Induction of cyclooxygenase 2 in gastric mucosal lesions and its inhibition by the specific antagonist delays healing in mice

CXCL17, an orphan chemokine, acts as a novel angiogenic and anti-inflammatory factor

Chemokines play pivotal roles in the recruitment of various immune cells to diverse tissues in both physiological and pathological conditions. CXCL17 is an orphan chemokine preliminarily found to be involved in tumor angiogenesis. However, its protein nature, as well as its endogenous bioactivity, has not been well clarified. Using real-time PCR, immunohistochemical staining, and Western blotting, we found that CXCL17 is highly expressed in both a constitutive and inducible manner in the rat gastric mucosa, where it undergoes endoproteolysis during protein maturation. The mature CXCL17 exhibited strong chemoattractant abilities targeting monocytes and macrophages, potentially through ERK1/2 and p38 but not JNK signaling. CXCL17 also induced the production of proangiogenic factors such as vascular endothelial growth factor A from treated monocytes. Furthermore, in contrast to other CXC chemokines that accelerate inflammatory responses, CXCL17 showed novel anti-inflammatory effects on LPS-activated macrophages. Therefore, our data suggest that CXCL17 in the gastric lamina propria may play an important role in tissue repair and anti-inflammation, both of which help to maintain the integrity of the gastric mucosa.

Advent of novel phosphatidylcholine-associated nonsteroidal anti-inflammatory drugs with improved gastrointestinal safety

The mucosa of the gastrointestinal (GI) tract exhibits hydrophobic, nonwettable properties that protect the underlying epithelium from gastric acid and other luminal toxins. These biophysical characteristics appear to be attributable to the presence of an extracellular lining of surfactant-like phospholipids on the luminal aspects of the mucus gel layer. Phosphatidylcholine (PC) represents the most abundant and surface-active form of gastric phospholipids. PC protected experimental rats from a number of ulcerogenic agents and/or conditions including nonsteroidal anti-inflammatory drugs (NSAIDs), which are chemically associated with PC. Moreover, preassociating a number of the NSAIDs with exogenous PC prevented a decrease in the hydrophobic characteristics of the mucus gel layer and protected rats against the injurious GI side effects of NSAIDs while enhancing and/or maintaining their therapeutic activity. Bile plays an important role in the ability of NSAIDs to induce small intestinal injury. NSAIDs are rapidly absorbed from the GI tract and, in many cases, undergo enterohepatic circulation. Thus, NSAIDs with extensive enterohepatic cycling are more toxic to the GI tract and are capable of attenuating the surface hydrophobic properties of the mucosa of the lower GI tract. Biliary PC plays an essential role in the detoxification of bile salt micelles. NSAIDs that are secreted into the bile injure the intestinal mucosa via their ability to chemically associate with PC, which forms toxic mixed micelles and limits the concentration of biliary PC available to interact with and detoxify bile salts. We have worked to develop a family of PC-associated NSAIDs that appear to have improved GI safety profiles with equivalent or better therapeutic efficacy in both rodent model systems and pilot clinical trials.

Pharmaceutical therapy for osteoarthritis

There are a variety of oral and topical pharmaceutical agents for the treatment of osteoarthritis. To date there is no pharmacologic agent proved to prevent disease progression. This article focuses primarily on the medications used for symptomatic relief and palliation of pain. The article reviews the medications' mechanisms of action and the available efficacy literature, as well as indications, contraindications, and common adverse effects.

H(2)S-releasing aspirin protects against aspirin-induced gastric injury via reducing oxidative stress

The aim of this study was to examine the effect of ACS14, a hydrogen sulfide (H(2)S)-releasing derivative of aspirin (Asp), on Asp-induced gastric injury. Gastric hemorrhagic lesions were induced by intragastric administration of Asp (200 mg/kg, suspended in 0.5% carboxymethyl cellulose solutions) in a volume of 1 ml/100 g body weight. ACS14 (1, 5 or 10 mg/kg) was given 30 min before the Asp administration. The total area of gastric erosions, H(2)S concentration and oxidative stress in gastric tissues were measured three hours after administration of Asp. Treatment with Asp (200 mg/kg), but not ACS14 (430 mg/kg, at equimolar doses to 200 mg/kg Asp), for 3 h significantly increased gastric mucosal injury. The damage caused by Asp was reversed by ACS14 at 1-10 mg/kg in a concentration-dependent manner. ACS14 abrogated Asp-induced upregulation of COX-2 expression, but had no effect on the reduced PGE(2) level. ACS14 reversed the decreased H(2)S concentrations and blood flow in the gastric tissue in Asp-treated rats. Moreover, ACS14 attenuated Asp-suppressed superoxide dismutase-1 (SOD-1) expression and GSH activity, suggesting that ACS14 may stimulate antioxidants in the gastric tissue. ACS14 also obviously inhibited Asp-induced upregulation of protein expression of oxidases including XOD, p47(phox) and p67(phox). In conclusion, ACS14 protects Asp induced gastric mucosal injury by inhibiting oxidative stress in the gastric tissue.

Managing the adverse effects of nonsteroidal anti-inflammatory drugs

Conventional medical treatment for rheumatoid arthritis and osteoarthritis includes the use of NSAIDs (traditional and selective inhibitors of cyclooxygenase [COX]-2), because they provide unmistakable and significant health benefits in the treatment of pain and inflammation. However, they are associated with an increased risk of serious gastrointestinal (GI) and cardiovascular (CV) adverse events. Both beneficial and adverse effects are due to the same mechanism of action, which is inhibition of COX-dependent prostanoids. Since CV and GI risk are related to drug exposure, a reduction in the administered dose is recommended. However, this strategy will not eliminate the hazard owing to a possible contribution of individual genetic background. Further studies will be necessary to develop genetic and/or biochemical markers predictive of the CV and GI risk of NSAIDs.

NSAID gastropathy and enteropathy: distinct pathogenesis likely necessitates distinct prevention strategies

The mechanisms underlying the ability of nonsteroidal anti-inflammatory drugs (NSAIDs) to cause ulceration in the stomach and proximal duodenum are well understood, and this injury can largely be prevented through suppression of gastric acid secretion (mainly with proton pump inhibitors). In contrast, the pathogenesis of small intestinal injury induced by NSAIDs is less well understood, involving more complex mechanisms than those in the stomach and proximal duodenum. There is clear evidence for important contributions to NSAID enteropathy of enteric bacteria, bile and enterohepatic recirculation of the NSAID. There is no evidence that suppression of gastric acid secretion will reduce the incidence or severity of NSAID enteropathy. Indeed, clinical data suggest little, if any, benefit. Animal studies suggest a significant exacerbation of NSAID enteropathy when proton pump inhibitors are co-administered with the NSAID. This worsening of damage appears to be linked to changes in the number and types of bacteria in the small intestine during proton pump inhibitor therapy. The distinct mechanisms of NSAID-induced injury in the stomach/proximal duodenum versus the more distal small intestine likely dictate distinct strategies for prevention.

Evaluation of Barrett's esophagus with CK7, CK20, p53, Ki67, and COX2 expressions using chromoendoscopical examination

Barrett's esophagus (BE) is a complication of chronic gastroesophageal reflux disease and can be diagnosed when there is an endoscopically irregular Z-line and intestinal metaplasia (IM) in a biopsy obtained lower esophagus. It is still not clear whether IM in the gastric cardia or columnar mucosa without IM in the lower esophagus have any significance as BE, which is considered as preneoplastic. The aim of the study was to determine the immunohistochemical features of BE and columnar mucosa in the distal esophagus and also to evaluate the value of chromoendoscopy in the diagnosis of BE in a prospective manner. A total of 12 chromoendoscopic biopsies (six from normal-looking unstained esophagus and six from esophageal mucosa stained with methyl blue suspicious of BE) were taken from 111 cases who underwent endoscopy because of a variety of upper gastrointestinal symptoms. Immunohistochemical analysis was performed using CK7, CK20, p53, Ki67, and cyclooxygenase 2 (COX2). Of the 111 cases, 19 cases with carcinoma (nine adeno, six squamous, four undifferentiated carcinomas) and 17 cases with normal squamous epithelium were excluded, while 75 cases showing columnar epithelium, including 46 (61.3%) with IM and 29 (38,7%) without IM, were further evaluated immunohistochemically. CK7 was observed in surface, crypt, and glandular epithelium, whereas CK20 was expressed in surface and superficial crypt epithelium. No significant difference was observed between the Barrett and non-Barrett type of CK7/20 staining pattern (P > 0,05). Expression of p53 did not show any difference between BE and columnar mucosa without IM, whereas COX2 expression was significantly increased in BE (P < 0.05) in comparison with columnar mucosa without IM. Ki67 expression was significiantly higher both in upper and lower crypts in BE (P < 0.05). The present study showed that a Barrett pattern does not seem to exist; however, the analysis of COX2 expression and the Ki67 proliferation fraction by immunohistochemistry can be used to separate BE from non-Barrett's metaplasia of the distal esophagus. In our point of view, the immunohistochemical detection of p53 expression in Barrett's metaplasia stage is useless as a marker for early detection of high-risk patients.

Clinical pharmacology of nonsteroidal anti-inflammatory drugs in dogs

OBJECTIVES

To discuss the clinical pharmacology of currently licensed veterinary NSAIDs and to review gastrointestinal and renal adverse effects as well as drug-drug interactions that have been reported with these drugs. To review the use of NSAIDs in the peri-operative setting and their use in patients with osteoarthritis. To further review the reported effects of NSAIDs on canine articular cartilage and liver as well as the clinical relevance of a washout period.

DATABASES USED

PubMed, CAB abstracts and Google Scholar using dog, dogs, nonsteroidal anti-inflammatory drugs and NSAID(s) as keywords.

CONCLUSIONS

A good understanding of the mechanisms by which NSAIDs elicit their analgesic effect is essential in order to minimize adverse effects and drug-drug interactions. Cyclooxygenase (COX) is present in at least two active isoforms in the body and is the primary pharmacologic target of NSAIDs. Inhibition of COX is associated with the analgesic effects of NSAIDs. COX is present in the gastrointestinal tract and kidneys, along with other areas of the body, and is also the likely reason for many adverse effects including gastrointestinal and renal adverse effects. The newer veterinary approved NSAIDs have a lower frequency of gastrointestinal adverse effects in dogs compared to drugs such as aspirin, ketoprofen and flunixin, which may be due to differential effects on the COX isoforms. There are currently no published reports demonstrating that the newer NSAIDs are associated with fewer renal or hepatic adverse effects in dogs. NSAIDs remain the cornerstone of oral therapy for osteoarthritis unless contraindicated by intolerance, concurrent therapies or underlying medical conditions. NSAIDs are also effective and frequently used for the management of post-operative pain.

Effect of COX-2 inhibitor lumiracoxib and the TNF-α antagonist etanercept on TNBS-induced colitis in Wistar rats

Crohn's disease (CD) is associated with gut barrier dysfunction. Besides the baseline barrier defect, a subgroup of patients also expresses an intestinal barrier hyperresponsiveness to nonsteroidal anti-inflammatory drugs. On the other hand, the anti-tumour necrosis factor alpha (TNF-α) treatment has brought benefits to these patients. Thus, this study aimed to evaluate the effect of lumiracoxib, a selective-cyclooxygenase-2 (COX-2) inhibitor, and Etanercept (ETC), a TNF-α antagonist on the 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced experimental colitis. A total of 47 Wistar rats were randomized into seven groups, as follows: (1) Sham: sham induced-colitis; (2) TNBS: nontreated induced-colitis; (3) Lumiracoxib control; (4) Lumiracoxib-treated induced-colitis; (5) ETC control; (6) ETC-treated induced-colitis; (7) Lumiracoxib-ETC-treated induced-colitis. Rats from groups 6 and 7 presented significant improvement of macroscopic and histopathological damages in the distal colon. The gene expression of COX-2 mRNA, as well of TNF-α mRNA, decreased significantly in groups 6 and 7 compared to the TNBS nontreated and lumiracoxib-treated groups. The treatment only with lumiracoxib did not reduce the inflammation on TNBS-induced experimental colitis. ETC attenuated the damage seen in the colon and reduced the inflammation caused by TNBS. Our results suggest that down-regulation of TNF-α and COX-2 resulted in a decrease in inflammation caused by TNBS and thus provided some protection from the colonic damage caused by TNBS.

Glycosylation of human cyclooxygenase-2 (COX-2) decreases the efficacy of certain COX-2 inhibitors

Prostanoids play an important role in a variety of physiological and pathophysiological processes including inflammation and cancer. The rate-limiting step in the prostanoid biosynthesis pathway is catalyzed by cyclooxygenase-2 (COX-2). COX-2 exists as two glycoforms, 72 and 74 kDa, the latter resulting from an additional glycosylation at Asn(580). In this study, Asn(580) was mutated, and the mutant and wild-type COX-2 genes were expressed in COS-1 cells to determine how glycosylation affects the inhibition of COX-2 activity by aspirin, flurbiprofen, ibuprofen, celecoxib, and etoricoxib. Results indicate that certain inhibitors were 2-5 times more effective at inhibiting COX-2 activity when the glycosylation site was eliminated, indicating that glycosylation of COX-2 at Asn(580) decreases the efficacy of some inhibitors.

Acid-induced COX-2 expression and prostaglandin E2 production via activation of ERK1/2 and p38 MAPK in cultured feline esophageal smooth muscle cells

Cyclooxygenase (COX)-2 is known to play an important role in inflammatory conditions such as reflux esophagitis resulting from acid reflux. In this study, we tested whether an acidic medium (pH 4.0) induces an increase in COX-2 expression or PGE(2) production, and explored the implication of mitogen-activated protein kinases (MAPKs) activation in these responses in cultured cat esophageal smooth muscle cells. Acidic cytotoxicity was assessed and expression changes in COXs or phosphorylated MAPKs were analyzed by Western blotting. PGE(2) production was measured by immunoassay. No significant decrease in cell viability was observed for 6 h exposure to acidic medium. COX-2 expression and PGE(2) production significantly increased to maximal levels at 6 h exposure to acidic medium. The cells also exhibited significant activation of ERK1/2 and p38 MAPK, but not JNK within 10 min under acidic medium. The increments of COX-2 expression and PGE(2) production by acidic medium were decreased by pretreatment with PD98059 or SB202190, respectively. These results suggest that acidic environments may enhance the COX-2 expression and PGE(2) production through activation of ERK1/2 and p38 MAPK in the cultured cat esophageal smooth muscle cells.

Inhibition of cyclooxygenase-2 causes regression of gastric adenomas in trefoil factor 1 deficient mice

Cyclooxygenase-2 (Cox-2) expression is a marker of reduced survival in gastric cancer patients, and inhibition of Cox-2 suppresses gastrointestinal carcinogenesis in experimental animal models. To investigate the role of Cox-2 in gastric carcinogenesis in vivo, we utilized trefoil factor 1 (Tff1) deficient mice, which model the neoplastic process of the stomach by developing gastric adenomas with full penetrance. These tumors express Cox-2 protein and mRNA, and we have now investigated the effects of genetic deletion of the mouse Cox-2 gene [also known as prostaglandin-endoperoxide synthase 2 (Ptgs2)] and a Cox-2 selective drug celecoxib. Our results show that genetic deletion of Cox-2 in the Tff1 deleted background resulted in reduced adenoma size and ulceration with a chronic inflammatory reaction at the site of the adenoma. To characterize the effect of Cox-2 inhibition in more detail, mice that had already developed an adenoma were fed with celecoxib for 8-14 weeks, which resulted in disruption of the adenoma that ranged from superficial erosion to deep ulcerated destruction accompanied with chronic inflammation. Importantly, mice fed with celecoxib for 16 weeks, followed by control food for 9 weeks, redeveloped a complete adenoma with no detectable inflammatory process. Finally, we determined the identity of the Cox-2 expressing cells and found them to be fibroblasts. Our results show that inhibition of Cox-2 is sufficient to reversibly disrupt gastric adenomas in mice.

Novel biphasic role of LipoxinA(4) on expression of cyclooxygenase-2 in lipopolysaccharide-stimulated lung fibroblasts

Fibroblasts are important to host defence and immunity, can also as initiators of inflammation as well. As the endogenous “braking signal”, Lipoxins can regulate anti-inflammation and the resolution of inflammation. We investigated the effect of lipoxinA₄ on the expression of cyclooxygenase-2 in lipopolysaccharide-stimulated lung fibroblasts. We demonstrated that the expression of cyclooxygenase-2 protein was significantly increased and peaked initially at 6 hours, with a second increase, with maximal levels occurring 24 hours after lipopolysaccharide challenge. ProstaglandinE₂ levels also peaked at 6 hours, and prostaglandinD₂ levels were increased at both 6 and 24 hours. Exogenous lipoxinA₄ inhibited the first peak of cyclooxygenase-2 expression as well as the production of prostaglandinE₂ induced by lipopolysaccharide in a dose-dependent manner. In contrast, exogenous lipoxinA₄ increased the second peak of cyclooxygenase-2 expression as well as the production of prostaglandinD₂ induced by lipopolysaccharide in a dose-dependent manner. LipoxinA₄ receptor mRNA expression was markedly stimulated by lipopolysaccharide but inhibited by lipoxinA₄. We present evidence for a novel biphasic role of lipoxinA₄ on the expression of cyclooxygenase-2 in lipopolysaccharide-stimulated lung fibroblasts, whereby LXA₄ has an anti-inflammatory and proresolving activity in lung fibroblasts following LPS stimulation.

Delayed production of arachidonic acid contributes to the delay of proteinase-activated receptor-1 (PAR1)-triggered prostaglandin E2 release in rat gastric epithelial RGM1 cells

Proteinase-activated receptor-1 (PAR1), upon activation, exerts prostanoid-dependent gastroprotection, and increases prostaglandin E(2) (PGE(2)) release through cyclooxygenase-2 (COX-2) upregulation in rat gastric mucosal epithelial RGM1 cells. However, there is a big time lag between the PAR1-triggered PGE(2) release and COX-2 upregulation in RGM1 cells; that is, the former event takes 18 h to occur, while the latter rapidly develops and reaches a plateau in 6 h. The present study thus aimed at clarifying mechanisms for the delay of PGE(2) release after PAR1 activation in RGM1 cells. Although a PAR1-activating peptide, TFLLR-NH(2), alone caused PGE(2) release at 18 h, but not 6 h, TFLLR-NH(2) in combination with arachidonic acid dramatically enhanced PGE(2) release even for 1-6 h. TFLLR-NH(2) plus linoleic acid caused a similar rapid response. CP-24879, a Δ(5)/Δ(6)-desaturase inhibitor, abolished the PGE(2) release induced by TFLLR-NH(2) plus linoleic acid, but not by TFLLR-NH(2) alone. The TFLLR-NH(2)-induced PGE(2) release was not affected by inhibitors of cytosolic phospholipase A(2) (cPLA(2)), Ca(2+)-independent PLA(2) (cPLA(2)) or secretory PLA(2) (sPLA(2)), but was abolished by their mixture or a pan-PLA(2) inhibitor. Among PLA(2) isozymes, mRNA of group IIA sPLA(2) (sPLA(2)-IIA) was upregulated following PAR1 stimulation for 6-18 h, whereas protein levels of PGE synthases were unchanged. These data suggest that the delay of PGE(2) release after COX-2 upregulation triggered by PAR1 is due to the poor supply of free arachidonic acid at the early stage in RGM1 cells, and that plural isozymes of PLA(2) including sPLA(2)-IIA may complementarily contribute to the liberation of free arachidonic acid.

Muc-2-deficient mice display a sex-specific, COX-2-related impairment of gastric mucosal repair

Mucus is known to contribute significantly to the prevention and repair of mucosal damage throughout the gastrointestinal tract. Although not normally expressed in the stomach, mucin-2 (MUC-2, encoded by the MUC2 gene) is expressed in certain disease states. The aim of this study was to determine in a mouse model whether the absence of Muc-2 would result in impaired susceptibility to and healing of gastric mucosal injury. Acute gastric damage was induced in mice deficient in Muc-2 and in wild-type controls, through oral administration of indomethacin. Chronic gastric ulcers were induced by serosal application of acetic acid. The extent of injury and the extent of healing of the damage over time were examined in both models. Indomethacin administration caused similar levels of gastric damage in Muc-2-deficient and wild-type mice, but the erosions healed more slowly in the former. Acetic acid-induced gastric ulcers were initially similar in size in Muc-2-deficient and wild-type mice of both sexes, but ulcer healing was significantly impaired in male Muc-2-deficient mice. Induction of cyclooxygenase-2 in the stomach, in response to indomethacin- or acetic acid-induced ulceration, was significantly reduced in male Muc-2-deficient mice. This phenomenon, and the sex specificity, was also apparent in bone marrow-derived macrophages stimulated with endotoxin. These results demonstrate a marked impairment of gastric mucosal repair in male Muc-2-deficient mice that may be related to an insufficient induction of cyclooxygenase-2, an enzyme known to contribute to mucosal repair.

Cyclooxygenase-2 (COX-2) polymorphisms and risk of inflammatory bowel disease in a Scottish and Danish case-control study

BACKGROUND

Inflammatory bowel diseases (IBDs) are a result of interactions between luminal pathogens and the intestinal immune response. Cyclooxygenase-2 (COX-2) plays a key role in the regulation of the inflammatory response upon stimulation by luminal pathogens via Toll-like receptors.

METHODS

Genotypes of the COX-2/PTGS2/PGHS2 A-1195G (rs689466), G-765C (rs20417), and T8473C (rs5275) polymorphisms were assessed in a Scottish and Danish case-control study including 732 Crohn's disease (CD) cases, 973 ulcerative colitis (UC) cases, and 1157 healthy controls using logistic regression.

RESULTS

Carriers of the COX-2 A-1195G variant allele had increased risk of UC (odds ratio [OR], 95% confidence interval [CI] = 1.25 [1.02-1.54], P = 0.03) and of both UC and IBD among never smokers (OR [95% CI] = 1.47 [1.11-1.96], P = 0.01 and OR [95% CI] = 1.37 [1.06-1.77], P = 0.02, respectively). Furthermore, this variant genotype was associated with increased risk of diagnosis of UC before age 40 years and with extensive UC (OR [95% CI] = 1.34 [1.11-1.62], P = 0.002 and OR [95% CI] = 1.32 [1.03-1.69], P = 0.03, respectively).

CONCLUSIONS

COX-2 A-1195G polymorphism was associated with the risk of UC, especially among never-smokers, suggesting that low activity of COX-2 may predispose to UC. Our results suggest that inclusion of smoking status may be essential for the evaluation of the role of genetic predisposition to IBD.

Organotypic 3D cell culture models: using the rotating wall vessel to study host-pathogen interactions

Appropriately simulating the three-dimensional (3D) environment in which tissues normally develop and function is crucial for engineering in vitro models that can be used for the meaningful dissection of host-pathogen interactions. This Review highlights how the rotating wall vessel bioreactor has been used to establish 3D hierarchical models that range in complexity from a single cell type to multicellular co-culture models that recapitulate the 3D architecture of tissues observed in vivo. The application of these models to the study of infectious diseases is discussed.

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.

Abarema cochliacarpos: gastroprotective and ulcer-healing activities

ETHNOPHARMACOLOGICAL RELEVANCE

Abarema cochliacarpos (Gomes) Barneby & Grimes (Mimosaceae) is a species--in folk medicine of Lagarto city, Sergipe state, northeastern Brazil--reputed to heal gastric ulcer and gastritis.

AIM OF THE STUDY

Chloroform (CE) and methanolic (ME) extracts as well as ethyl acetate fraction (AF), butanolic fraction (AC) and aqueous fraction (AQF) of the methanolic extract of Abarema cochliacarpos bark were evaluated against acute gastric ulcer. The AC fraction was selected to assess its activity in ulcer healing and its gastroprotective effects via mucus and gastric secretion.

MATERIAL AND METHODS

The gastroprotective action of CE and ME extracts and the fractions of the latter were evaluated in a rodent experimental model. The action mechanisms, involvements of the antisecretory action and mucus production, toxicological and healing activity of the AC (150 mg/kg, p.o.) were evaluated. We also used histological analysis (HE and PAS) and immunohistochemical (PCNA, COX-2, VEGF and HSP-70) assays to evaluate the effects of Abarema cochliacarpos.

RESULTS

CE (200 and 400 mg/kg, p.o.) and ME (100, 200 and 400 mg/kg, p.o.) extracts were able to protect gastric mucosa against absolute ethanol. Respective inhibitions produced were: 65.31% and 83.80% by the first; 91.69%, 96.75% and 99.80% by the second; and 74.24% by the AC fraction. Antisecretory and mucus production effects were exhibited by the AC fraction, which also accelerated the healing of ulcerated gastric mucosa by stimulating proliferation factors (PCNA) and induced healing factors including COX-2, VEGF and HSP-70.

CONCLUSION

All these results suggest that Abarema cochliacarpos (Gomes) Barneby & Grimes presents gastroprotective effects and wound-healing properties.

Prostaglandin EP receptors involved in modulating gastrointestinal mucosal integrity

Endogenous prostaglandins (PGs) play an important role in modulating the mucosal integrity and various functions of the gastrointestinal tract, and E type PGs are most effective in these actions. PGE₂ protected against acid-reflux esophagitis and prevented the development of gastric damage induced by ethanol or indomethacin, the effects mimicked by EP1 agonists and attenuated by an EP1 antagonist. Adaptive cytoprotection induced by mild irritants was also attenuated by the EP1 antagonist. On the other hand, the acid-induced duodenal damage was prevented by EP3/EP4 agonists and worsened by EP3/EP4 antagonists. Similarly, the protective effect of PGE₂ on indomethacin-induced small intestinal damage or DSS-induced colitis was mimicked by EP3/EP4 agonists or EP4 agonists, respectively. The mechanisms underlying these actions of PGE₂ are related to inhibition of stomach contraction (EP1), stimulation of duodenal HCO₃⁻ secretion (EP3/EP4), inhibition of small intestinal contraction (EP4), and stimulation of mucus secretion (EP3/EP4) or down-regulation of cytokine secretion in the colon (EP4), respectively. PGE₂ also showed a healing-promoting effect on gastric ulcers and intestinal lesions through the activation of EP4 receptors, the effect associated with stimulation of angiogenesis via an increase in VEGF expression. These findings should aid the development of new strategies for treatment of gastrointestinal diseases.

Variability among nonsteroidal antiinflammatory drugs in risk of upper gastrointestinal bleeding

OBJECTIVE

Traditional nonsteroidal antiinflammatory drugs (NSAIDs) increase the risk of upper gastrointestinal (GI) bleeding/perforation, but the magnitude of this effect for coxibs in the general population and the degree of variability between individual NSAIDs is still under debate. This study was undertaken to assess the risk of upper GI bleeding/perforation among users of individual NSAIDs and to analyze the correlation between this risk and the degree of inhibition of whole blood cyclooxygenase 1 (COX-1) and COX-2 in vitro.

METHODS

We conducted a systematic review of observational studies on NSAIDs and upper GI bleeding/perforation published between 2000 and 2008. We calculated pooled relative risk (RR) estimates of upper GI bleeding/perforation for individual NSAIDs. Additionally, we verified whether the degree of inhibition of whole blood COX-1 and COX-2 in vitro by average circulating concentrations predicted the RR of upper GI bleeding/perforation.

RESULTS

The RR of upper GI bleeding/perforation was 4.50 (95% confidence interval [95% CI] 3.82-5.31) for traditional NSAIDs and 1.88 (95% CI 0.96-3.71) for coxibs. RRs lower than that for NSAIDs overall were observed for ibuprofen (2.69 [95% CI 2.17-3.33]), rofecoxib (2.12 [95% CI 1.59-2.84]), aceclofenac (1.44 [95% CI 0.65-3.2]), and celecoxib (1.42 [95% CI 0.85-2.37]), while higher RRs were observed for ketorolac (14.54 [95% CI 5.87-36.04]) and piroxicam (9.94 [95% CI 5.99-16.50). Estimated RRs were 5.63 (95% CI 3.83-8.28) for naproxen, 5.57 (95% CI 3.94-7.87) for ketoprofen, 5.40 (95% CI 4.16-7.00) for indomethacin, 4.15 (95% CI 2.59-6.64) for meloxicam, and 3.98 (95% CI 3.36-4.72) for diclofenac. The degree of inhibition of whole blood COX-1 did not significantly correlate with RR of upper GI bleeding/perforation associated with individual NSAIDs (r(2) = 0.34, P = 0.058), but a profound and coincident inhibition (>80%) of both COX isozymes was associated with higher risk. NSAIDs with a long plasma half-life and with a slow-release formulation were associated with a greater risk than NSAIDs with a short half-life.

CONCLUSION

The results of our analysis demonstrate that risk of upper GI bleeding/perforation varies between individual NSAIDs at the doses commonly used in the general population. Drugs that have a long half-life or slow-release formulation and/or are associated with profound and coincident inhibition of both COX isozymes are associated with a greater risk of upper GI bleeding/perforation.

Novel anti-inflammatory functions for endothelial and myeloid cyclooxygenase-2 in a new mouse model of Crohn's disease

Cyclooxygenase-2 (COX-2) is an important regulator of inflammation implicated in the development of a variety of diseases, including inflammatory bowel disease (IBD). However, the regulation of intestinal inflammation by COX-2 is poorly understood. We previously reported that COX-2(-/-) mice fed a cholate-containing high-fat (CCHF) diet had high mortality of unknown mechanisms attributable to severe intestinal inflammation in the ileo-ceco-colic junction that presented characteristics similar to Crohn's disease (CD). To further characterize the role of COX-2 in intestinal inflammation, we established cell-specific conditional COX-2(-/-) mice. Endothelial cell-specific (COX-2(-E/-E)) and myeloid cell-specific (COX-2(-M/-M)) COX-2(-/-) mice, but not wild-type mice, on the CCHF diet developed localized CD-like pathology at the ileo-ceco-colic junction that was associated with cellular infiltration, increased expression of myeloperoxidase and IL-5, and decreased IL-10 expression. The CD-like pathology in COX-2(-E/-E) mice was also accompanied by increased expression of cytokines (IL-6, TNF-alpha, and INF-gamma), compared with wild-type mice and COX-2(-M/-M) mice. In contrast, the ileo-ceco-colic inflammation in COX-2(-M/-M) mice was associated with more pronounced infiltration of granulocytes and macrophages than COX-2(-E/-E) mice. COX-2(-ME/-ME) (COX-2(-M/-M) x COX-2(-E/-E)) mice on the CCHF diet developed CD-like pathology in the ileo-ceco-colic junction reminiscent of total COX-2(-/-) mice on CCHF diet and wild-type mice on CCHF diet treated with COX-2 inhibitor, celecoxib. The pathology of diet-mediated ileo-ceco-colic inflammation in COX-2(-/-) mice offers an excellent model system to elucidate the protective roles of endothelial and myeloid COX-2 and the molecular pathogenesis of CD.

Recombinant Human Epidermal Growth Factor Alleviates Gastric Antral Ulcer Induced by Naproxen: A Non-steroidal Anti Inflammatory Drug

BACKGROUND

To study the effect (s) of recombinant human Epidermal Growth Factor (rhEGF) on naproxen induced gastric ulcer in Wistar NIN rats.

METHODS

Male Wistar NIN rats were randomly divided into six experimental groups: Group I - Control, Group II - Naproxen treated, Group III - Naproxen with rhEGF/7 days, Group IV - Naproxen without rhEGF/7 days, Group V - Naproxen with rhEGF/14 days, and Group VI - Naproxen without rhEGF/14 days. Gastric ulcer was induced with naproxen at a concentration of 80 mg/kg by oral administration. After 24 hours of induction of ulcer, rhEGF treatment was started at a concentration of 100 µg/kg. Ulcer presence and healing were confirmed by histopathology study and molecular markers.

RESULTS

Naproxen per se induced gastric antral ulcers in Wistar NIN rats. Compared with control rats, naproxen induced rats had increased lipid peroxide content in serum. Subsequent decrease in lipid peroxide was observed in rhEGF treated groups. Treatment with rhEGF significantly resulted in healing of the ulcers, which was evident by 7 days of rhEGF treatment with total healing seen by 14 days. Significant increase in immunoreactivity for Cox-2 was observed when compared to control groups, whereas less immunoreactivity of Cox-2 was observed in rhEGF treated group. Compared with control group, naproxen induced group exhibited more gene expression of both Cox-2 and TGF beta while gene expression of Cox-2 and TGF beta in rhEGF group was comparable to control group.

CONCLUSIONS

The beneficial effects of rhEGF in the management of ulcer healing can be understood. Oral rhEGF can promote healing of the rats with gastric ulcer by stimulating Cox-2 and TGF-beta expression.

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.

Increased expression and cellular localization of lipocalin-type prostaglandin D synthase in Helicobacter pylori-induced gastritis

Immunological responses in the host can result in different disease outcomes of Helicobacter pylori-induced gastritis. Prostaglandin E2 derived from cyclooxygenase (COX) and prostaglandin E synthase contribute to gastric protection. Recently, prostaglandin D2 was shown to be involved in host immunity by chemotactic activity through chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2), but its role in H. pylori-induced gastritis has not been clarified. We determined the expression levels of mRNAs for haematopoietic PGD synthase (H-PGDS) and lipocalin-type PGDS (L-PGDS), MIP-1 alpha, IFN-gamma, IL-4, and CDX2 in H. pylori-induced gastritis mucosa by quantitative RT-PCR. We found that L-PGDS was constitutively expressed in the epithelium of the glandular base. L-PGDS, but not H-PGDS, was induced on fibroblasts close to infiltrating cells in the H. pylori-infected gastric mucosa. These fibroblasts co-expressed COX-2. The level of L-PGDS mRNA expression decreased as gastritis became more severe. In most of the H. pylori-infected gastric mucosa, CCR5(+) cells had more actively infiltrated than had CRTH2(+) cells. However, the expression level of IFN-gamma was lower in the mucosa of the CRTH2(+) cells-dominantly infiltrating group than that of the less CRTH2-infiltrating group. Exogenously added PGD2 decreased the H. pylori-induced expression of IFN-gamma in peripheral blood mononuclear cells in vitro. The data suggest that PGD2 derived from the gastric mucosa and fibroblasts plays protective roles against inflammatory changes in H. pylori-induced gastritis.

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.

Markedly reduced toxicity of a hydrogen sulphide-releasing derivative of naproxen (ATB-346)

BACKGROUND AND PURPOSE

Hydrogen sulphide is an important mediator of gastric mucosal defence. The use of non-steroidal anti-inflammatory drugs continues to be limited by their toxicity, particularly in the upper gastrointestinal tract. We evaluated the gastrointestinal safety and anti-inflammatory efficacy of a novel hydrogen sulphide-releasing derivative of naproxen, ATB-346 [2-(6-methoxy-napthalen-2-yl)-propionic acid 4-thiocarbamoyl-phenyl ester].

EXPERIMENTAL APPROACH

The ability of ATB-346 versus naproxen to cause gastric damage was evaluated in healthy rats and in rats with compromised gastric mucosal defence. Effects on the small intestine and on the healing of ulcers were also assessed. The ability of ATB-346 to inhibit cyclooxygenase-1 and 2 and to reduce inflammation in vivo was also evaluated.

KEY RESULTS

ATB-346 suppressed gastric prostaglandin E(2) synthesis as effectively as naproxen, but produced negligible damage in the stomach and intestine. In situations in which the gastric mucosa was rendered significantly more susceptible to naproxen-induced damage (e.g. ablation of sensory afferent nerves, inhibition of endogenous nitric oxide or hydrogen sulphide synthesis, co-administration with aspirin, antagonism of K(IR)6.x channels), ATB-346 did not cause significant damage. Unlike naproxen and celecoxib, ATB-346 accelerated healing of pre-existing gastric ulcers. In a mouse airpouch model, ATB-346 suppressed cyclooxygenase-2 activity and inhibited leukocyte infiltration more effectively than naproxen. ATB-346 was as effective as naproxen in adjuvant-induced arthritis in rats, with a more rapid onset of activity. Unlike naproxen, ATB-346 did not elevate blood pressure in hypertensive rats.

CONCLUSIONS AND IMPLICATIONS

ATB-346 exhibits anti-inflammatory properties similar to naproxen, but with substantially reduced gastrointestinal toxicity.

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.

Emotion recollected in tranquility: lessons learned from the COX-2 saga

Nonsteroidal antinflammatory drugs (NSAIDs) inhibit prostaglandin formation by cyclooxygenases (COX) 1 and 2. NSAIDs selective for inhibition of COX-2 are less likely than traditional drugs to cause serious gastrointestinal adverse effects, but predispose to adverse cardiovascular events, such as heart failure, myocardial infarction, and stroke. Evidence from human pharmacology and genetics, genetically manipulated rodents, and other animal models and randomized trials indicates that this is consequent to suppression of COX-2-dependent cardioprotective prostagladins, particularly prostacyclin. Lessons drawn from how this saga unfolded are relevant to how we approach drug surveillance and regulation, integrate diversifed forms of information and might pursue a more personalized approach to drug efficacy and risk.

In vivo models to study cyclooxygenase products in health and disease: Introduction to Part III

Inflammation is a primordial response that protects against injury and infection with the ultimate aim of restoring damaged tissue to its normal physiological functioning state. In fact, our well-being and survival depends upon its efficiency and carefully balanced control and to which we are alerted in the form of pain, swelling, and redness. Prostaglandins (PG), lipids derived from arachidonic acid metabolism by the enzyme cyclooxygenase, are historically one of the most well-studied mediators of the acute inflammatory response; so much so that their inhibition by so-called non-steroidal anti-inflammatory drugs (NSAIDs) has been the mainstay for the treatment of diseases where inflammation becomes a pathological driving force. However, while NSAIDs relieve the symptoms of dyregulated inflammatory responses, they do not cure the underlying disease and have associated gastrointestinal and renal toxicity. These side effects arose from inhibiting constitutively expressed, protective cyclooxygenase (COX-1). Finding another inducible COX (COX-2) expressed only at sites of injury provided a new era in inflammation research and a new era in treating inflammation-driven diseases. The hope was that high levels of COX-2 expression at sites of pain and tissue injury drove that disease process and that its inhibition would possess all the benefits of traditional NSAIDS without the side effects that arise from the inhibition of protective COX-1. However, by discussing data derived from experimental disease models of acute inflammation, in this chapter we suggest that delineating between the roles of COX-1 and COX-2 might not be as simple as once thought. We provide examples of data where a pathological role for COX-1 is evident and where COX-2 is clearly protective.

Cancer-stromal cell interaction and tumor angiogenesis in gastric cancer

Recent studies in molecular and cellular biology have shown that tumor growth and metastasis are not determined by cancer cells alone but also by a variety of stromal cells. The stroma constitutes a large part of most solid tumors, and cancer-stromal cell interaction contributes functionally to tumor growth and metastasis. Angiogenesis is the result of an imbalance between positive and negative angiogenic factors released by tumor and host cells into the microenvironment of the neoplastic tissue. In gastric cancer, tumor cells and stromal cells produce various angiogenic factors, including vascular endothelial growth factor, interleukin-8, and platelet-derived endothelial cell growth factor. The microenvironment in the gastric mucosa may also influence the angiogenic phenotype of gastric cancer. Helicobacter pylori infection increases expression of several angiogenic factors by tumor cells. Activated fibroblasts and macrophages in tumor stroma also play an important role in angiogenesis and tumor progression. We review the current understanding of cancer-stromal cell interaction as it pertains to tumor angiogenesis in gastric cancer.

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.

Effect of COX-2 inhibitor after TNBS-induced colitis in Wistar rats

Inflammatory bowel disease (IBD) is a common chronic gastrointestinal disorder characterized by alternating periods of remission and active intestinal inflammation. Some studies suggest that antiinflammatory drugs are a promising alternative for treatment of the disease. Thus, this study aimed to evaluate the effect of lumiracoxib, a selective-cyclooxygenase-2 (COX-2) inhibitor, on 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced experimental colitis. Wistar rats (n = 25) were randomized into four groups, as follows: Group (1) Sham group: sham induced-colitis rats; Group (2) TNBS group: nontreated induced-colitis rats; Group (3) Lumiracoxib control group; and Group (4) Lumiracoxib-treated induced-colitis rats. Our results showed that rats from groups 2 and 4 presented similar histopathological damage and macroscopic injury in the distal colon as depicted by significant statistically differences (P < 0.01; P < 0.05) compared to the other two groups. Weak expression of COX-2 mRNA was detected in normal colon cells, while higher levels of COX-2 mRNA were detected in group 2 and group 4. Therapy with lumiracoxib reduced COX-2 expression by 20-30%, but it was still higher and statistically significant compared to data obtained from the lumiracoxib control group. Treatment with the selective COX-2 inhibitor lumiracoxib did not reduce inflammation-associated colonic injury in TNBS-induced experimental colitis. Thus, the use of COX-2 inhibitors for treating IBD should be considered with caution and warrants further experimental investigation to elucidate their applicability.

Anti-inflammatory effects of caffeic acid phenethyl ester (CAPE), a nuclear factor-kappaB inhibitor, on Helicobacter pylori-induced gastritis in Mongolian gerbils

Nuclear factor-kappaB (NF-kappaB) plays a major role in host inflammatory responses and carcinogenesis and as such is an important drug target for adjuvant therapy. In this study, we examined the effect of caffeic acid phenethyl ester (CAPE), an NF-kappaB inhibitor, on Helicobacter pylori (H. pylori)-induced NF-kappaB activation in cell culture and chronic gastritis in Mongolian gerbils. In AGS gastric cancer cells, CAPE significantly inhibited H. pylori-stimulated NF-kappaB activation and mRNA expression of several inflammatory factors in a dose-dependent manner, and prevented degradation of IkappaB-alpha and phosphorylation of p65 subunit. To evaluate the effects of CAPE on H. pylori-induced gastritis, specific pathogen-free male, 6-week-old Mongolian gerbils were intragastrically inoculated with H. pylori, fed diets containing CAPE (0-0.1%) and sacrificed after 12 weeks. Infiltration of neutrophils and mononuclear cells and expression of NF-kappaB p50 subunit and phospho-IkappaB-alpha were significantly suppressed by 0.1% CAPE treatment in the antrum of H. pylori-infected gerbils. Labeling indices for 5'-bromo-2'-deoxyuridine both in the antrum and corpus and lengths of isolated pyloric glands were also markedly reduced at the highest dose, suggesting a preventive effect of CAPE on epithelial proliferation. Furthermore, in the pyloric mucosa, mRNA expression of inflammatory mediators including tumor necrosis factor-alpha, interferon-gamma, interleukin (IL)-2, IL-6, KC (IL-8 homologue), and inducible nitric oxide synthase was significantly reduced. These results suggest that CAPE has inhibitory effects on H. pylori-induced gastritis in Mongolian gerbils through the suppression of NF-kappaB activation, and may thus have potential for prevention and therapy of H. pylori-associated gastric disorders.

NSAID-induced antral ulcers are associated with distinct changes in mucosal gene expression

BACKGROUND

The basis for individual variation in gastroduodenal vulnerability to NSAIDs is not well understood.

AIM

To assess whether a gene expression signature is associated with susceptibility to gastroduodenal ulcerations.

METHODS

Twenty-five Helicobacter pylori negative adults were treated for 7 days with naproxen 500 mg b.d. Subjects underwent baseline and post-treatment endoscopy, during which biopsies were taken from antrum and duodenum. RNA extraction and cDNA synthesis were performed, followed by PCR of 23 genes relevant to mucosal injury and repair. Fold changes in gene expression were compared between subjects who developed ulcers and those who did not.

RESULTS

Compared with subjects who did not develop ulcers (n = 18), subjects who developed antral ulcers (n = 7) had significantly greater mucosal up-regulation of interleukin-8 [Fold change = 33.5 (S.E.M. = 18.5) vs. -7.7 (3.2)] and of cyclo-oxygenase-2 [2.3 (1.7) vs. -10.8 (2.2)]. Conversely, non-ulcer subjects had significantly greater up-regulation of toll-like receptor-4, cyclo-oxygenase-1 and hepatocyte growth factor [14.0 (2.2) vs. -0.8 (1.0), 9.8 (2.4) vs. 0.0 (0.7) and 8.2 (2.6) vs. -2.2 (0.3) respectively].

CONCLUSIONS

NSAID-induced antral ulcers are associated with a specific pattern of gastroduodenal mucosal gene expression. These patterns may provide an insight into the molecular basis of individual susceptibility to mucosal injury.

Cyclooxygenase as a target for chemoprevention in colorectal cancer: lost cause or a concept coming of age?

COX-2 is upregulated at an early stage in colorectal carcinogenesis and generates prostaglandins, which promote cancer cell proliferation, impair apoptosis and enhance angiogenesis, promoting tumour growth and metastasis. There are ample data from animal models and human studies to demonstrate enhanced tumour progression associated with COX-2 activity in cancer cells. Conversely, NSAIDs including aspirin inhibit COX-2 and, therefore, have anti-neoplastic properties. There has been sustained interest in COX-2 as a chemopreventive target in colorectal cancer (CRC) and although both aspirin and COX-2 selective NSAIDs have demonstrated efficacy, adverse effects have limited their widespread adoption. In particular, evidence of the cardiovascular effects of COX-2 selective inhibitors has led to questioning of the suitability of COX-2 as a target for chemoprevention. This review examines the basis for targeting COX-2 in CRC chemoprevention, evaluates the efficacy and safety of the approach and examines future strategies in this area.

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.

COX-2 from the injury milieu is critical for the initiation of periosteal progenitor cell mediated bone healing

Although a critical role of COX-2 in bone repair has been established, the mechanism involved remains unclear. During early inflammatory phase of bone healing, COX-2 is produced by the surrounding inflammatory cells as well as bone/cartilage progenitors. Based on the temporal and spatial expression of COX-2 during the early phase of fracture healing, we hypothesize that COX-2 from both sources is critical for progenitor cell activation, proliferation and differentiation. To directly test this we utilized a murine femoral grafting model, in which live segmental grafts from the same strains were transplanted and donor versus host cell involvement in healing was assessed. Specifically, fresh femur cortical bone grafts of 4 mm in length from COX-2(-/-) (KO) mice were transplanted into wild type (WT) mice with the same sized segmental defect in femurs. Similarly, grafts from WT were transplanted into the defects in KO mice. As controls, transplantations between wild types, and transplantations between KO were also performed. Histologic analyses showed that WT-to-WT transplantation resulted in normal endochondral bone healing as evidenced by markedly induction of neovascularization and periosteal bone formation on donor graft. In contrast, transplantation of KO graft into KO host led to 96% reduction of bone formation and near elimination of donor cell-initiated periosteal bone formation. Similarly, transplantation of WT graft into a KO host resulted in 87% reduction of bone formation (n=8, p>0.05), indicating that KO host impaired WT donor progenitor cell expansion and differentiation. When a KO graft was transplanted into WT host, KO donor periosteal cell-initiated endochondral bone formation was restored. Histomorphometric analyses demonstrated 10-fold increase in bone formation and 3-fold increase in cartilage formation compared to KO-to-KO transplantation (n=8, p<0.05), suggesting that COX-2 deficient donor cells were capable to differentiate and form bone when placed in a WT host. Taken together, our data strongly suggest that COX-2 is critical for initiation of periosteal cortical bone healing. The early induction of COX-2 constitutes a crucial host-healing environment for activation and differentiation of donor periosteal progenitors. Elimination of COX-2 at the early stage of healing could lead to detrimental effects on periosteal progenitor cell-initiated cortical bone repair.

Mechanism of action of celecoxib on normal and acid-challenged gastric mucosa

Selective COX-2 inhibitor, celecoxib, delays the healing of gastric ulcers by inhibiting prostaglandins synthesis. Therefore, the effect of celecoxib on normal and acid-challenged gastric mucosa was studied. Wistar rats were distributed into four groups: group-1 (vehicle treated), group-2 (celecoxib treated), group-3 (given 0.6N HCl) and group-4 (HCl+celecoxib treated). The gastric mucosa was assessed histopathologically and by evaluating gastric adherent mucus. To assess the role of oxidative stress, the levels of free radicals and antioxidants were measured. The histopathological examination showed mild inflammation in group-2, moderate inflammation in group-3 and severe inflammation in group-4. The results showed an increase in malondialdehyde and a decrease in gastric adherent mucus, nitrite, reactive thiols and glutathione in groups-2-4 as compared to control group. Activity of superoxide dismutase, catalase and glutathione-s-transferase was increased in all the groups except the group-1. The present study suggested that celecoxib aggravated the gastric damage caused by acid which may be mediated by altering the balance between free radicals and antioxidants.

Role of coxibs in the strategies for gastrointestinal protection in patients requiring chronic non-steroidal anti-inflammatory therapy

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most commonly prescribed drugs due to their high efficacy in the treatment of pain, fever, inflammation and rheumatic disorders. However, their use is associated with the occurrence of adverse effects at the level of digestive tract, ranging from dyspeptic symptoms, gastrointestinal erosions and peptic ulcers to more serious complications, such as overt bleeding or perforation. To overcome problems related to NSAID-induced digestive toxicity, different therapeutic strategies can presently be considered, including the co-administration of drugs endowed with protective activity on the upper gastrointestinal tract, such as the proton pump inhibitors, or the prescription of coxibs, which have been clinically developed as anti-inflammatory/analgesic drugs characterized by reduced damaging activity on gastrointestinal mucosa. The availability of different treatment options, to reduce the risk of NSAID-induced adverse digestive effects, has fostered intensive preclinical and clinical research aimed at addressing a number of unresolved issues and to establish rational criteria for an appropriate use of coxibs in the medical practice. Particular attention is being paid to the management of patients with high degrees of digestive risk, resulting by concomitant treatment with low-dose aspirin for anti-thrombotic prophylaxis or ongoing symptomatic gastroduodenal ulcers. The present review discusses the most relevant lines of evidence concerning the position of coxibs in the therapeutic strategies for gastrointestinal protection in patients who require NSAID therapy and hold different levels of risk of developing adverse effects at the level of digestive tract.

Prostaglandins, NSAIDs, and gastric mucosal protection: why doesn't the stomach digest itself?

Except in rare cases, the stomach can withstand exposure to highly concentrated hydrochloric acid, refluxed bile salts, alcohol, and foodstuffs with a wide range of temperatures and osmolarity. This is attributed to a number of physiological responses by the mucosal lining to potentially harmful luminal agents, and to an ability to rapidly repair damage when it does occur. Since the discovery in 1971 that prostaglandin synthesis could be blocked by aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs), there has been great interest in the contribution of prostaglandins to gastric mucosal defense. Prostaglandins modulate virtually every aspect of mucosal defense, and the importance of this contribution is evident by the increased susceptibility of the stomach to injury following ingestion of an NSAID. With chronic ingestion of these drugs, the development of ulcers in the stomach is a significant clinical concern. Research over the past two decades has helped to identify some of the key events triggered by NSAIDs that contribute to ulcer formation and/or impair ulcer healing. Recent research has also highlighted the fact that the protective functions of prostaglandins in the stomach can be carried out by other mediators, in particular the gaseous mediators nitric oxide and hydrogen sulfide. Better understanding of the mechanisms through which the stomach is able to resist injury in the presence of luminal irritants is helping to drive the development of safer anti-inflammatory drugs, and therapies to accelerate and improve the quality of ulcer healing.