Inhibition by 16,16-dimethyl PGE2 of ethanol-induced gastric mucosal damage and leukotriene B4 and C4 formation

The effects of PGE2 and its stable analogue, 16,16 dimethyl PGE2 (dmPGE2) were investigated on ethanol-induced gastric mucosal haemorrhagic lesions and leukotriene formation in the rat. Exposure of the rat gastric mucosa to ethanol in-vivo, produced a concentration-related increase in the mucosal formation of leukotriene B4 (LTB4) which was correlated with macroscopically-apparent haemorrhagic damage to the mucosa. Challenge with absolute ethanol likewise enhanced the mucosal formation of LTC4 whereas the mucosal formation of 6-keto-PGF1 alpha was unaffected. Challenge of the rat gastric mucosa in vitro with ethanol induced a concentration-dependent increase in the formation of LTB4 and LTC4, but not 6-keto PGF1 alpha. Pretreatment with PGE2 (200-500 micrograms/kg p.o.) prevented the haemorrhagic mucosal damage induced by oral administration of absolute ethanol but not the increased formation of leukotrienes by the mucosa. In contrast, pretreatment with a high dose of dmPGE2 (20 micrograms/kg p.o.) prevented both the gastric mucosal lesions and the increase mucosal leukotriene formation. The differences in the effects of these prostaglandins may be related to the nature or degree of protection of the gastric mucosa. Thus, high doses of dmPGE2 but not PGE2 may protect the cells close to the luminal surface of the mucosa and hence reduce the stimulation of leukotriene synthesis by these cells.     

Protection from nonsteroidal anti-inflammatory drug (NSAID)-induced gastric ulcers by dietary nitrate

Nitrate is abundant in our diet with particularly high levels in many vegetables. Ingested nitrate is concentrated in saliva and reduced to nitrite by bacteria in the oral cavity. We recently reported that application of nitrite-containing saliva to the gastric mucosa increases superficial blood flow and mucus generation via acid-catalyzed formation of bioactive nitrogen oxides including nitric oxide. Here we studied if dietary supplementation with nitrate would protect against gastric damage caused by a nonsteroidal anti-inflammatory drug. Rats received sodium nitrate in the drinking water for 1 week in daily doses of 0.1 or 1 mmol kg(-1). Control rats received 1 mmol kg(-1) sodium chloride. Diclofenac (30 mg kg(-1)) was then given orally and the animals were examined 4 h later. In separate experiments we studied the effects of dietary nitrate on intragastric NO levels and mucus formation. Luminal levels of NO gas were greatly increased in nitrate-fed animals. The thickness of the mucus layer increased after nitrate supplementation and gene expression of MUC6 was upregulated in the gastric mucosa. Nitrate pretreatment dose dependently and potently reduced diclofenac-induced gastric lesions. Inflammatory activity was reduced in the rats receiving nitrate as indicated by lower mucosal myeloperoxidase activity and expression of inducible NO synthase. We conclude that dietary nitrate protects against diclofenac-induced gastric ulcers likely via enhanced nitrite-dependent intragastric NO formation and concomitant stimulation of mucus formation. Future studies will reveal if a diet rich in nitrate can offer an additional nutritional approach to preventing and treating peptic ulcer disease.     

The multicomponent phytopharmaceutical SKI306X inhibits in vitro cartilage degradation and the production of inflammatory mediators

Clinical studies have demonstrated that SKI306X, a purified preparation of three medicinal plants, relieves joint pain and improves functionality in osteoarthritis patients. To study the biological action of SKI306X, bovine cartilage explants and human peripheral blood mononuclear cells (PBMC) were stimulated with IL-1β and lipopolysaccharide (LPS) respectively, in the presence or absence of SKI306X and its individual composites. All tested compounds inhibited dose-dependently IL-1β-induced proteoglycan release and nitric oxide production by cartilage, indicating cartilage protective activity. SKI306X and two of its compounds inhibited PGE₂, TNF- and IL-1β production by LPS-stimulated PBMC, indicating anti-inflammatory activity. These results demonstrate that the biological effect of SKI306X is at least bipartite: (1) cartilage protective and (2) anti-inflammatory. The observed anti-inflammatory effects may provide an explanation for the outcome of the clinical studies. Long-term clinical trails are necessary to elucidate whether the in vitro cartilage protective activity results in disease-modifying effects.     

Effects of tepoxalin, a dual inhibitor of cyclooxygenase/5-lipoxygenase, on events associated with NSAID-induced gastrointestinal inflammation

Prostaglandins and thromboxanes are products of arachidonic acid metabolism via the cyclooxygenase (CO) enzyme and are responsible for the pain and swelling common to sites of inflammation. Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit the production of these substances and are used in the treatment of inflammatory diseases such as arthritis. However, one of the major side-effects of NSAID therapy is gastric ulceration. It is possible that inhibition of prostaglandin production and a related increase in the formation of leukotrienes via the 5-lipoxygenase (5-LO) enzymatic pathway are responsible for attracting inflammatory cells, causing local sites of inflammation and producing ulceration. To determine the effects of 5-LO inhibition on this hypothesis, studies were performed in rats to evaluate the effects of tepoxalin, a dual CO/LO inhibitor on leukotriene B₄ levels in gastric mucosa and neutrophil adhesion in mesenteric venules. In rats, chronic oral administration of an NSAID, indomethacin (2 mg/kg daily over 4 days), resulted in 40% mortality, accompanied by intestinal adhesions and perforations when evaluated 24 h after the fourth dose of drug. Additionally, neutrophil adhesion was increased in the mesenteric venules and cell infiltration was evident in the mesenteric interstitium. These gastrointestinal side-effects were inhibited in a separate group of rats administered tepoxalin (20 mg/kg, p.o) 30 min prior to each daily indomethacin treatment. Further studies were performed to determine tepoxalin's effects on early events associated with NSAID-induced gastrointestinal inflammation, including neutrophil adhesion, lipid peroxide generation and LTB₄ production. Indomethacin (100 mg/kg, p.o.) produced elevated levels of LTB₄ in rat gastric mucosa 90 min after administration. Additionally, neutrophil adhesion in mesenteric venules was increased at this dose and with the administration of another NSAID, naproxen. No generation of lipid peroxides was evident in the gastric mucosa at this timepoint. Tepoxalin (up to 400 mg/kg, p.o.) did not have an effects on gastric mucosal LTB₄ generation and lipid peroxide levels. A decrease in neutrophil adhesion was observed at the highest dose. In another study, pretreatment with tepoxalin (ED₅₀=7.5 mg/kg, p.o.) or the selective 5-LO inhibitor zileuton (100 mg/kg, p.o.) prevented the increases in gastric mucosal LTB₄ levels and neutrophil adhesion induced by indomethacin (100 mg/kg, p.o.). These data suggest that LO inhibition may play a vital role in the prevention of NSAID-induced gastric inflammation, providing insight into the lack of ulcerogenicity with tepoxalin and new approaches to anti-inflammatory therapy which may prevent gastric side effects.     

Inhibition by 16, 16-dimethyl PGE2 of ethanol-induced gastric mucosal damage and leukotriene B4 and C4 formation

The effects of PGE₂ and its stable analogue, 16, 16 dimethyl PGE₂ (dmPGE₂) were investigated on ethanol-induced gastric mucosal haemorrhagic lesions and leukotriene formation in the rat. Exposure of the rat gastric mucosa to ethanol , produced a concentration-related increase in the mucosal formation of leukotriene B₄ (LTB₄) which was correlated with macroscopically-apparent haemorrhagic damage to the mucosa. Challenge with absolute ethanol likewise enhanced the mucosal formation of LTC₄ whereas the mucosal formation of 6-keto-PGF_1α was unaffected. Challenge of the rat gastric mucosa with ethanol induced a concentration-dependent increase in the formation of LTB₄ and LTC₄, but not 6-keto PGF_1α. Pretreatment with PGE₂ (200–500μg/kg p.o.) prevented the haemorrhagic mucosal damage induced by oral administration of absolute ethanol but not the increased formation of leukotrienes by the mucosa. In contrast, pretreatment with a high dose of dmPGE₂ (20μg/kg p.o.) prevented both the gastric mucosal lesions and the increase mucosal leukotriene formation. The differences in the effects of these prostaglandins may be related to the nature or degree of protection of the gastric mucosa. Thus, high doses of dmPGE₂ but not PGE₂ may protect the cells close the luminal surface of the mucosa and hence reduce the stimulation of leukotriene synthesis by these cells.     

Glucocorticoid-induced gastric mucosal damage: inhibition of leukotriene, but not prostaglandin biosynthesis

The effects of daily administration of ulcerogenic doses of the glucocorticoids, dexamethasone and prednisolone, on gastric prostaglandin and leukotriene synthesis were examined in the rat. Significant gastric damage was not observed until the fourth day of treatment with dexamethasone and until the sixth day of treatment with prednisolone. However, the onset of gastric damage was not accompanied by any significant effect of these drugs on gastric 6-keto prostaglandin Fl alpha synthesis. Conversely, both drugs caused a reduction in gastric leukotriene C4 synthesis, with dexamethasone producing a highly significant (p less than 0.001) effect. Furthermore, there was a highly significant (p less than 0.001) correlation between the ability of these drugs to inhibit gastric leukotriene C4 synthesis, and their ability to reduce gastric tissue levels of the neutrophilic enzyme myeloperoxidase. Thus, glucocorticoid-induced gastric damage does not appear to be related to inhibitory effects of these drugs on prostaglandin synthesis. Whether or not effects of these drugs on gastric leukotriene C4 synthesis and myeloperoxidase activity are relevant to the mechanism of ulceration is unclear.     

Gastroprotective effect of Terminalia arjuna bark on diclofenac sodium induced gastric ulcer

AIM: The present study was aimed to evaluate the effect of methanolic extract of Terminalia arjuna (TA) on diclofenac sodium induced gastric ulcer in experimental rats. METHODS: Animals were induced for gastric ulcer with diclofenac sodium (DIC) (80mg/kg bodyweight in water, orally) and treated orally with TA in various doses ranging from 100mg/kg bodyweight to 500mg/kg bodyweight. The effective dose was 400mg/kg bodyweight, since this dose elicited a maximum reduction in lesion index. The gastroprotective effect of TA was assessed from volume of gastric juice, pH, free and total acidity, pepsin concentration, acid output in gastric juice, the levels of non-protein sulfhydryls (NP-SH), lipid peroxide (LPO), reduced glutathione (GSH), and activities of enzymic antioxidants--super oxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST) and myeloperoxidase (MPO) in gastric mucosa. The levels of DNA, protein bound carbohydrate complexes--hexose, hexoseamine, sialic acid, fucose in gastric mucosa and gastric juice and the levels of RNA in gastric mucosa were assessed. The stomach tissues were used for adherent mucus content and also for the histological examination. RESULTS: A significant reduction in lesion index was observed in ulcer induced animals treated with TA (DIC+TA) compared to ulcerated rats (DIC). A significant increase was observed in pH, NP-SH, GSH, enzymic antioxidants, protein bound carbohydrate complexes, adherent mucus content, nucleic acids with a significant decrease in volume of gastric juice, free and total acidity, pepsin concentration, acid output, LPO levels and MPO activities in DIC+TA rats compared to DIC rats. Histological studies confirmed the gastroprotective activity of TA. CONCLUSION: From the data presented in this study it could be concluded that T. arjuna acts as an gastroprotective agent probably due to its free radical scavenging activity and cytoprotective nature.     

The membrane-stabilizing action of zinc carnosine (Z-103) in stress-induced gastric ulceration in rats

Zinc compounds have been shown to antagonize various types of gastric ulceration in rats. Zinc carnosine (Z-103), a newly developed agent was, therefore, examined for its antiulcer effect in stress-induced ulceration and also its membrane stabilizing action in rat stomachs. Cold-restraint (restrained at 4 degrees C for 2 h) stress induced severe hemorrhagic lesions together with increased mast cell degranulation and beta-glucuronidase release in the gastric glandular mucosa. Z-103 pretreatment with a single oral dose (3, 10 or 30 mg/kg) reversed these actions in a dose-dependent manner. When the compound was incubated in concentrations of 10(-7, 10(-6), 10(-5) or 10(-4) M, with isolated hepatic lysosomes, it significantly reduced the spontaneous release of beta-glucuronidase in the medium. The present study not only demonstrates the antiulcer effect of Z-103 but also indicates that the protective action is likely to be mediated by its membrane-stabilizing action on mast cells and lysosomes in the gastric glandular mucosa.     

Study of the damaging effects of acetazolamide on gastric mucosa in rats

The present study demonstrated that acetazolamide (100 and 200 mg/kg, s.c.) induced severe gastric hemorrhagic ulceration in rats. The ulceration was aggravated by oral administration of HCl, but was inhibited by NaHCO3. Furthermore, the severity of ulceration was also decreased by pretreatment with methysergide, chlorpheniramine, or cimetidine. These protective effects were accompanied by an increase in serotonin and histamine released from the stomach. Acetazolamide injection also increased the protein level but reduced the sialic acid content in the gastric secretion, indicating that the gastric mucosal barrier may have been damaged. Prostaglandin E2 content of the gastric mucosa was not affected by the drug; however, carbonic anhydrase activity was markedly reduced in a dose-dependent manner. Thus, it is suggested that the ulceration induced by acetazolamide is mainly due to the inhibition of carbonic anhydrase activity and mucus secretion. The increase in serotonin and histamine release also may have been the contributing factors for gastric ulcer formation.     

Value of the "gastric chamber", new technic performed ex vivo, for the study of the gastric mucosa of the rat]

The "gastric chamber" technique, performed in the anaesthetised rat, enables the study of gastric mucosal fragility induced by doses of phenylbutazone, which do not themselves cause ulceration or exulceration. The perfusion of buffered solution at pH 2-8 into the gastric chamber shows that prior oral administration of phenylbutazone 50 mg/kg increases the fragility of the mucosa. The optimal delay separating this administration from the time of experimentation is 6 hours. The effects seen are essentially vascular disorders.     

Transforming growth factor alpha-mediated gastroprotection against stress ulceration in the rat: involvement of capsaicin-sensitive sensory neurons

Exogenously administered TGF alpha has been shown to protect rodent gastric mucosa against injury caused by acid-dependent and acid-independent injury. The present study examined whether the gastroprotective effects of TGF alpha on stress-induced gastric ulceration in the rat involves activation of capsaicin-sensitive sensory neurons. Fasted male SD rats were subjected to water restraint stress (WRS) for four hours. Thereafter, rats were euthanized; the stomach opened and macroscopic areas of gastric ulceration quantitated (mm(2)). Gastric tissue contents of TGF alpha and the sensory neuropeptide, calcitonin gene-related peptide (CGRP) were determined by radioimmunoassay. Prior to stress rats received TGF alpha 50, 100 or 200 microg/kg by intraperitoneal injection. Sensory denervation was accomplished by high dose capsaicin treatment. WRS caused severe ulceration in the gastric corpus; 46.1 + 6.6 mm(2). Parenteral administration of TGF alpha caused dose-dependent reduction in gastric injury: 34.7 + 4.9 mm(2) with 50 microg/kg (p < 0.05); 25.4 + 3.6 mm(2) with 100 microg/kg (p < 0.001) and 9.4 + 0.8 mm(2) with 200 microg/kg (p < 0.001). The gastroprotective action of TGF alpha (200 microg/kg, i.p.) was abolished by capsaicin-induced sensory denervation. In addition, WRS ulceration was associated with significant reduction in gastric CGRP (-42%) and TGF alpha (-48%) content. Reduction in CGRP content was prevented by TGF alpha pretreatment. We conclude that: 1) TGF alpha caused dose-dependent gastroprotection against WRS ulceration, 2) TGF alpha-mediated gastric mucosal protection was prevented by capsaicin-induced sensory denervation and, 3) stress-induced injury was associated with significant reduction in gastric content of both TGF alpha and CGRP.     

Effects of sucralfate on gastric prostaglandin and leukotriene synthesis: relationship to protective actions

The mechanism of the protective actions of sucralfate against ethanol-induced gastric mucosal damage in the rat has been investigated. In particular, the role of prostaglandins as mediators of such protection was assessed. Oral administration of sucralfate at a dose causing a significant reduction of ethanol-induced gastric damage (500 mg/kg) did not significantly alter gastric 6-ketoprostaglandin F1 alpha synthesis. Pretreatment with indomethacin at a dose that inhibited gastric cyclooxygenase activity by an average of 88% did not affect the protective actions of sucralfate. To further investigate the mechanism of action of sucralfate, an ex vivo gastric chamber model was used in which sucralfate could be applied to only one side of the mucosa. Sucralfate did not affect gastric prostaglandin synthesis, but did cause a significant increase in leukotriene C4 synthesis, a fall in transmucosal potential difference, and a significant decrease in gastric myeloperoxidase activity on the side exposed to sucralfate. These observations suggest that sucralfate has an irritant action on the mucosa. The release of mediators in response to such irritation may play an important role in the protective action of sucralfate. The present study supports the hypothesis that prostaglandins do not mediate the protection afforded by exposure to sucralfate.     

The effect of cocaine on gastric mucosal PGE(2), LTC(4) and ulcerations

The association between cocaine use and acute gastroduodenal perforation is known. The effect of cocaine and stress on gastric mucosal ulceration and the levels of prostaglandin E(2) (PGE(2)) and leukotriene C(4) (LTC(4)) was studied in 40 Sprague-Dawley rats. Controls received intraperitoneal (i.p.) saline, ten received i.p. cocaine (35 mg/kg), ten were stressed by the cold restraint method, and ten had i.p. cocaine and stress. Cocaine alone did not induce ulceration, but decreased PGE(2) levels. Stress alone caused ulceration, but was not associated with a change in either PGE(2) or LTC(4) levels. When combined with stress, however, cocaine caused a three-fold increase in ulceration and a significant increase in PGE(2) and LTC(4) levels. Stress may predispose the cocaine addict to loss of gastroduodenal mucosal integrity, which is related to an imbalance of PGE(2) and LTC(4) synthesis.     

Influence of the position of the side chain hydroxy group on the gastric antisecretory and antiulcer actions of E1 prostaglandin analogs.

The influence of transposing the C-15 hydroxy group of prostaglandin E1 methyl ester (PGE2ME) on gastric antisecretory and antiulcer actions was investigated. The compound (+/-)15-deoxy- 16alpha, beta-hydroxy PGE1ME (SC-28904) was equipotent to the reference standard PGE1ME in suppressing histamine-stimulated gastric secretion in the Heidenhain pouch (HP) dog. In contrast to PGE1ME, SC-28904 was longer acting when administered intravenously and also showed significant oral activity in the histamine-stimulated gastric fistula dog. SC-28904 was also equipotent to PGE1ME (range of active doses of 0.5 to 5.0 mg/kg, s.c.) in inhibiting forced-exertion gastric ulceration in rats. The compound (+/-)15-deocy-17alpha, beta-hydroxy PGE1ME (SC-30963) was an inactive antisecretory agent in the dog at the 1.0 mg/kg i.v. bolus dose. This dose was 100 times greater than the active antisecretory dose of PGE1ME. Likewise, SC-30693, when administered subcutaneously at a 5.0 mg/kg dose, was also totally inactive in preventing gastric ulcers induced by forced exertion in rats. The important implications of this work are that some of the receptor sites for the PGE1 molecule could easily accomodate the side chain hydroxy group either in the C-15 or C-16 position. Moreover, the hydroxy group in the latter position significantly improved the biological activity of PGE1ME.     

A PPAR-gamma ligand, 15-deoxy-Delta12,14-prostaglandin J(2), inhibited gastric mucosal injury induced by ischemia-reperfusion in rats

INTRODUCTION: Recent studies have demonstrated the anti-inflammatory action of 15-deoxy-Delta12,14-prostaglandin J(2) (15d-PGJ(2)), a derivative of the PGD(2) metabolic pathway. Acute inflammation, including neutrophil activation, plays a critical role in the pathogenesis of ischemia-reperfusion (I/R). The aim of the present study was to determine the effect of 15d-PGJ(2) on I/R-induced gastric mucosal injury in rats.METHODS: Gastric mucosal damage was induced in male Wistar rats by clamping the celiac artery for 30 min followed by reperfusion. 15d-PGJ(2) (0.01-1.0 mg/kg) was given to the rats intraperitoneally 1 h before the vascular clamping. The area of gastric mucosal erosions (erosion index) was measured. Thiobarbituric acid reactive substances (TBARS) and tissue-associated myeloperoxidase (MPO) activity were measured in the gastric mucosa as indices of lipid peroxidation and neutrophil infiltration. The expression of tumor necrosis factor-alpha (TNF-alpha) in gastric mucosa was measured by ELISA. In addition, to elucidate whether the protective effects of 15d-PGJ(2) are related to the activation of the PPAR-gamma receptor, we also investigated the effects of a PPAR-gamma antagonist, GW9662.RESULTS: After 60 min of reperfusion, the area of gastric erosion index had significantly increased from the mean basal levels. The increase in the erosion index was significantly inhibited by pretreatment with 15d-PGJ(2) in a dose-dependent manner. On the other hand, GW9662 reversed the protective effect of 15d-PGJ(2). The concentration of TBARS and MPO activity in the gastric mucosa were both significantly increased after I/R, and pretreatment with 15d-PGJ(2) significantly reduced these increases. The TNF-alpha content was significantly higher in the I/R group than in the sham-operated group. However, the increase in TNF-alpha was significantly inhibited by pretreatment with 15d-PGJ(2).CONCLUSIONS: 15d-PGJ(2) significantly inhibited the severity of acute gastric mucosal injury induced by I/R in rats through PPAR-gamma-dependent mechanisms. This effect may be due, in part, to a reduction in the infiltration of neutrophils into the gastric mucosa, possibly via the inhibition of inflammatory cytokine.     

Protective effects of nebivolol against cold restraint stress-induced gastric ulcer in rats: role of NO, HO-1, and COX-1,2

Nebivolol, a β(1)-adrenoceptor antagonist, exhibits vasodilatory and anti-oxidative properties that rendering it attractive candidate for protecting against gastric ulcer. The aim of this study therefore is to evaluate the protective effects of nebivolol against cold restraint stress (CRS)-induced gastric ulcer in rats. Rats were restrained, and maintained at 4°C for 3 h. Nebivolol (5 mg/kg, p.o.) was suspended in 0.5% aqueous solution of carboxymethyl cellulose and was administered 30 min before CRS. Nebivolol exhibited gastroprotective effects as evidenced by significant decreases in ulcer index as well as free and total acid output, and pepsin activity in gastric juice in addition to gastric mucosal malondialdehyde concentration, with concomitant increases in gastric juice pH and mucin concentration along with gastric mucosal reduced glutathione and nitric oxide (NO) concentrations compared with CRS rats. Moreover, immunohistochemical analysis demonstrated that nebivolol treatment markedly enhanced heme oxygenase-1 as well as cyclooxygenase-1 and cyclooxygenase-2 expressions. The protective effects of nebivolol were confirmed by gastric histopathological examination. Pretreatment with N(ω)-nitro-L-arginine, a NO synthase inhibitor, partly altered the protection afforded by nebivolol. In conclusion, nebivolol protected rats' gastric mucosa against CRS-induced gastric ulceration possibly through anti-oxidant activity, enhancement of gastric mucosal barrier and reduction in acid secretory parameters.     

Dexamethasone makes the gastric mucosa susceptible to ulceration by inhibiting prostaglandin synthetase and peroxidase - two important gastroprotective enzymes

The plausible mechanism by which dexamethasone makes the gastric mucosa susceptible to ulceration has been studied. As acid aggravates ulcer, the role of dexamethasone on acid secretion was first investigated. Dexamethasone stimulates both basal and drug (mercaptomethylimidazole)-induced gastric acid secretion by 100 and 50% respectively in male Wister rats 24 h after intramuscular administration at the dose of 1 mg/kg body wt. This stimulated acid secretion is 93% blocked by cimetidine indicating increased liberation of histamine in the process. Pretreatment of dexamethasone before 24 h produces ulcer in 30% of the pylorus- ligated rats and aggravates the ulcer index by 82% in both pylorus and esophagus ligated rats. The incidence of ulceration in the latter cases is also increased by 25%. As mucosal prostaglandin synthetase and peroxidase play an important role in gastroprotection through biosynthesis of prostaglandin and by scavenging endogenous H₂O₂ respectively, the effect of dexamethasone on the activities of these gastroprotective enzymes were studied. Prostaglandin synthetase and peroxidase activities of the mucosa are significantly inhibited by 87 and 83% respectively by 24-h pretreatment with dexamethasone. The results indicate that dexamethasone makes the mucosa prone to ulceration by inhibiting the activity of prostaglandin synthetase to block the gastroprotective action of prostaglandin and also by inhibiting the peroxidase, thereby elevating the endogenous H₂O₂ level to generate more reactive hydroxyl radical responsible for the mucosal damage.     

Toxicoproteomic analysis of a mouse model of nonsteroidal anti-inflammatory drug-induced gastric ulcers

Nonsteroidal anti-inflammatory drugs (NSAIDs) are valuable agents; however, their use has been limited by their association with mucosal damage in the upper gastrointestinal tract. NSAIDs inhibit cyclooxygenase and consequently block the synthesis of prostaglandins, which have cytoprotective effects in gastric mucosa; these effects on prostaglandins have been thought to be major cause of NSAID-induced ulceration. However, studies indicate that additional NSAID-related mechanisms are involved in formation of gastric lesions. Here, we used a toxicoproteomic approach to understand cellular processes that are affected by NSAIDs in mouse stomach tissue during ulcer formation. We used fluorogenic derivatization-liquid chromatography-tandem mass spectrometry (FD-LC-MS/MS)-which consists of fluorogenic derivatization, separation and fluorescence detection by LC, and identification by LC-tandem mass spectrometry-in this proteomic analysis of pyrolic stomach from control and diclofenac (Dic)-treated mice. FD-LC-MS/MS results were highly sensitive; 10 differentially expressed proteins were identified, and all 10 were more highly expressed in Dic-treated mice than in control mice. Specifically, expression levels of 78 kDa glucose-regulated protein (GRP78), heat shock protein beta-1 (HSP27), and gastrin were more than 3-fold higher in Dic-treated mice than in control mice. This study represents a first step to ascertain the precise actors of early NSAID-induced ulceration.     

The gastric ulcer protective effect of boswellic acids, a leukotriene inhibitor from Boswellia serrata, in rats

Aim of the study is to evaluate the anti-ulcer efficacy of the boswellic acids (BA), a triterpenoid known as anti-inflammatory/anti-arthritic agent, which is in clinical use. The reason for the study is that, the known non-steroidal anti-inflammatory drugs (NSAIDs) are full of side effects especially ulceration which is at the top. BA, although, used as an anti-arthritic agent yet it is not only devoid of ulcer production but protective also. The activity evaluation was done by the following universally accepted animal models viz., pyloric ligation, ethanol–HCl, acetylsalicylic acid, indomethacin and cold restrained stress-induced ulceration in rats. Results of the present study revealed that BA possess a dose dependent antiulcer effect against different experimental models. It showed different degree of inhibition of the ulcer score towards different ulcerogenic agents. The ulcer score against various ulcer inducing agents viz., pyloric ligation, ethanol/HCl, (acute and chronic) acetylsalicylic acid, indomethacin and cold restraint stress, was inhibited by 39%, 38%, 51%, 31%, 37% and 42% respectively at 250 mg/kg. From the data it is concluded that BA inhibited ulcer production non-specifically in all the experimental models, whereby, it is not possible to propose a single specific mechanism. Nevertheless it is possible that BA might be acting by increasing the gastric mucosal resistance and local synthesis of cytoprotective prostaglandins and inhibiting the leukotriene synthesis.     

Expression of HSP72 in the gastric mucosa is regulated by gastric acid in rats-correlation of HSP72 expression with mucosal protection

BACKGROUND AND AIM: The real mechanism of adaptive cytoprotection in the gastric mucosa is not well established. In the present study, we investigated the effect of acid suppressing agents on a 72-kDa heat shock protein (HSP72) expression, which is known as endogenous cytoprotective factor, in the gastric mucosa. Also, the association of gastric mucosal protective function against HCl-challenge was compared between HSP72-induced and -reduced group. MATERIALS AND METHODS: Expression of HSP72 was measured by Western blotting in the gastric mucosa before and after administration of famotidine or omeprazole. The gastric mucosal protective function against 0.6 N HCl was compared between control group and HSP72-reduced group. Also, the effect of increased expression of gastric HSP72 by additional administration of zinc sulfate or zinc L-carnosine, which is known as HSP72-inducer, on mucosal protective function was studied. RESULTS: HSP72 expression in the gastric mucosa was reduced by acid suppressing agents. The lowest expression level of HSP72 was observed 12 h (famotidine, H2-receptor antagonist) or 48 h (omeprazole, proton pump inhibitor) after administration. The gastric mucosal protective ability against 0.6 N HCl was also reduced when HSP72 expression was decreased by famotidine or omeprazole. This phenomenon was reversed by HSP72 induction by additional administration of zinc derivatives. CONCLUSION: Our results might indicate that the expression of HSP72 in the gastric mucosa is physiologically regulated by gastric acid, and that HSP72 induction could be important in view of mucosal protection especially when HSP72 expression is reduced by administration of acid suppressing agents such as proton pump inhibitor or H2 receptor antagonist.