Lansoprazole induces mucosal protection through gastrin receptor-dependent up-regulation of cyclooxygenase-2 in rats

Lansoprazole protects hepatic cells against cisplatin-induced oxidative stress through the p38 MAPK/ARE/Nrf2 pathway

Lansoprazole, a proton pump inhibitor, can exert antioxidant effects through the induction of the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway, independently of the inhibition of acid secretion in the gastrointestinal tract. Lansoprazole has been reported to provide hepatoprotection in a drug-induced hepatitis animal model through the Nrf2/heme oxygenase-1 (HO1) pathway. We sought to investigate the molecular mechanism of cytoprotection by lansoprazole. An in vitro experimental model was conducted using cultured rat hepatic cells treated with lansoprazole to analyze the expression levels of Nrf2 and its downstream genes, the activity of Nrf2 using luciferase reporter assays, cisplatin-induced cytotoxicity, and signaling pathways involved in Nrf2 activation. Lansoprazole treatment of rat liver epithelial RL34 cells induced transactivation of Nrf2 and the expression of the Nrf2-dependent antioxidant genes encoding HO1, NAD(P)H quinone oxidoreductase-1, and glutathione S-transferase A2. Furthermore, cycloheximide chase experiments revealed that lansoprazole prolongs the half-life of the Nrf2 protein. Notably, cell viability was significantly increased by lansoprazole treatment in a cisplatin-induced cytotoxicity model. Moreover, the siRNA knockdown of Nrf2 fully abolished the cytoprotective effect of lansoprazole, whereas the inhibition of HO1 by tin-mesoporphyrin only partially abolished this. Finally, lansoprazole promoted the phosphorylation of p38 mitogen-activated protein kinase (MAPK) but not that of the extracellular signal-regulated kinase or the c-Jun N-terminal kinase. Using SB203580, a specific inhibitor for p38 MAPK, the lansoprazole-induced Nrf2/antioxidant response elements pathway activation and cytoprotective effects were shown to be exclusively p38 MAPK dependent. Lansoprazole was shown by these results to exert a cytoprotective effect on liver epithelial cells against the cisplatin-induced cytotoxicity through the p38 MAPK signaling pathway. This could have potential applications for the prevention and treatment of oxidative injury in the liver.

Interaction between the effects of proton pump inhibitors and aspirin on gastric wall sestamibi uptake on myocardial perfusion imaging

BACKGROUND

Increased gastric wall activity on myocardial perfusion imaging (MPI) is associated with proton pump inhibitor (PPI) therapy; however, the mechanism is unknown. We proposed a role for gastric mucosal prostaglandin synthesis and asked whether concurrent use of aspirin would antagonize this effect.

METHODS

An observational study was performed of 319 patients undergoing technetium-99m sestamibi (MIBI) rest/stress MPI. We assessed the effects of taking PPIs, aspirin and their interaction on the principle outcome of clinically significant gastric wall activity.

RESULTS

The outcome was observed in 13% of patients taking neither a PPI nor aspirin, 22% of those taking aspirin only, 51% taking a PPI only and 33% of those taking both. Adjusted odd ratios (95% confidence intervals) were 6.3 (CI 2.8-14.0; p < .001) for taking a PPI only, 1.8 (CI 0.8-3.9; p = .16) for taking aspirin only, and 3.0 (CI 1.4-6.5; p = .005) for taking the combination of a PPI and aspirin. There was evidence of negative statistical interaction between the two drug effects using additive (p = .006) and multiplicative (p = .016) scales.

CONCLUSIONS

PPI use was strongly associated with enhanced gastric wall activity on MPI; however, concurrent aspirin appears to reduce the effect. Enhanced local prostaglandin synthesis may mediate the PPI effect.

Gastroprotective activity of Loranthus acaciae flower extract in a rodent model of ethanol-induced ulcer

Loranthus acaciae (Loranthaceae) is a perennial green semi-parasitic plant used in ethnopharmacological medicine for healing wounds. The protective effect of L. acaciae on gastric ulcer induced by ethanol was investigated in a rat model. Ulcer index and total glutathione level were measured and histological and immunohistochemical studies for the expression of cyclooxygenase-2 were performed. Furthermore, chemical constituents of the flower extract were analyzed. Ulcer index was significantly lowered in L. acaciae-treated groups. Protection ratios were 75.9%, 98.9%, and 70.7% for 250 mg/kg and 500 mg/kg of L. acaciae and 40 mg/kg of esomeprazole, respectively. Histological examination revealed fewer hemorrhage in mucosa and less edema in submucosa of L. acaciae-treated groups compared with control. In the esomeprazole-treated group, there was mild disruption in the surface epithelium and mild hemorrhage. However, edema and leucocytes infiltration in the submucosa layer were present. Immunohistochemical staining of stomach sections for cyclooxygenase-2 (COX-2) was negative in the control group as well as in the L. acaciae-treated groups. Total glutathione level in mucosa layer of the stomach was higher in L. acaciae-treated groups compared with control. Liquid chromatography-mass spectrometric analysis revealed the presence of loranthin and rutin as the major constituents. It can be concluded that L. acaciae imparted a gastroprotective action against ethanol-induced ulcer in rats.

Novelty 500 mg/kg L. acaciae protected the stomach by 98.9% from ulcerogenic effect of ethanol. L. acaciae increased total glutathione level but not COX-2 expression in gastric mucosa. Loranthin and rutin were the major constituents in L. acaciae flower extract.

Prophylactic and curative anti-ulcerogenic activity and the possible mechanisms of action of some desert plants

The present study aimed to evaluate the anti-ulcerogenic activities and the possible mechanisms of action of seven desert plants from different families. Conyza dioscoridis (L.) Desf. (Asteraceae), Euphorbia hirta L. (Euphorpiaceae), Origanum syriacum L., Salvia lanigera L. (Lamiaceae), Sisymbrium irio L., Solanum nigrum Linn. (Solanaceae) and Solenostemma arghel (Del.) Hayne. (Asclepiadaceae), were tested using prophylactic and curative models of absolute ethanol-induced ulcer, at three doses (125, 250 & 500 mg/kg) of each extract.

The investigated extracts possessed dose dependent anti-ulcerogenic activities in both models, with LD₅₀ higher than 5 g/kg. The most effective extracts were C. dioscoridis and S. irio with percent protection of control ulcer; 91.1% and 85.4% respectively. The antisecretory activity of both C. dioscoridis and S. irio appears to be mainly related to the suppression of gastrin release. The in vitro potential radical (DPPH) scavenging activities of the investigated extracts were well supported with the reduction in gastric MDA (50.6% and 43.3%) and enhancing the level of reduced GSH (2.84, 2.59 mg/g tissue) for C. dioscoridis and S. irio respectively. In addition, suppression of the inflammatory mediator TNF-α may be one of the possible mechanisms of action. The alcohol extracts of C. dioscoridis and S. irio showed no alteration on liver and kidney functions. Phytochemical screening of the investigated extracts revealed the presence of flavonoids, tannins and sterols which could be related to the activities.

Gastroprotective effects of hydroethanolic root extract of Arrabidaea brachypoda: Evidences of cytoprotection and isolation of unusual glycosylated polyphenols

The hydroethanolic root extract of Arrabidaea brachypoda, from Bignoniaceae family, a Brazilian medicinal plant, demonstrated significant in vivo gastroprotective effects using different in vivo assays. The activity was evaluated in several models of experimental gastric ulcer in rats (absolute ethanol, glutathione depletion, nitric oxide depletion, non-steroidal anti-inflammatory drugs, pylorus ligation and acetic acid). Using 300 mg/kg (p.o.) the extract significantly reduced gastric injury in all models. In depth phytochemical investigation of this extract led to the isolation of two previously undescribed phenylethanoid glycosides derivatives and seven unusual glycosylated dimeric flavonoids. The structures were elucidated using UV, NMR and HRMS analysis. Absolute configuration of the dimeric flavonoids was performed by electronic circular dichroism (ECD) spectroscopy.

Advances in prevention and treatment of chemotherapy-induced gastrointestinal mucositis with proton pump inhibitors

Proton pump inhibitors (PPIs) are potent acid-suppressive medications commonly used for management of acid-related diseases. Over the past decade, gastrointestinal injury following chemotherapy has attracted wide attention from oncologists. Two international clinical practice guidelines, the National Comprehensive Cancer Network (NCCN) and the Multinational Association of Supportive Care in Cancer (MASCC) antiemesis guidelines, recommend omeprazole for the treatment of chemotherapy-induced epigastric pain. In recent years, PPIs have been widely used for the prevention and treatment of chemotherapy-induced gastrointestinal mucositis. This paper summarizes the mechanisms by which chemotherapy causes damage to the gastrointestinal tract, the mechanisms underlying the protection afforded by PPIs against gastrointestinal injury induced by chemotherapy, and their clinical applications.

Gastric secretion

PURPOSE OF REVIEW

The review summarizes the past year's literature, basic science and clinical, regarding the neural, paracrine, hormonal, and intracellular regulation of gastric acid secretion.

RECENT FINDINGS

Gastric acid facilitates the digestion of protein as well as the absorption of iron, calcium, vitamin B(12), and certain medications (e.g. thyroxin). It also kills ingested microorganisms and prevents bacterial overgrowth, enteric infection, and possibly spontaneous bacterial peritonitis. Stimulants of acid secretion include histamine, gastrin, acetylcholine, and ghrelin. Inhibitors include somatostatin, nefstatin-1, interleukin-11, and calcitonin gene-related peptide. Helicobacter pylori stimulates or inhibits acid secretion depending upon the time course of infection and the area of the stomach predominantly infected. Acute infection activates calcitonin gene-related peptide sensory neurons coupled to inhibition of histamine and acid secretion. Serum chromogranin A, a marker for neuroendocrine tumors, is elevated in patients taking proton pump inhibitors.

SUMMARY

Progress continues in our understanding of the regulation of gastric acid secretion in health and disease, as well as the function of gastric neuroendocrine cells. The recognition that gastrin is not only a secretagogue but also a trophic hormone has led to new research into the role of gastrin and its receptor (cholecystokinin-2 receptor) in carcinogenesis and the development of cholecystokinin-2 receptor antagonists.

Antiulcer and antioxidant activities of a new steroid from Morus alba

AIMS

Morus alba is a plant that is well known for its medicinal properties. In Asian countries, it is traditionally used for anti-inflammatory, hypoglycemic, hypolipidemic and antioxidant applications. The aim of this study was to evaluate the antiulcer and antioxidant activity of a new steroid from M. alba.

MAIN METHODS

Column chromatography was employed to isolate different compounds from M. alba. The molecular structures of the compounds were characterized via IR, UV, (1)H NMR, (13)C NMR and mass spectroscopic methods. A newly isolated compound was tested for antiulcer activity in pylorus-ligation- and ethanol-induced ulcer models and biochemically estimated for SOD, CAT, GR, GPx, GSH and LPO levels.

KEY FINDINGS

Five new compounds were isolated; one of these was a new steroid named albosteroid. This new compound exhibits significant (P<0.05, P<0.01 and P<0.001) antiulcer activity in pylorus-ligation- and ethanol-induced ulcer models. Furthermore, this compound showed significant dose-dependent reversal of ethanol-diminished activity in antioxidant enzymes, such as SOD, CAT, GPx and GSH, and reduced the ethanol-elevated levels of GR and LPO.

SIGNIFICANCE

The present study clearly demonstrates the anti-ulcer and antioxidant potential of compound 1, which was supported by macroscopic and histopathological studies of stomach wall tissues of differently treated groups of rats.

COX-2 mRNA is increased in oesophageal mucosal cells by a proton pump inhibitor

BACKGROUND

Barrett's oesophagus develops in some individuals with gastro-oesophageal reflux and is the precursor to oesophageal adenocarcinoma. Proton pump inhibitors (PPIs) suppress gastric acid production and are used to treat reflux. Clinical trials suggest that cyclooxygenase (COX) inhibitors might prevent oesophageal cancer, although PPIs could offset this by increasing COX-2 expression in Barrett's oesophagus. To investigate this, we evaluated the impact of a PPI on COX expression in oesophageal mucosal cells.

METHODS

The effect of the PPI esomeprazole on COX-1 and COX-2 mRNA levels in oesophageal cells was determined. Oesophageal cell lines OE33 (adenocarcinoma-derived) and HET-1A (immortalized squamous cells) and a control intestinal cell line HT29 (colon carcinoma) were treated for 24 h, with increasing concentrations of the esomeprazole.

RESULTS

COX-2, but not COX-1, mRNA levels dose-dependently increased in OE33 and HET-1A cells versus esomeprazole concentration. COX-2 mRNA levels did not increase in HT29 cells.

CONCLUSIONS

Exposure to esomeprazole increases COX-2 mRNA in oesophageal cells. This might contribute to the lack of benefit for COX inhibitors for oesophageal cancer prevention in recent clinical studies.

Mechanisms of action underlying the gastric antiulcer activity of the Rhizophora mangle L

ETHNOPHARMACOLOGICAL RELEVANCE

Rhizophora mangle, the red mangrove, has long been known as a traditional antiulcer medicine. The present work evaluated the mechanisms of action involved in the anti-ulcer properties of the Rhizophora mangle bark extracts.

MATERIALS AND METHODS

Gastroprotection of Rhizophora mangle was evaluated in rodent experimental models (ethanol). To elucidate the mechanisms of action the antisecretory action and involvement of NO, SH, mucus and PGE(2) were evaluated. The acetic acid-induced gastric ulcer model, Western blotting assay (COX-1, COX-2 and EGF) and immunohistochemical localization of HSP-70, PCNA and COX-2 were also used to evaluate the Rhizophora mangle healing properties.

RESULTS

Results showed that Rhizophora mangle bark crude extract (CE), as well as ethyl acetate (EtOAc) and butanolic fractions (BuOH) provided significant gastroprotection at all the tested doses. Thereby, the following protocols were performed using the lowest dose capable of producing the most effective gastroprotection, which was the BuOH 0.5mg/kg (P<0.001). Several mechanisms are involved in the antiulcer activity of Rhizophora mangle, such as, participation of NO, SH and mucus. The enhancement of PGE(2) levels and the upregulation of COX-2 and EGF seem to be directly linked to the antisecretory, cytoprotective and healing effects of BuOH. HSP-70 and PCNA are also involved in this cicatrisation process. No sign of toxicity was observed in this study, considering the analyzed parameters.

CONCLUSION

Our study reinforces its traditional medicinal use. Considering that the current therapies are based on the use of antisecretory or cytoprotective drugs, the Rhizophora mangle arises as a promising alternative antiulcer therapy.

Effects of lansoprazole on the expression of VEGF and cellular proliferation in a rat model of acetic acid-induced gastric ulcer

BACKGROUND

A recent study reported that in addition to their inhibitory effect on gastric acid secretion, some proton pump inhibitors also exert a cytoprotective effect on the gastric mucosa. We investigated the effects of lansoprazole (LPZ) on the epithelial cell cycle, and on the expressions of vascular endothelial growth factor (VEGF) and matrix metalloproteinase-2 (MMP-2).

METHODS

We examined the effects of 25 and 5 mg/kg LPZ on ulcer healing in an acetic acid-induced ulcer model in rats with and without indomethacin (IND) treatment. On days 14 and 28 after ulcer formation, we compared the ulcer diameter, bromodeoxyuridine (BrdU) uptake, apoptosis, vascular density, and the expressions of VEGF and MMP-2 in the different groups.

RESULTS

LPZ administration increased the BrdU uptake that was reduced by IND administration. LPZ administration also increased VEGF expression at the ulcer margin in a dose-dependent manner. However, LPZ administration did not increase VEGF expression following IND pretreatment. Administration of IND alone significantly decreased MMP-2 expression at the ulcer margin; on the other hand, subsequent administration of LPZ increased the MMP-2 expression.

CONCLUSION

One of the mechanisms of ulcer healing brought about by LPZ may be the involvement of endogenous prostaglandin (PG) secretion. The effect of endogenous PG secretion may be related to the induction of VEGF expression. On the other hand, LPZ administration increased MMP-2 expression, and this effect was not influenced by the inhibition of PG synthesis. The mechanisms of LPZ on ulcer healing may be involved by VEGF expression through endogenous PGs secretion. Additionally, the stimulated expression of MMP-2, which is not secreted by endogenous PGs, is another important factor for ulcer healing by LPZ.

Omeprazole promotes gastric epithelial cell migration

Proton pump inhibitors (PPIs) are effective at preventing non-steroidal anti-inflammatory drug (NSAID)-induced gastric ulcers. They are also superior to histamine H2-receptor antagonists and misoprostol in treating NSAID-induced gastric ulcer healing. This study explored whether omeprazole, a PPI, can modulate ulcer healing through epithelial cell proliferation and/or cell migration using a rat normal gastric epithelial cell line (RGM-1). Flow cytometry was used to determine cell proliferation and an artificial wound model was used to measure cell migration. Western blot analysis was performed to evaluate the possible mechanisms of action. Omeprazole treatment (10−8, 10−6 and 10−4M) for 12 and 24 h did not promote cell proliferation. However, similar doses of the drug (10−6 and 10−4 M) incubated for 24–48 h significantly promoted the basal cell migration of gastric epithelial cells. Further, the higher concentration of omeprazole (10−4M) reversed the inhibitory action of indometacin (10−5M) on cell migration. Western blot results showed that omeprazole did not increase cyclooxygenase-2 expression and did not activate signal transduction pathways, including extracellular signal-regulated kinase (ERK1/ERK2), P38 mitogenic-activated protein kinase, and phosphatidyl inositol 3-kinase. The results suggest that omeprazole is beneficial in basal ulcer healing and it reversed the adverse action of indometacin on ulcer repair under acid-independent conditions. These actions are likely to be mediated through the promotion of gastric epithelial cell migration but not cell proliferation.

Molecular mechanism and functional consequences of lansoprazole-mediated heme oxygenase-1 induction

AIM: To investigate the molecular mechanism and functional consequences of heme oxygenase-1 (HO-1) activation by lansoprazole in endothelial cells and macrophages.

METHODS: Expression of HO-1 mRNA was analyzed by Northern blotting. Western blotting was used to determine the HO-1 and ferritin protein levels. NADPH-dependent reactive oxygen species (ROS) formation was measured with lucigenin-enhanced chemiluminescence. HO-1 promoter activity in mouse fibroblasts, stably transfected with a 15-kb HO-1 gene that drives expression of the reporter gene luciferase, was assessed using in vivo bioluminescence imaging.

RESULTS: Lansoprazole increased HO-1 mRNA levels in endothelial cells and HO-1 protein levels in macrophages. In addition, lansoprazole-induced ferritin protein levels in both cell systems. Moreover, induction of the antioxidant proteins HO-1 and ferritin by lansoprazole was followed by a decrease in NADPH-mediated ROS formation. The radical scavenging properties of lansoprazole were diminished in the presence of the HO inhibitor, chromium mesoporphyrin IX. Induction of HO-1 gene expression by lansoprazole was not related to oxidative stress or to the activation of the mitogen-activated protein kinase pathway. However, the phosphatidylinositol 3-kinase inhibitor LY294002 showed a concentration-dependent inhibition of HO-1 mRNA and promoter activity.

CONCLUSION: Activation of HO-1 and ferritin may account for the gastric protection of lansoprazole and is dependent on a pathway blocked by LY294002.

Characterization of mechanisms underlying the effects of esomeprazole on the impairment of gastric ulcer healing with addition of NSAID treatment

BACKGROUND

The efficacy of proton pump inhibitors in patients at high risk of gastrointestinal injury receiving non-steroidal anti-inflammatory drugs is currently debated.

AIMS

To evaluate the effects of esomeprazole on the impairment of gastric ulcer healing associated with non-steroidal anti-inflammatory drug treatment.

METHODS

Gastric ulcers were induced in rats by acetic acid. Four days later, animals were treated daily with equivalent acid-inhibiting doses of esomeprazole or famotidine, alone or in combination with indomethacin. At day 3 or 7 of treatment, ulcerated tissues were processed to assess: ulcer area; malondialdehyde; prostaglandin E(2); nuclear factor-kB; proliferating cell nuclear antigen and caspase-3 (Western blot).

RESULTS

In indomethacin-treated animals, esomeprazole was more effective than famotidine or the antioxidant melatonin in promoting ulcer healing. Malondialdehyde levels were increased by indomethacin, and this effect was counteracted by esomeprazole, but not famotidine. Esomeprazole and famotidine, given alone or in combination with indomethacin, increased proliferating cell nuclear antigen expression. Increased levels of prostaglandin E(2) were detected in ulcerated tissues. Ulcer prostaglandin E(2) production was reduced by indomethacin, alone or in combination with esomeprazole or famotidine, while it was enhanced when esomeprazole or famotidine were tested alone. The activation of caspase-3 was induced by indomethacin, and this effect was prevented by esomeprazole, but not famotidine. In the presence of indomethacin, esomeprazole, but not famotidine, enhanced nuclear factor-kB activation in gastric ulcers.

CONCLUSIONS

Esomeprazole counteracts the detrimental action of indomethacin on ulcer repair through both acid-dependent and acid-independent effects. The acid-independent actions are related to decrease in tissue oxidation and apoptosis and to enhancement of nuclear factor-kB activation.

Management of NSAID-induced gastrointestinal toxicity: focus on proton pump inhibitors

The association between NSAIDs and the presence of upper gastrointestinal (GI) complications is well established. Evidence that acid aggravates NSAID-induced injury provides a rationale for minimizing such damage by acid suppression. Proton pump inhibitors (PPIs) appear to be very effective in treating NSAID-related dyspepsia, and also in healing gastric and duodenal ulcers in patients continuing to receive the NSAID. An analysis of data from comparative studies of PPIs versus ranitidine, misoprostol and sucralfate shows a therapeutic advantage in favour of the PPI. Several studies now confirm the efficacy of co-therapy with PPIs in the short- and long-term prevention of NSAID-induced upper GI injury. PPIs are more effective than histamine H(2)-receptor antagonists at standard dosages in reducing the risk of gastric and duodenal ulcer, and are superior to misoprostol in preventing duodenal but not gastric lesions. However, when balancing effectiveness and tolerance, PPIs may be considered the treatment of choice in the short- and long-term prevention of NSAID-related mucosal lesions. To date, there are only a few published articles dealing with the role of PPIs in the prevention of upper GI complications. Recent epidemiological and interventional studies provide some evidence that PPIs are of benefit. However, more controlled studies using clinical outcomes are needed to establish the best management strategy (PPIs combined with traditional NSAIDs or with cyclo-oxygenase-2 selective inhibitors) especially in patients with multiple risk factors, in patients using concomitant low-dose aspirin, corticosteroids or anticoagulants (high risk group), or in patients with a history of ulcer complications (very high risk group). Furthermore, it should be underlined that Helicobacter pylori infection positively interacts with the gastroprotective effect of PPIs; therefore, the true efficacy of these drugs in preventing NSAID-related ulcer complications should be reassessed without the confounding influence of this microorganism.

The antiulcer effect of Croton cajucara Benth in normoproteic and malnourished rats

The aim of the present study is to investigate the antiulcerogenic effects of the essential oil (EO) of Croton cajucara Benth in rats fed with a normal protein (NP) and low-protein diet (MN). NP and MN rats were treated with the essential oil for 15 days after chronic ulceration was induced. The EO accelerated healing of acetic acid-induced gastric lesions in NP and MN rats (p<0.05). In a similar experiment on chronic ulceration, Epidermal Growth Factor (EGF) mRNA expression increased in NP rats but not in MN rats. In assays of acute antiulcerogenic activity, C. cajucara increased somatostatin plasma levels and decreased gastrin plasma levels in both animal groups. The EO significantly prevented ethanol-induced gastric ulcers in NP and MN rats (p<0.001). Histological examination showed initial regeneration, formation of inflammatory infiltrate and angiogenesis in the epithelium surface of acetic acid-induced ulcers in NP and MN rats. C. cajucara prevented gastric lesions in both animal groups when ethanol methodology was used. We concluded that the EO showed an antiulcerogenic activity mediated by increased somatostatin secretion and EGF mRNA expression.

Effects of esomeprazole on glutathione levels and mitochondrial oxidative phosphorylation in the gastric mucosa of rats treated with indomethacin

Proton pump inhibitors exert their preventive and healing effects on gastropathy induced by nonsteroidal anti-inflammatory drug (NSAIDs) by a dual action: the antisecretory and the antioxidant effect. The latter was investigated by using esomeprazole against indomethacin-induced gastric mucosa lesions in rats and assessed by a histomorphometric analysis. Treatment by intragastric gavage were 1% methocel as vehicle; esomeprazole 10, 30, or 60 micromol/kg; indomethacin 100 micromol/kg; and esomeprazole 10, 30, or 60 micromol/kg plus indomethacin 100 micromol/kg. The evaluation of glutathione (GSH) levels and respiratory chain complex activities [nicotinamide adenine dinucleotide, reduced (NADH)-ubiquinone oxidoreductase, succinate dehydrogenase, cytochrome C reductase, cytochrome oxidase] was performed in the isolated gastric mucosa. Esomeprazole (10-60 micromol/kg) dose dependently reversed, up to complete recovery, the inhibitory effect of indomethacin on GSH levels (approximately 60% inhibition) and mitochondrial enzyme activities (inhibition ranging from 60% to 75%). Indomethacin-induced mucosal injuries were reduced by esomeprazole. Thus, in addition to inhibiting acid secretion, the gastroprotective effect of esomeprazole can be ascribed to a reduction in gastric oxidative injury.

Blockade of cholecystokinin-2 receptor and cyclooxygenase-2 synergistically induces cell apoptosis, and inhibits the proliferation of human gastric cancer cells in vitro

Gastrin and cyclooxygenase-2 (COX-2) play important roles in the carcinogenesis and progression of gastric cancer. However, it remains unknown whether the combination of cholecystokinin-2 (CCK-2) receptor antagonist plus COX-2 inhibitor exerts synergistic anti-tumor effects on human gastric cancer. Here, we demonstrated that the combination of AG-041R (a CCK-2 receptor antagonist) plus NS-398 (a selective COX-2 inhibitor) treatment had synergistic effects on proliferation inhibition, apoptosis induction, down-regulation of Bcl-2 and up-regulation of Bax expression in MKN-45 cells. These results indicate that simultaneous targeting of CCK-2 receptor and COX-2 may inhibit gastric cancer development more effectively than targeting either molecule alone.

Gastric mucosal levels of prostaglandins and leukotrienes in patients with gastric ulcer after treatment with rabeprazole in comparison to treatment with ranitidine

AIM

Prostaglandins (PGs) and leukotrienes (LTs) are major factors involved in the defense of the gastric mucosa against ulcer formation. However, little is still known about the gastromucosa-protecting action of proton pump inhibitors (PPIs) and histamine H(2) receptor antagonists (H(2) blockers) in patients with gastric ulcer. We therefore examined the effectiveness of a PPI in protecting the gastric mucosa.

METHODS

We compared the PGE(2) and LTB(4) levels and the expression levels of cyclooxygenase (COX)-1 and COX-2 mRNA in the gastric mucosa in gastric ulcer patients between the group treated for 8 weeks with a PPI, rabeprazole (PPI group; n=5), and the group treated for 8 weeks with an H(2) blocker, ranitidine (H(2) blocker group; n=6), as well as in nonulcer subjects (control group; n=5).

RESULTS

The mucosal levels of PGE(2) and COX-2 mRNA expression were significantly lower in the ulcer patients than those in the nonulcer patients, whereas the LTB(4) level was significantly higher in the ulcer patients than that in the nonulcer patients, and it was also significantly lower in the ulcerated mucosa than that in the nonulcerated mucosa. The PPI group had a significantly increased PGE(2) and decreased LTB(4) levels in comparison to the H(2) blocker group during the ulcer-healing stage. The COX-1 mRNA expression showed no difference among the PPI and H(2) blocker groups or between before and after the treatment. However, the COX-2 mRNA expression increased in the PPI group more than that in the H(2) blocker group during the ulcer-healing stage.

CONCLUSION

These findings demonstrated the significant gastric-mucosa-protecting effect of PPI by increasing the PGE(2) production and reducing the LTB(4) production.

Protective effects of proton pump inhibitors against indomethacin-induced lesions in the rat small intestine

Proton pump inhibitors (PPIs) have been shown to be effective in preventing gastric and duodenal ulcers in high-risk patients taking nonsteroidal anti-inflammatory drugs (NSAIDs); by contrast, scarce information is available concerning the effects of PPIs on intestinal damage induced by NSAIDs in humans or in experimental animals. We examined the effects of lansoprazole and omeprazole on the intestinal injury induced by indomethacin in the conscious rat. PPIs were administered by the intragastric route at 30, 60 and 90 micromol/kg, 12 h and 30 min before and 6 h after indomethacin treatment. The effects of omeprazole and lansoprazole were evaluated on: (1) macroscopic and histologic damage; (2) mucosal polymorphonuclear cell infiltration; (3) oxidative tissue damage and (4) bacterial translocation from lumen into the intestinal mucosa. Lansoprazole and omeprazole (at 90 micromol/kg) significantly decreased (P<0.01) the macroscopic and histologic damage induced by indomethacin in the rat small intestine. Furthermore, both drugs greatly reduced (P<0.01) the associated increases in myeloperoxidase levels and lipid peroxidation induced by indomethacin, whereas they only moderately affected (P<0.05) the translocation of enterobacteria from lumen into the intestinal mucosa. These data demonstrate that omeprazole and lansoprazole can protect the small intestine from the damage induced by indomethacin in the conscious rat. The intestinal protection, possibly related to antioxidant and anti-inflammatory properties of these drugs, may suggest new therapeutic uses of PPIs in intestinal inflammatory diseases.

Systematic review: Cyclo-oxygenase-2 in human oesophageal adenocarcinogenesis

BACKGROUND

Published in vitro and animal in vivo studies have demonstrated that cyclo-oxygenase-2 plays an important role during oesophageal adenocarcinogenesis. However, the extent to which these studies are directly relevant to events in the human lower oesophagus is questionable.

AIM

To perform a systematic review of all available human studies that have evaluated levels of cyclo-oxygenase-2 expression during the progression from Barrett's metaplasia to oesophageal adenocarcinoma.

METHODS

A literature search was performed to identify all studies which qualitatively or quantitatively assessed cyclo-oxygenase-2 protein or gene expression in either Barrett's, dysplastic or adenocarcinoma tissue in humans.

RESULTS

A total of 27 studies met the inclusion criteria. There was general agreement that cyclo-oxygenase-2 was either absent or very weakly expressed in normal oesophageal squamous mucosa, but considerable disagreement regarding the presence of cyclo-oxygenase-2 in Barrett's and low-grade dysplasia. All studies agreed that high-grade dysplasia and adenocarcinoma expressed cyclo-oxygenase-2 to some extent although levels varied considerably between tissue samples.

CONCLUSIONS

There is conflicting evidence in the literature for cyclo-oxygenase-2 playing an important role in early oesophageal adenocarcinogenesis. Other non-cyclo-oxygenase-2 targets may account for the epidemiological data supporting the use of non-steroidal anti-inflammatory drugs in the chemoprevention of oesophageal adenocarcinoma.

Endoplasmic reticulum stress response is involved in the pathogenesis of stress induced gastric lesions in rats

Stress gastric ulcer is a serious complication, but the mechanism involved is not fully clarified. It is well known that mucosal cell apoptosis plays a crucial role in the pathogenesis of gastric ulceration. Recent studies have shown that endoplasmic reticulum (ER) stress is an important pathway leading to cellular apoptosis. To investigate the role of ER stress in the pathogenesis of stress gastric ulcer, we studied the alteration in the expression of ER stress markers GRP78 (glucose-regulated protein 78) and caspase-12 (an ER stress-specific proapoptotic molecule) and their relations with gastric mucosal apoptosis during development of stress gastric lesions in the water-immersion and restraint stress (WRS) model in rats. Rats developed severe gastric lesions after 6 h of WRS. Typical apoptosis was observed at the edge cells of WRS induced gastric lesions. Western blot analysis showed that GRP78 and activated caspase-12 were over-expressed in the gastric tissues of WRS rats. Immunohistochemical analysis demonstrated that increased GRP78 and caspase-12 were distributed only under the lesions. In addition, dithiothreitol and tunicamycin (ER stress inducers), which increased the expression of GRP78 and activated caspase-12, caused gastric mucosal injury and mucosal cell apoptosis in vitro. These findings suggest that ER stress might be involved in the development of stress gastric ulcer through an apoptotic mechanism.

Beyond gastric acid reduction: Proton pump inhibitors induce heme oxygenase-1 in gastric and endothelial cells

Proton pump inhibitors (PPIs) have been demonstrated to prevent gastric mucosal injury by mechanisms independent of acid inhibition. Here we demonstrate that both omeprazole and lansoprazole protect human gastric epithelial and endothelial cells against oxidative stress. This effect was abrogated in the presence of the heme oxygenase-1 (HO-1) inhibitor ZnBG. Exposure to either PPI resulted in a strong induction of HO-1 expression on mRNA and protein level, and led to an increased activity of this enzyme. Expression of cyclooxygenase isoforms 1 and 2 remained unaffected, and COX-inhibitors did not antagonize HO-1 induction by PPIs. Our results suggest that the antioxidant defense protein HO-1 is a target of PPIs in both endothelial and gastric epithelial cells. HO-1 induction might account for the gastroprotective effects of PPIs independently of acid inhibition, especially in NSAID gastropathy. Moreover, our findings provide additional perspectives for a possible but yet unexplored use of PPIs in vasoprotection.

Antiulcerogenic and ulcer healing effects of Solanum nigrum (L.) on experimental ulcer models: possible mechanism for the inhibition of acid formation

Solanum nigrum, an herbal plant which is recommended in ayurveda for the management of gastric ulcers. Therefore, the purpose of the study was to investigate the antiulcer effect of Solanum nigrum fruits extract (SNE) on cold restraint stress (CRU), indomethacin (IND), pyloric ligation (PL) and ethanol (EtOH) induced gastric ulcer models and ulcer healing activity on acetic acid induced ulcer model in rats. The treatment with SNE at higher dose significantly inhibited the gastric lesions induced by CRU (76.6%), IND (73.8%), PL (80.1%) and EtOH (70.6%), respectively, with equal or higher potency than omeprazole. SNE showed concomitant attenuation of gastric secretory volume, acidity and pepsin secretion in ulcerated rats. In addition, SNE (200 and 400mg/kgb.w.) accelerated the healing of acetic acid induced ulcers after the treatment for 7 days. Further, to ascertain the antisecretory action, the effects of SNE on H(+)K(+)ATPase activity and plasma concentration of gastrin hormone in ulcerated rats were determined. SNE significantly inhibits H(+)K(+)ATPase activity and decreases the gastrin secretion in EtOH-induced ulcer model. The severity of the reaction of ulcerogen and the reduction of ulcer size by SNE was evident by histological findings. Toxicity studies of SNE have also been carried out for its safety evaluation. SNE, thus, offers antiulcer activity by blocking acid secretion through inhibition of H(+)K(+)ATPase and decrease of gastrin secretion. These results further suggest that SNE was found to possess antiulcerogenic as well as ulcer healing properties, which might also be due to its antisecretory activity.

Involvement of cyclooxygenase-2 in gastric mucosal hypertrophy in gastrin transgenic mice

Gastrin promotes gastric mucosal growth, and hypergastrinemia induces gastric mucosal hypertrophy. Recently, it has been reported that gastrin induces cyclooxygenase-2 (COX-2) in human gastric and colorectal cancer cell lines. However, whether COX-2 is involved in gastrin-induced gastric mucosal growth in vivo is unknown. We investigated the role of COX-2 in gastrin-induced gastric mucosal hypertrophy using gastrin transgenic mice. Hypergastrinemic mice [mice with mutated gastrin under the control of the beta-actin promoter (ACT-GAS mice)] received the COX-2 inhibitor celecoxib (0, 200, or 500 mg/kg of diet) from 5 wk of age and were killed at 16 or 24 wk. Some ACT-GAS mice received celecoxib from 16 wk and were killed at 24 wk. Eighty-week-old ACT-GAS mice without celecoxib treatment were also examined. The thickness of the gastric mucosa, cell populations, COX-2 expression, and PGE(2) levels were evaluated. All ACT-GAS mice showed gastric mucosal hypertrophy, and four of six 80-wk-old ACT-GAS mice developed gastric cancer. COX-2 was expressed in interstitial cells of the hypertrophic gastric mucosa and gastric cancers. Moreover, PGE(2) levels in the gastric mucosa of ACT-GAS mice were significantly higher than those of normal mice. With treatment with celecoxib, PGE(2) levels, the gastric mucosal thickness, and the number of total gastric cells per gastric gland of ACT-GAS mice were significantly decreased. The decrease in gastric mucosal thickness was caused by a reduction of foveolar hyperplasia. The thickness of glandules and the number of Ki67-positive cells were not significantly changed. In conclusion, COX-2 contributes to gastrin-induced mucosal hypertrophy of the stomach.

Cyclo-oxygenase-2 expression and prostaglandin E2 production in experimental chronic gastric ulcer healing

Prostaglandin, a key molecule that stimulates the complex array of ulcer healing mechanism, gets synthesized in the mucosal cells by cyclooxygenase (COX) enzymes: COX-1 and COX-2. High expression level of COX-2 protein at healing ulcer margins highlights its role in ulcer healing and hypothesized to be an important contributing factor in healing mechanism of anti-ulcer drugs. In the present study we have compared the expression profile of COX-2 protein, prostaglandin E2 (PGE2) levels and myeloperoxidase activity in acetic acid induced chronic gastric ulcer model in rats treated with omeprazole, misoprostol and COX-2 selective nonsteroidal anti-inflammatory drug (NSAID) celecoxib. Both COX-2 expression and PGE2 level have shown differential pattern in different treated groups parallel to the differential effects of these drugs on ulcer healing. Omeprazole has significantly elevated the expression level of COX-2 protein, PGE2 level (19.37%), and decreased myeloperoxidase activity (81.92%), thereby causing the most effective ulcer healing (89.74%). Similar trend was observed with misoprostol, but with relatively less pronounced ulcer healing and COX-2 expression. Celecoxib has retarded COX-2 expression and delayed ulcer healing. Therefore, induction of COX-2 expression leading to higher level of prostaglandin appears to be an important contributing factor in drug mediated ulcer healing apart from the respective mechanisms of different drugs.

Mechanisms of protection by pantoprazole against NSAID-induced gastric mucosal damage

The use of nonsteroidal anti-inflammatory drugs (NSAIDs) can be associated with severe adverse digestive effects. In clinical settings, proton pump inhibitors have proven to be effective in preventing and healing NSAID-induced gastroduodenal lesions. The present study investigates the mechanisms of protection afforded by pantoprazole against gastric injury induced by different NSAIDs in rats. Animals were orally treated with indomethacin (100 micromol/kg), diclofenac (60 micromol/kg), piroxicam (150 micromol/kg) or ketoprofen (150 micromol/kg). Thirty minutes before NSAIDs, animals received pantoprazole 6 or 60 micromol/kg orally. Four hours after NSAIDs, the following parameters were assessed: histomorphometric evaluation of gastric mucosal damage; gastric mucosal levels of myeloperoxidase (MPO), malondialdehyde (MDA), reduced glutathione as an index of non-proteic sulfhydryl compounds (GSH), and prostaglandin E2 (PGE2); mucosal cyclooxygenase-1 and -2 (COX-1, COX-2) mRNA expression by reverse transcription-polymerase chain reaction (RT-PCR). Separate experiments were carried out to assay the effects of pantoprazole on gastric acid secretion in pylorus-ligated rats. The in vitro influence of pantoprazole (1-10 microM) on the oxidation of low density lipoproteins (LDLs) induced by copper sulphate was also examined. All NSAIDs elicited mucosal necrotic lesions associated with neutrophil infiltration and reduction of PGE2 levels. Increments of MPO and MDA contents, as well as a decrease in GSH levels, were detected in the gastric mucosa of indomethacin-, piroxicam- or ketoprofen-treated animals. Indomethacin enhanced mucosal COX-2 expression, while not affecting COX-1. At the oral dose of 6 micromol/kg pantoprazole did not affect NSAID-induced mucosal damage, whereas at 60 micromol/kg it markedly reduced injuries provoked by all test NSAIDs. Pantoprazole 60 micromol/kg also reversed the effects of NSAIDs on MPO, MDA, and GSH mucosal contents, without interfering with the decrease in PGE2 levels or indomethacin-induced COX-2 expression. However, at both doses, pantoprazole inhibited acid secretion in pylorus-ligated rats. Furthermore, pantoprazole concentration dependently reduced the in vitro oxidation of LDLs. Our results suggest that besides inhibiting acid secretion, the protection afforded by pantoprazole against NSAID-induced gastric damage depends on a reduction in mucosal oxidative injury, which may also account for an increment of sulfhydryl radical mucosal bioavailability. It is also suggested that pantoprazole does not influence the down-regulation of gastric prostaglandin production associated with NSAID treatment.

Lansoprazole prevents experimental gastric injury induced by non-steroidal anti-inflammatory drugs through a reduction of mucosal oxidative damage

AIM: This study investigated the mechanisms of protection afforded by the proton pump inhibitor lansoprazole against gastric injury induced by different non-steroidal anti-inflammatory drugs (NSAIDs) in rats.

METHODS: Male Sprague-Dawley rats were orally treated with indomethacin (100 µmol/kg), diclofenac (60 µmol/kg), piroxicam (150 µmol/kg) or ketoprofen (150 µmol/kg). Thirty minutes before NSAIDs, animals were orally treated with lansoprazole 18 or 90 µmol/kg. Four hours after the end of treatments, the following parameters were assessed: gastric mucosal PGE2, malondialdehyde (MDA), myeloperoxidase (MPO) or non-proteic sulfhydryl compounds (GSH) levels; reverse transcription-polymerase chain reaction (RT-PCR) of mucosal COX-2 mRNA; gastric acid secretion in pylorus-ligated animals; in vitro effects of lansoprazole (1-300 µmol/L) on the oxidation of low density lipoproteins (LDLs) induced by copper sulphate.

RESULTS: All NSAIDs elicited mucosal necrotic lesions which were associated with neutrophil infiltration and reduction of PGE2 levels. Increments of MPO and MDA contents, as well as a decrease in GSH levels were detected in the gastric mucosa of indomethacin- or piroxicam-treated animals. Indomethacin enhanced mucosal cyclooxygenase-2 expression, while not affecting cyclooxygenase-1. At the oral dose of 18 µmol/kg lansoprazole partly counteracted diclofenac-induced mucosal damage, whereas at 90 µmol/kg it markedly prevented injuries evoked by all test NSAIDs. Lansoprazole at 90 µmol/kg reversed also the effects of NSAIDs on MPO, MDA and GSH mucosal contents, without interfering with the decrease in PGE2 levels or indomethacin-induced cyclooxygenase-2 expression. However, both lansoprazole doses markedly inhibited acid secretion in pylorus-ligated rats. Lansoprazole concentration-dependently reduced the oxidation of LDLs in vitro.

CONCLUSION: These results suggest that, besides the inhibition of acid secretion, lansoprazole protection against NSAID-induced gastric damage depends on a reduction in mucosal oxidative injury, which is also responsible for an increment of sulfhydryl radical bioavailability. It is also suggested that lansoprazole does not influence the down-regulation of gastric prostaglandin production associated with NSAID treatment.

Neuroendocrinology of gastric H+ and duodenal HCO3- secretion: the role of brain-gut axis

Gastric H+ and duodenal HCO3- secretions are precisely regulated by neuro-hormonal mechanisms at central and peripheral levels to match the rate of these secretions with the type of stimulation of sensory receptors in the head area (sight, smell, taste, etc.) and in the gastro-intestinal system. Two-way communication pathways operate between the brain and the gut, each comprising afferent fibers signaling sensory information from the gut to the brain and efferent fibers transmitting signals in opposite direction. Short intramural and long extramural reflexes are triggered as well as various gut hormones are released by feeding that "cooperate" with the "brain-gut axis" in the alteration of exocrine and endocrine gastro-duodenal secretion, motility and blood circulation. The malfunction of gastric or duodenal secretory mechanisms may lead to disturbances of gastric H+-pepsin or duodenal mucus-HCO3- secretion and to gastro-duodenal disorders and diseases. This review presents recent advances in pathophysiological mechanisms underlying gastro-duodenal secretory disorders.

Modulation of gastrin and epidermal growth factor by pyrrolizidine alkaloids obtained from Senecio brasiliensis in acute and chronic induced gastric ulcers

We investigated the antiulcerogenic activity of pyrrolizidine alkaloids (PAs) integerrimine, retrorsine, senecionine, usaramine and seneciplhylline, an alkaloidal extract obtained from Senecio brasiliensis. The PA extract demonstrated significantly activity in both, acute and chronic gastric ulcers on rats. The effects of PA extract were dose dependent. The mechanisms implicated on this activity were evaluated by determination of gastrin plasma levels in rats subjected to the acute treatment with PA extract and by expression of mRNA of Epidermal Growth Factor (EGF) after chronic treatment with this extract. The results showed that the PA extract increased both the levels of gastrin and the expression of EGF on these animals. Moreover, the histological examinations showed a reduction of exfoliation of superficial cells, hemorrhages and blood cell infiltration. We concluded that the PAs showed an important and qualitative antiulcerogenic activity mediated by increase in gastrin secretion and mRNA expression of EGF.

Mechanisms of gastroprotection by lansoprazole pretreatment against experimentally induced injury in rats: role of mucosal oxidative damage and sulfhydryl compounds

This study investigated the mechanisms involved in the protective actions exerted by lansoprazole against experimental gastric injury. Following the intraluminal injection of ethanol-HCl, the histomorphometric analysis of rat gastric sections demonstrated a pattern of mucosal lesions associated with a significant increase in the mucosal contents of malondialdehyde and 8-iso-prostaglandin F(2alpha) (indices of lipid peroxidation), as well as a decrease in the levels of mucosal sulfhydryl compounds, assayed as reduced glutathione (GSH). Pretreatment with lansoprazole 90 micromol/kg, given intraduodenally as single dose or once daily by intragastric route for 8 days, significantly prevented ethanol-HCl-induced gastric damage. The concomitant changes in the mucosal levels of malondialdehyde, 8-iso-prostaglandin F(2alpha) and GSH elicited by ethanol-HCl were also counteracted by lansoprazole. In separate experiments, performed on animals undergoing 2-h pylorus ligation, lansoprazole did not enhance the concentration of prostaglandin E(2), bicyclo-prostaglandin E(2), or nitric oxide (NO) metabolites into gastric juice. Western blot analysis revealed the expression of both type 1 and 2 cyclooxygenase (COX) isoforms in the gastric mucosa of pylorus-ligated rats. These expression patterns were not significantly modified by single-dose or repeated treatment with lansoprazole. Lansoprazole also exhibited direct antioxidant properties by reducing 8-iso-prostaglandin F(2alpha) generation in an in vitro system where human native low-density lipoproteins were subjected to oxidation upon exposure to CuSO(4). The present results suggest that the protective effects of lansoprazole can be ascribed to a reduction of gastric oxidative injury, resulting in an increased bioavailability of mucosal sulfhydryl compounds. It is also proposed that lansoprazole does not exert modulator effects on the gastric expression of COX isoforms as well as on the activity of NO pathways.

Gastric secretion

PURPOSE OF REVIEW

Gastric acid facilitates the digestion of protein and the absorption of iron, calcium, and vitamin B12. It also protects against bacterial overgrowth and enteric infection, including prion disease. When homeostatic mechanisms malfunction, the volume and concentration of acid may overwhelm mucosal defense mechanisms, leading to duodenal ulcer, gastric ulcer, and gastroesophageal reflux disease. This article reviews recent knowledge contributing to understanding of the regulation of gastric acid secretion at the central, peripheral, and intracellular levels.

RECENT FINDINGS

The vagus nerve contains afferent fibers that transmit sensory information from the stomach to the nucleus of the solitary tract. Input from the nucleus of the solitary tract is relayed to vagal efferent neurons that originate from two brain stem nuclei: the nucleus ambiguus and the dorsal motor nucleus of the vagus. The latter is also influenced by thyrotropin-releasing hormone neurons that act centrally to stimulate acid secretion. The main peripheral stimulants of acid secretion are the hormone gastrin and the paracrine amine histamine. Gastrin stimulates acid secretion directly and, more importantly, indirectly by releasing histamine from fundic enterochromaffin-like cells. Gastrin also exerts trophic effects on various tissues, including the gastric and intestinal mucosa. The main inhibitor of acid secretion is somatostatin. Somatostatin, acting via ssTR2 receptors, exerts a tonic paracrine inhibitory influence on the secretion of gastrin, histamine, and acid secretion. Calcitonin gene-related peptide, adrenomedullin, amylin, atrial natriuretic peptide, and pituitary adenylate cyclase-activating polypeptide all stimulate somatostatin secretion and thus inhibit acid secretion. HK-ATPase, the proton pump of the parietal cell, is stored within cytoplasmic tubulovesicles during the resting state, but during stimulation, it is shuttled to the canalicular membrane by a poorly understood mechanism that probably involves soluble N-ethylmaleimide-sensitive factor attachment protein receptor proteins. The proton pump inhibitor, pantoprazole, is unique in that it binds cysteine 822, located deep within the membrane domain of the alpha-subunit. The difficulty that reducing agents, such as glutathione, have in reaching cysteine 822 may be responsible for the longer half-time for acid recovery observed with pantoprazole. Hypergastrinemia, induced by proton pump inhibitors, enhances expression of cyclooxygenase-2 and hence prostaglandins within parietal cells, a feedback pathway that may protect the stomach against acid-induced damage.

SUMMARY

In the past year, significant advances have been made in understanding of the regulation of gastric acid secretion. Ultimately, these advances should lead to improved therapies to prevent and treat acid-related disorders. Gastric acid secretion must be precisely controlled at a variety of levels to prevent disease caused by hyperchlorhydria and hypochlorhydria. The mechanisms include neural (central and peripheral), hormonal, paracrine, and intracellular pathways that operate in concert to switch acid secretion on during ingestion of a meal and off during the interdigestive period. A better understanding of the physiology of acid secretion in health and disease should eventually lead to improved therapies to prevent and treat acid-related disorders.

Gastrin and EGF synergistically induce cyclooxygenase-2 expression in Swiss 3T3 fibroblasts that express the CCK2 receptor

Over-expression of cyclooxygenase-2 (COX-2) has been demonstrated to be tumorigenic in transgenic mice. Chronic treatment with NSAIDs is chemoprotective for colorectal cancer. Gastrin is a growth factor for gastric mucosa and has been shown to promote proliferation of colorectal cells. Recent studies suggest that COX-2 expression levels could mediate the growth effects of gastrin. Here, we report that gastrin increased PGE2 secretion in Swiss 3T3 cells expressing the CCK2 receptor. Gastrin dose dependently induced COX-2 protein levels in a time dependent manner. COX-2 mRNA levels were rapidly induced by a dose dependent increase in gastrin. Prior treatment of the cells with the CCK2 receptor specific antagonist, L365,260, inhibited gastrin-induced COX-2 protein and mRNA expression. Pretreatment with L364,714, the CCK1 receptor specific antagonist did not block COX-2 induction by gastrin. Inhibition of de novo protein synthesis by cycloheximide did not block COX-2 mRNA induction by gastrin. Also, gastrin-dependent COX-2 expression did not require PKC activity, activation of ERK, or transactivation of EGFR. However, co-stimulation with EGF and gastrin synergistically induced COX-2 protein and mRNA expression and PGE2 secretion. Measurements of COX-2 mRNA stability and COX-2 gene transcription reveal that EGF significantly increased the half-life of COX-2 mRNA with only a slight increase in the COX-2 transcription rate. Conversely, gastrin significantly increased COX-2 gene transcription rates but did not enhance COX-2 mRNA stability.