Roles of cyclooxygenase-2 and prostacyclin/IP receptors in mucosal defense against ischemia/reperfusion injury in mouse stomach

Oxidative stress is important in the pathogenesis of stress-related mucosal disease

Stress-related mucosal disease (SRMD) is a common complication in patients in the intensive care unit (ICU). The aim of the present study was to investigate the possible mechanisms for the pathogenesis of SRMD. In total, 38 patients with SRMD were enrolled from an ICU, as well as 15 healthy volunteers. The disease severity of patients in ICU was evaluated using the Acute Physiology and Chronic Health Evaluation (APACHE) II score. Gastric mucosa with the most severe lesions were biopsied for hematoxylin and eosin staining and then assessed by pathological damage scoring. The serum levels of malondialdehyde (MDA), superoxide dismutase (SOD) and ischemic modified albumin (IMA) were also detected. In addition, claudin-3 and inducible nitric oxide (NO) synthase (iNOS) in the gastric mucosa were assessed by western blotting and immunohistochemistry. The average APACHE II score of the patients with SRMD was significantly higher compared with the controls. Moreover, the levels of MDA (4.74±2.89 nmol/ml) and IMA (93.61±10.78 U/ml) in patients with SRMD were significantly higher compared with the controls (P<0.001), while those of SOD (89.66±12.85 U/ml) in the patients with SRMD were significantly lower compared with the controls (P<0.001). Furthermore, compared with the control, iNOS expression was significantly higher (P=0.034), while the expression of claudin-3 was significantly lower in patients with SRMD (P<0.001). The results indicated that APACHE II score was positively correlated with pathological damage score (r=0.639, P<0.001) and levels of MDA (r=0.743, P<0.001), but negatively correlated with the level of SOD (r=-0.392, P=0.015). In addition, MDA was positively correlated with IMA (r=0.380, P=0.018), but negatively correlated with claudin-3 (r=-0.377, P=0.020). Therefore, it was speculated that oxidative stress may play an important role in the pathogenesis of SRMD, and NO levels and cell membrane permeability are altered during this process.

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.

Elucidation of the Mechanisms through Which the Reactive Metabolite Diclofenac Acyl Glucuronide Can Mediate Toxicity

We have previously reported that mice lacking the efflux transporter Mrp3 had significant intestinal injury after toxic diclofenac (DCF) challenge, and proposed that diclofenac acyl glucuronide (DCF-AG), as a substrate of Mrp3, played a part in mediating injury. Since both humans and mice express the uptake transporter OATP2B1 in the intestines, OATP2B1 was characterized for DCF-AG uptake. In vitro assays using human embryonic kidney (HEK)-OATP2B1 cells demonstrated that DCF-AG was a substrate with a maximal velocity (Vmax) and Km of 17.6 ± 1.5 pmol/min per milligram and 14.3 ± 0.1 μM, respectively. Another key finding from our in vitro assays was that DCF-AG was more cytotoxic compared with DCF, and toxicity occurred within 1-3 hours of exposure. We also report that 1 mM DCF-AG caused a 6-fold increase in reactive oxygen species (ROS) by 3 hours. Investigation of oxidative stress through inhibition of superoxide dismutase (SOD) revealed that DCF-AG had 100% inhibition of SOD at the highest tested dose of 1 mM. The SOD and ROS results strongly suggest DCF-AG induced oxidative stress in vitro. Lastly, DCF-AG was screened for pharmacologic activity against COX-1 and COX-2 and was found to have IC50 values of 0.620 ± 0.105 and 2.91 ± 0.36 μM, respectively, which represents a novel finding. Since cyclooxygenase (COX) inhibition can lead to intestinal ulceration, it is plausible that DCF-AG can also contribute to enteropathy via COX inhibition. Taken in context, the work presented herein demonstrated the multifactorial pathways by which DCF-AG can act as a direct contributor to toxicity following DCF administration.

Production of prostaglandin E2 induced by cigarette smoke modulates tissue factor expression and activity in endothelial cells

Cigarette smoke (CS) increases the incidence of atherothrombosis, the release of prostaglandin (PG) E2, and the amount of tissue factor (TF). The link between PGE2 and TF, and the impact of this interaction on CS-induced thrombosis, is unknown. Plasma from active smokers showed higher concentration of PGE2, TF total antigen, and microparticle-associated TF (MP-TF) activity compared with never smokers. Similar results were obtained in mice and in mouse cardiac endothelial cells (MCECs) after treatment with aqueous CS extracts (CSEs) plus IL-1β [CSE (6.4 puffs/L)/IL-1β (2 μg/L)]. A significant correlation between PGE2 and TF total antigen or MP-TF activity were observed in both human and mouse plasma or tissue. Inhibition of PGE synthase reduced TF in vivo and in vitro and prevented the arterial thrombosis induced by CSE/IL-1β. Only PG E receptor 1 (EP1) receptor antagonists (SC51089:IC50 ∼ 1 μM, AH6809:IC50 ∼ 7.5 μM) restored the normal TF and sirtuin 1 (SIRT1) levels in MCECs before PGE2 (EC50 ∼ 2.5 mM) or CSE/IL-1β exposure. Similarly, SIRT1 activators (CAY10591: IC50 ∼ 10 μM, resveratrol: IC50 ∼ 5 μM) or prostacyclin analogs (IC50 ∼ 5 μM) prevented SIRT1 inhibition and reduced TF induced by CSE/IL-1β or by PGE2. In conclusion, PGE2 increases both TF expression and activity through the regulation of the EP1/SIRT1 pathway. These findings suggest that EP1 may represent a possible target to prevent prothrombotic states.

Importance of cyclooxygenase-1/prostacyclin in modulating gastric mucosal integrity under stress conditions

BACKGROUND AND AIM

We investigated the roles of cyclooxygenase (COX) isozymes and prostaglandins (PGs) and their receptors in mucosal defense against cold-restraint stress (CRS)-induced gastric lesions.

METHODS

Male C57BL/6 wild-type (WT) mice and those lacking COX-1 or COX-2 as well as those lacking EP1, EP3, or IP receptors were used after 18 h fasting. Animals were restrained in Bollman cages and kept in a cold room at 10°C for 90 min.

RESULTS

CRS induced multiple hemorrhagic lesions in WT mouse stomachs. The severity of these lesions was significantly worsened by pretreatment with the nonselective COX inhibitors (indomethacin, loxoprofen) or selective COX-1 inhibitor (SC-560), while neither of the selective COX-2 inhibitors (rofecoxib and celecoxib) had any effect. These lesions were also aggravated in animals lacking COX-1, but not COX-2. The expression of COX-2 mRNA was not detected in the stomach after CRS, while COX-1 expression was observed under normal and stressed conditions. The gastric ulcerogenic response to CRS was similar between EP1 or EP3 knockout mice and WT mice, but was markedly worsened in animals lacking IP receptors. Pretreating WT mice with iloprost (the PGI2 analog) significantly prevented CRS-induced gastric lesions in the presence of indomethacin. PGE2 also reduced the severity of these lesions, and the effect was mimicked by the EP4 agonist, AE1-329.

CONCLUSIONS

These results suggest that endogenous PGs derived from COX-1 play a crucial role in gastric mucosal defense during CRS, and this action is mainly mediated by PGI2 /IP receptors and partly by PGE2 /EP4 receptors.

Type 2 lysophosphatidic acid receptor in gastric surface mucous cells: Possible implication of prostaglandin E2 production

Lysophosphatidic acid (LPA) is a lipid mediator that induces various cell responses via its specific receptors. Recently, we found that orally administered LPA and phosphatidic acid (PA) ameliorate stress- or aspirin-induced stomach injury. However, the mechanisms underlying these effects have not been elucidated yet. In this study, we examined effect of LPA on prostaglandin (PG) E2 production in MKN74 cells, a gastric cell-line expressing type 2 LPA receptor (LPA2). When the cells were treated with LPA, the level of mRNA of COX-2 but not COX-1 was upregulated. The LPA effect was abolished when the cells were pretreated with pertussis toxin (PTX), suggesting the involvement of receptor(s) coupled with Gi. Pretreatment of MKN74 cells with LPA enhanced the PGE2 production triggered by calcium ionophore A23187. Again, PTX abolished the LPA effect. Fluorescent immunohistochemistry using an antibody against LPA2 showed that surface mucous cells (pit cells) in gastric mucosa of mice express LPA2 on the apical side of the plasma membrane. These results suggest that LPA in the diet or its digestion may contribute to the epithelial integrity of stomach mucosa by enhancement of PGE2 production via activation of LPA2.

Tocotrienol Attenuates Stress-Induced Gastric Lesions via Activation of Prostaglandin and Upregulation of COX-1 mRNA

The present study aims to distinguish the effect of tocotrienol on an important gastric protective factor, prostaglandin E2 (PGE2), in stress-induced gastric injury. Twenty-eight Wistar rats were divided into four groups of seven rats each. Two control groups were fed commercial rat diet, and two treatment groups were fed the same diet but with additional dose of omeprazole (20 mg/kg) or tocotrienol (60 mg/kg). After 28 days, rats from one control group and both treated groups were subjected to water-immersion restraint stress for 3.5 hours once. The rats were then sacrificed, their stomach isolated and gastric juice collected, lesions examined, and gastric PGE2 content and cyclooxygenase (COX) mRNA expression were determined. Both the regimes significantly attenuated the total lesion area in the stomach compared to the control. Gastric acidity, which was increased in stress, was significantly reduced in rats supplemented with omeprazole and tocotrienol. The PGE2 content was also significantly higher in the rats given tocotrienol supplementation compared to the control followed by an increase in COX-1 mRNA expression. We conclude that tocotrienol supplementation protected rat gastric mucosa against stress-induced lesions possibly by reducing gastric acidity and preserving gastric PGE2 by increasing COX-1 mRNA.

Protective effect of rutin against acute gastric mucosal lesions induced by ischemia-reperfusion

CONTEXT

Rutin, a flavonoid commonly present in onions, apples and tea, has been suggested to have a variety of pharmacological activities, including immunomodulator, anti-inflammatory and antioxidant activities.

OBJECTIVES

The present study was to examine the protective effects of rutin on gastric mucosal damage induced by gastric ischemia-reperfusion (I/R) in rats.

MATERIALS AND METHODS

Rutin (50, 100, 200 mg/kg) was administered intragastrically for five consecutive days before ischemia. Sixty minutes after the last administration of rutin, under anesthesia, the celiac artery was clamped for 30 min, and then the clamp was removed for 60 min reperfusion. After reperfusion, the stomach was removed for biochemical and histological examinations.

RESULTS

As compared with the I/R group (116.7 ± 21.5), administration of rutin at doses of 50, 100 and 200 mg/kg significantly prevented the increase of gastric mucosal injury index induced by gastric I/R (73.4 ± 14.8, 65.9 ± 9.6 and 26.9 ± 5.7, respectively). ED50 value was 138.7 mg/kg. Moreover, rutin at doses of 50, 100 and 200 mg/kg showed an inhibition on the increased myeloperoxidase (24.6, 41.3 and 53.1% reduction) activity and malondialdehyde levels (27.4, 40.3 and 50.7% reduction) in gastric mucosa. Also, the elevation of inducible NO synthase (iNOS) activity as well as the decrease of constitutive NO synthase (cNOS) in the gastric mucosa were significantly prevented by rutin pretreatment.

CONCLUSION

These results suggested that rutin has a protective effect against gastric mucosal injury induced by gastric I/R and that the gastroprotection was related to the NOS/NO pathway and its antioxidant activity.

Activation of the MyD88 signaling pathway inhibits ischemia-reperfusion injury in the small intestine

Toll-like receptors (TLRs) recognize microbial components and trigger the signaling cascade that activates innate and adaptive immunity. Recent studies have shown that the activation of TLR-dependent signaling pathways plays important roles in the pathogenesis of ischemia-reperfusion (I/R) injuries in many organs. All TLRs, except TLR3, use a common adaptor protein, MyD88, to transduce activation signals. We investigated the role of MyD88 in I/R injury of the small intestine. MyD88 and cyclooxygenase-2 (COX-2) knockout and wild-type mice were subjected to intestinal I/R injury. I/R-induced small intestinal injury was characterized by infiltration of inflammatory cells, disruption of the mucosal epithelium, destruction of villi, and increases in myeloperoxidase activity and mRNA levels of TNF-α and the IL-8 homolog KC. MyD88 deficiency worsened the severity of I/R injury, as assessed using the histological grading system, measuring luminal contents of hemoglobin (a marker of intestinal bleeding), and counting apoptotic epithelial cells, while it inhibited the increase in mRNA expression of TNF-α and KC. I/R significantly enhanced COX-2 expression and increased PGE(2) concentration in the small intestine of wild-type mice, which were markedly inhibited by MyD88 deficiency. COX-2 knockout mice were also highly susceptible to intestinal I/R injury. Exogenous PGE(2) reduced the severity of injury in both MyD88 and COX-2 knockout mice to the level of wild-type mice. These findings suggest that the MyD88 signaling pathway may inhibit I/R injury in the small intestine by inducing COX-2 expression.

Effect of propofol on proliferation and apoptosis of gastric mucosal cells in gastric ischemia-reperfusion injury in mice

AIM: To observe the changes in proliferation and apoptosis of gastric mucosal cells in gastric ischemia-reperfusion (I/R) injury, and to clarify whether propofol has a gastric protection effect and the possible mechanisms involved.

METHODS: Seventy-two Kunming mice were randomly divided into four groups: sham operation group, I/R injury group, fat emulsion group, and propofol group. Except the sham operation group, I/R injury was induced in other groups by clamping the celiac artery for 30 min and allowing reperfusion for 1h. The mice were finally sacrificed to observe morphological changes and investigate gastric mucosal damage index (GMDI). The histological changes of the stomach were observed using light microscopy. The content of malondialdehyde (MDA) and activity of superoxide dismutas (SOD) in gastric mucosal cells were measured by colorimetry analysis. Immunohistochemistry and TdT-mediated d-UTP-biotin nick end-labeling (TUNEL) assay were used to observe PCNA expression and apoptosis in gastric mucosa, and the expression of Bax and Bcl-2 proteins was determined by Western blot.

RESULTS: Severe mucosal lesions induced by gastric I/R were considerably reduced following administration of propofol (25 mg/kg); mucosal and submueosal hyperemia, edema, and deep erosion were improved significantly. Compared to the I/R group, treatment with propofol significantly reduced gastric mucosal MDA content and cell apoptosis (33.9% ± 1.3% vs 60.8% ± 6.9%, P < 0.01), enhanced SOD activity, promoted cell proliferation (16.0% ± 1.8% vs 6.4% ± 1.2%, P < 0.01), and regulated Bax (0.453 ± 0.025 vs 0.268 ± 0.023, P < 0.01) and Bcl-2 (0.513 ± 0.014 vs 0.752 ± 0.015, P < 0.01) protein expression.

CONCLUSION: Propofol protects against gastric gastric I/R injury possibly by promoting gastric mucosal cell proliferation and inhibiting apoptosis.

International Union of Basic and Clinical Pharmacology. LXXXIII: classification of prostanoid receptors, updating 15 years of progress

It is now more than 15 years since the molecular structures of the major prostanoid receptors were elucidated. Since then, substantial progress has been achieved with respect to distribution and function, signal transduction mechanisms, and the design of agonists and antagonists (http://www.iuphar-db.org/DATABASE/FamilyIntroductionForward?familyId=58). This review systematically details these advances. More recent developments in prostanoid receptor research are included. The DP(2) receptor, also termed CRTH2, has little structural resemblance to DP(1) and other receptors described in the original prostanoid receptor classification. DP(2) receptors are more closely related to chemoattractant receptors. Prostanoid receptors have also been found to heterodimerize with other prostanoid receptor subtypes and nonprostanoids. This may extend signal transduction pathways and create new ligand recognition sites: prostacyclin/thromboxane A(2) heterodimeric receptors for 8-epi-prostaglandin E(2), wild-type/alternative (alt4) heterodimers for the prostaglandin FP receptor for bimatoprost and the prostamides. It is anticipated that the 15 years of research progress described herein will lead to novel therapeutic entities.

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.

Advances in research on the protective mechanisms of ischemic postconditioning against hepatic ischemia-reperfusion injury

Liver transplantation is the only effective treatment for end-stage liver diseases. Ischemia-reperfusion injury remains a major cause of post-transplantation liver dysfunction and even failure. Ischemic postconditioning is defined as rapid intermittent periods of reperfusion and ischemia in the early phase of repefusion after long ischemia of the tissues and organs. Many investigations have demonstrated that ischemic postconditioning has a protective effect against hepatic ichemia-reperfusion injury. Ischemic postconditioning exerts protective effects through many possible mechanisms such as oxygen free radicals, calcium overload, polymorphonuclear neutrophils, cytokines, cell apoptosis and mitochondria.

Pathogenic importance of cysteinyl leukotrienes in development of gastric lesions induced by ischemia/reperfusion in mice

We examined the role of cysteinyl leukotrienes (CysLTs) in the gastric ulcerogenic response to ischemia/reperfusion (I/R) in mice. Experiments were performed in male C57BL/6J mice after 18-h fasting. Under urethane anesthesia, the celiac artery was clamped for 30 min, and then reperfusion was achieved by removing the clamp. The stomach was examined for lesions 60 min thereafter. The severity of I/R-induced gastric damage was reduced by prior administration of pranlukast [CysLT receptor type 1 (CysLT(1)R) antagonist] as well as 1-[[5'-(3''-methoxy-4''-ethoxycarbonyl-oxyphenyl)-2',4'-pentadienoyl]aminoethyl]-4-diphenylmethoxypiperidine [TMK688; 5-lipoxygenase (5-LOX) inhibitor]. On the contrary, these lesions were markedly worsened by pretreatment with indomethacin, and this response was abrogated by the coadministration of TMK688 or pranlukast. The gene expression of CysLT(1)R but not 5-LOX was up-regulated in the stomach after I/R, but both expressions were increased under I/R in the presence of indomethacin. I/R slightly increased the mucosal CysLT content of the stomach, yet this increase was markedly enhanced when the animals were pretreated with indomethacin. The increased CysLT biosynthetic response to indomethacin during I/R was attenuated by TMK688. Indomethacin alone caused a slight increase of CysLT(1)R expression and markedly up-regulated 5-LOX expression in the stomach. We concluded that I/R up-regulated the expression of CysLT(1)R in the stomach; CysLTs play a role in the pathogenesis of I/R-induced gastric damage through the activation of CysLT(1)R; and the aggravation by indomethacin of these lesions may be brought about by the increase of CysLT production and the up-regulation of 5-LOX expression, in addition to the decreased prostaglandin production.

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.

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.

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.

Donor heart preservation with iloprost supplemented St. Thomas Hospital cardioplegic solution in isolated rat hearts

This study was designed to assess the influence of St. Thomas Hospital cardioplegic solution (St. Th.) on heart preservation in rat hearts subjected to 6h ischemia when supplemented with iloprost. In the control group (n=8), nothing was added to St. Th., whereas 10 or 1000 nmol L(-1) iloprost was added in the second (n=7) and third (n=8) groups, respectively. Mechanical contraction parameters, cardiac tissue damage and oxidative stress markers were evaluated. The 10 nmol/L iloprost group peak systolic pressure (71.0+/-30.9 versus 41.0+/-9.4 mm Hg) and -dp/dtmax (1103.8+/-94.3 versus 678.6+/-156.8 mm Hg s(-1)) were significantly higher than control group at 30 min of reperfusion (p<0.05). Iloprost supplemented groups had higher GSH and catalase levels of coronary perfusate at reperfusion, in comparison with initial values (p<0.05). AST, CK, CK-MB values increased at 0 min of reperfusion and cTnI values at 45 min of reperfusion (p<0.05) in all groups with no difference between groups. According to our results, iloprost supplementation had mild but significant improvement in postischemic values in mechanical and oxidative stress parameters, resulting in better heart preservation.

An evaluation of the effect of a gastric ischemia-reperfusion model with laser Doppler blood perfusion imaging

The objectives of this study are to establish a gastric ischemia-reperfusion model and test it using the laser Doppler blood perfusion imaging (LDPI) method and to evaluate the role of the LDPI technique in the measure of gastric blood circulation. The right gastric artery of the rat was clamped for 30 min and then reperfused. The LDPI was used to display the blood circulation of the whole gastric surface during this process. The blood flow perfusion image of the gastric surface was displayed clearly. After the right gastric artery was clamped, the blood flow perfusion on the gastric surface decreased very significantly until the clamp was loosened. Following reperfusion, the blood flow suddenly increased. Within the first 10 min, the blood-flow perfusion exceeded the level before the clamping and then gradually became smooth and steady. The right gastric artery is a main pathway for gastric blood supply. LDPI can display successfully the blood circulation state of the stomach and the course of ischemia-reperfusion of a large area with an image.