Inhibitory effect of non-steroidal anti-inflammatory drugs on mucosal cell proliferation associated with gastric ulcer healing

Is the new potent acid-inhibitory drug vonoprazan effective for healing idiopathic peptic ulcers? A multicenter observational study in Akita Prefecture, Japan

BACKGROUND

The incidence of peptic ulcers unrelated to H. pylori infection and non-steroidal anti-inflammatory drugs (NSAIDs), termed idiopathic peptic ulcers (IPUs), has increased worldwide. We recently reported that IPUs were refractory to proton pump inhibitor (PPI) treatment. Vonoprazan, which was recently developed in Japan, has shown a more potent acid-inhibitory effect than ordinary PPIs. In the present study, we compared the healing rates among peptic ulcers of different etiologies following treatment with vonoprazan.

METHOD

A multicenter observational study was performed at six participating hospitals in Akita Prefecture, Japan. Consecutive patients who had endoscopically confirmed gastro-duodenal ulcers were enrolled between August 2016 and March 2018. For each patient, the Helicobacter pylori infection status and NSAID use, including aspirin, were checked, and 20 mg vonoprazan was administered for 6 weeks for duodenal ulcers and 8 weeks for gastric ulcers. The healing status was checked by endoscopy at the end of vonoprazan treatment. Patients were divided into four subgroups according to the H. pylori status and NSAID usage.

RESULTS

The proportion of IPUs was 18.2%. A total of 162 patients completed the study protocol. The healing rate of IPUs was marginally lower than that of simple H. pylori-associated ulcers (81.2% vs. 93.5%, P = 0.05). Similarly, the healing rate of NSAID-related ulcers, irrespective of concomitant H. pylori infection, was significantly lower than that of simple H. pylori-associated ulcers.

CONCLUSIONS

Six- or 8-week vonoprazan treatment still seems to be insufficient for healing IPUs. Longer-term vonoprazan or another treatment option may be required to heal potentially refractory peptic ulcers.

Gastro-Protective and Anti-Oxidant Potential of Althaea officinalis and Solanum nigrum on Pyloric Ligation/Indomethacin-Induced Ulceration in Rats

Recently, an alternative disease treatment approach is the research of medicaments from traditional medicine. Plants with anti-oxidant capabilities are used as herbal treatments for ulcer diseases. Medicinal/herbal extracts containing phytoconstituents have significant anti-ulcer activities in in vivo experiments on animal models, compared to reference drugs. The current study aims to inspect gastro-protective as well as in vitro and in vivo anti-oxidant potential of Althaea officinalis and Solanum nigrum extracts on pyloric-ligation/indomethacin-induced gastric-ulceration in rats. Rats were divided into six groups: normal control, gastric ulcer control, two standard pretreatment groups receiving omeprazole and misoprostol, and two test pretreatment groups receiving Althaea officinalis and Solanum nigrum. Pretreatments were administrated orally for 14 days. On the 15th day, animals, excluding the normal control group, were exposed to pyloric-ligation followed by indomethacin injection. After four hours, the rat’s stomachs were removed and gastric juice and blood samples were collected. Pyloric-ligation/indomethacin administration caused considerable elevation in ulcer number, ulcer index, acid and pepsin productivity, aggressive factors, and gastric mucosal lipid-peroxide contents. Moreover, reduction in titratable acidity, gastric mucosal nitric-oxide, anti-oxidant contents, and protective factors accompanied gastric-ulceration. Additionally, elevation in pro-inflammatory cytokines content and reduction in cystathionine-β-synthase and heme-oxygenase-1 expression was witnessed. Omeprazole, misoprostol, Althaea officinalis, and Solanum nigrum pretreatments fixed blood and tissue biomarkers, thereby protecting them from pyloric-ligation/indomethacin-induced gastric-ulceration in rats, which is hopeful for clinical examinations.

Influence of perioperative nonsteroidal anti-inflammatory drugs on complications after gastrointestinal surgery: A meta-analysis

BACKGROUND

Nonsteroidal anti-inflammatory drugs (NSAIDs) are a key part of multimodal perioperative analgesia. This study aimed to evaluate the influence of perioperative NSAIDs application on complications after gastrointestinal surgery by using meta-analysis.

METHODS

A systematic review of published literature was conducted by searching computerized databases including PubMed, CBM, Springer, Chinese Academic Journals, and China Info since the databases were published until June 2015. The articles and retrospective references regarding complications after gastrointestinal surgery were collected to compare postoperative complications associated with NSAIDs or other analgesics. After they were assessed by randomized controlled trials and extracted by the standard of the Jadad systematic review, the homogeneous studies were pooled using RevMan 5.3 software. The meta-analysis was performed on five postoperative complications: postoperative anastomotic leak, cardiovascular events, surgical site infection, nausea and vomiting, and intestinal obstruction.

RESULTS

Twelve randomized controlled trials involving 3829 patients met the inclusion criteria. The results of meta-analyses showed the following: (1) postoperative anastomotic leak: NSAIDs (including selective and nonselective NSAIDs) increased the incidence of anastomotic leak [odds ratio (OR)=3.02, 95% confidence interval (CI): 2.16-4.23, p=0.00001]. Further results showed that nonselective NSAIDs significantly increased the incidence of anastomotic leak (OR=2.96, 95% CI: 1.99-4.42, p<0.00001), and selective NSAIDs had no significant difference as compared with the control group using other analgesics (OR=2.27, 95% CI: 0.68-7.56, p=0.18); (2) postoperative cardiovascular events: NSAIDs (selective and nonselective NSAIDs) had no difference when compared with other analgesics (OR=0.50, 95% CI: 0.23-1.12, p=0.09); (3) postoperative surgical site infection: NSAIDs (selective and nonselective NSAIDs) and other analgesics had no difference in surgical site infection (OR=0.77, 95% CI: 0.52-1.15, p=0.20); (4) postoperative nausea and vomiting: NSAIDs (selective and nonselective NSAIDs) decreased the incidence of nausea and vomiting (OR=0.53, 95% CI: 0.34-0.81, p=0.003); (5) postoperative intestinal obstruction: NSAIDs (selective and nonselective NSAIDs) decreased the incidence of intestinal obstruction (OR=0.35, 95% CI: 0.13-0.89, p=0.03).

CONCLUSIONS

The meta-analysis suggests that postoperative NSAIDs, especially nonselective NSAIDs, could increase the incidence of anastomotic leak. NSAIDs could decrease postoperative nausea and vomiting and intestinal obstruction, but showed no difference in cardiovascular events and surgical site infection as compared with other analgesics.

Analyzing the influence of gastric intestinal metaplasia on gastric ulcer healing in Helicobacter pylori-infected patients without atrophic gastritis

BACKGROUND

Gastric epithelial hyper-proliferation was reported in patients with Helicobacter pylori (H. pylori)-infected gastric mucosa with intestinal metaplasia (IM) changes. In patients with gastric ulcer (GU) and IM, the GU may have a different healing rate in comparison to patients without IM. This study aimed to compare the difference in GU healing between H. pylori-infected patients with IM and those without IM.

METHODS

We retrospectively analyzed patients at the Keelung Chung Gung Memorial Hospital during the period from March 2005 to January 2011. The inclusion criteria were: 1) endoscopic findings of GU and biopsy histological examination plus rapid urease test indicating H. pylori infection; 2) gastric IM adjacent to a GU but with no atrophic gastritis changes; 3) patients receiving H. pylori eradication triple therapy and 8 weeks of maintenance therapy with a proton pump inhibitor; and 4) patients receiving follow-up endoscopy within the 3^rd and the 4^th months after treatment.

RESULTS

In total, 327 patients with GU and H. pylori infection (136 with IM and 191 without IM) were included. Patients with IM had a higher GU healing rate than those without IM (91.9% vs. 84.3%, P = 0.040). Multivariate logistical regression analysis revealed that failure of H. pylori eradication (Odds = 4.013, 95% CI: 1.840-8.951, P < 0.001) and gastric IM (Odds = 0.369, 95% CI: 0.168-0.812, P = 0.013) were the predictors of non-healing GU following treatment.

CONCLUSIONS

Patient with gastric IM change may have a higher GU healing rate than those without gastric IM. However, successful H. pylori eradication is a more important factor for GU healing than gastric IM.

Antiulcer activity of the ethanolic extract and ethyl acetate fraction of the leaves of Markhamia tomentosa in rats

ETHNOPHARMACOLOGICAL RELEVANCE

The leaves of Markhamia tomentosa (Benth.) K. Schum. Ex Engl. (Bignoniaceae) are used traditionally in the treatment of skin afflictions, sores, ulcers and inflammation. The aim of the study was to investigate the antiulcer activity of the crude ethanolic extract from the leaves of Markhamia tomentosa, determine the active fraction(s) of the extract and identify the chemical constituents in the active fraction by LC-MS.

MATERIALS AND METHODS

The antiulcer activity of the crude extract (50, 100 and 150mg/kg, p.o.) was evaluated in ethanol and indomethacin-induced models while the solvent fractions (150mg/kg) were screened using ethanol-induced gastric lesions in rats. Furthermore, anti-ulcer activity of the active fraction (50, 100 and 150mg/kg, p.o.) was performed using indomethacin and pylorus ligation models. Parameters such as gastric volume, pH and acidity were determined in the pylorus ligation model. LC-ESI-MS analysis was used to identify the components in the active fraction.

RESULTS

The extract at the dose of 50, 100 and 150mg/kg caused a significant (p<0.05) dose-dependent inhibition of ulcer in the ethanol and indomethacin-induced ulcer models, respectively. The ethyl acetate (EtOAc) fraction showed the most potent antiulcer activity from all the fractions tested. This fraction produced 72% and 92% inhibition of indomethacin and pylorus-induced ulcer at a dose of 150mg/kg respectively. Acteoside, luteolin, luteolin-7-rutinoside, Luteolin-3',7-di-O-glucoside, carnosol, dilapachone, tormentic acid, oxo-pomolic acid and ajugol were detected in the EtOAc fraction.

CONCLUSION

Our data provide a rational base for the folkloric use of Markhamia tormentosa in the treatment of ulcers.

Novel mechanisms and signaling pathways of esophageal ulcer healing: the role of prostaglandin EP2 receptors, cAMP, and pCREB

Clinical studies indicate that prostaglandins of E class (PGEs) may promote healing of tissue injury e.g., gastroduodenal and dermal ulcers. However, the precise roles of PGEs, their E-prostanoid (EP) receptors, signaling pathways including cAMP and cAMP response element-binding protein (CREB), and their relation to VEGF and angiogenesis in the tissue injury healing process remain unknown, forming the rationale for this study. Using an esophageal ulcer model in rats, we demonstrated that esophageal mucosa expresses predominantly EP2 receptors and that esophageal ulceration triggers an increase in expression of the EP2 receptor, activation of CREB (the downstream target of the cAMP signaling), and enhanced VEGF gene expression. Treatment of rats with misoprostol, a PGE1 analog capable of activating EP receptors, enhanced phosphorylation of CREB, stimulated VEGF expression and angiogenesis, and accelerated esophageal ulcer healing. In cultured human esophageal epithelial (HET-1A) cells, misoprostol increased intracellular cAMP levels (by 163-fold), induced phosphorylation of CREB, and stimulated VEGF expression. A cAMP analog (Sp-cAMP) mimicked, whereas an inhibitor of cAMP-dependent protein kinase A (Rp-cAMP) blocked, these effects of misoprostol. These results indicate that the EP2/cAMP/protein kinase A pathway mediates the stimulatory effect of PGEs on angiogenesis essential for tissue injury healing via the induction of CREB activity and VEGF expression.

Animal model of acid-reflux esophagitis: pathogenic roles of acid/pepsin, prostaglandins, and amino acids

Esophagitis was induced in rats within 3 h by ligating both the pylorus and transitional region between the forestomach and glandular portion under ether anesthesia. This esophageal injury was prevented by the administration of acid suppressants and antipepsin drug and aggravated by exogenous pepsin. Damage was also aggravated by pretreatment with indomethacin and the selective COX-1 but not COX-2 inhibitor, whereas PGE₂ showed a biphasic effect depending on the dose; a protection at low doses, and an aggravation at high doses, with both being mediated by EP1 receptors. Various amino acids also affected this esophagitis in different ways; L-alanine and L-glutamine had a deleterious effect, while L-arginine and glycine were highly protective, both due to yet unidentified mechanisms. It is assumed that acid/pepsin plays a major pathogenic role in this model of esophagitis; PGs derived from COX-1 are involved in mucosal defense of the esophagus; and some amino acids are protective against esophagitis. These findings also suggest a novel therapeutic approach in the treatment of esophagitis, in addition to acid suppressant therapy. The model introduced may be useful to test the protective effects of drugs on esophagitis and investigate the mucosal defense mechanism in the esophagus.

NSAID, aspirin delays gastric ulcer healing with reduced accumulation of CXCR4(+)VEGFR1(+) cells to the ulcer granulation tissues

BACKGROUND

Ulcer healing is a complex process, which involves cell migration, proliferation, angiogenesis and re-epithelialization. Several growth factors have been implicated in this process but the precise mechanism is not well understood. This study examined the involvement of VEGFR1 signaling in the gastric ulcer healing.

METHODS

Gastric ulcers were induced by the serosal application of 100% acetic acid, and the areas of the ulcers were measured thereafter.

RESULTS

The healing of acetic acid induced ulcers and the progenitor cells expressing CXCR4(+)VEGFR1(+) cell were significantly delayed in NSAID treated mice. The areas of the ulcer was significantly suppressed in tyrosine kinase-deficient VEGFR1 mice (VEGFR1TKKO) compared with wild type (WT) mice. The plasma level of SDF-1 and stem cell factor (SCF) and bone marrow level of pro-matrix metallopeptidase 9 (pro-MMP-9) were significantly reduced in VEGFR1TKKO mice. In VEGFR1 TKKOmice, the progenitor cells expressing CXCR4(+)VEGFR1(+) cell from bone marrow and the recruitment of these cells in healing ulcer were suppressed. Furthermore, VEGFR1 TKKO mice treated with NSAID did not suppress gastric ulcer healing compared to vehicle mice. These results suggested that NSAID suppressed VEGFR1 TK signaling plays a critical role in ulcer healing through mobilization of CXCR4(+)VEGFR1(+) cells.

CONCLUSION

VEGFR1 signaling is required for healing of NSAID induced gastric ulcer and angiogenesis with increased recruitment of CXCR4(+)VEGFR1(+) cells to the ulcerative lesion.

Risk of anastomotic leakage with use of NSAIDs after gastrointestinal surgery

PURPOSE

Analgesic regimes to avoid opioid-related adverse effects have been recommended in gastrointestinal surgery. Non-steroidal anti-inflammatory drugs (NSAIDs) are an important component of opioid sparing regimes in that these drugs indirectly reduce pain by inhibiting inflammation. Although beneficial for most surgical patients, animal studies and recent clinical studies suggest a harmful effect on new intestinal anastomoses by increasing the rate of leakage. NSAIDs may indirectly disturb anastomotic healing by inhibiting inflammation as an integrated part of the wound healing process in an early, critical phase after surgery.

METHODS

A literature review based on a structured search in PubMed of clinical and experimental studies investigating the effects of NSAIDs on anastomotic healing and leakage rates after intestinal surgery, as well as proposed mechanisms and effects studied in animal models.

RESULTS

Three recent observational cohort studies (accumulated n = 882) indicate an increased rate of anastomotic leakages (15-21%) associated with cyclooxygenase-2 (COX-2) selective NSAIDs after intestinal surgery compared to the leakage rates in controls or historical cohorts (1-4%). Three prospective studies on related topics contain relevant data on NSAIDs and are compared to these studies. Several experimental animal studies support an increased risk for anastomotic leakage with the use of NSAIDs.

CONCLUSION

The reported effects of NSAIDs on anastomotic healing suggest an increased risk for leakage. A better understanding of the complex interactions of NSAID-induced inhibition on anastomotic healing is a prerequisite for the safe use of NSAIDs. Until more data are available, a careful use of NSAIDs may be warranted in gastrointestinal anastomotic surgery.

Role of microsomal prostaglandin E synthase-1 in the facilitation of angiogenesis and the healing of gastric ulcers

The importance of prostaglandin E(2) in various pathophysiological events emphasizes the necessity of understanding the role of PGE synthases (PGESs) in vivo. However, there has been no report on the functional relevance of microsomal PGES-1 (mPGES-1) to the physiological healing processes of gastric ulcers, or to angiogenesis, which is indispensable to the healing processes. In this report, we tested whether mPGES-1 plays a role in the healing of gastric ulcers and in the enhancement of angiogenesis using mPGES-1 knockout mice (mPGES-1 KO mice) and their wild-type (WT) counterparts. Gastric ulcers were induced by the serosal application of 100% acetic acid, and the areas of the ulcers were measured thereafter. mPGES-1 together with cyclooxygenase-2 were induced in the granulation tissues compared with normal stomach tissues. The healing of acetic acid-induced ulcers was significantly delayed in mPGES-1 KO mice compared with WT. This was accompanied with reduced angiogenesis in ulcer granulation tissues, as estimated by CD31 mRNA levels determined by real-time PCR and the microvessel density in granulation tissues. The mRNA levels of proangiogenic growth factors, such as transforming growth factor-β, basic fibroblast growth factor, and connective tissue growth factor in ulcer granulation tissues determined were reduced in mPGES-1 KO mice compared with WT. The present results suggest that mPGES-1 enhances the ulcer-healing processes and the angiogenesis indispensable to ulcer healing, and that a selective mPGES-1 inhibitor should be used with care in patients with gastric ulcers.

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.

Endogenous prostaglandin E2 accelerates healing of indomethacin-induced small intestinal lesions through upregulation of vascular endothelial growth factor expression by activation of EP4 receptors

BACKGROUND AND AIMS

The effects of an EP4 agonist/antagonist on the healing of lesions produced by indomethacin in the small intestine were examined in rats, especially in relation to the expression of vascular endothelial growth factor (VEGF) and angiogenesis.

METHODS

Animals were given indomethacin (10 mg/kg s.c.) and killed at various time points. To impair the healing of these lesions, a small dose of indomethacin (2 mg/kg p.o.) or AE3-208 (EP4 antagonist: 3 mg/kg i.p.) was given once daily for 6 days after the ulceration was induced, with or without the co-administration of AE1-329 (EP4 agonist: 0.1 mg/kg i.p.).

RESULTS

Indomethacin (10 mg/kg) caused severe damage in the small intestine, but the lesions healed rapidly decreasing to approximately one-fifth of their initial size within 7 days. The healing process was significantly impaired by indomethacin (2 mg/kg) given once daily for 6 days after the ulceration. This effect of indomethacin was mimicked by the EP4 antagonist and reversed by co-administration of the EP4 agonist. Mucosal VEGF expression was upregulated after the ulceration, reaching a peak on day 3 followed by a decrease. The changes in VEGF expression paralleled those in mucosal cyclooxygenase-2 expression, as well as prostaglandin E(2) (PGE(2)) content. Indomethacin (2 mg/kg) downregulated both VEGF expression and angiogenesis in the mucosa during the healing process, and these effects were significantly reversed by co-treatment with the EP4 agonist.

CONCLUSION

The results suggest that endogenous PGE(2) promotes the healing of small intestinal lesions by stimulating angiogenesis through the upregulation of VEGF expression mediated by the activation of EP4 receptors.

Cytoprotection and healing: two unequal brethren

The promotion of the concept of cytoprotection has fostered hopes that the use of co-prescribed mucosal protective agents would revolutionize the prevention of NSAID-induced ulcers and supply the basis for novel ulcer therapy. Prostaglandins do not, however, accelerate ulcer healing when applied at doses that exert an unequivocal cytoprotective activity. Attempts have therefore been made in recent years to create new less-toxic NSAIDs, such as combined lipoxygenase/cyclo-oxygenase inhibitors, NSAIDs coupled to an NO donor and so-called COX-2 inhibitors. All these preparations do in fact exert a diminished gastrointestinal toxicity. There is however increasing evidence accumulating from studies performed in and outside our laboratories that in chromic ulcer models their increased gastrointestinal tolerance is not necessarily reflected by non-interference with ulcer healing. It is thus mandatory to distinguish between cytoprotective and healing properties of drugs interfering with the cyclo-oxygenase pathway.

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.

EP4 agonist alleviates indomethacin-induced gastric lesions and promotes chronic gastric ulcer healing

AIM: To investigate EP4-selective agonist effect on indomethacin-induced gastric lesions and on the spontaneous healing of chronic gastric ulcers.

METHODS: In a mouse model of gastric bleeding with high dose of indomethacin (20 mg/kg), an EP4-selective agonist was administered orally. Stomach lesions and gastric mucous regeneration were monitored. In a mouse model of chronic gastric ulcer induced by acetic acid, EP4 agonist effect on the healing of chronic gastric ulcer was evaluated in the presence or absence of low dose indomethacin (3 mg/kg). In cultured human gastric mucous cells, EP4 agonist effect on indomethacin-induced apoptosis was assessed by flow cytometry.

RESULTS: The EP4-selective agonist reduced high dose indomethacin-induced acute hemorrhagic damage and promoted mucous epithelial regeneration. Low-dose indomethacin aggravated ulcer bleeding and inflammation, and delayed the healing of the established chronic gastric ulcer. The EP4 agonist, when applied locally, not only offset indomethacin-induced gastric bleeding and inflammation, but also accelerated ulcer healing. In the absence of indomethacin, the EP4 agonist even accelerated chronic gastric ulcer healing and suppressed inflammatory cell infiltration in the granulation tissue. In vitro, the EP4 agonist protected human gastric mucous cells from indomethacin-induced apoptosis.

CONCLUSION: EP4-selective agonist may prevent indomethacin-induced gastric lesions and promote healing of existing and indomethacin-aggravated gastric ulcers, via promoting proliferation and survival of mucous epithelial cells.

A randomized, placebo-controlled study of the effects of naproxen, aspirin, celecoxib or clopidogrel on gastroduodenal mucosal healing

BACKGROUND

Many individuals with gastroduodenal ulcers require on-going, non-steroidal anti-inflammatory drug (NSAID) or anti-platelet therapy.

AIMS

To evaluate the effects of these agents on gastroduodenal mucosal healing.

METHODS

Helicobacter pylori-negative volunteers were randomized to receive naproxen, celecoxib, aspirin, clopidogrel or placebo. Antral and duodenal lesions were created endoscopically with a biopsy forceps. After 7 days of medication dosing, each lesion was scored [from 0 (low) to 8 (high)] using a validated methodology. The primary endpoint was the mean injury score. The secondary endpoint was the percentage of subjects with > or = 1 unhealed lesion.

RESULTS

In all, 108 subjects completed the study. Naproxen impaired antral lesion healing more than placebo, clopidogrel, aspirin or celecoxib (mean injury score of 4.3 vs. 3.0, 2.7, 3.2, and 3.2, respectively, P < 0.05). Naproxen impaired duodenal lesion healing more than placebo, clopidogrel or aspirin (mean injury score of 4.0 vs. 2.4, 2.6, and 2.2, respectively, P < 0.05). More subjects taking naproxen than placebo or clopidogrel had > or =1 unhealed antral lesions (72.2% vs. 36.0% and 32.0%, respectively, P < 0.05) and unhealed duodenal lesions (61.1% vs. 16.0% and 28.0%, respectively, P < 0.05).

CONCLUSIONS

Naproxen may impair gastroduodenal healing more than aspirin or celecoxib in H. pylori negative subjects. Clopidogrel did not impair mucosal healing.

Protective role of ascorbic acid isolated from Cissus quadrangularis on NSAID induced toxicity through immunomodulating response and growth factors expression

The present study investigate the effect of ascorbic acid, the major bioactive component isolated from Cissus quadrangularis extract (CAA) on inflammatory cytokines and growth factors in non-steroidal anti-inflammatory drug (NSAID) induced gastric ulcer. Analysis of serum cytokine profile using enzymelinked immunosorbent assay (ELISA) showed a drastic increase in interleukin (IL)-1beta, IL-6, tumour necrosis factor-alpha (TNF)-alpha, interferon-gamma (IFN-gamma) and decrease in IL-10, Il-4 and prostaglandin E2 (PGE2) levels in NSAID (aspirin) treated rats. The reduction of growth factors such as transforming growth factor-alpha (TGF)-alpha and vascular endothelial cell growth factor (VEGF) by aspirin was determined by immunohistochemistry method. Administration of CAA produced significant protection against aspirin induced gastric toxicity by showing significant increase in PGE2, TGF-alpha, VEGF expression and accompanied by a significant inhibition of nitric oxide and regulating the levels of cytokines in rats. These findings suggest that CAA prevents gastric ulcer formation due to its immunomodulatory effect, antioxidant activity along with the ability to modulate PG synthesis and up-regulation of the growth factors.

Cyclooxygenase-2/prostaglandin E2 accelerates the healing of gastric ulcers via EP4 receptors

We examined the involvement of cyclooxygenase (COX)-1 as well as COX-2 in the healing of gastric ulcers and investigated which prostaglandin (PG) EP receptor subtype is responsible for the healing-promoting action of PGE2. Male SD rats and C57BL/6 mice, including wild-type, COX-1(-/-), and COX-2(-/-), were used. Gastric ulcers were produced by thermocauterization under ether anesthesia. Gastric ulcer healing was significantly delayed in both rats and mice by indomethacin and rofecoxib but not SC-560 given for 14 days after ulceration. The impaired healing was also observed in COX-2(-/-) but not COX-1(-/-) mice. Mucosal PGE2 content increased after ulceration, and this response was significantly suppressed by indomethacin and rofecoxib but not SC-560. The delayed healing in mice caused by indomethacin was significantly reversed by the coadministration of 11-deoxy-PGE1 (EP3/EP4 agonist) but not other prostanoids, including the EP1, EP2, and EP3 agonists. By contrast, CJ-42794 (selective EP(4) antagonist) significantly delayed the ulcer healing in rats and mice. VEGF expression and angiogenesis were both upregulated in the ulcerated mucosa, and these responses were suppressed by indomethacin, rofocoxib, and CJ-42794. The expression of VEGF in primary rat gastric fibroblasts was increased by PGE2 or AE1-329 (EP4 agonist), and these responses were both attenuated by coadministration of CJ-42794. These results confirmed the importance of COX-2/PGE2 in the healing mechanism of gastric ulcers and further suggested that the healing-promoting action of PGE2 is mediated by the activation of EP4 receptors and is associated with VEGF expression.

Recruitment of a prostaglandin E receptor subtype, EP3-expressing bone marrow cells is crucial in wound-induced angiogenesis

E-type prostaglandins have been reported to be proangiogenic in vivo. Thus, we examined prostaglandin receptor signaling relevant to wound-induced angiogenesis. Full-thickness skin wounds were created on the backs of mice, and angiogenesis in wound granulation tissues was estimated. Wound closure and re-epithelization in EP3 receptor knockout mice (EP3-/-) were significantly delayed compared with their wild-type (WT) mice, whereas those in EP1-/-, EP2-/-, and EP4-/- were not delayed. Wound-induced angiogenesis estimated with CD31 immunohistochemistry in EP3-/- mice was significantly inhibited compared with that in WT mice. Immunoreactive vascular endothelial growth factor (VEGF) in wound granulation tissues in EP3-/- mice was markedly less than that in WT mice. Wound closure in WT mice was delayed significantly by VEGF neutralizing antibody compared with control IgG. Wound-induced angiogenesis and wound closure were significantly suppressed in EP3-/- bone marrow transplantation mice compared with those in WT bone marrow transplantation mice. These were accompanied with the reductions in accumulation of VEGF-expressing cells in wound granulation tissues and in mobilization of VEGF receptor 1-expressing leukocytes in peripheral circulation. These results indicate that the recruitment of EP3-expressing cells to wound granulation tissues is critical for surgical wound healing and angiogenesis via up-regulation of VEGF.

Role of endogenous nitric oxide (NO) and NO synthases in healing of indomethacin-induced intestinal ulcers in rats

We examined the roles of nitric oxide (NO) and NO synthase (NOS) isozymes in the healing of indomethacin-induced small intestinal ulcers in rats. Animals were given indomethacin (10 mg/kg, s.c.) and killed 1, 4 and 7 days after the administration. Indomethacin (2 mg/kg), N(G)-nitro-L-arginine methyl ester (L-NAME: a nonselective NOS inhibitor: 10 mg/kg) and aminoguanine (a relatively selective iNOS inhibitor: 20 mg/kg) were given s.c. once daily for 6 days, the first 3 days or the last 3 days during a 7-day experimental period. Both indomethacin and L-NAME significantly impaired healing of these lesions, irrespective of whether they were given for 6 days, first 3 days or last 3 days. The healing was also impaired by aminoguanine given for the first 3 days but not for the last 3 days. Expression of iNOS mRNA in the intestine was up-regulated after ulceration, persisting for 2 days thereafter, and the Ca(2+)-independent iNOS activity also markedly increased with a peak response during 1-2 days after ulceration. Vascular content in the ulcerated mucosa as measured by carmine incorporation was decreased when the healing was impaired by indomethacin and L-NAME given for either the first or last 3 days as well as aminoguanidine given for the first 3 days. These results suggest that endogenous NO plays a role in healing of intestinal lesions, in addition to prostaglandins, yet the NOS isozyme mainly responsible for NO production differs depending on the stage of healing: iNOS in the early stage and cNOS in the late stage.

Roles of endogenous prostaglandins and cyclooxygenase isozymes in healing of indomethacin-induced small intestinal lesions in rats

The role of prostaglandins (PGs)/cyclooxygenase (COX) in the healing of indomethacin-induced small intestinal ulcers was examined in rats. Animals were given indomethacin (10 mg/kg s.c.) and killed 1, 2, 3, 5, and 7 days later. Indomethacin (2 mg/kg), 5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-trifluoromethylpyrazole (SC560; COX-1 inhibitor; 3 mg/kg), and rofecoxib (COX-2 inhibitor; 3 mg/kg) were given p.o. once daily for 6 days, during the first 3 days or last 3 days of the experimental period. All COX inhibitors given for 6 days significantly impaired the healing of these ulcers. Healing was also impaired by rofecoxib given for the first 3 days or by SC560 given for the last 3 days. The expression of COX-2 mRNA in the intestine was up-regulated after ulceration, persisting for 3 days and dissipating thereafter. Mucosal PGE2 contents decreased within 3 h after ulceration, recovered 24 h later, and increased above normal 1 approximately 3 days later. The PGE2 content at 4 days after ulceration was decreased by rofecoxib but not SC560, whereas that at 7 days was suppressed by SC560 but not rofecoxib. Vascular content in the ulcerated mucosa decreased when the healing was impaired by COX inhibitors. The deleterious effect of indomethacin on healing was mimicked by a prostacyclin E receptor (EP) 4 antagonist and reversed by coadministration of PGE2 as well as an EP4 agonist. In conclusion, endogenous PGs play a role in the healing of intestinal ulcers through EP4 receptors, yet the COX isozyme involved differs depending on the stage of healing; COX-2 in the early stage and COX-1 in the late stage.

The effect of Aloe vera A. Berger (Liliaceae) on gastric acid secretion and acute gastric mucosal injury in rats

The effect of varying doses of ethanol extract of Aloe vera (Liliaceae) on acute gastric mucosal lesions induced by 0.6 M HCl and acid output was studied in the pylorus ligated and lumen perfuse rats, respectively. Acid secretion was determined by titration of the collected gastric juice to pH 7.0. Intraperitoneal injection of Aloe vera, dose dependently inhibited gastric acid secretion. The plant was more active as a gastroprotective agent at lower concentration against mucosal injury induced by 0.6 M HCl. In conclusion, Aloe vera is endowed with gastric acid anti-secretory activity and could protect the gastric mucosa at low concentrations against injurious agents.

Dual coated erodible microcapsules for modified release of diclofenac sodium

Diclofenac sodium was formulated as novel enteric microcapsules for improved delivery to the intestine using the polymers cellulose acetate phthalate (CAP) and ethyl cellulose (EC). The enteric coating was given using an innovative technique combining the wet granulation and thermal change methods. The novel process was analysed for its capability to produce microcapsules of uniform size, good flowability, uniform drug loading and maximum entrapment efficacy and the absence of interaction between drug and process parameters as well as the polymers. In vitro release study was carried out in simulated gastric fluid (SGF) for first 2 h and simulated intestinal fluid (SIF) for next 6 h. The best formulation that contained cellulose acetate phthalate and ethyl cellulose in the concentration of 10:90 at 1:1.5 drug-polymer ratio (B3) was further evaluated using in vivo for its pharmacodynamic efficacy and ulcerogenicity. In addition to sustained and uniform release of drug, the formulation B3 showed better anti-inflammatory activity than the marketed formulation and retarded drug release in the gastric medium. The biological examination of incised stomach showed no histological alterations in term of mucous surface cells and glands.

Effects of flunixin meglumine or etodolac treatment on mucosal recovery of equine jejunum after ischemia

OBJECTIVE

To examine the effects of flunixin meglumine and etodolac treatment on recovery of ischemic-injured equine jejunal mucosa after 18 hours of reperfusion.

ANIMALS

24 horses.

PROCEDURE

Jejunum was exposed to 2 hours of ischemia during anesthesia. Horses received saline (0.9% NaCl) solution (12 mL, i.v., q 12 h), flunixin meglumine (1.1 mg/kg, i.v., q 12 h), or etodolac (23 mg/kg, i.v., q 12 h). Tissue specimens were obtained from ischemic-injured and nonischemic jejunum immediately after ischemia and 18 hours after recovery from ischemia. Transepithelial electric resistance (TER) and transepithelial flux of tritium-labeled mannitol measured mucosal permeability. Denuded villous surface area and mean epithelial neutrophil count per mm2 were calculated. Western blot analysis for cyclooxygenase (COX)-1 and -2 was performed. Pharmacokinetics of flunixin and etodolac and eicosanoid concentrations were determined.

RESULTS

Ischemic-injured tissue from horses treated with flunixin and etodolac had significantly lower TER and increased permeability to mannitol, compared with that from horses treated with saline solution. Epithelial denudation after ischemia and 18 hours after recovery was not significantly different among treatments. Both COX-1 and -2 were expressed in ischemic-injured and nonischemic tissues. Ischemia caused significant upregulation of both COX isoforms. Eicosanoid concentrations were significantly lower in tissues from flunixin and etodolac-treated horses, compared with that from horses treated with saline solution.

CONCLUSIONS AND CLINICAL RELEVANCE

Flunixin and etodolac treatment retarded recovery of intestinal barrier function in jejunal mucosa after 18 hours of reperfusion, whereas tissues from horses treated with saline solution recovered baseline values of TER and permeability to mannitol.

Physiopathologie des lésions gastro-duodénales induites par les anti-inflammatoires non stéroïdiens

The pathogenesis of the gastroduodenal lesions induced by non-steroidal anti-inflammatory drugs and aspirin is primarily caused by a reduction in mucosal blood flow, which is the consequence of inhibition of cyclooxygenase-producing vasodilator prostaglandins. The subsequent phase is adherence of leukocytes to the endothelium, which may depend on cyclooxygenase-2. Endothelial lesions accentuate the fall of mucosal blood flow and promote the inflammatory process in the gastric mucosa. The inflammatory process is amplified by expression of TNFalpha in polymorphonuclears induced by non-steroidal anti-inflammatory drugs. A few days after starting treatment, epithelial proliferation and increased mucosal blood flow, partly dependent on cyclooxygenase-2 and nitric oxide expression, compensates for the damaging process. Selective inhibitors of inducible cyclooxygenase-2 have reduced gastrointestinal toxicity, which could partially be explained by the protection effect of cyclooxygenase-2 on the gastrointestinal mucosa during inflammation or epithelial repair. Selective inhibitors may worsen inflammatory bowel disease. Non-steroidal inflammatory drugs and aspirin, but perhaps not selective inhibitors, increase the mucosal lesions associated with Helicobacter pylori-induced gastritis. Co-administration of selective inhibitors and aspirin leads to gastrointestinal toxicity equivalent to that of non-specific anti-inflammatory drugs.

Gastroduodenal ulcer protective activity of Asparagus racemosus: an experimental, biochemical and histological study

Asparagus racemosus is an Ayurvedic rasayana, which finds mention in ancient Indian texts for treatment of gastric ulcers. The ulcer protective effect of methanolic extract of fresh roots of A. racemosus (ARM), 25-100 mg/kg given orally, twice daily for 5 days, was studied on different gastroduodenal ulcer models. ARM 50 mg/kg, twice daily, orally (total saponins 0.9%) showed significant protection against acute gastric ulcers induced by cold restraint stress (CRS), pyloric ligation, aspirin plus pyloric ligation, and duodenal ulcers induced by cysteamine. ARM in the above dose also significantly healed chronic gastric ulcers induced by acetic acid after 10 days treatment. However, ARM was ineffective against aspirin- and ethanol-induced gastric ulcers. Further, gastric juice and mucosal studies showed that ARM significantly increased the mucosal defensive factors like mucus secretion, cellular mucus, life span of cells and also possessed significant anti-oxidant effect, but had little or no effect on offensive factors like acid and pepsin.

Healing of duodenal ulcers is not impaired by indomethacin or rofecoxib, the selective COX-2 inhibitor, in rats

BACKGROUND/AIM

Studies have demonstrated an important role for endogenous PG and NO in the healing of chronic gastric ulcers. We investigated the effects of COX and NOS inhibitors on the healing of duodenal ulcers, in comparison with gastric ulcers, in rats.

METHODS

Gastric and duodenal ulcers were induced by serosal application of acetic acid (0.1 ml of 100% acetic acid) for 60 and 20 s, respectively. Indomethacin (a nonselective COX inhibitor) or rofecoxib (a selective COX-2 inhibitor) was given p.o. once daily for 14 days from 3 days after ulcer induction, while N(G)-nitro-L-arginine methyl ester (L-NAME: a nonselective NOS inhibitor) or aminoguanidine (a relatively selective iNOS inhibitor) was given s.c. twice daily during this period.

RESULTS

Both gastric and duodenal ulcers induced by acetic acid healed spontaneously within 17 days to a minimal size. Daily administration of indomethacin or rofecoxib significantly delayed the healing of gastric but not duodenal ulcers. In contrast, the healing of both gastric and duodenal ulcers was delayed by repeated administration of either L-NAME or aminoguanidine. Ulceration markedly increased the PGE(2) content of the ulcerated mucosa in both the stomach and duodenum, and the increased PG biosynthetic response was inhibited by either indomethacin or rofecoxib in both tissues. The expression of both COX-2 and iNOS mRNAs was upregulated in the ulcerated mucosa of the stomach and duodenum.

CONCLUSION

These results suggest that COX-2/PG is actively involved in the healing of gastric but not duodenal ulcers, although the mRNA for COX-2 is expressed in the duodenal mucosa after ulceration, as potently as in the gastric mucosa. In contrast, NO produced by both cNOS and iNOS plays a role in the healing of both gastric and duodenal ulcers.

Heat shock preconditioning modulates proliferation and apoptosis after superficial injury in isolated guinea pig gastric mucosa via an eicosanoid and protein synthesis-dependent mechanism

AIM

In restitution after superficial injury of the gastric mucosa, the epithelial continuity is restored by cellular migration. We have shown that heat shock preconditioning inhibits restitution after superficial injury. This study investigates the effect of heat shock preconditioning on tissue proliferation and apoptosis.

EXPERIMENTAL DESIGN

Paired guinea pig gastric mucosae were mounted and perfused in Ussing chambers (37 degrees C). After heat shock preconditioning (42 degrees C) (30 min) and normothermic recovery (37 degrees C) (150 min) or normothermic perfusion, a superficial injury was induced by luminal exposure to 1.25 mol/L NaCl (5 min) followed by a 3 h restitution. During perfusion, the mucosa was exposed to 30 micromol/L arachidonic acid (AA) to enhance heat shock response, to 50 micromol/L quercetin (Q) to inhibit the metabolism of arachidonic acid via lipoxygenases, to 50 micromol/L indomethacin (In) to inhibit the metabolism of arachidonic acid via cyclo-oxygenases, or to 150 micromol/L cycloheximide (CHX) to inhibit de novo protein synthesis. After the experiment the mucosa was prepared for immunohistochemical analysis of the expression of Mib-1 proliferation antigen and pro-apoptotic protein Bax.

RESULTS

Heat shock decreased Mib-1/Bax ratio and this effect was maintained after superficial injury and exposure to Q, to AA+CHX or to In+CHX. Exposure to CHX, to AA, to In+Q, to In+AA, In+AA+Q or to In+AA+CHX, however, blocked the effect of heat shock preconditioning. The decreasing effect of heat shock preconditioning on Mib-1/Bax ratio could be reversed by exposure to AA+Q or to In.

CONCLUSION

The heat-preconditioning-induced effects on the mucosa are reversible and sensitive to exogenous pharmacological modulation. Heat shock preconditioning inhibits proliferation of superficially injured isolated gastric mucosa by a mechanism involving eicosanoid pathways and de novo protein synthesis.

Acceleration of gastric ulcer healing by omeprazole in portal hypertensive rats. Is its action mediated by gastrin release and the stimulation of epithelial proliferation?

BACKGROUND

Gastric ulcer healing is delayed in patients with portal hypertension (PHT) and often responds poorly to histamine H(2) blockers. Although proton pump inhibitors are more effective anti-ulcer agents, there is little information regarding their efficacy for gastric ulcer in cases of PHT. Therefore, we investigated the effects of a proton pump inhibitor, omeprazole, on the healing of acetic-acid-induced gastric ulcer in PHT rats.

METHODS

Animals studied were 80 male Sprague-Dawley rats aged 7 weeks, of which half underwent two-staged portal vein ligation (PHT rats) and half underwent a sham operation (SO rats). Gastric ulcers were induced by acetic acid. Starting from day 4 after ulcer induction, rats received omeprazole or vehicle orally (50 mg/kg) for 5 or 10 days. Ulcer area, proliferating cell nuclear antigen labelling index (PCNA LI), and serum gastrin levels were recorded.

RESULTS

PHT significantly inhibited epithelial cell proliferation and delayed gastric ulcer healing as indicated by a decreased PCNA LI at the ulcer margin and almost 2-fold larger ulcer area in PHT versus SO rats 14 days after ulcer induction. Ten-day treatment with omeprazole (vs. vehicle) significantly accelerated ulcer healing to a similar extent in both PHT and SO rats. Serum gastrin levels were significantly higher in PHT rats than in SO rats following treatment with omeprazole. Omeprazole (vs. vehicle) restored the decreased PCNA LI at the ulcer margin in PHT rats to that noted in SO rats.

CONCLUSIONS

In PHT rats, omeprazole accelerates gastric ulcer healing, stimulates epithelial cell proliferation at the ulcer margin, and increases serum gastrin levels. Since gastrin is a potent stimulator of gastric epithelial cell proliferation, increased serum gastrin levels may be an important factor in omeprazole-induced stimulation of epithelial cell proliferation and acceleration of gastric ulcer healing in conditions of PHT.

NSAID inhibition of RGM1 gastric monolayer wound re-epithelialization: comparison of selective Cox-2 versus non-selective Cox inhibitors

Clinical studies indicate that specific cyclooxygenase-2 (Cox-2) inhibitors are less ulcerogenic than their non-selective predecessors (e.g. indomethacin). However, Cox-2 inhibitors may also interfere with ulcer healing. Re-epithelialization is a crucial factor in both gastrointestinal mucosal injury and ulcer healing. This study was aimed to compare the effects of selective Cox-2 inhibitor (NS398) versus non-selective Cox inhibitor (indomethacin) on basal and basic fibroblast growth factor (bFGF) - stimulated gastric wound re-epithelialization. In-vitro epithelial wounds were created in confluent monolayers of RGM1 rat gastric epithelial cells by a razor blade scrape. Following wounding there was a significant re-epithelialization by 24 hrs. Indomethacin (0.25 mM and 0.5 mM) significantly inhibited basal wound re-epithelialization in a dose dependent manner. In contrast, selective Cox-2 inhibitor NS398 did not inhibit the basal re-epithelialization process. Basic FGF treatment produced significant enhancement of wound re-epitheliazation at the various concentrations [10, 20, 30, 40, 50 and 70 ng/ml] studied. Both indomethacin and NS398 inhibited bFGF stimulated wound re-epithelialization, with indomethacin having a greater inhibitory effect. The extent of NS398 inhibition was limited to the bFGF-stimulated component, whereas indomethacin inhibition extended to both the bFGF-stimulated and the basal re-epithelialization components. These findings indicate that specific Cox-2 inhibitor (NS398) does not interfere with the basal re-epithelialization but significantly inhibits the bFGF - stimulated re-epithelialization, whereas indomethacin interferes with both the basal as well as the bFGF-stimulated wound re-epithelialization.

Chronic gastric ulcer healing in rats subjected to selective and non-selective cyclooxygenase-2 inhibitors

The influence of different nonsteroidal anti-inflammatory drugs (NSAIDs) and of a proton pump inhibitor on the healing parameters of a chronic gastric ulcer was evaluated. Wistar rats were used after the induction of a chronic acetic acid ulcer. The animals were treated orally for 8 and 15 days, twice daily, with the conventional NSAID, piroxicam (0.35 mg/kg), the non-narcotic analgesic, metamizol (33 mg/kg), the selective cyclooxygenase-2 inhibitor, celecoxib (1.8 mg/kg) and the proton pump inhibitor, omeprazole (0.35 mg/kg). Macroscopic ulcer index, myeloperoxidase activity and prostaglandin E(2) content (both biochemical parameters were evaluated in ulcerated and in intact tissue) as well as histological and immunohistochemical evaluations were carried out at 8 and 15 days. Omeprazole accelerated ulcer healing at 8 and 15 days (P<0.05), while celecoxib delayed healing significantly at 15 days (P<0.01). At 8 days, the prostaglandin E2 content decreased with all NSAIDs at the ulcer site as well as in intact tissue. The same happened at 15 days except for celecoxib, which only diminished prostaglandins in intact mucosa. Immunohistochemistry showed differences in the location of cyclooxygenase-2 and -1. The highest cyclooxygenase-2 expression was found with piroxicam and the lowest expression was with celecoxib.

CONCLUSIONS

Down-regulation of cyclooxygenase-2 expression as well as a possible involvement of the chemical structure of celecoxib, a 1,5-dirarylpirazole with a sulphonamide moiety, may account for the delay in ulcer healing.

[Effect of exogenous administration of platelet-derived growth factor and epidermal growth factor on duodenal ulcer healing in rats treated with indomethacin]

BACKGROUND

Nonsteroidal anti-inflammatory drugs (NSAIDs) delay peptic ulcer healing through mechanisms that are still not entirely understood. Growth factors play a significant role in healing.

AIM

To evaluate whether exogenous administration of platelet-derived growth factor (PDGF) reverses the effect of indomethacin in experimental duodenal ulcers in rats and to define the potential mechanisms involved in this process.

METHOD

Duodenal ulcer was induced in male Wistar rats with acetic acid. The rats were then administered indomethacin (2 mg/kg/day), PDGF-BB (30 ng/100 g/day), epidermal growth factor (EGF) (50 /kg/day) or famotidine (positive control) or the possible combinations of these. Macroscopic area, reduction in microscopic diameter, epithelial and granulation tissue proliferation, collagen secretion by granulation tissue, and gastric acid secretion were analyzed.

RESULTS

Indomethacin delayed duodenal ulcer healing by decreasing cellular proliferation and inhibiting collagen secretion. PDGF and EGF accelerated healing and reversed the effects of indomethacin. The mechanisms involved were associated with an increase in collagen proliferation and secretion without affecting gastric acid secretion. Famotidine also accelerated healing and reversed the effect of indomethacin, and these effects were associated with a marked inhibition of gastric acid secretion and increase in collagen secretion by granulation tissue.

CONCLUSIONS

Exogenous administration of PDGF and EGF accelerated healing and reversed the harmful effects of indomethacin in an experimental model of duodenal ulcer.

Selective cyclooxygenase-2 blocker delays healing of esophageal ulcers in rats and inhibits ulceration-triggered c-Met/hepatocyte growth factor receptor induction and extracellular signal-regulated kinase 2 activation

Nonsteroidal anti-inflammatory drugs, both nonselective and cyclooxygenase-2 (COX-2) selective, delay gastric ulcer healing. Whether they affect esophageal ulcer healing remains unexplored. We studied the effects of the COX-2 selective inhibitor, celecoxib, on esophageal ulcer healing as well as on the cellular and molecular events involved in the healing process. Esophageal ulcers were induced in rats by focal application of acetic acid. Rats with esophageal ulcers were treated intragastrically with either celecoxib (10 mg/kg, once daily) or vehicle for 2 or 4 days. Esophageal ulceration triggered increases in: esophageal epithelial cell proliferation; expression of COX-2 (but not COX-1); hepatocyte growth factor (HGF) and its receptor, c-Met; and activation of extracellular signal-regulated kinase 2 (ERK2). Treatment with celecoxib significantly delayed esophageal ulcer healing and suppressed ulceration-triggered increases in esophageal epithelial cell proliferation, c-Met mRNA and protein expression, and ERK2 activity. In an ex vivo organ-culture system, exogenous HGF significantly increased ERK2 phosphorylation levels in esophageal mucosa. A structural analog of celecoxib, SC-236, completely prevented this effect. These findings indicate that celecoxib delays esophageal ulcer healing by reducing ulceration-induced esophageal epithelial cell proliferation. These actions are associated with, and likely mediated by, down-regulation of the HGF/c-Met-ERK2 signaling pathway.

Mucosal defense and repair. Role of prostaglandins in the stomach and duodenum

When considering the diseases of the stomach and duodenum, peptic ulcer disease has been the one of greatest clinical impact. Although there are several components that contribute mechanistically to ulcer disease, it is recognized that gastroduodenal mucosal prostaglandins play a central pathogenic role, especially in ulcers related to the use of NSAIDs. As a result of understanding the mechanisms of NSAID-induced ulceration, the crucial function that gastroduodenal mucosal prostaglandins have in mucosal defense and repair is appreciated. It now is held widely that mucosal prostaglandin deficiency increases susceptibility to ulcer formation and that exogenous administration of supplemental prostaglandins reduces ulcer risk. This article reviews the role that mucosal prostaglandins play in defense of the gastric and duodenal mucosa against injury and ulceration.

Effects of NSAIDs on cryoprobe-induced gastric ulcer healing in rats

BACKGROUND

Failure of ulcer healing may be critically important to the development of serious gastrointestinal complications in patients on long-term NSAIDs.

AIM

To determine the effect of indometacin, celecoxib, a cyclooxygenase-2-specific inhibitor, and nabumetone, a pro-drug, on ulcer healing rates in the rat.

METHODS

Gastric ulcers were induced using a cryoprobe. An NSAID or a vehicle control was administered to groups of eight rats for 3 or 6 days (2 mg/kg indometacin, 9 mg/kg celecoxib or 40 mg/kg nabumetone). The ulcer area was measured and epithelial proliferation at the ulcer margins was measured histochemically. The effect of the drugs on intestinal prostaglandin levels was also assessed.

RESULTS

The mean ulcer sizes in the four groups on day 3 were comparable. On day 6, control animals and those receiving nabumetone showed significant ulcer healing (P < 0.02), while the mean ulcer sizes in the indometacin (P < 0.01) and celecoxib (P < 0.02) groups were significantly larger than those in the control group. Higher doses of nabumetone (160 mg/kg), however, impaired healing. Intestinal prostaglandins were reduced (P < 0.01) only in indometacin-treated animals. The epithelial proliferation index was significantly lower among indometacin- (P=0.02) and celecoxib-treated (P=0.03) animals compared to controls at day 3.

CONCLUSIONS

Celecoxib and indometacin both decreased the epithelial proliferative response and delayed healing of cryoprobe-induced gastric ulcers. In contrast, nabumetone impaired ulcer healing only at very high doses.

Interleukin-1beta induces cyclo-oxygenase-2 expression in gastric cancer cells by the p38 and p44/42 mitogen-activated protein kinase signaling pathways

BACKGROUND AND AIMS

Cyclo-oxygenase-2 (COX-2) is the inducible enzyme in the gastric mucosa responsible for prostaglandin production during inflammation and ulcer healing. The regulation of COX-2 gene expression in gastric epithelial cells is not well understood. In this study, we investigated the effect of interleukin (IL)-1beta on COX-2 expression in the human gastric cancer cell, and explored the signaling pathways involved.

METHODS

Gastric cancer cell line AGS was treated with IL-1beta or the inhibitors of mitogen-activated protein-Erk kinase (MEK) and p38 mitogen-activated protein (MAP) kinase prior to the addition of IL-1beta. The COX-2 mRNA or protein levels were measured by using RT-PCR or western blot analysis, respectively. Prostaglandin E2 (PGE2) production/secretion was determined by using the prostaglandin E2 EIA assay. The phosphorylation/activation of p44/42 and p38 MAP kinases were determined by using western blot analysis and using phospho-specific antibodies.

RESULTS

Interleukin-1beta treatment dose- and time-dependently increased COX-2 mRNA and protein expression levels, and enhanced PGE2 production/secretion in AGS cells. In contrast, IL-1beta had no effect on the level of the constitutively expressed COX-1. In parallel to the increase of COX-2, we showed that p44/42 and p38 MAP kinase activities were also upregulated by IL-1beta treatment. To demonstrate the cause-effect relationship, we showed that inhibition of MEK and p38 MAP kinase with specific inhibitors suppressed IL-1beta-mediated increases in COX-2 mRNA and protein levels, and the PGE2 production.

CONCLUSIONS

Our results demonstrated that in human gastric cancer cells, IL-1beta upregulates the COX-2 gene expression through the activation of MEK/p44/42 and p38 MAP kinases pathway.

Role of acid suppressants in prophylaxis of NSAID damage

Gastric acid contributes to the pathogenesis of non-steroidal anti-inflammatory drug (NSAID)-induced ulceration via several mechanisms, including conversion of superficial to deeper injury, impairment of haemostasis, and interference with ulcer healing. The suppression of acid secretion has been shown to reduce the severity of NSAID-induced mucosal damage in experimental models and clinical studies. Current evidence indicates that proton pump inhibitors (PPIs) are the preferred treatment for the healing of gastric ulcers when NSAIDs cannot be discontinued. PPIs are superior to standard-dose H(2)-receptor antagonists and equivalent to low-dose misoprostol in preventing NSAID-induced gastric ulcers. Whether there is any significant advantage of PPIs over higher doses of H(2)-receptor antagonists or misoprostol is unknown. The efficacy of PPIs is enhanced in the presence of H. Pylori infection. Omeprazole has been shown to be effective for the secondary prevention of ulcer bleeding in H. pylori -infected NSAID users. The efficacy of PPIs for the prevention of ulcer complications in H. pylori-negative NSAID users remains uncertain.

Nonsteroidal anti-inflammatory drug gastropathy at the new millennium: mechanisms and prevention

OBJECTIVES

Nonsteroidal anti-inflammatory drug (NSAID)-induced gastrointestinal (GI) toxicity remains the most frequent adverse drug event in the United States. The objective of this review is to update clinicians in recent advances in basic and clinical investigation regarding the pathogenesis and management of NSAID gastropathy.

METHODS

Based upon an extensive review of the published literature and abstracts of key work within the past decade, the framework for new approaches to the prevention and treatment of NSAID-associated ulceration is summarized.

RESULTS

The pathophysiology of NSAID-induced injury to the GI tract is multifaceted and includes both prostaglandin-dependent and independent components. The pharmaceutical industry has capitalized on the identification of two different isoforms of cyclooxygenase, enabling the development of specific inhibitors of one isoform that minimizes prostaglandin-dependent mechanisms that contribute to NSAID-induced injury. Clinical trials support the efficacy and reduced toxicity of these agents. Because acid exacerbates the injury initiated by NSAIDs, potent acid suppressive therapy, typically with proton pump inhibitors, is another common approach to the treatment of NSAID-related dyspepsia as well as NSAID-induced ulcer disease.

CONCLUSIONS

Recent improvements in the understanding of NSAID-induced damage and new drug development have provided the opportunity for effective anti-inflammatory therapy with reduced GI toxicity. This illustrates the importance of identifying patients at risk for potential complications and the appropriate use of strategies to prevent and treat NSAID-induced complications.

Collagen secretion by human gastric and skin fibroblasts: implications for ulcer healing

Fibroblasts (FIB) play an important role in the wound-healing process. It is not known whether human skin and gastric FIB show different responses to regulatory compounds. In this study, we have examined the collagen production by these FIB after different stimuli. In vitro release of collagen into the medium by steady-state confluent human FIB cultures was assessed over a 24-hour period by 3H-proline incorporation into collageneous protein. Serum and epidermal growth factor increased collagen secretion in both types of FIB, but gastric FIB produced less collagen than skin FIB. Prostaglandin E1 inhibited collagen production in both types of FIB, but nonsteroidal anti-inflammatory drugs and interleukin-1beta, a cytokine involved in the wound-healing process, had opposite effects on gastric and skin FIB. The effects of lipoxygenase metabolites on collagen secretion was small, but different in both types of FIB. We conclude that, when compared to skin FIB, human gastric FIB produce less collagen and show pronounced different responses to different agents, which might be relevant to explain (in part) their clinical effects on ulcer healing. These data provide new insights into the wound-healing process.

Gastroprotective and ulcer healing effects of nitric oxide-releasing non-steroidal anti-inflammatory drugs

BACKGROUND & AIM

New class of nitric oxide-releasing non-steroidal anti-inflammatory drugs was shown to inhibit cyclooxygenase and prostaglandin generation without causing mucosal damage but whether these agents are capable of affecting gastric mucosal damage induced by strong irritants and healing of chronic gastric ulcers remains to be studied. In this investigation, effects of nitric oxide-releasing aspirin and nitric oxide-releasing naproxen were compared with those of native agents on gastric lesions provoked by 100% ethanol and on healing of chronic acetic acid ulcers.

RESULTS

Both, nitric oxide-releasing aspirin and naproxen dose-dependently attenuated ethanol-induced damage and produced a significant rise in gastric blood flow but did not delay healing of gastric ulcers while native aspirin and naproxen had no influence on ethanol-induced gastric damage but significantly prolonged ulcer healing, reduced gastric blood flow and suppressed mucosal generation of prostaglandin E2. The gastroprotective and hyperaemic effects of both nitric oxide-non-steroidal anti-inflammatory drugs were completely abolished by ODQ, an inhibitor of guanylyl cyclase-cGMP system but not influenced by suppression of nitric oxide-synthase with L-NNA. The damaging effects of native acetyl salicylate acid or naproxen were aggravated by acidification of these non-steroidal anti-inflammatory drugs but the exogenous acid added to nitric oxide-acetyl salicylate acid or nitric oxide-naproxen failed to influence their effect. Despite inhibiting of PGE2 generation, both nitric oxide-releasing derivatives and native aspirin and naproxen failed to affect expression of cyclooxygenase-1 mRNA but upregulated the cyclooxygenase-2 mRNA. Concurrent inhibition of cyclooxygenase-2 by selective inhibitor NS-398 which by itself delayed ulcer healing and attenuated the gastric blood flow at ulcer margin, significantly worsened the effects of these nitric oxide-non-steroidal anti-inflammatory drugs and their parent drugs on ulcer healing and the gastric blood flow at the ulcer margin.

CONCLUSIONS

1) Coupling of nitric oxide to aspirin or naproxen attenuates ethanol-induced damage, possibly due to an increase in gastric microcirculation mediated by excessive release and action of nitric oxide that probably compensates for PG deficiency induced by non-steroidal anti-inflammatory drugs; and 2) nitric oxide-non-steroidal anti-inflammatory drug, unlike classic non-steroidal anti-inflammatory drugs, does not affect intact gastric mucosa and fails to delay the healing of pre-existing ulcers.

Nonsteroidal anti-inflammatory drug gastropathy

By inhibiting prostaglandin synthesis, nonsteroidal anti-inflammatory drugs (NSAIDs) compromise gastroduodenal defense mechanism including blood flow and mucus/bicarbonate secretion. This has led to NSAIDs being the most widely reported drug cause of adverse events. While NSAIDs also cause dyspepsia, inhibition of prostaglandin synthesis may reduce this from even higher levels that would otherwise prevail and mask ulcer-related dyspepsia, making anticipatory management difficult. On average, the risk of ulcer complications increases 4-fold, resulting in 1.25 additional hospitalizations per 100 patient-years according to one estimate. Older patients, those with a past history, and those taking anticoagulants or corticosteroids are at higher risk. Risk is dose dependent and is lower with ibuprofen at low doses than with other NSAIDs. It is unlikely that Helicobacter pylori increases the risk, and under some circumstances it may be protective. Selective inhibitors of the inducible cyclooxygenase 2 spare gastric mucosal prostaglandin synthesis and do not damage the gastric mucosa. Their place in therapy, compared with use of misoprostol or proton pump inhibitors, is currently emerging. Future competitors may include nitric oxide-donating, zwitterionic, or R-enantiomer NSAIDs.

Cyclo-oxygenase-2 inhibitors suppress epithelial cell kinetics and delay gastric wound healing in rats

BACKGROUND AND AIMS

The present study examined the effects of NS-398, a specific cyclo-oxygenase-2 inhibitor, on gastric mucosal cell kinetics and gastric wound healing following acid-induced injury.

METHODS

Male Sprague-Dawley rats were fasted for 24 h and then 0.6 mol/L hydrochloric acid (HCl; 1 mL) was administered into the stomach; NS-398 or indomethacin was administered to the animals 10 min after the acid. Levels of constitutive cyclo-oxygenase (COX-1) and mitogen-inducible cyclo-oxygenase (COX-2) in the gastric mucosa were analysed using western blotting and immunohistochemical staining. The grade of the lesion was assessed using planimetry and histological examination, including immunohistochemistry for proliferating cell nuclear antigen (PCNA).

RESULTS

Although there was strong expression of COX-1, there was minimal expression of COX-2 in the gastric mucosa. Expression of COX-2 was enhanced mainly in surface epithelial cells and neck cells following HCl administration. Gastric mucosal ulcers and erosions healed within 48 h, during which time the proliferative zone expanded in the control animals. Indomethacin and NS-398 suppressed the expansion of the proliferative zone and delayed the healing of the gastric injury.

CONCLUSION

The present study demonstrated that cyclo-oxygenase-2 inhibitors delay gastric wound healing by suppressing expansion of the mucosal proliferative zone. These results provide evidence that cyclo-oxygenase-2 has an important role in gastric mucosal regeneration.