Up-regulation of COX-2 by inhibition of COX-1 in the rat: a key to NSAID-induced gastric injury

Gastroretentive Raft Forming System for Enhancing Therapeutic Effect of Drug-Loaded Hollow Mesoporous Silica on Gastric Ulcers

Gastric ulcers are characterized by damage to the stomach lining and are often triggered by substances such as ethanol and non-steroidal anti-inflammatory drugs. Patchouli alcohol (PA) has demonstrated effectiveness in treating gastric ulcers through antioxidative and anti-inflammatory effects. However, the water insolubility of PA and rapid gastric emptying cause low drug concentration and poor absorption in the stomach, resulting in limited treatment efficacy of PA. This study develops an oral gastroretentive raft forming system (GRFDDS) containing the aminated hollow mesoporous silica nanoparticles (NH2-HMSN) for PA delivery. The application of NH2-HMSN can enhance PA-loading capacity and water dispersibility, promoting bio-adhesion to the gastric mucosa and sustained drug release. The incorporation of PA-loaded NH2-HMSN (NH2-HMSN-PA) into GRFDDS can facilitate gastric drug retention and achieve long action, thereby improving therapeutic effects. The results reveal that NH2-HMSN-PA protects the gastric mucosa damage by inhibiting NLRP3-mediated pyroptosis. The GRFDDS, optimized through orthogonal design, demonstrates the gastric retention capacity and sustained drug release, exhibiting significant therapy efficacy in an ethanol-induced acute gastric ulcers model and an aspirin-induced chronic gastric ulcers model through antioxidation, anti-pyroptosis, and anti-inflammation. This study provides a potential strategy for enhancing druggability of insoluble natural compounds and therapeutic management of gastric ulcers.

Molecular docking, characterization, ADME/toxicity prediction, and anti-ulcer activity of new quercetin derivatives on indomethacin-induced gastric ulcer in mice

Gastric ulcer (GU) is a serious upper gastrointestinal tract disorder that affects people worldwide. The drugs now available for GU treatment have a high rate of relapses and drug interactions, as well as mild to severe side effects. As a result, new natural therapeutic medications for treating GU with fewer negative side effects are desperately needed. Because of quercetin's (QCT) diverse pharmacological effects and unique structural features, we decided to semi-synthesize new QCT derivatives and test them for antiulcer activity. Docking assays were performed on the synthesized compounds to determine their affinity for TLR-4/MD-2, MyD88/TIR, and NF-κB domains, an important inflammatory pathway involved in GU development and progression. Mice were given oral famotidine (40 mg/kg/day), QCT, QCT pentamethyl (QPM), or QCT pentaacetyl (QPA) (50 mg/kg/day) for 5 days before GU induction by a single intraperitoneal injection of indomethacin (INDO; 18 mg/kg). QPM and QPA have a stronger binding affinity for TLR-4/MD-2, MyD88/TIR and NF-κB domains than QCT. In comparison, they demonstrated the greatest reduction in ulcer score and index, gastric MDA and nitric oxide (NO) contents, MyD88 and NF-κB expressions, and gastric TLR-4 immunostaining. They also enhanced the levels of GSH, CAT, COX-1, and COX-2 in the gastric mucosa, as well as HO-1 and Nrf2 expression, with histological regression in gastric mucosal lesions, with QPA-treated mice demonstrating the best GU healing. QPA is safe against all of the target organs and adverse pathways studied, with good ADME properties. However, further in vitro experiments are necessary to demonstrate the inhibitory effects of QPM and QPA on the protein targets of interest. In addition, preclinical research on its bioavailability and safety is essential before clinical management can be undertaken. Overall, the new QPA derivative could one day serve as the basis for a new class of potential antiulcer drugs.

Discovery of 5-Methylthiazole-Thiazolidinone Conjugates as Potential Anti-Inflammatory Agents: Molecular Target Identification and In Silico Studies

A series of previously synthesized 5-benzyliden-2-(5-methylthiazole-2-ylimino)thiazoli- din-4-one were evaluated for their anti-inflammatory activity on the basis of PASS predictive outcomes. The predictive compounds were found to demonstrate moderate to good anti-inflammatory activity, and some of them displayed better activity than indomethacin used as the reference drug. Structure-activity relationships revealed that the activity of compounds depends not only on the nature of the substituent but also on its position in the benzene ring. The most active compounds were selected to investigate their possible mechanism of action. COX and LOX activity were determined and found that the title compounds were active only to COX-1 enzymes with an inhibitory effect superior to the reference drug naproxen. As for LOX inhibitory activity, the derivatives failed to show remarkable LOX inhibition. Therefore, COX-1 has been identified as the main molecular target for the anti-inflammatory activity of our compounds. The docking study against COX-1 active site revealed that the residue Arg 120 was found to be responsible for activity. In summary, the 5-thiazol-based thiazolidinone derivatives have been identified as a novel class of selective COX-1 inhibitors.

Pharmacogenomics of NSAID-Induced Upper Gastrointestinal Toxicity

Non-steroidal anti-inflammatory drugs (NSAIDs) are a group of drugs which are widely used globally for the treatment of pain and inflammation, and in the case of aspirin, for secondary prevention of cardiovascular disease. Chronic non-steroidal anti-inflammatory drug use is associated with potentially serious upper gastrointestinal adverse drug reactions (ADRs) including peptic ulcer disease and gastrointestinal bleeding. A few clinical and genetic predisposing factors have been identified; however, genetic data are contradictory. Further research is needed to identify clinically relevant genetic and non-genetic markers predisposing to NSAID-induced peptic ulceration.

Network pharmacology approach to decipher signaling pathways associated with target proteins of NSAIDs against COVID-19

Non-steroidal anti-inflammatory drugs (NSAIDs) showed promising clinical efficacy toward COVID-19 (Coronavirus disease 2019) patients as potent painkillers and anti-inflammatory agents. However, the prospective anti-COVID-19 mechanisms of NSAIDs are not evidently exposed. Therefore, we intended to decipher the most influential NSAIDs candidate(s) and its novel mechanism(s) against COVID-19 by network pharmacology. FDA (U.S. Food & Drug Administration) approved NSAIDs (19 active drugs and one prodrug) were used for this study. Target proteins related to selected NSAIDs and COVID-19 related target proteins were identified by the Similarity Ensemble Approach, Swiss Target Prediction, and PubChem databases, respectively. Venn diagram identified overlapping target proteins between NSAIDs and COVID-19 related target proteins. The interactive networking between NSAIDs and overlapping target proteins was analyzed by STRING. RStudio plotted the bubble chart of the KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway enrichment analysis of overlapping target proteins. Finally, the binding affinity of NSAIDs against target proteins was determined through molecular docking test (MDT). Geneset enrichment analysis exhibited 26 signaling pathways against COVID-19. Inhibition of proinflammatory stimuli of tissues and/or cells by inactivating the RAS signaling pathway was identified as the key anti-COVID-19 mechanism of NSAIDs. Besides, MAPK8, MAPK10, and BAD target proteins were explored as the associated target proteins of the RAS. Among twenty NSAIDs, 6MNA, Rofecoxib, and Indomethacin revealed promising binding affinity with the highest docking score against three identified target proteins, respectively. Overall, our proposed three NSAIDs (6MNA, Rofecoxib, and Indomethacin) might block the RAS by inactivating its associated target proteins, thus may alleviate excessive inflammation induced by SARS-CoV-2.

Protective Effects of Quercetin and Melatonin on Indomethacin Induced Gastric Ulcers in Rats

BACKGROUND

Medications to prevent the development of NSAID-induced gastric ulcers have a large range of unpleasant side effects. Recent efforts have been focused on determining safer alternative nontoxic and natural forms of anti-ulcer treatments.

METHODS

Twenty-four male rats were divided into 4 groups: 1: control group that received no treatment; 2: the ndomethacin-treated group that received 20 mg/kg of indomethacin for 2 days to induce the development of gastric ulcers; 3: quercetin-treated group that in addition to the indomethacin treatment, received 50 mg/kg of quercetin 6 hours after and then daily for 14 days and; 4: the melatonin-treated group which received 20 mg/kg of melatonin 6 hours after each indomethacin treatment and then daily for 14 days. All drugs were administered orally. The following parameters were assessed in each group: mean ulcer index of gastric tissue, gastric acid volume and pH, oxidative stress markers: malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH), inflammatory markers: PGE-2, TNF-α, and IL-10, nitric oxide (NO) levels and the relative gene expression of BAX, BCL-2 and COX-2 by real time PCR.

RESULTS

Our findings revealed that the indomethacin-treated group had a significantly increased (p< 0.05) ulcer index, gastric acid volume, and elevated levels of stress, inflammatory, and apoptotic markers compared to controls. In the groups that received quercetin or melatonin, these factors were all significantly decreased (p< 0.05). Between quercetin and melatonin, there was no significant difference in their gastroprotective effect.

CONCLUSION

Both quercetin and melatonin had protective antioxidant, anti-inflammatory and antiapoptotic activity against indomethacin-induced gastric ulcers.

Curcumin-loaded PLA-PEG copolymer nanoparticles for treatment of liver inflammation in streptozotocin-induced diabetic rats

This report focused on loading curcumin (CUR) drug into biodegradable Polylactide-poly(ethylene glycol) (PLA-PEG) copolymer nanoparticles as an effective anti-inflammatory agent in vivo to overcome the limitations resulted from the free CUR. By a simple nano-emulsification technique, hydrophobic CUR was loaded into hydrophobic polymer's segments and stabilized by cationic surfactant. They were then characterized by DLS, TEM, and SEM techniques providing monodispersed and spherical nanoparticles with an average diameter of 117 nm and high surface charge of +35 mV. Thereafter, they were orally administrated into five groups of rats, typically, control (healthy rats), streptozotocin (STZ)-induced diabetic rats, diabetics treated with free CUR, diabetics treated with PLA-PEG NPs, and diabetics treated with CUR-encapsulated PLA-PEG NPs. Next, complete blood analyses were assessed including alanine aminotransferase (ALT), aspartate aminotransferase (AST), and nuclear factor kappa B (NF-ҡB), reduced glutathione (GSH), malondialdehyde (MDA), nitric oxide (NO), cyclooxygenase (COX-2), Peroxisome proliferator-activated receptors (PPAR-γ) and transforming growth factor-β1 (TGF-β1). The obtained results demonstrated that diabetes initially produced liver inflammation in rats manifested by leveraging the mean levels of serum AST, ALT inducing oxidative stress resulting in a clear increase in the levels of hepatic MDA and NO concomitant with a remarkable decrease in GSH. Moreover, diabetes significantly increased serum NF-ҡB, hepatic COX-2 and TGF-β1, while highly reduced hepatic PPAR-γ. In contrast, both CUR free and CUR-encapsulated NPs ameliorated the negative changes in diabetes but CUR-encapsulated NPs showed more pronounced treated effect than free CUR. In addition, histopathological investigations were performed on the liver tissues of all groups, showing a mitigation in inflammation while treating with CUR-NPs.

In vivo effect of Piper sarmentosum methanolic extract on stress-induced gastric ulcers in rats

INTRODUCTION

Piper sarmentosum (Piperaceae) is traditionally used by Asians to treat numerous common ailments including asthma, fever and gastritis. The aim of the research was to determine and compare the effects of Piper sarmentosum (PS) with omeprazole (OMZ) on gastric parameters in rats exposed to restraint stress.

MATERIAL AND METHODS

The methanolic extract of PS was prepared in the dose of 500 mg/kg. Twenty-eight male Wistar rats were assigned to 4 equal sized groups: two control groups and two treated groups which were supplemented with either PS or OMZ orally at a dose of 500 mg/kg and 20 mg/kg body weight respectively. After 28 days of treatment, one control group, the PS and OMZ group were subjected to a single exposure of water-immersion restraint stress for 3.5 h. After the last exposure to stress, the stomach was excised for evaluation of the parameters.

RESULTS

Oral supplementation of PS was as effective in preventing the formation of gastric lesion when compared with OMZ (p < 0.05). The increased gastric acidity and MDA due to stress was also reduced with supplementation of PS and OMZ. Only PS had the ability to reduce prostaglandin E₂ loss (p = 0.0067) and have the ability to down regulate cyclooxygenase-2 (COX-2) mRNA expression (p = 0.01) with stress exposure.

CONCLUSIONS

Piper sarmentosum possesses a similar protective effect against stress-induced gastric lesions as omeprazole. The protective effect was associated with decreased lipid peroxidation, increased prostaglandin E₂, reduction in gastric acidity and reduction in COX-2 mRNA expression which was altered by stress.

Using human iPS cell-derived enterocytes as novel in vitro model for the evaluation of human intestinal mucosal damage

OBJECTIVE AND DESIGN

The primary component in gut mucus is mucin 2 (MUC2) secreted by goblet cells. Fluctuations in MUC2 expression are considered a useful indicator for evaluating mucosal damage and protective effect of various agents using animal studies. However, there are few in vitro studies evaluating mucosal damage using MUC2 as the indicator. Hence, we attempted to establish a novel in vitro model with MUC2 as the indicator for evaluating drug-induced mucosal damage and protective effect using enterocytes derived from human iPS cells.

METHODS

Compounds were added into enterocytes derived from human iPS cells, and MUC2 mRNA and protein expression levels were evaluated. Further, the effect of compounds on membrane permeability was investigated.

RESULTS

Nonsteroidal anti-inflammatory drugs were found to decrease MUC2 mRNA expression in enterocytes, whereas mucosal protective agents increased mRNA levels. Changes in MUC2 protein expression were consistent with those of mRNA. Additionally, our results indicated that indomethacin caused mucosal damage, affecting membrane permeability of the drug. Moreover, we observed protective effect of rebamipide against the indomethacin-induced permeability increase.

CONCLUSIONS

The developed model could facilitate evaluating drug-induced mucosal damage and protective effects of various agents and could impact drug development studies regarding pharmacological efficacy and safety.

Highly selective CB2 receptor agonist A836339 has gastroprotective effect on experimentally induced gastric ulcers in mice

Cannabinoid type 2 (CB₂) receptors are distributed in central and peripheral tissues, including immunocytes and the gastrointestinal (GI) tract, suggesting that CB₂ receptor agonists represent potential therapeutics in GI inflammatory states. In this study, we investigated the effect of highly selective CB₂ agonist, A836339, on the development of gastric lesions. We used two models of gastric ulcer (GU) induced by ethanol (EtOH) and diclofenac. To confirm the involvement of CB₂ receptors, a selective CB₂ antagonist, AM630 was used. Clinical parameters for gastroprotection were assessed based on inhibition of the gastric lesion area. To investigate the anti-inflammatory effect of A836339, the expression of TNF-α and IL-1β was assessed. To establish the mechanism of gastroprotective action, catalase (CAT), superoxide dismutase (SOD) activity and H₂O₂ and glutathione (GSH) levels were measured. Moreover, expression of CB₂ and cyclooxygenase-2 (COX-2) was characterized using immunohistochemistry (IHC). A836339 reduced ulcer index in a dose-dependent manner in both EtOH- and diclofenac-induced GU models. This effect was reversed by the CB₂ antagonist AM630. Administration of A836339 reduced TNF-α and IL-1β levels in gastric tissue. Furthermore, A836339 exhibited potent anti-oxidant activity, as demonstrated by reduced H₂O₂ levels and increased CAT and SOD activities. IHC studies revealed a co-localization of CB₂ receptors and COX-2 in the gastric tissue. Activation of CB₂ receptors exhibited gastroprotective effect through enhancement of anti-oxidative pathways in the stomach. Activation of CB₂ receptors may thus become a novel therapeutic approach in the treatment of GU.

Benexate hydrochloride betadex modulates nitric oxide synthesis and cytokine expression in gastric ulcers

The present study investigated benexate hydrochloride betadex (BHB)-mediated ulcer healing, and changes to microcirculation modulated through nitric oxide synthase (NOS) and anti-inflammatory activity. A rat model of gastric mucosal injury was established through injection of a 60% acetic acid solution into the stomach. Following ulcer induction, the rats were administered BHB orally for 5 days at doses of 0, 100, 300 or 1,000 mg/kg. The highest dose of BHB was also administered with or without L-NG-nitroarginine methyl ester (L-NAME). The area of gastric ulcers was determined by planimetry, and expression of cyclooxygenases (COX), cytokines and NOS in stomach tissues were measured using western blotting. Compared with the control group, gastric ulcer size was significantly decreased in the 1,000 mg/kg BHB-treated group (P<0.05). Administration of BHB led to a significant increase in endothelial (e)NOS expression (P<0.05). Although acetic acid co-treatment with L-NAME induced more severe mucosal damage, BHB decreased COX expression and tumor necrosis factor-α levels when administered with the nitric oxide inhibitor, L-NAME (P<0.05). BHB exhibited protective effects in a rat model of gastric ulcers, which were associated with a decrease in pro-inflammatory cytokine levels and the activation of eNOS.

Aspirin inhibits expression of sFLT1 from human cytotrophoblasts induced by hypoxia, via cyclo-oxygenase 1

INTRODUCTION

Elevated circulating soluble FLT1 (sFLT1) levels seen in preeclampsia may play a role in its development. Aspirin is recommended for prevention of preeclampsia. We hypothesized that aspirin may inhibit the production of sFlt1.

METHODS

Placentas from women with and without preeclampsia were collected. Primary cytotrophoblasts (CTBs) were cultured from normal placentas and treated with aspirin, sc-560, a COX1 inhibitor or celecoxib, a COX2 inhibitor. The expression of sFLT1, FLT1, COX1 and COX2 was studied. The effect of aspirin on sFlt1 expression was also studied in HEK293 cells and in HTR-8/SVNeo cells.

RESULTS

The expression of sFLT1 was increased in preeclamptic placentas compared to control placentas and the expression and release of sFLT1 increased in CTBs exposed to 2% O2 compared to controls. Aspirin at 3 and 12 mM concentration reduced the expression and release of sFLT1 in CTBs. Aspirin also inhibited sFlt1 expression from HTR-8/SVNeo and HEK293 cells. Sc-560, but not celecoxib, reduced sFLT1 expression and release from CTBs. Aspirin and sc-560 also reduced hypoxia-induced FLT1 mRNA expression and inhibited COX1 mRNA in CTBs.

DISCUSSION

This study confirms that sFLT1 expression is increased in preeclamptic placentas and in CTBs exposed to hypoxia. Aspirin inhibits the production sFLT1 in CTBs and in HTR-8/SVNeo. Sc-560 recapitulated the effects of aspirin on sFLT1 expression and release in CTBs suggesting that the aspirin effect may be mediated via inhibition of COX1. The study increases our understanding of the mechanisms regulating sFlt1 expression and provides a plausible explanation for the effect of aspirin to prevent preeclampsia.

Pharmacological and alimentary alteration of the gastric barrier

The gastric barrier contains several lines of defence which protect the epithelium from harmful microbes and toxins. Pre-mucosal defence mechanisms include secreted acid (HCl 0.1 mmol/L) and pepsin, which are capable of denaturing tissue. A tightly adherent mucous layer provides the next line of defence, and physically separates any potentially hazardous substance in the lumen from the mucosal surface. Apical secretion of HCO3(-) maintains a non-acidic microenvironment at the mucosal surface. Membrane-bound phospholipids repel soluble toxins, and sulphydryls scavenge reactive oxygen species. However, when noxious agents overwhelm these mechanisms, the epithelium is damaged. Herein, we discuss the pathological and physiological basis for several disease states which are associated with a breakdown in one or more components of the gastric barrier, including: Helicobacter pylori-associated gastritis, atrophic gastritis, stress-related mucosal disease, age-related gastropathy and portal hypertensive gastropathy. The effect of non-steroidal anti-inflammatory drugs and proton pump inhibitors on the gastric mucosa, is explored. Finally, we outline the alterations in mucosal defence caused by alcohol, caffeine, minerals and vitamins.

Gastroprotective activity of ethyl-4-[(3,5-di-tert-butyl-2-hydroxybenzylidene) amino]benzoate against ethanol-induced gastric mucosal ulcer in rats

BACKGROUND

The study was carried out to determine the cytotoxic, antioxidant and gastro-protective effect of ethyl-4-[(3,5-di-tert-butyl-2-hydroxybenzylid ene)amino] benzoate (ETHAB) in rats.

METHODOLOGY/PRINCIPAL FINDINGS

The cytotoxic effect of ETHAB was assessed using a MTT cleavage assay on a WRL68 cell line, while its antioxidant activity was evaluated in vitro. In the anti-ulcer study, rats were divided into six groups. Group 1 and group 2 received 10% Tween 20 (vehicle). Group 3 received 20 mg/kg Omeprazole. Groups 4, 5 and 6 received ETHAB at doses of 5, 10, and 20 mg/kg, respectively. After an hour, group 1 received the vehicle. Groups 2-6 received absolute ethanol to induce gastric mucosal lesions. In the WRL68 cell line, an IC50 of more than 100 µg/mL was observed. ETHAB results showed antioxidant activity in the DPPH, FRAP, nitric oxide and metal chelating assays. There was no acute toxicity even at the highest dosage (1000 mg/kg). Microscopy showed that rats pretreated with ETHAB revealed protection of gastric mucosa as ascertained by significant increases in superoxide dismutase (SOD), pH level, mucus secretion, reduced gastric lesions, malondialdehyde (MDA) level and remarkable flattened gastric mucosa. Histologically, pretreatment with ETHAB resulted in comparatively better gastric protection, due to reduction of submucosal edema with leucocyte infiltration. PAS staining showed increased intensity in uptake of Alcian blue. In terms of immunohistochemistry, ETHAB showed down-expression of Bax proteins and over-expression of Hsp70 proteins.

CONCLUSION/SIGNIFICANCE

The gastroprotective effect of ETHAB may be attributed to antioxidant activity, increased gastric wall mucus, pH level of gastric contents, SOD activity, decrease in MDA level, ulcer area, flattening of gastric mucosa, reduction of edema and leucocyte infiltration of the submucosal layer, increased PAS staining, up-regulation of Hsp70 protein and suppressed expression of Bax.

Effect of hesperidin and neohesperidin from bittersweet orange (Citrus aurantium var. bigaradia) peel on indomethacin-induced peptic ulcers in rats

Hesperidin and neohesperidin are the major flavanones isolated from bittersweet orange. It was recently reported that they have potent anti-inflammatory effects in various inflammatory models. In the present study, the effects of hesperidin and neohesperidin on indomethacin-induced ulcers in rats and the underlying mechanisms were investigated. Gastric ulcers were induced in rats with a single dose of indomethacin. The effects of pretreatment with hesperidin and neohesperidin were assessed in comparison with omeprazole as reference standard. Ulcer index, gene expression of gastric cyclooxygenase-2 (COX-2), tumor necrosis factor alpha (TNF-α), lipid peroxidation product, malondialdhyde (MDA), and reduced glutathione (GSH) content in stomach were measured. Furthermore, gross and histopathological examination was performed. Our results indicated that both hesperidin and neohesperidin significantly aggravated gastric damage caused by indomethacin administration as evidenced by increased ulcer index and histopathological changes of stomach.

Highly pathogenic porcine reproductive and respiratory syndrome virus induces prostaglandin E2 production through cyclooxygenase 1, which is dependent on the ERK1/2-p-C/EBP-β pathway

Atypical porcine reproductive and respiratory syndrome (PRRS) caused by highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) is characterized by high fever and high mortality. However, the mechanism underlying the fever induction is still unknown. Prostaglandin E2 (PGE2), synthesized by cyclooxygenase type 1/2 (COX-1/2) enzymes, is essential for inducing fever. In this study, we found that PGE2, together with COX-1, was significantly elevated by HP-PRRSV. We subsequently demonstrated that extracellular signal-regulated kinase 1/2 (ERK1/2) and phosphorylated ERK (p-ERK) were the key nodes to trigger COX-1 expression after HP-PRRSV infection. Furthermore, we proved the direct binding of p-C/EBP-β to the COX-1 promoter by luciferase reporter and chromatin immunoprecipitation assays. In addition, silencing of C/EBP-β remarkably impaired the enhancement of COX-1 production induced by HP-PRRSV infection. Taken together, our results indicate that HP-PPRSV elicits the expression of COX-1 through the ERK1/2-p-C/EBP-β signaling pathway, resulting in the increase of PGE2, which might be the cause of high fever in infected pigs. Our findings might provide new insights into the molecular mechanisms underlying the pathogenesis of HP-PRRSV infection.

IMPORTANCE

The atypical PRRS caused by HP-PRRSV was characterized by high fever, high morbidity, and high mortality in pigs of all ages, yet how HP-PRRSV induces high fever in pigs remains unknown. In the present study, we found out that HP-PRRSV infection could increase PGE2 production by upregulation of COX-1, and we subsequently characterized the underlying mechanisms about how HP-PRRSV enhances COX-1 production. PGE2 plays a critical role in inducing high temperature in hosts during pathogen infections. Thus, our findings here could help us have a better understanding of HP-PRRSV pathogenesis.

ASP6537, a novel highly selective cyclooxygenase-1 inhibitor, exerts potent antithrombotic effect without "aspirin dilemma"

INTRODUCTION

Aspirin inhibits both the cyclooxygenase (COX)-1-dependent production of thromboxane A2 (TXA2) in platelets and COX-2-dependent production of anti-aggregatory prostaglandin I2 (PGI2) in vessel walls, resulting in "aspirin dilemma." Our objective is to investigate whether ASP6537 can overcome aspirin dilemma and exert a potent antithrombotic effect without a concurrent ulcerogenic effect.

METHODS

We evaluated the inhibitory effects of ASP6537 on recombinant human COX-1 (rhCOX-1) and rhCOX-2 activities using a COX-1/2 selectivity test. To determine whether ASP6537 induces aspirin dilemma, we examined the effects of ASP6537 on in vitro TXA2 and PGI2 metabolite production from platelets and isolated aorta of guinea pigs, and on plasma concentrations of TXA2 and PGI2 metabolites in aged rats. Finally, we evaluated the antithrombotic effects and ulcerogenic activity of ASP6537 using an electrically induced carotid arterial thrombosis model and a gastric ulcer model in guinea pigs.

RESULTS

The IC50 ratios of rhCOX-2 to rhCOX-1 for ASP6537 and aspirin were >142,000 and 1.63 fold, respectively. ASP6537 inhibited TXA2 production more selectively than aspirin in in vitro and in vivo TXA2/PGI2 production studies. ASP6537 exerted a significant antithrombotic effect at ≥3 mg/kg, while aspirin tended to inhibit thrombosis at 300 mg/kg but it was not statistically significant. Further, ASP6537 did not induce ulcer formation at 100 mg/kg, whereas aspirin exhibited an ulcerogenic effect at doses of ≥100 mg/kg.

CONCLUSIONS

ASP6537 functions as a highly selective COX-1 inhibitor with a superior ability to aspirin for normalizing TXA2/PGI2 balance, and exerts antithrombotic effect without ulcerogenic effect.

Cost Effectiveness Associated with Helicobacter pylori Screening and Eradication in Patients Taking Nonsteroidal Anti-Inflammatory Drugs and/or Aspirin

BACKGROUND/AIMS

This study was performed to investigate the cost effectiveness of Helicobacter pylori screening/eradication in South Korean patients treated with nonsteroidal anti-inflammatory drugs (NSAIDs) and/or aspirin.

METHODS

A decision Markov model was used to estimate the effectiveness and economic impact of an H. pylori screening/eradication strategy compared to a no-screening strategy among patients who were included in the model at the age of 40 years. Utility weights were applied to four of the health status groups to reflect quality-adjusted life years (QALY). The costs of screening, H. pylori eradication, and managing peptic ulcer and ulcer complications were obtained from South Korea-specific data.

RESULTS

The total costs per patient were US $2,454 for the H. pylori screening/eradication and US $3,182 for the no-screening strategy. The QALYs for the two strategies were 16.05 and 15.73, respectively. The results were robust for the analyses of all different cohort groups who entered the model at the age of 30, 50, or 60 years and for NSAIDs-naïve patients. Through the probabilistic sensitivity analysis, the robustness of our study's results was also determined.

CONCLUSIONS

The H. pylori screening/eradication strategy was found to be less expensive and more effective compared to the no-screening strategy among South Korean patients taking NSAIDs and/or aspirin.

Pathogenesis of NSAID-induced gastric damage: importance of cyclooxygenase inhibition and gastric hypermotility

This article reviews the pathogenic mechanism of non-steroidal anti-inflammatory drug (NSAID)-induced gastric damage, focusing on the relation between cyclooxygenase (COX) inhibition and various functional events. NSAIDs, such as indomethacin, at a dose that inhibits prostaglandin (PG) production, enhance gastric motility, resulting in an increase in mucosal permeability, neutrophil infiltration and oxyradical production, and eventually producing gastric lesions. These lesions are prevented by pretreatment with PGE₂ and antisecretory drugs, and also via an atropine-sensitive mechanism, not related to antisecretory action. Although neither rofecoxib (a selective COX-2 inhibitor) nor SC-560 (a selective COX-1 inhibitor) alone damages the stomach, the combined administration of these drugs provokes gastric lesions. SC-560, but not rofecoxib, decreases prostaglandin E₂ (PGE₂) production and causes gastric hypermotility and an increase in mucosal permeability. COX-2 mRNA is expressed in the stomach after administration of indomethacin and SC-560 but not rofecoxib. The up-regulation of indomethacin-induced COX-2 expression is prevented by atropine at a dose that inhibits gastric hypermotility. In addition, selective COX-2 inhibitors have deleterious influences on the stomach when COX-2 is overexpressed under various conditions, including adrenalectomy, arthritis, and Helicobacter pylori-infection. In summary, gastric hypermotility plays a primary role in the pathogenesis of NSAID-induced gastric damage, and the response, causally related with PG deficiency due to COX-1 inhibition, occurs prior to other pathogenic events such as increased mucosal permeability; and the ulcerogenic properties of NSAIDs require the inhibition of both COX-1 and COX-2, the inhibition of COX-1 upregulates COX-2 expression in association with gastric hypermotility, and PGs produced by COX-2 counteract the deleterious effect of COX-1 inhibition.

Review article: cellular and molecular mechanisms of NSAID-induced peptic ulcers

BACKGROUND

Nonsteroidal anti-inflammatory drugs (NSAIDs) are some of the most prescribed drugs worldwide and have now probably overtaken Helicobacter pylori as the most common cause of gastrointestinal injury in Western countries. Further understanding of the pathogenesis of NSAID-induced ulcers is important to enable the development of novel and effective preventive strategies.

AIMS

To provide an update on recent advances in our understanding of the cellular and molecular mechanisms involved in the development of NSAID-induced ulcers.

METHODS

A Medline search was performed to identify relevant literature using search terms including 'nonsteroidal anti-inflammatory drugs, aspirin, gastric ulcer, duodenal ulcer, pathogenesis, pharmacogenetics'.

RESULTS

The mechanisms of NSAID-induced ulcers can be divided into topical and systemic effects and the latter may be prostaglandin-dependent (through COX inhibition) or prostaglandin-independent. Genetic factors may play an important role in determining individual predisposition.

CONCLUSIONS

The pathogenesis of NSAID-induced peptic ulcers is complex and multifactorial. Recent advances in cellular and molecular biology have highlighted the importance of various prostaglandin-independent mechanisms. Pharmacogenetic studies may provide further insights into the pathogenetic mechanisms of NSAID-induced ulcers and help identify patients at increased risk.

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.

Lack of effects of acemetacin on signalling pathways for leukocyte adherence may explain its gastrointestinal safety

BACKGROUND AND PURPOSE

Acemetacin is a non-steroidal anti-inflammatory drug which is rapidly bioconverted to indomethacin, but produces significantly less gastric damage than indomethacin. This study was performed to investigate several possible mechanisms that could account for the gastrointestinal tolerability of acemetacin.

EXPERIMENTAL APPROACH

The gastric and intestinal damaging effects of acemetacin and indomethacin were examined in the rat. Effects of the drugs on blood levels of leukotriene B(4) and thromboxane B(2), on leukocyte-endothelial adherence in post-capillary mesenteric venules, and on gastric expression of tumour necrosis factor-alpha (TNF-alpha) were determined. The two drugs were also compared for gastric toxicity in rats pretreated with inhibitors of COX-2 and NOS.

KEY RESULTS

Acemetacin induced significantly less gastric and intestinal damage than indomethacin, despite markedly suppressing COX activity. Indomethacin, but not acemetacin, significantly increased leukocyte adherence within mesenteric venules, and gastric expression of TNF-alpha. Pretreatment with L-nitro-arginine methyl ester or lumiracoxib increased the severity of indomethacin-induced gastric damage, but this was not the case with acemetacin.

CONCLUSIONS AND IMPLICATIONS

The increased gastric and intestinal tolerability of acemetacin may be related to the lack of induction of leukocyte-endothelial adherence. This may be attributable to the reduced ability of acemetacin to elevate leukotriene-B(4) synthesis and TNF-alpha expression, compared to indomethacin, despite the fact that acemetacin is rapidly bioconverted to indomethacin after its absorption.

Gastric mucosal defense and cytoprotection: bench to bedside

The gastric mucosa maintains structural integrity and function despite continuous exposure to noxious factors, including 0.1 mol/L HCl and pepsin, that are capable of digesting tissue. Under normal conditions, mucosal integrity is maintained by defense mechanisms, which include preepithelial factors (mucus-bicarbonate-phospholipid "barrier"), an epithelial "barrier" (surface epithelial cells connected by tight junctions and generating bicarbonate, mucus, phospholipids, trefoil peptides, prostaglandins (PGs), and heat shock proteins), continuous cell renewal accomplished by proliferation of progenitor cells (regulated by growth factors, PGE(2) and survivin), continuous blood flow through mucosal microvessels, an endothelial "barrier," sensory innervation, and generation of PGs and nitric oxide. Mucosal injury may occur when noxious factors "overwhelm" an intact mucosal defense or when the mucosal defense is impaired. We review basic components of gastric mucosal defense and discuss conditions in which mucosal injury is directly related to impairment in mucosal defense, focusing on disorders with important clinical sequelae: nonsteroidal anti-inflammatory drug (NSAID)-associated injury, which is primarily related to inhibition of cyclooxygenase (COX)-mediated PG synthesis, and stress-related mucosal disease (SRMD), which occurs with local ischemia. The annual incidence of NSAID-associated upper gastrointestinal (GI) complications such as bleeding is approximately 1%-1.5%; and reductions in these complications have been demonstrated with misoprostol, proton pump inhibitors (PPIs) (only documented in high-risk patients), and COX-2 selective inhibitors. Clinically significant bleeding from SRMD is relatively uncommon with modern intensive care. Pharmacologic therapy with antisecretory drugs may be used in high-risk patients (eg, mechanical ventilation >or=48 hours), although the absolute risk reduction is small, and a decrease in mortality is not documented.

Gastroduodenal defense

PURPOSE OF REVIEW

The gastroduodenum resists mucosal injury despite continuous exposure to concentrated gastric acid. The mucosal barrier consists of a preepithelial mucus HCO3- layer, intercellular tight junctions connecting the epithelial cells, and submucosal acid sensors, prostaglandins, cytokines, enteric nerves and blood flow. In the past year, study of these defensive mechanisms has revealed new insight into the observed sex differences in ulcer prevalence, the protective role of transforming growth factor, the role of serotonin in regulating HCO3- secretion, the role of mechanisms in ulcer healing, the interaction of trefoil factors with the mucus gel, the interaction of glucocorticoids with cyclooxygenase and the characterization of novel, mucosal sparing antiinflammatory agents.

RECENT FINDINGS

Transforming growth factor, melatonin, serotonin, trefoil factors and H2S all enhance mucosal barrier function or accelerate ulcer healing. Newer coxibs may have safety and advantages over existing compounds. Existing nonsteroidal antiinflammatory drugs may be safer than originally thought.

SUMMARY

The continued elucidation of basic defense mechanisms has led to the development of several new compounds designed to enhance barrier function and repair mechanisms.

Dexamethasone damages the rat stomach but not small intestine during inhibition of COX-1

We previously reported that inhibition of both COX-1 and COX-2 is required for the gastrointestinal ulcerogenic properties of nonsteroidal anti-inflammatory drugs (NSAIDs). Inhibition of COX-1 up-regulates COX-2 expression, and the prostaglandins (PGs) produced by COX-2 help to maintain the mucosal integrity during inhibition of COX-1. In the present study we investigated whether dexamethasone damages rat gastrointestinal mucosa during inhibition of COX-1 and further developed the idea that COX-2 expression is a key event in the ulcerogenic actions of NSAIDs. Dexamethasone was given p.o. in the absence or presence of SC-560 (a selective COX-1 inhibitor), and the stomach or intestine was examined 8 or 24 hr later, respectively. Neither dexamethasone nor SC-560 alone damaged the gastrointestinal mucosa. In the presence of SC-560, however, dexamethasone damaged the stomach but not small intestine. SC-560 decreased PGE(2) levels in both tissues, with a gradual recovery accompanying the up-regulation of COX-2 expression, and both the recovery of PGE(2) levels and the expression of COX-2 were inhibited by dexamethasone. In the animals treated with SC-560, iNOS expression was up-regulated in the intestinal but not the gastric mucosa, and this response was also inhibited by dexamethasone. These results suggest a risk from steroid therapy in the stomach when COX-2 expression is up-regulated. Dexamethasone does not provoke damage in the intestine, despite inhibiting the up-regulation of COX-2 expression under conditions of PG deficiency; at least one of the reasons is that this agent prevents the expression of iNOS, a major factor in the pathogenesis of intestinal lesions.

Cyclooxygenase-2 mediates the sensitizing effects of systemic IL-1-beta on excitotoxic brain lesions in newborn mice

Epidemiological and experimental data implicate maternal-fetal infection and an associated increase in circulating cytokines in the etiology of cerebral palsy. We have previously shown that pretreatment of newborn mice with systemic interleukin-1-beta exacerbates ibotenate-induced excitotoxic brain lesions. Such lesions are consistent with those observed in cerebral palsy. The present study builds on this murine model to assess the role of cyclooxygenase in interleukin-1-beta-induced brain toxicity. Pups pretreated with interleukin-1-beta developed greater ibotenate-induced brain damage than controls, an effect blocked by the co-administration of nimesulide (cyclooxygenase-2 inhibitor) or indomethacin (cyclooxygenase-1 and -2 inhibitor). Cyclooxygenase inhibitor administration prevented the interleukin-1-beta-induced increase in the production of brain prostaglandin E(2) (a cyclooxygenase metabolite) and changes in the expression of brain interleukin-6, interleukin-18, tumor necrosis factor-alpha, and brain-derived neurotrophic factor. It also stimulated the expression of brain interleukin-10. Our data suggest that the sensitizing effects of circulating inflammatory cytokines on the brain are mediated by the inducible isoform cyclooxygenase-2, which generates excess prostaglandin E(2). Some of these deleterious effects could involve an autocrine/paracrine loop leading to a disruption of the balance between pro- and anti-inflammatory cytokines in the brain.

Preconditioning stress prevents cold restraint stress-induced gastric lesions in rats: roles of COX-1, COX-2, and PLA2

We investigated the protective effect of mild stress on gastric lesions induced by cold-restraint stress, especially concerning prostaglandins (PGs)/cyclo-oxygenase (COX) isozymes. Rats were exposed to severe stress (cold-restraint stress at 10 degrees C for 6 hr) or mild stress (cold-restraint stress at 10 degrees C for 30 min and kept at room temperature for 60 min) followed by severe stress. Severe stress induced gastric lesions, with a concomitant decrease in body temperature (BT). The ulcerogenic response was inhibited by atropine but worsened by indomethacin and SC-560 but not rofecoxib, although none of these agents had any effect on the change in BT. Mild stress suppressed the gastric ulceration and the decrease in BT induced by severe stress, and these effects were reversed by both COX-1 and COX-2 inhibitors. The expression of COX-2 in the stomach was up-regulated from 4 hr after severe stress and this response was slightly expedited by mild stress. COX-2 was also expressed in the hypothalamus under normal and stressed conditions. Quinacrine (phospholipase A(2) inhibitor) attenuated the protective effect of mild stress on the ulceration and decrease in BT caused by severe stress. TA-0910 (TRH analogue) at a low dose also prevented the gastric ulceration and the decrease in BT induced by severe stress. These results suggest that mild stress protects against cold-restraint stress-induced gastric ulceration, and the effect is peripherally and centrally mediated by PGs derived from both COX-1 and COX-2 through the activation of phospholipase A(2). TRH may also be involved in the protective effect of mild stress, probably through regulation of the thermogenic system.

Effect of azoxymethane and curcumin on transcriptional levels of cyclooxygenase-1 and -2 during initiation of colon carcinogenesis

BACKGROUND

Curcumin is well documented as an effective colonic chemopreventive agent in preclinical studies. Inhibition of arachidonic acid metabolism has been considered one of anticarcinogenic mechanisms of curcumin. We recently reported resistance of middle-aged F344 male rats to inhibition of azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) by curcumin (Nutr Cancer, 48, 37-43). It was important to confirm this finding and to find potential mechanisms responsible, as loss of preventive activity of curcumin due to aging was a novel finding, with important implications for human intervention trials.

METHODS

To confirm our previous findings, and investigate arachidonic acid metabolism as a potential mechanism of age-related differences in response to curcumin, middle-aged F344 male rats were given AOM injections after being fed their experimental diets, 0.6% curcumin or control diet. Colonic ACF were evaluated and colonic levels of cyclooxygenase (COX)-1 and 2 mRNA and prostaglandin E2 (PGE2) were measured. Next, we investigated the short-term effect of AOM and curcumin on arachidonic acid metabolism in young rats. Six week-old rats were given injections of either AOM or untreated following their experimental diets. Colonic COX-1 and COX-2 mRNA as well as PGE2 levels were measured shortly after AOM treatment. Lastly, three different ages of F344 rats were treated with either AOM or saline, and colonic COX-1 and COX-2 mRNA levels were measured shortly after the injections to find if aging alters the effect of AOM on COX mRNA expression.

RESULTS

In middle-aged rats, dietary curcumin did not reduce the number of ACF and surprisingly increased colonic levels of COX-2 mRNA. Colonic COX-2 and PGE2 levels were also significantly increased in young rats fed curcumin after AOM injections. Interestingly, AOM did not affect COX-2 but decreased COX-1 expression in all ages.

CONCLUSIONS

Our study suggests that during initiation, AOM inhibits colonic COX-1 expression without affecting COX-2 and dietary curcumin may increase COX-2 expression to compensate AOM-induced reduction of COX-1 expression.

Effects of cyclooxygenase inhibition on the gastrointestinal tract

Cyclooxygenase (COX) is a rate-limiting enzyme that catalyzes the conversion of arachidonic acid, an essential fatty acid present in cell membrane phospholipids and liberated by phospholipase, into prostaglandins (PGs) and prostanoids. COX has two distinct membrane-anchored isoenzymes; COX-1 and COX-2. COX-1 is a constitutively expressed and found in most normal body tissues; COX-2 is expressed in normal tissues at low levels and is highly induced by pro-inflammatory mediators in the setting of inflammation, injury, and pain. Inhibitors of COX activity include: (1) conventional non-selective non-steroidal anti-inflammatory drugs (ns-NSAIDs); (2) selective COX-2 inhibitors (COXIBs); and (3) COX-1 inhibitors. Non-selective NSAIDs, at therapeutic doses, inhibit both COX-1 and COX-2. The anti-inflammatory benefits of these drugs are primarily derived from COX-2 inhibition, while inhibition of COX-1 often elicits gastrointestinal (GI) toxicity. Therefore, COXIBs were developed to provide a selective COX-2 agent, i.e., one, that at fully therapeutic doses demonstrated comparable therapeutic benefit to non-selective NSAIDs, without the attendant COX-1-mediated GI toxicities. In this review, we evaluate available literature describing the pathophysiologic role of cyclooxygenases and the effects of their inhibition in GI system in experimental and domestic animal species.

Prostaglandin/cyclooxygenase pathway in ghrelin-induced gastroprotection against ischemia-reperfusion injury

Ghrelin is involved in the control of food intake, but its role in gastroprotection against the formation of gastric mucosal injury has been little elucidated. We studied the effects of peripheral (i.p.) and central (i.c.v.) administration of ghrelin on gastric secretion and gastric mucosal lesions induced by 3 h of ischemia/reperfusion (I/R) with or without inhibition of ghrelin growth hormone secretagogue type 1a receptor (GHS-R1a) by using ghrelin antagonist, d-Lys(3)-GHRP-6; blockade of cyclooxygenase (COX)-1 (indomethacin, SC560 [5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-trifluoromethylpyrazole]) and COX-2 (rofecoxib); and bilateral vagotomy or capsaicin denervation. I/R produced typical gastric erosions, a significant fall in the gastric blood flow (GBF), an increase in gastric myeloperoxidase (MPO) activity and malonyldialdehyde (MDA) content, and the up-regulation of mucosal ghrelin mRNA. Ghrelin dose-dependently increased gastric acid secretion and significantly reduced I/R-induced gastric erosions, while producing a significant rise in the GBF and mucosal PGE(2) generation and a significant fall in MPO activity and MDA content. The protective and hyperemic activities of ghrelin were significantly attenuated in rats pretreated with d-Lys(3)-GHRP-6 and capsaicin denervation and completely abolished by vagotomy. Indomethacin, SC560, and rofecoxib, selective COX-1 and COX-2 inhibitors, attenuated ghrelin-induced protection that was restored by supplying the methyl analog of prostaglandin (PG) E(2). The expression of mRNA for COX-1 was unaffected by ghrelin, but COX-2 mRNA and COX-2 protein were detectable in I/R injured mucosa and further up-regulated by exogenous ghrelin. We conclude that ghrelin exhibits gastroprotective and hyperemic activities against I/R-induced erosions, the effects that are mediated by hormone activation of GHS-R1a receptors, COX-PG system, and vagal-sensory nerves.

Gastroprotective action of glucocorticoid hormones during NSAID treatment

In this article we present an overview of the results of our studies suggesting that endogenous glucocorticoid hormones play a role as natural defensive factors in maintaining the integrity of the gastric mucosa during treatment with non-steroidal anti-inflammatory drugs (NSAIDs). In-domethacin and aspirin at ulcerogenic doses induce a rise in corticosterone, which helps the gastric mucosa to resist the harmful actions of these ulcerogenic agents. The gastroprotective action of glucocorticoids during NSAID treatment may be mediated by multiple actions, including maintenance of glucose homeostasis, mucus production and attenuation of enhanced gastric motility and microvascular permeability. According to our findings, glucocorticoid hormones also participate in the healing processes of NSAID-induced gastric injury. It was demonstrated that there is some cooperative interaction between glucocorticoids and prostaglandins (PGs) in gastroprotection, in a way that a deficiency of one protective factor can lead to an apparently compensatory increase of the other. The gastric mucosa becomes more susceptible to injury during deficiency of both glucocorticoids and PGs.

Development of intestinal, but not gastric damage caused by a low dose of indomethacin in the presence of rofecoxib

The ulcerogenic effect of rofecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, on the gastrointestinal mucosa was investigated in the presence of a low dose of indomethacin. Indomethacin at 3 mg/kg did not cause any damage in both the stomach and small intestine, despite inhibiting prostaglandin (PG) production. Rofecoxib had no effect on PG production and did not cause any damage in these tissues. In the presence of indomethacin, however, rofecoxib provoked damage in the small intestine but not the stomach. Indomethacin at 3 mg/kg induced hypermotility and COX-2 expression in the intestine but not in the stomach, both in an atropine-sensitive manner. These results suggest that a low dose of indomethacin produces damage in the small intestine but not in the stomach when administered together with rofecoxib. The PG deficiency caused by a low dose of indomethacin produces hypermotility and COX-2 expression in the small intestine, and results in damage when COX-2 is inhibited. It is assumed that the hypermotility response is a key event in the expression of COX-2 and thereby important in the development of mucosal damage in the gastrointestinal tract.

Dexamethasone Impairs the Gastric Mucosal Integrity in Rats Treated with a Cyclooxygenase-1 but Not with a Cyclooxygenase-2 Inhibitor

In rats, neither the cyclooxygenase-1 inhibitor SC-560 nor the cyclooxygenase-2 inhibitor rofecoxib damages the gastric mucosa. Coadministration of dexamethasone induced injury in SC-560- but not in rofecoxib-treated rats. High levels of cyclooxygenase-1 protein occurred in the gastric mucosa of control rats, with no change after administration of SC-560. In contrast, the gastric cyclooxygenase-2 protein levels were low in control rats, but increased in a time-dependent manner after administration of SC-560. Dexamethasone prevented the increase in cyclooxygenase-2 protein levels. Our findings show that inhibition of cyclooxygenase-1 upregulates cyclooxygenase-2. When the upregulation is prevented by dexamethasone, gastric damage develops, suggesting that induction of cyclooxygenase-2 represents a compensatory mechanism that counteracts the injurious effect of cyclooxygenase-1 inhibition.

Noninvasive Mapping of Reactive Oxygen Species by in Vivo Electron Spin Resonance Spectroscopy in Indomethacin-Induced Gastric Ulcers in Rats

Reactive oxygen species (ROS) are thought to be involved in the gastric ulcer formation induced by indomethacin, a typical nonsteroidal anti-inflammatory drug. However, the location and the time course of ROS generation remain unknown. To assess the sites of ROS generation, we applied the noninvasive measurement of ROS to indomethacin-treated rats. By giving orally a membrane-permeable or impermeable probe, the spectra were collected as a function of time by in vivo 300-MHz electron spin resonance (ESR) spectroscopy. The ESR signal-decay rates of membrane-permeable probes, hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) and 3-methoxycarbonyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl, in the gastric mucosal region were significantly enhanced 1 h after indomethacin treatment, and they both caused the protection of ulcer formation; however, membrane-impermeable probes, carboxy- and trimethylammonium-TEMPO, which did not exhibit the enhanced signal decay, had no effect on ulcer formation. The enhanced signal decay in the gastric mucosa was suppressed by coadministration of the antioxidants tiron or dimethylthiourea with the nitroxyl probe. The results suggest that the enhanced signal-decay rates in the gastric ulcers observed by in vivo ESR are associated with protective effects. The enhanced signal decay caused by ROS generation in stomach, contributing to the ulcer formation induced by indomethacin, is also suggested to occur at the gastric mucus layer or the interface or the intracellular compartment of epithelial cells. Overall, these results show the potentials of noninvasive assessment of ROS production and the sites of damage by in vivo ESR using nitroxyl probes directed to specific subcellular regions.

Clinical implications of cyclo-oxygenase-2 inhibitors for acute dental pain management: benefits and risks

BACKGROUND; Cyclo-oxygenase-2 inhibitors (COX-2i) demonstrate analgesic efficacy for patients who require gastrointestinal safety. The authors discuss the potential benefits and risks of these novel, but expensive, analgesics when used in dentistry.

METHODS

The authors conducted a MEDLINE search focused on the subject headings of common analgesic drugs and COX-2i, using peer-reviewed journals limited to the English language. They selected for review 127 articles that met the criteria. They also tried to identify any randomized controlled trials pertinent to dentistry and indicative of evidence-based medicine. RESULTS. When comparing COX isoforms (COX-1 and COX-2), the authors found that overlapping and mutually exclusively properties coexist. COX-2i originally were developed to minimize interference with the gastroprotective properties of the COX-1 isoform, while selectively preventing prostanoid synthesis expressed solely at sites of bodily trauma or other inflammation. COX-2i were found to provide pain relief equal to or slightly exceeding that offered by many mild narcotics. They may avoid some of the serious side effects that can occur with even short-term use of nonselective nonsteroidal anti-inflammatory drugs.

CONCLUSIONS

The pharmacodynamics of COX-2i reveal an agent that includes analgesic, anti-inflammatory and gastroprotective properties but also allows for an undesirable disruption of the delicate hemodynamic balance.

CLINICAL IMPLICATIONS

Symptomatic and asymptomatic gastroparietic patients who do not have severe cardiovascular, cerebral or renal ischemic disease benefit from use of COX-2i. Long-term use of these agents in medically compromised patients may prove disastrous.

Differential expression of COX-1 and COX-2 in the gastrointestinal tract of the rat

The aim of this study was to use immunohistochemistry with morphometry to investigate COX-1 and COX-2 expression in the normal rat gastrointestinal (GI) tract and examine if sites of ulceration previously observed with long-term COX-2 inhibitor administration in mice correlate with differential COX-1/COX-2 expression. COX-2 positive cells were observed predominantly in the apical lamina propria of intestinal villi with fewer cells in the mucosal epithelium. The highest level of COX-2 expression was observed at the ileocaecal junction (ICJ). COX-2 expression was also present in parasympathetic ganglia of the submucosa and muscularis. In the stomach, the highest grade of COX-2 expression was observed in the apical lamina propria of the fundus adjacent to the junctional ridge. In contrast, COX-1 positive cells within the lamina propria were evenly distributed along the GI tract but were present in higher numbers than COX-2 positive cells. The mean level of COX-1 expression at the ICJ was not significantly different from the ileum and caecum. Evidence that the highest level of COX-2 expression in normal rats is located on the ileal side of the ICJ provides the first mechanism to explain spontaneous ulceration and perforation of the distal ileum in COX-2 -/- animals.

Selective cyclooxygenase (COX) inhibition causes damage to portal hypertensive gastric mucosa: roles of nitric oxide and NF-kappaB

Portal hypertension (PHT) is associated with increased susceptibility of the gastric mucosa to injury by a variety of factors, including nonsteroidal anti-inflammatory drugs (NSAIDs) that nonselectively inhibit both isoforms of cyclooxygenase (COX-1 and -2). PHT gastric mucosa also has excessive nitric oxide (NO) production that contributes to the general increased susceptibility to injury. Using a rat model of PHT, we studied whether selective COX inhibition, which does not damage normal (normotensive) gastric mucosa, is sufficient to cause PHT gastric damage and, if so, whether and how excessive NO is involved. Indomethacin, a nonselective NSAID, caused 2.4-fold more gastric injury to PHT vs. normotensive sham-operated (SO) control rats. Neither NS-398 nor celecoxib, selective COX-2 inhibitors, caused gastric damage in either SO or PHT rats. SC-560, a selective COX-1 inhibitor, did not cause gastric damage in SO rats but dose-dependently caused gastric damage in PHT rats. There was a compensatory increase in COX-2 expression and activity in SC-560-treated SO rats but not SC-560-treated PHT rats. Partial inhibition of NO production restored gastric COX-2 expression and activity levels in SC-560-treated PHT rats to those of SC-560-treated SO rats, by a mechanism consistent with induction of NF-kappaB, and significantly reduced gastric damage. These studies indicate that, in contrast to normotensive gastric mucosa, inhibition of COX-1 alone is sufficient to cause PHT gastric damage as a result of excessive NO that prevents the induction of NF-kappaB and the compensatory increase in COX-2.

Rofecoxib produces intestinal but not gastric damage in the presence of a low dose of indomethacin in rats

Indomethacin in small doses is known to inhibit prostaglandin (PG) production, yet it does not damage the gastrointestinal mucosa. We examined whether a cyclooxygenase (COX)-2 inhibitor induces gastrointestinal damage in the presence of a low dose of indomethacin and investigated the ulcerogenic mechanism in relation to COX-2 expression. Rats with or without 18-h fasting were administered rofecoxib (a selective COX-2 inhibitor; 10 or 30 mg/kg p.o.) in the absence or presence of indomethacin (3 mg/kg p.o.), and the gastric or intestinal mucosa was examined 8 and 24 h later, respectively. Neither indomethacin nor rofecoxib alone caused damage in the stomach or small intestine. However, indomethacin damaged the small intestine in the presence of rofecoxib, yet the same treatment did not damage the stomach. Indomethacin reduced the mucosal PGE2 content in both tissues, whereas rofecoxib did not. The COX-2 mRNA was up-regulated in the intestine but not the stomach after indomethacin treatment, and the reduced PGE2 content was significantly recovered later only in the small intestine, in a rofecoxib-inhibitable manner. Indomethacin produced hypermotility in the small intestine but not the stomach, whereas rofecoxib had no effect. These results suggest that the PG deficiency caused by a low dose of indomethacin produces hypermotility and COX-2 expression in the small intestine but not the stomach, resulting in damage when COX-2 is inhibited. It is assumed that the hypermotility response is a key event in the expression of COX-2 and thereby important in the development of mucosal damage in the gastrointestinal tract.

Rofecoxib decreases renal injury in obese Zucker rats

The present study tested the hypothesis that altered vascular regulation of arachidonic acid enzymes in obese Zucker rats contributes to renal damage. Protein expression of CYP450 (cytochrome P450) and COX (cyclo-oxygenase) enzymes in renal microvessels was studied in obese and lean Zucker rats at 20–21 weeks of age. Body weight and blood glucose averaged 649±13 g and 142±10 mg/dl in obese Zucker rats compared with 437±10 g and 111±5 mg/dl in age-matched lean Zucker rats. Renal microvascular CYP4A and COX-2 protein levels were increased and CYP2C protein levels decreased in obese Zucker rats. TX (thromboxane) B2 excretion was 2-fold higher and PG (prostaglandin) E2 excretion significantly lower in obese Zucker rats. Additional studies investigated the ability of the COX-2 inhibitor, rofecoxib, to slow the progression of renal injury in obese Zucker rats. Rofecoxib treatment decreased urinary PGF2α and 8-isoprostane levels in obese Zucker rats. Renal microvessel mRNA expression of pro-inflammatory chemokines was decreased in COX-2-inhibitor-treated obese Zucker rats. Urinary albumin excretion, an index of kidney damage, averaged 95±11 mg/day in vehicle-treated and 9±1 mg/day in rofecoxib-treated obese Zucker rats. Glomerulosclerosis, characterized by mesangial expansion, tubulo-interstitial fibrosis and extracellular matrix accumulation, was prominent in obese Zucker rats compared with a lack of damage in age-matched lean Zucker rats and rofecoxib-treated obese Zucker rats. These results suggest that altered vascular arachidonic acid enzymes contribute to the renal damage, and that COX-2 inhibition decreases glomerular injury in obese Zucker rats.

The effects of aspirin on gastric mucosal integrity, surface hydrophobicity, and prostaglandin metabolism in cyclooxygenase knockout mice

BACKGROUND & AIMS

Insight into the role of the different cyclooxygenase isoforms in prostaglandin biosynthesis, surface hydrophobicity, and gastric mucosal barrier integrity can be gained by comparing the effects of luminal damaging agents in wild-type and cyclooxygenase knockout mice.

METHODS

Fasted wild-type, cyclooxygenase-1, and cyclooxygenase-2 knockout mice were intragastrically administered saline, 0.6N HCl, or aspirin (aspirin 20 mmol/L) in combination with 0.6N HCl and killed 1 hour later, at which time the gastric lesion score was assessed and biopsy samples were taken for surface, biochemical, and morphological analyses.

RESULTS

The gastric mucosa of cyclooxygenase-1 knockout mice was more severely injured by both HCl alone and aspirin/HCl than that of wild-type and cyclooxygenase-2 knockout mice. HCl alone and aspirin/HCl also induced a more profound decrease in surface hydrophobicity in cyclooxygenase-1 knockout mice than in wild-type mice, whereas this surface property was unaffected in cyclooxygenase-2 knockout mice. The gastric injury induced by aspirin/HCl in cyclooxygenase-1 knockout mice could be prevented if the animals were treated with phosphatidylcholine-associated aspirin. Aspirin/HCl, in comparison to saline or HCl alone, induced a 4-6-fold increase in gastric mucosal prostaglandin E(2) concentration in the cyclooxygenase-1 knockout mice, whereas it decreased prostaglandin E(2) levels in wild-type and cyclooxygenase-2 knockout mice. This paradoxical aspirin-induced increase in gastric prostaglandin E(2) in cyclooxygenase-1 knockout mice seemed to correspond to an increase in cyclooxygenase-2 messenger RNA and protein expression. The gastric lesion score seemed to be significantly associated with alterations in surface hydrophobicity but not with mucosal prostaglandin E(2) concentration.

CONCLUSIONS

Our evidence on cyclooxygenase knockout mice suggests that aspirin predominantly causes gastric injury by a non-prostaglandin mechanism, perhaps by attenuating surface hydrophobicity, a possibility supported by the low gastric toxicity of phosphatidylcholine/aspirin. However, prostaglandins generated by cyclooxygenase-1 may play an important permissive role in maintaining gastric mucosal barrier integrity. Aspirin seems to paradoxically increase the gastric mucosal prostaglandin E(2) concentration in cyclooxygenase-1 knockout mice, possibly by the induction of cyclooxygenase-2.

Both selective COX-1 and COX-2 inhibitors aggravate gastric damage induced in rats by 2-deoxy-D-glucose. relation to gastric hypermotility and COX-2 expression

BACKGROUND/AIM

2-deoxy-D-glucose (2DG), despite causing gastric hypermotility via vagal stimulation, does not by itself induce damage in the stomach but produces gross lesions under prostaglandin (PG) deficiency induced by non-ulcerogenic dose of indomethacin. In this study, we examined the roles PG and cyclo-oxygenase (COX) isozymes play in the gastric ulcerogenic effect of 2DG in the rat stomach under PG deficiency caused by indomethacin.

METHODS

The animals were given 2DG i.v. (200 mg/kg as a bolus injection followed by an infusion at 100 mg/kg), and the mucosa was examined for lesions 8 h later. SC-560 or/and rofecoxib was given p.o. 1 h before 2DG treatment.

RESULTS

2DG alone caused slight damage in the stomach despite causing acid hypersecretion and hypermotility. Neither SC-560 nor rofecoxib alone caused any damage in the stomach, yet these agents significantly aggravated 2DG-induced gastric lesions; the severity of damage was much greater when SC-560 was given together with 2DG. SC-560, but not rofecoxib, enhanced both acid secretion and gastric motility in response to 2DG, with a decrease in mucosal PGE2 content. Expression of COX-2 was up-regulated in the stomach as early as 2 h after 2DG treatment, and the PGE2 content was increased when determined 6 h later, in a COX-2-dependent/rofecoxib-sensitive manner. Both the expression of COX-2 and gastric hypermotility during 2DG treatment were inhibited by prior administration of atropine but not omeprazole, although 2DG-induced gastric lesions were prevented by both agents.

CONCLUSION

These results suggest that potentiation by indomethacin of 2DG-induced gastric lesions is related to inhibition of both COX-1 and COX-2, and that 2DG up-regulates COX-2 in the gastric mucosa, the event occurring in association with gastric hypermotility and contributing to suppression of later extension of the damage.