corticosterone and gastric lesions in rats exposed to water-immersion restraint stress (WIRS).

MATERIAL AND METHODS

Sixty male Sprague-Dawley rats (200-250 g) were divided into three groups. Group I: 20 rats as a control group were given a normal diet. Group II: 20 rats received oral supplementation of PVE at 60 mg/kg body weight. Group III: 20 rats received oral supplementation of α-TF at 60 mg/kg body weight. After the treatment period of 28 days, each group was further subdivided into two groups: 10 rats not exposed to stress, and the other 10 rats subjected to WIRS for 3.5 h. Blood samples were taken to measure the ACTH and corticosterone levels. The rats were then sacrificed and the stomach excised and opened along the greater curvature and examined for lesions.

RESULTS

Rats exposed to WIRS had lesions in their stomach mucosa. Our findings showed that dietary supplementation of PVE or α-TF was able to reduce gastric lesions significantly in comparison to the stressed controls. The WIRS increased plasma ACTH and corticosterone significantly. Palm vitamin E and α-TF treatments reduced these parameters significantly compared to the stressed controls.

CONCLUSIONS

Supplementation with either PVE or α-TF reduces the formation of gastric lesions, probably by inhibiting the elevation of ACTH and corticosterone levels induced by stress.

Investigation of the effects of the chronic administration of some antihypertensive drugs on enzymatic and non-enzymatic oxidant/antioxidant parameters in rat ovarian tissue

OBJECTIVE

In this study, effects of chronic antihypertensive drug (clonidine, methyldopa, amlodipine, ramipril, and rilmenidine) treatment on antioxidant-oxidant parameters were investigated in rat ovarian tissue.

STUDY DESIGN

Chronic drug administration for 30 days and at the end, biochemical examinations (total glutathione (tGSH), glutathione peroxidase (GPO), glutathione reductase (GR), glutathione s-transferase (GST), superoxide dismutase (SOD), nitric oxide (NO), catalase (CAT), malondialdehyde (MDA), and myeloperoxidase (MPO) analyses) were performed.

RESULTS

The levels of glutathione (GSH) and NO, and the activities of GPO, GR, GST, SOD, and CAT were measured the lowest in ramiprile group. Also in ramiprile group, the level of MDA and the activity of MPO was the highest.

CONCLUSION

We divided the drugs into four groups according to their biochemical side effect potentials in ovarian tissue: (I) Drugs which have no clear negative effect on ovarian tissue: clonidine, rilmenidine; (II) Drugs which have mild negative effect on ovarian tissue: methyldopa; (III) Drugs which have moderate negative effect on ovarian tissue: amlodipine; (IV) Drugs which have severe negative effect on ovarian tissue: ramipril. These data might be useful in the selection of the least toxic antihypertensive drug in pregnant and/or normal females.

Role of the COX-independent pathways in the ulcer-healing action of epigallocatechin gallate

The modulation of the cyclooxygenase-independent pathway by the green tea-derived polyphenol, epigallocatechin gallate (EGCG) during its healing action against indomethacin (IND)-induced stomach ulceration in mice was investigated. On the 3rd day of its administration, IND (18 mg kg(-1)) induced maximum stomach ulceration which was associated with increased myeloperoxidase (MPO) activity (2.1-fold, p < 0.001), and inducible nitric oxide synthase (iNOS) expression (2.5-fold, p < 0.001), along with augmented levels of serum nitrite (1.3-fold, p < 0.001), selectins and cell adhesion molecules (CAMs), as well as reduced endothelial nitric oxide synthase (eNOS) expression (53%, p < 0.001). Treatment with EGCG (2 mg kg(-1)) and omeprazole (3 mg kg(-1)) for 3 days reversed these parameters, and provided excellent (76-77%) ulcer healing.

Ginger extract and polaprezinc exert gastroprotective actions by anti-oxidant and growth factor modulating effects in rats

BACKGROUND AND AIM

Contemporary medications used in the treatment of gastric ulcers involve the use of novel mucosal protective drugs. The present study aimed to investigate the gastroprotective effect of ginger extract and polaprezinc in a rat model of acetic acid-induced gastric ulcer.

METHODS

'Kissing' ulcers were induced in male Sprague-Dawley rats by using 60% acetic acid. Rhizoma Zingiber officinale (ginger) extract (1.5-5 g/kg) or polaprezinc (30 and 60 mg/kg) was orally given to the animals once daily for three consecutive days after ulcer induction. All animals were killed on day 5 by an overdose of ketamine.

RESULTS

Both ginger extract and polaprezinc significantly reduce the gastric ulcer area in a dose-dependent manner, with concomitant attenuation of the elevated activities of xanthine oxidase and myeloperoxidase, as well as malondialdehyde level in the ulcerated mucosa. Nevertheless, only polaprezinc could restore the mucosal glutathione level. Polaprezinc also causes the overexpression of basic fibroblast growth factor, vascular endothelial growth factor and ornithine decarboxylase, whereas ginger extract only increases the expression of the two growth factors in the gastric mucosa. Furthermore, polaprezinc could consistently downregulate the protein expression of tumor necrosis factor (TNF)-α, interleukin-1β, macrophage inflammatory protein-2 and cytokine-induced neutrophil chemoattractant-2α that have been activated in the ulcerated tissues, whereas ginger extract mainly inhibits the expression of the chemokines and to some extent TNF-α.

CONCLUSION

Ginger extract and polaprezinc both show anti-oxidation that consequently alleviates gastric mucosal damage and promotes ulcer healing, which together serve as effective mucosal protective agents.

Vitamin E protects against stress-induced gastric mucosal lesions in rats more effectively than vitamin C

In this study, we examined the protective effects of vitamin E (VE) against gastric mucosal lesions induced by water immersion restraint stress (WIRS) in rats in comparison with that of vitamin C (VC). The gastric mucosa of rats with 6 h of WIRS showed lesions with bleeding, decrease in nonprotein SH, VC, VE, and adherent mucus concentrations and constitutive nitric oxide synthase activity, and increase in lipid peroxide and NOx (nitrite/nitrate) concentrations and myeloperoxidase, xanthine oxidase, and inducible nitric oxide synthase activities. Either VE (0.05 or 0.5 mmol/kg) or VC (0.5 or 1.5 mmol/kg) was orally administered to rats with 6 h of WIRS just before the onset of the stress. Both doses of pre-administered VE prevented gastric mucosal lesion development and attenuated all these changes in gastric mucosal components and enzymes studied, whereas only the higher dose of pre-administered VC suppressed the changes in all parameters studied. These results indicate that orally administered VE protects against WIRS-induced gastric mucosal lesions in rats more effectively than orally administered VC. These results also suggest that the administered VE protects against gastric mucosal lesions in rats with WIRS through its antioxidant and anti-inflammatory actions in the gastric mucosa in the same way as the administered VC.

Protective effect of L-ascorbic acid against oxidative damage in the liver of rats with water-immersion restraint stress

We examined whether L-ascorbic acid (AA) (or reduced ascorbic acid) protects against oxidative damage in the liver of rats subjected to water-immersion stress (WIRS). AA (100, 250 or 500 mg/kg) was orally administered at 0.5 h before the onset of WIRS. Rats with 6 h of WIRS had increased serum corticosterone, glucose, total ascorbic acid (T-AA), AA, lipid peroxide (LPO), and NOx concentrations and alanine aminotransferase and aspartate aminotrasferase activities. The stressed rats had increased hepatic LPO, NOx, and dehydroascorbic acid concentrations and myeloperoxidase activity, decreased hepatic T-AA, AA, reduced glutathione concentrations and superoxide dismutase activity, and unchanged hepatic vitamin E concentration. Pre-administered AA attenuated the stress-induced changes in serum LPO and NOx concentrations and alanine aminotransferase and aspartate aminotrasferase activities and hepatic LPO, NOx, and T-AA, AA, dehydroascorbic acid, and reduced glutathione concentrations and myeloperoxidase and superoxide dismutase activities dose-dependently. Pre-administered AA did not affect the stress-induced changes in serum corticosterone and glucose concentrations. These results indicate that pre-administered AA protects against oxidative damage in the liver of rats with WIRS possibly by attenuating disruption of the antioxidant defense system and increases in NO generation and neutrophil infiltration in the tissue.

Roles of NADPH oxidase in occurrence of gastric damage and expression of cyclooxygenase-2 during ischemia/reperfusion in rat stomachs

NADPH oxidase is an enzyme that converts molecular oxygen into reactive oxygen species, which cause severe damage in several organs. Cyclooxygenase (COX)-2 is an inducible enzyme that is important in gastric mucosal defense and repair processes. It is unclear whether NADPH oxidase is related to COX expression in the gastric mucosa, so we investigated the correlation. Under urethane anesthesia, a male Sprague Dawley rat stomach was mounted in an ex-vivo chamber, and ischemia/reperfusion (I/R) was performed through a cannula in the femoral vein. I/R significantly increased NADPH oxidase activity, H(2)O(2) production, and myeloperoxidase (MPO) activity. In contrast, ischemia alone clearly enhanced both NADPH oxidase activity and H(2)O(2) production but not MPO activity. Pretreatment with the NADPH oxidase inhibitor diphenylene iodonium (DPI) suppressed I/R-induced mucosal damage. On the other hand, the selective COX-2 inhibitor rofecoxib exhibited a tendency to enhance the severity of gastric damage induced by I/R, although the selective COX-1 inhibitor SC-560 and the nonselective COX inhibitor indomethacin had no effect. I/R also increased the expression of COX-2, and this increase was suppressed by pretreatment with DPI. These findings suggest that the increase in NADPH oxidase activity is involved in the occurrence of gastric mucosal damage induced by I/R and that this enzyme activity may be causally related to the upregulation of COX-2 during I/R.

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.

Beneficial effects of vegetable oils (corn, olive and sunflower oils) and alpha-tocopherol on anti-inflammatory and gastrointestinal profiles of indomethacin in rats

Nonsteroidal anti-inflammatory drugs (NSAIDs) such as indomethacin are widely used in the treatment of inflammation, fever and pain. However, NSAIDs cause gastric damage as a major adverse reaction. In this study, the effects of vegetable oils (corn, olive and sunflower oils) and alpha-tocopherol on anti-inflammatory and gastrointestinal profiles of indomethacin were evaluated in rats. Results showed that indomethacin given with sunflower, corn and olive oils reduced paw edema induced by carrageenan by 79.5%, 74.0% and 60.5%, whereas individual indomethacin and diclofenac reduced paw edema by 56.2% and 50.7%, respectively. Furthermore, it has been found that the vegetable oils possess significant anti-inflammatory effect against paw edema when given alone. These results showed that the vegetable oils have beneficial effects on reduction paw edema induced by carrageenan. Besides, the administration of indomethacin together with the vegetable oils and alpha-tocopherol did not cause a statistically significant gastric damage in rats (P>0.05). However, indomethacin caused statistically significant gastric lesions as compared with untreated rats (P<0.05). Moreover, it was also found that the effects of the vegetable oils and alpha-tocopherol improved the levels of antioxidant defense systems in rat stomach tissues against oxidative damage. These results suggest that indomethacin as well as other NSAIDs do not have any adverse effect on the gastrointestinal tract when they are used together with vegetable oils and vitamin E or as the preparations of the oils.

Protective effect of palm vitamin E and α-tocopherol against gastric lesions induced by water immersion restraint stress in Sprague-Dawley rats

OBJECTIVE

Stress can lead to various changes in the gastrointestinal tract of rats. The present study was designed to compare the effect of palm vitamin E (PVE) and α-tocopherol (α-TF) supplementations on the gastric parameters important in maintaining gastric mucosal integrity in rats exposed to water immersion restraint stress (WRS). These parameters include gastric acidity, plasma gastrin level, gastric prostaglandin E(2) (PGE(2)), and gastric lesions.

MATERIALS AND METHODS

Sixty male Sprague-Dawley rats (200-250 g) were divided into three equal groups: a control group, which received a normal rat diet (RC), and two treatment groups, receiving oral supplementation of either PVE or α-TF at 60 mg/kg body weight for 28 days. Each group was further divided into two groups: the nonstress and stress groups. The stress groups were subjected to 3.5 h of WRS once at the end of the treatment period. Blood samples were then taken to measure the gastrin level, after which the rats were killed. Gastric juice was collected for measurement of gastric acidity and gastric tissue was taken for measurement of gastric mucosal lesions and PGE(2).

RESULTS

Exposure to stress resulted in the production of gastric lesions. PVE and α-TF lowered the lesion indices as compared to the stress control group. Stress reduced gastric acidity but pretreatment with PVE and α-TF prevented this reduction. The gastrin levels in the stress group were lower as compared to that in the nonstress control. However, following treatment with PVE and α-TF, gastrin levels increased and approached the normal level. There was also a significant reduction in the gastric PGE(2) content with stress exposure, but this reduction was blocked with treatment with both PVE and α-TF.

CONCLUSION

In conclusion, WRS leads to a reduction in the gastric acidity, gastrin level, and gastric PGE(2) level and there is increased formation of gastric lesions. Supplementation with either PVE or α-TF reduces the formation of gastric lesions, possibly by blocking the changes in the gastric acidity, gastrin, and gastric PGE(2) induced by stress. No significant difference between PVE and α-TF was observed.

Activation of p38 MAPK by reactive oxygen species is essential in a rat model of stress-induced gastric mucosal injury

Stress ulceration is a common complication in critically ill patients and can result in significant upper gastrointestinal bleeding associated with a high morbidity and mortality. At present, little is known of the molecular mechanisms underlying the incidence of this type of gastric damage. In the present study, we investigated the temporal activation of the redox-sensitive p38 signaling transduction cascade and its roles in a well-defined experimental model of cold immobilization stress-induced gastric ulceration. Exposure of Sprague-Dawley rats to 6 h of cold immobilization stress led to a rapid activation of p38 in the gastric mucosa at as early as 15 min after stress, and this activation was maximal after 1.5 h of stress and still persisted until the end of stress. Selectively blocking p38 by pretreatment with SB 239063, a potent and selective p38 inhibitor, suppressed the stress-promoted TNF-alpha, IL-1beta, and CINC-1 production and then prevented the subsequent neutrophil infiltration, gastric mucosal epithelial necrosis and apoptosis, and the ulcerative lesions formation. Prior administration of the free radical scavengers, tempol and N-acetyl-L-cysteine, abolished the stress induction of p38 activation and the resulting mucosal inflammation and gastric injury. These results demonstrate that reactive oxygen species-mediated p38 activation plays an essential role in the pathogenesis of stress-induced gastric inflammatory damage in the rat model of cold immobilization stress. Our findings suggested that inhibition of p38 activation might be a potential strategy for the prophylaxis and treatment of stress ulceration.

Sustained activation of nuclear factor-kappaB by reactive oxygen species is involved in the pathogenesis of stress-induced gastric damage in rats

OBJECTIVE

Stress ulceration is a common complication in critically ill patients, but the mechanisms involved are poorly understood. In this study we investigated the temporal activation of the redox-sensitive transcription factor nuclear factor-kappaB and its roles in an experimental model of cold immobilization stress-induced gastric mucosal lesions.

DESIGN

Prospective, controlled, and randomized animal study.

SETTING

University research laboratory.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

The rats were subjected to cold immobilization stress for a total of 6 hrs. The temporal profiles of nuclear factor-kappaB activation and expression of tumor necrosis factor-alpha, interleukin-1beta, cytokine-induced neutrophil chemoattractant-1 (CINC-1), intercellular adhesion molecule-1 (ICAM-1), and inducible nitric oxide synthase (iNOS) were determined in the gastric corpus mucosa of stressed rats. To study the roles of nuclear factor-kappaB activation, rats received an intravenous bolus of a specific nuclear factor-kappaB inhibitor Bay 11-7082 (20 mg/kg) 1 hr before stress. For antioxidant administration, rats were treated with intravenous injection of a free radical scavenger pyrrolidine dithiocarbamate (50, 100, and 200 mg/kg) 1 hr before stress.

MEASUREMENTS AND MAIN RESULTS

Exposure of rats to 6 hrs of stress led to a rapid and persistent activation of nuclear factor-kappaB, which was associated with transient degradation of inhibitory protein IkappaBalpha and slower but sustained degradation of IkappaBbeta. Nuclear factor-kappaB activation preceded the induction of tumor necrosis factor-alpha, interleukin-1beta, CINC-1, ICAM-1, and iNOS messenger RNAs, all of which were linearly increased with the duration of stress. Bay 11-7082 selectively blocked the stress-induced nuclear factor-kappaB activation and up-regulation of tumor necrosis factor-alpha, interleukin-1beta, CINC-1, ICAM-1, and iNOS messenger RNAs. Inhibition of expression of these proinflammatory genes prevented the increases in myeloperoxidase activity (an indicator of neutrophil infiltration) in gastric mucosa and the development of gastric damage. Pyrrolidine dithiocarbamate dose-dependently inhibited the stress-induced nuclear factor-kappaB pathway activation and consequential proinflammatory gene expression, neutrophil infiltration, and gastric damage, suggesting the involvement of reactive oxygen species in these processes.

CONCLUSIONS

Sustained activation of nuclear factor-kappaB by reactive oxygen species is an important in vivo mechanism mediating stress-induced gastric inflammatory damage in rats.

IL-18 mediates the formation of stress-induced, histamine-dependent gastric lesions

A role of IL-18 in the induction of gastric lesions by water immersion and restraint stress (WRS) was investigated. When wild-type BALB/c mice were exposed to WRS, levels of IL-18 in the serum and stomach increased rapidly with the development of acute gastric lesions. In IL-18-deficient mice [IL-18 knockout (KO) mice] similarly exposed to WRS, no gastric lesions were observed, but the administration of IL-18 before exposure to WRS resulted in the induction of WRS-induced gastric lesions. WRS enhanced gastric histidine decarboxylase (HDC) activity with concomitant increases in gastric histamine content. In IL-18 KO mice, the WRS-induced elevation of gastric HDC activity and histamine levels was much less than that in wild-type mice, but it was augmented by prior administration of IL-18. Treatment of wild-type mice with cimetidine, a histamine H2 receptor antagonist, inhibited the formation of WRS-induced gastric lesions with no effect on the induction of gastric IL-18 by WRS. Levels of corticosterone, one of the stress indicators, were lower in IL-18 KO mice than in wild-type mice. The glucocorticoid receptor antagonist mifepristone had no effect on gastric IL-18 and histamine levels but aggravated the stress-induced gastric lesions, indicating that corticosterone was not involved in the IL-18-mediated formation of stress-induced gastric lesions. These results indicate that IL-18 is involved in the induction of gastric lesions by WRS through augmentation of HDC activity and production of histamine in the stomach.

Investigation of the Mechanisms Underlying the Gastroprotective Effect of Nicorandil

AIM

This study investigated possible mechanisms underlying the gastroprotective effect of nicorandil on experimentally-induced gastric lesions in rats.

METHODS

Rats were randomly assigned to vehicle-, nicorandil (10 mg/kg)-, glibenclamide (6 mg/kg)-, nicorandil + glibenclamide- and cimetidine-pretreated groups, in addition to non-stressed control group, to demonstrate whether the K(ATP )channel opening contributed to nicorandil's gastroprotection. Lesions were induced by water immersion-restraint stress (WIRS) and ulcer indices were determined. Gastric juice parameters (pH, acid output, pepsin and mucin concentrations) were determined. Another set of rats was divided into control, saline-pretreated and nicorandil (10 mg/kg)-pretreated groups. Rats underwent WIRS and their stomachs were used for determination of gastric mucosal lipid peroxides, histamine, PGE(2), and total nitrites levels.

RESULTS

Nicorandil displayed significant protection against gastric lesions formation, abolished by concomitant administration of glibenclamide. Nicorandil significantly reduced gastric acid and pepsin secretion, but upon coadministration with glibenclamide, these effects were blocked. Additionally, nicorandil significantly reduced gastric mucosal lipid peroxides and total nitrites, but did not affect PGE(2) and histamine levels.

CONCLUSION

Results confirm a gastroprotective effect for nicorandil, the mechanism of which comprises K(ATP) channel opening, free radical scavenging, decrease of pepsin and acid secretion and prevention of the detrimental rise in nitric oxide during WIRS.

Effect of ghrelin administration on phagocytic activity in acute cold-restraint stress exposed rats

Ghrelin, an endogenous ligand for growth hormone secretagogue receptor, was identified in the rat stomach. This peptide acts through nitric oxide (NO) by expressing endothelial nitric oxide synthase (eNOS) and down regulating inducible nitric oxide synthase (iNOS) at its gastroproprotective effect against restraint stress induced damage. Recently the ghrelin receptor has also been detected in peripheral systems including immune tissue. We have investigated the possible effect of ghrelin on phagocytic activity of peritoneal macrophages in acute cold-restraint stress (ACRS) exposed rats. The rats were divided into control, stress and ghrelin groups. In ghrelin groups, single dose and three days consecutive dose of ghrelin (20 microg/kg. i.p.) were applied to rats that were exposed to ACRS for 4 h. 1 ml of saline was injected i.p. after ACRS for 3 consecutive days to the rats of the stress groups. Ghrelin administration reduced the increased phagocytic activity induced by ACRS. We conclude that ghrelin exerts an important role at macrophage phagocytic activity in ACRS exposed rats.

Effects of L-carnitine on neutrophil-mediated ischemia-reperfusion injury in rat stomach

Reactive oxygen metabolites play an important role in ischemia-reperfusion related gastric injury. Primary sources of reactive oxygen metabolites seem to be the xanthine/xanthine oxidase system and neutrophils accumulating within the reperfused tissue. Tissue myeloperoxidase activity is an important index of neutrophil accumulation. The purpose of the present study was to clarify the effect of L-carnitine on the accumulation of neutrophils and neutrophil-induced gastric mucosal damage in rats exposed to ischemia-reperfusion. Rats were randomly divided into three groups: sham-operated, ischemia-reperfusion and ischemia-reperfusion plus L-carnitine groups. Ischemia was induced by clamping the celiac artery for 30 min and then reperfusion was established for 60 min. Gastric injury was assessed by measuring myeloperoxidase activity in gastric tissue. The neutrophil accumulation and hemorrhagic lesions due to ischemia-reperfusion in gastric mucosa were ascertained in a histological study. L-Carnitine (100 mg kg(-1)) administrated intravenously 5 min before ischemia significantly reduced both the gastric injury and myeloperoxidase activity compared with the ischemia-reperfusion group. The results suggest that L-carnitine provides marked protection against ischemia-reperfusion-related gastric injury which could be due to its ability to reduce neutrophil accumulation in ischemic tissue.

The inhibition of gastric mucosal lesion, oxidative stress and neutrophil-infiltration in rats by the lichen constituent diffractaic acid

The antiulcerogenic effect of diffractaic acid (DA) isolated from Usnea longissima, a lichen species, on indomethacin (IND)-induced gastric lesions was investigated in rats. Administration of 25, 50, 100 and 200 mg/kg doses of DA and ranitidine (RAN) (50 mg/kg dose) reduced the gastric lesions by 43.5%, 52.9%, 91.4%, 96.7% and 72.7%, respectively. It is known that oxidative stress leads to tissue injury in organisms. Thus, in all treated groups of rats, the in vivo activities of the antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and the levels of reduced glutathione (GSH) and lipid peroxidation (LPO) were evaluated. IND caused oxidative stress, which resulted in LPO in tissues, by decreasing the levels of GPx, SOD and GSH as compared to healthy rats. In contrast to IND, the administration of DA and RAN showed a significant decrease in LPO level and an increase in tissue SOD, GPx and GSH levels. However, while CAT activity was significantly increased by the administration of IND, the administration of DA and RAN decreased CAT activity. The administration of IND also increased the myeloperoxidase (MPx) activity, which shows neutrophil infiltration into the gastric mucosal tissues. In contrast to IND, the administration of DA and RAN decreased MPx activity. The changes in activities of gastric mucosal nitric oxide synthases (NOS) throughout the development of gastric mucosal damage induced by IND were also studied. A decrease in constitutive NOS (cNOS) activity and an increase in inducible NOS (iNOS) activity were determined in gastric damaged tissues induced by IND. The administration of DA (100 mg/kg dose) and RAN reversed the activities of iNOS and cNOS. These results suggest that the gastroprotective effect of DA can be attributed to its enhancing effects on antioxidant defense systems as well as reducing effects of neutrophil infiltration.

Role of gastric mucosal ascorbic acid in gastric mucosal lesion development in rats with water immersion restraint stress

We examined the role of gastric mucosal ascorbic acid (AA) in gastric mucosal lesion development in rats with water immersion restraint stress (WIRS). When fasted rats were subjected to WIRS for 1, 3 or 6 h, gastric mucosal lesions developed at 3 and 6 h. Gastric mucosal AA concentration decreased at 3 and 6 h after the onset of WIRS, while gastric mucosal non-protein SH concentration decreased at 1, 3, and 6 h and gastric mucosal vitamin E concentration decreased at 6 h. Gastric mucosal lipid peroxide concentration and myeloperoxidase activity increased at 3 and 6 h of WIRS. Pre-administration of AA (250 mg/kg) prevented gastric mucosal development with attenuation of the decreased gastric mucosal AA, non-protein SH and vitamin E concentrations, and the increased gastric mucosal lipid peroxide concentration and myeloperoxidase activity. These results suggest that gastric mucosal AA plays an important role in WIRS-induced gastric mucosal lesion development.