Cyclooxygenase-1 and an alternatively spliced mRNA in the rat stomach: effects of aging and ulcers

Expression of Transcript Variants of PTGS1 and PTGS2 Genes among Patients with Chronic Rhinosinusitis with Nasal Polyps

To date, there has been no reliable test to identify unfavorable course of Chronic Rhinosinusitis with Nasal Polyps (CRSwNP), especially in aspirin intolerant patients. The research aimed to analyze the expression of transcript variants of PTGS1 and PTGS2 genes in the pathobiology of the disease. The study was performed on 409 adult patients: 206 CRSwNP patients including 44 (21.36%) aspirin intolerant patients and 203 healthy volunteers in the control group. Transcript variants of the PTGS1 and PTGS2 genes named as follows: COX1.1 for NM_000962, COX1.2 for NM_080591, COX1.3 for NM_001271165.1, COX1.4 for NM_001271368.1, COX1.5 for NM_001271166.1, COX2.1 for NM_000963.3, COX2.2 for AY_151286 and COX2.3 for BQ_722004 were confirmed using direct sequencing and quantified using targeted qPCR. The coexistence of all examined transcript variants in the study and the control group and significant differences between both were found. In aspirin sensitive patients, the levels of COX1.2, COX1.3, COX1.4 and COX1.5 isoforms were higher compared to aspirin-tolerant patients. The severity of symptoms was bigger in patients with higher expressions of variants: COX1.1 (R with dCt = −0.134; p = 0.0490), COX1.3 (R = −0.1429; p = 0.0400) and COX1.5 (Rs = −0.1499; p = 0.032). The expression of COX1.1 (Rs = −0.098; p = 0.049) and COX1.5 (Rs = −0.141; p = 0.043) isoforms increased with polyposis advancement in endoscopy. With the CT extent of sinuses opacification, COX1.1 isoform also significantly increased (Rs = −0.163; p = 0.020). The isoforms COX1.3, COX1.4, COX1.5 and COX2.1 may promote milder CRSwNP course. On the contrary, the variants COX1.1, COX1.2 and COX2.2 may be involved in a more aggressive disease.

Risk of upper gastrointestinal bleeding from different drug combinations

BACKGROUND & AIMS

Concomitant use of nonsteroidal anti-inflammatory drugs (NSAIDs) and low-dose aspirin increases the risk of upper gastrointestinal bleeding (UGIB). Guidelines suggest avoiding certain drug combinations, yet little is known about the magnitude of their interactions. We estimated the risk of UGIB during concomitant use of nonselective (ns)NSAIDs, cyclooxygenase -2 selective inhibitors (COX-2 inhibitors), and low-dose aspirin with other drugs.

METHODS

We performed a case series analysis of data from 114,835 patients with UGIB (930,888 person-years of follow-up) identified from 7 population-based health care databases (approximately 20 million subjects). Each patient served as his or her own control. Drug exposure was determined based on prescriptions of nsNSAIDs, COX-2 inhibitors, or low-dose aspirin, alone and in combination with other drugs that affect the risk of UGIB. We measured relative risk (incidence rate ratio [IRR] during drug exposure vs nonexposure) and excess risk due to concomitant drug exposure (relative excess risk due to interaction [RERI]).

RESULTS

Monotherapy with nsNSAIDs increased the risk of diagnosis of UGIB (IRR, 4.3) to a greater extent than monotherapy with COX-2 inhibitors (IRR, 2.9) or low-dose aspirin (IRR, 3.1). Combination therapy generally increased the risk of UGIB; concomitant nsNSAID and corticosteroid therapies increased the IRR to the greatest extent (12.8) and also produced the greatest excess risk (RERI, 5.5). Concomitant use of nsNSAIDs and aldosterone antagonists produced an IRR for UGIB of 11.0 (RERI, 4.5). Excess risk from concomitant use of nsNSAIDs with selective serotonin reuptake inhibitors (SSRIs) was 1.6, whereas that from use of COX-2 inhibitors with SSRIs was 1.9 and that for use of low-dose aspirin with SSRIs was 0.5. Excess risk of concomitant use of nsNSAIDs with anticoagulants was 2.4, of COX-2 inhibitors with anticoagulants was 0.1, and of low-dose aspirin with anticoagulants was 1.9.

CONCLUSIONS

Based on a case series analysis, concomitant use of nsNSAIDs, COX-2 inhibitors, or low-dose aspirin with SSRIs significantly increases the risk of UGIB. Concomitant use of nsNSAIDs or low-dose aspirin, but not COX-2 inhibitors, with corticosteroids, aldosterone antagonists, or anticoagulants produces significant excess risk of UGIB.

Key role of endothelial importin-α in VEGF expression and gastric angiogenesis: novel insight into aging gastropathy

Recent in vivo studies demonstrated that aging gastric mucosa has impaired angiogenesis and reduced expression of vascular endothelial growth factor (VEGF). Angiogenesis is triggered by hypoxia and VEGF gene activation, and the latter requires transport of transcription factor(s) into endothelial cell nuclei. We focused on gastric mucosal endothelial cells (GMEC), which are key targets and effectors of gastric angiogenesis, and determined whether and to what extent importin-α, a nuclear transport protein, regulates VEGF gene activation and gastric angiogenesis and the possible role of importin-α in aging gastropathy. GMEC were isolated from rats 3 and 24 mo of age, young (YGEC) and aging (AGEC), respectively. We examined in these cells 1) in vitro angiogenesis, 2) expression of VEGF and importin-α, 3) nuclear transport of hypoxia-inducible factor (HIF)-1α by importin-α, 4) binding of HIF-1α to the VEGF gene promoter, and 5) effects of importin-α silencing in YGEC and its upregulation in AGEC on angiogenesis and VEGF expression. AGEC exhibited significantly impaired in vitro angiogenesis by fourfold and decreased expression of VEGF, importin-α, and nuclear HIF-1α by 1.4-fold, 1.6-fold, and 2.9-fold, respectively, vs. YGEC. Upregulation of importin-α in AGEC significantly reversed all these abnormalities. In YGEC, knockdown of importins-α1 and -α3 significantly reduced in vitro angiogenesis by 93% and 73% and VEGF expression by 48% and 52%, respectively. The above findings demonstrate that importin-α is a novel and critical regulator of gastric angiogenesis. Its reduced expression in AGEC is the key mechanism for impaired angiogenesis and reduced VEGF.

Comparison of Indomethacin, Diclofenac and Aspirin-Induced Gastric Damage according to Age in Rats

Background/Aims

Aging gastric mucosa is known to have decreased mucosal defenses and increased susceptibility to injury by nonsteroidal anti-inflammatory drugs. Depending on the type of nonsteroidal anti-inflammatory drug (NSAID), the underlying mechanisms and the extent of damage to the stomach or intestine may differ. This study was performed to evaluate the acute gastric damage caused by different doses of indomethacin, diclofenac and aspirin in rats of various ages.

Methods

For the acute models, indomethacin (10, 20 or 40 mg/kg), diclofenac (40 or 80 mg/kg) or aspirin (100 mg/kg) was given to 7- and 25-week-old and 1-year-old Sprague-Dawley rats by intragastric gavage. The gross ulcer index, damage area as assessed by imaging, histological index, myeloperoxidase (MPO) activity, and cytosolic phospholipase A₂ (cPLA₂) levels were measured after 24 hours.

Results

The gross ulcer index and damage area increased with age in the presence of three NSAIDs (p<0.05). The increases in MPO levels induced by diclofenac and aspirin were significantly higher in 1-year-old than 7-week-old rats (p<0.05). cPLA₂ expression induced by indomethacin (10 and 40 mg/kg) was greater in the 1-year-old rats, compared with 7-week-old rats (p<0.05).

Conclusions

NSAID-induced acute gastric damage increased in a dose- and age-dependent manner.

Gastrointestinal-sparing effects of novel NSAIDs in rats with compromised mucosal defence

Nonsteroidal anti-inflammatory drugs are among the most commonly used prescription and over-the-counter medications, but they often produce significant gastrointestinal ulceration and bleeding, particularly in elderly patients and patients with certain co-morbidities. Novel anti-inflammatory drugs are seldom tested in animal models that mimic the high risk human users, leading to an underestimate of the true toxicity of the drugs. In the present study we examined the effects of two novel NSAIDs and two commonly used NSAIDs in models in which mucosal defence was expected to be impaired. Naproxen, celecoxib, ATB-346 (a hydrogen sulfide- and naproxen-releasing compound) and NCX 429 (a nitric oxide- and naproxen-releasing compound) were evaluated in healthy, arthritic, obese, and hypertensive rats and in rats of advanced age (19 months) and rats co-administered low-dose aspirin and/or omeprazole. In all models except hypertension, greater gastric and/or intestinal damage was observed when naproxen was administered in these models than in healthy rats. Celecoxib-induced damage was significantly increased when co-administered with low-dose aspirin and/or omeprazole. In contrast, ATB-346 and NCX 429, when tested at doses that were as effective as naproxen and celecoxib in reducing inflammation and inhibiting cyclooxygenase activity, did not produce significant gastric or intestinal damage in any of the models. These results demonstrate that animal models of human co-morbidities display the same increased susceptibility to NSAID-induced gastrointestinal damage as observed in humans. Moreover, two novel NSAIDs that release mediators of mucosal defence (hydrogen sulfide and nitric oxide) do not induce significant gastrointestinal damage in these models of impaired mucosal defence.

Effect of aging on gastric mucosal defense mechanisms: ROS, apoptosis, angiogenesis, and sensory neurons

Aging changes in the stomach lead to a decreased capacity for tissue repair in response to gastric acid. The aim of this study was to determine the mechanism associated with the increased susceptibility to injury of aging mucosa including reactive oxygen species (5), apoptosis, angiogenesis, and sensory neuron activity. Fischer 344 rats at four different ages (6, 31, 74 wk, and 2 yr of age) were studied. The connective tissue indicators [salt-soluble collagen and sulfated glycosaminoglycan (sGAG)], lipid hydroperoxide (LPO), myeloperoxidase (MPO), and hexosamine were assessed. We also evaluated the expression of early growth response-1 (Egr-1), phosphatase and tension homologue deleted on chromosome 10 (PTEN), caspase-9 (index of apoptosis), VEGF (index of angiogenesis), calcitonin gene-related peptide (CGRP, index of sensory neurons), and neuronal nitric oxide synthase (nNOS). The histological connective tissue area in the lower part of rat gastric mucosa increased with aging, with increase of salt-soluble collagen and sGAG. LPO and MPO in old rats were significantly greater than in the young rats, whereas hexosamine was significantly reduced. The old gastric mucosa had increased expression of Egr-1, PTEN, and caspase-9, whereas the VEGF, CGRP, and nNOS expression were significantly reduced. These results indicate that the lower part of rat gastric mucosa was found to be replaced by connective tissue with accumulation of oxidative products with aging. In addition, impairment of apoptosis, angiogenesis, and sensory neuron activity via the activation of Egr-1 and PTEN might increase the susceptibility of gastric mucosa to injury during aging.

Is stomach spontaneously ageing? Pathophysiology of the ageing stomach

During ageing, histological and physiological modifications occur in the stomach leading to a confirmed state of gastric frailty defined by a decreased capacity of tissue repairing after mucosa gastric aggression. The process of intrinsic gastric ageing may play a role in inducing abnormalities of gastric epithelial proliferation against injury but, most of the time, pathophysiological modifications observed in older people are the consequences of chronic insults, such as chronic Helicobacter pylori infection, polymedication, especially Proton-pump inhibitors (PPI) and Non-steroidal Anti-inflammatory Drugs (NSAID), and co morbidities. One of the major clinical consequences of the gastric frailty is the higher vulnerability to the occurrence of peptic ulcer disease during ageing. In this review recent data on gastric changes during ageing, focussing especially on histological modifications and motility disorders are summarized.

Polyphenol metabolites from colonic microbiota exert anti-inflammatory activity on different inflammation models

The polyphenols in fruits and vegetables may be partly responsible for the health-promoting effects attributed to fruit and vegetable intake. Although their properties have been relatively well studied, the activity of their metabolites, produced after ingestion, has been poorly investigated. Thus, the aim of this work was to study the potential anti-inflammatory effect of 18 polyphenol metabolites, derived from colon microbiota. They were screened by measuring prostaglandin E(2) (PGE(2)) production by CCD-18 colon fibroblast cells stimulated with IL-1beta. Metabolites that inhibited more than 50% PGE(2) production were hydrocaffeic (HCAF), dihydroxyphenyl acetic (dOHPA), and hydroferulic acid (HFER), that subsequently were tested with the writhing and paw pressure test in rodents where all three compounds showed an anti-inflammatory effect. The effect of HCAF administered orally (50 mg/kg) was also tested in the dextran sodium sulfate (DSS)-induced colitis model. Weight loss and fecal water content were more pronounced in DSS rats than in DSS-HCAF treated rats. HCAF treatment diminished the expression of the cytokines IL-1beta, IL-8, and TNF-alpha, reduced malonyldialdehyde (MDA) levels and oxidative DNA damage (measured as 8-oxo-2'-deoxyguanosine levels) in distal colon mucosa. These results indicate that HCAF, dOHPA, and HFER have anti-inflammatory activity in vitro and in vivo.

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.

Aging gastropathy-novel mechanisms: hypoxia, up-regulation of multifunctional phosphatase PTEN, and proapoptotic factors

BACKGROUND & AIMS

Aging gastric mucosa has impaired mucosal defense and increased susceptibility to injury. Our aims were to determine the mechanisms responsible for above abnormalities.

METHODS

We used Fisher F-344 rats, 3 and 24 months of age. We measured gastric mucosal blood flow; visualized mucosal hypoxia; examined expression of early growth response-1 transcription factor and phosphatase and tensin homologue deleted on chromosome 10 (PTEN); assessed apoptosis; and determined expression of caspase-3, caspase-9, and survivin. We also examined susceptibility of gastric mucosa of young and aging rats to ethanol injury and whether down-regulation of PTEN affects susceptibility of aging gastric mucosa to injury. To determine human relevance, we examined expression of PTEN and survivin in human gastric specimens of young and aging individuals.

RESULTS

Gastric mucosa of aging (vs young) rats has a 60% reduction in mucosal blood flow; prominent hypoxia; and increased early growth response-1 transcription factor and PTEN messenger RNAs, and proteins. It also has increased expression of proapoptotic proteins caspase-3 and capase-9, reduced survivin, and a 6-fold increased apoptosis vs mucosa of young rats. Ethanol-induced gastric mucosal injury in aging (vs young) rats was significantly increased. The down-regulation of PTEN in gastric mucosa of aging rats completely reversed its increased susceptibility to ethanol injury. In aging human gastric mucosa, PTEN expression was significantly increased, whereas survivin was significantly reduced.

CONCLUSIONS

(1) Gastric mucosa of aging rats has significantly reduced blood flow, tissue hypoxia, activation of Egr-1, PTEN; increased caspases; and reduced survivin. (2) These changes increase susceptibility of aging gastric mucosa to injury.

Current management of Helicobacter pylori infections in the elderly

Helicobacter pylori infection is a chronic gastric gram-negative infection that increases with age worldwide. However, the percentage age of H. pylori-positive elderly patients who are tested and treated for their infection remains very low. It is now demonstrated that H. pylori infection induces a whole cascade of events leading to gastric pathologies, such as peptic ulcer diseases, gastric precancerous lesions and gastric cancer. Recent data also demonstrated that H. pylori chronic infection can play a role in gastric aging, appetite regulation and extradigestive diseases, such as Alzheimer's disease, in the elderly. The diagnosis of H. pylori infection remains difficult to realize in the very old population, and the urea breath test obtains the best performance in this population. 1-week proton pump inhibitor-based triple therapy regimens are highly effective and well tolerated in elderly patients, and antibiotic resistance remains very low. Low compliance is the main factor related to treatment failure in this population.

Infection à Helicobacter pylori chez la personne âgée

PURPOSES

Helicobacter pylori (H. pylori) infection is a chronic gastric Gram-negative infection that increases with age. Acquired in childhood, H. pylori infection may induce a whole cascade of events leading to gastric pathologies such as peptic ulcer diseases, gastric precancerous lesions, and gastric lymphomas (MALT). The characteristics of the diagnosis and the treatment of this infection in geriatrics are thus particularly important to take into account.

MAIN POINTS

1) The incidence of gastric and duodenal ulcers and their bleeding complications is increasing in old-aged populations. Clinical signs such as anorexia and malnutrition are proven to be excellent indications for endoscopic explorations in the elderly. NSAID-use and H. pylori infection were shown to be independent and unrelated risk factors for peptic ulcer and gastroduodenal bleeding in elderly subjects; 2) H. pylori infection diagnosis is difficult to realize in the very old population, and the urea breath test is the test which obtain the best performances in this population.

PERSPECTIVES

Recent work showed the part played by H. pylori chronic infection in gastric aging and in appetite regulation in the elderly. Research tasks should be continued in this field in order to better understand the part played by this chronic infection in gastric aging and in other pathologies (i.e. neurological or cardiovascular diseases) in this population.

Risk factors for delayed postendoscopic mucosal resection hemorrhage in patients with gastric tumor

OBJECTIVE

Although endoscopic mucosal resection has been recognized as the standard treatment for gastric mucosal neoplasm, postendoscopic mucosal resection hemorrhage remains a major complication of endoscopic mucosal resection, and this problem seems to be increasing owing to the development of invasive techniques. The aims of this study were to determine the incidence and grade of postendoscopic mucosal resection hemorrhage and to identify risk factors for delayed postendoscopic mucosal resection hemorrhage in patients with gastric neoplasm.

METHODS

Data of endoscopic mucosal resections performed by three endoscopists were retrospectively collected over 8 years and then analyzed. Immediate postendoscopic mucosal resection hemorrhage was defined as bleeding during the procedure. Delayed postendoscopic mucosal resection hemorrhage was defined when two of the four following parameters were satisfied after the endoscopic mucosal resection period; (i) hematemesis, melena or dizziness, (ii) hemoglobin loss >2 g/dl, (iii) blood pressure decrease >20 mmHg or pulse rate increase >20/min and (iv) Forrest I or IIa-IIb on follow-up endoscopy.

RESULTS

A total of 157 patients (mean age: 64 years, male : female=44 : 113) were reviewed. Twenty-nine (18.5%) and 13 patients (8.3%) presented with immediate and delayed postendoscopic mucosal resection hemorrhage, respectively. Multivariate logistic regression analysis revealed that the patient's age (<or=65 years; odds ratio 6.11, 95% confidence interval 1.12-33.43), the size of lesion (>15 mm; odds ratio 5.90, 95% confidence interval 1.13-30.87) and the experience of the endoscopist (<or=5 years; odds ratio 16.31, 95% confidence interval 1.46-181.97) were significantly predictive variables for the delayed postendoscopic mucosal resection hemorrhage.

CONCLUSION

Considering the higher risk of delayed postendoscopic mucosal resection hemorrhage, careful preparation and close monitoring are required for patients who are less than 65 years, have large lesions over 15 mm or if the procedures were performed by an inexperienced endoscopist.

Assessment of Age-Related Changes in Abdominal Organ Structure and Function With Computed Tomography and Positron Emission Tomography

With the size of the aged population in the United States expected to grow considerably during the next several decades, the number of imaging studies performed on such aged individuals will similarly increase. Thus, it is important to understand normal age-related changes in the structural and functional imaging appearance of the abdominal organs. We therefore present preliminary data and a review of the literature relevant to structural and functional changes in the abdominal organs of children and older adults. In a retrospective study of both adult and pediatric populations, we used computed tomography (CT), positron emission tomography (PET), and PET/CT imaging to investigate age-associated changes in size, attenuation, and metabolic function of the abdominal organs. Organs of interest include the liver, spleen, pancreas, kidneys, adrenal glands, stomach, small bowel, colon, and rectum. Although volumes of adult liver, spleen, pancreas, and kidneys do not change significantly with age, adult left and right adrenal gland volumes do significantly increase with age (r = 0.2823, P = 0.0334, and r = 0.3676, P = 0.0049, respectively). Also, the attenuation of adult liver (r = -0.2122, P = 0.0412), spleen (r = -0.4508, P < 0.0001), pancreas (r = -0.5124, P = 0.0007), and left and right adrenal gland (r = -0.5835, P < 0.0001 and r = -0.6135, P < 0.0001, respectively) decrease significantly with increasing age. Every organ studied in the pediatric population demonstrates a positive association between organ volume and age. Significant age-related changes in organ function are noted in the adult liver and small bowel, with the liver demonstrating a positive association between metabolic activity and age (r = 0.4434, P = 0.0029) and the small bowel showing an inverse association between mean small bowel standardize uptake value and age (r = -0.2435, P = 0.0174). Also, the maximum overall small bowel and colon metabolic activity in children increases with age (r = 0.6478, P = 0.0008). None of the other organs studied (ie, spleen, pancreas, adrenal glands, stomach, colon, rectum) demonstrate significant changes in metabolism with advancing age. The metabolic volumetric product (calculated as the product of organ volume and mean organ SUV) of the liver and spleen does not change significantly with age. In conclusion, various abdominal organs demonstrate differential changes in volume, attenuation, and/or metabolism with increasing age in pediatric and adult populations.

Physiologic aspects of aging: impact on cancer management and decision making, part I

A gradual diminution in the physiologic reserve or functional capacity over time is the characteristic hallmark of aging, and this has a direct impact on the choice of cancer therapy and its toxicity profile in elderly patients with cancer. With the expected rapid rise of the older population as a subgroup, oncologists will increasingly treat elderly patients. Provision of competent care to this increasing pool of older patients with cancer necessitates that oncology professionals become familiar with age-associated changes in organ physiology and their impact on cancer treatment and toxicity. In this comprehensive review, we have listed changes in cardiovascular, gastrointestinal, pulmonary, and renal physiology with aging. Also enumerated is the impact of these changes on cancer therapy and toxicity in each organ system-based section. Cardiovascular changes primarily lead to reduction of the cardiac functional reserve, with a consequent increase in the risk of congestive heart failure. Changes in gastrointestinal physiology lead to increased mucosal damage. A reduction in pulmonary reserve has implications for postradiation complications, and a decline in renal function leads to an increased potential for nephrotoxicity. These changes impair the ability of older patients with cancer to tolerate cancer therapy and increase their risk of toxicities. This may lead to an overall decline in functional status, resulting frailty, poor quality of life, and ultimately poor outcomes. Becoming familiar with age-related physiologic changes is the first step for oncologists seeking to better tailor their treatments. This, combined with adoption of some of the clinical interventions suggested in this review, can help better manage the geriatric oncology patient. Further research is necessary for the development of more specific evidence-based recommendations.

Effect of age-related changes in gastric physiology on tolerability of medications for older people

Studies specifically examining the effect of age upon the stomach are limited and frequently uncontrolled for the high prevalence of Helicobacter pylori in this age group. Age-related changes in gastric physiology such as reduced mucosal protection, gastric blood flow and impaired repair mechanisms may all impact upon gastrointestinal adverse effects and how older people tolerate medicines. Understanding how the upper gastrointestinal tract changes with advancing age could allow interventions that lead to more appropriate prescribing for older people, potentially reduce adverse effects, increase compliance with treatment regimens, and may allow older people to take medications that they would not otherwise tolerate. This review emphasises how the stomach changes with age, and how understanding this will aid clinicians when prescribing medications with potential gastrointestinal adverse effects to older people.

Cyclooxygenase variants: The role of alternative splicing

Alternative splicing of cellular pre-mRNA is responsible for production of multiple mRNAs from individual genes. Splice variants are expressed in cell- and tissue-specific contexts that are important in development and physiology. Alternative splicing can serve as a regulatory mechanism whereby developmental programming and environmental factors/stimuli affect biological activities of translated proteins. Cyclooxygenase (COX)-1 and -2 genes produce splice variants whose biological expression, relevance, and activities have been of significant interest. COX variants are produced by a variety of splicing mechanisms. Four structural domains of the COX proteins (the amino terminal signal peptide, membrane-binding domain, dimerization domain, and catalytic domain) are defined by specific COX exons. COX splice variants may, therefore, result in potential changes in protein subcellular localization, dimerization, and activity. COX variant proteins may act in roles which diverge from those of COX-1 and -2.

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.

Acetaminophen and the cyclooxygenase-3 puzzle: sorting out facts, fictions, and uncertainties

Cyclooxygenase (COX)-3, a novel COX splice variant, was suggested as the key to unlocking the mystery of the mechanism of action of acetaminophen. Although COX-3 might have COX activity in canines, and this activity might be inhibited by acetaminophen, its low expression level and the kinetics indicate unlikely clinical relevance. In rodents and humans, COX-3 encodes proteins with completely different amino acid sequences than COX-1 or COX-2 and without COX activity; therefore, it is improbable that COX-3 in these species plays a role in prostaglandin-mediated fever and pain. The aim of this review is to evaluate the literature that seeks to point out critical theoretical and methodological limitations of the COX-3 studies that led several investigators to scientifically questionable conclusions.

Mechanism of action of paracetamol

Paracetamol (acetaminophen) is generally considered to be a weak inhibitor of the synthesis of prostaglandins (PGs). However, the in vivo effects of paracetamol are similar to those of the selective cyclooxygenase-2 (COX-2) inhibitors. Paracetamol also decreases PG concentrations in vivo, but, unlike the selective COX-2 inhibitors, paracetamol does not suppress the inflammation of rheumatoid arthritis. It does, however, decrease swelling after oral surgery in humans and suppresses inflammation in rats and mice. Paracetamol is a weak inhibitor of PG synthesis of COX-1 and COX-2 in broken cell systems, but, by contrast, therapeutic concentrations of paracetamol inhibit PG synthesis in intact cells in vitro when the levels of the substrate arachidonic acid are low (less than about 5 mumol/L). When the levels of arachidonic acid are low, PGs are synthesized largely by COX-2 in cells that contain both COX-1 and COX-2. Thus, the apparent selectivity of paracetamol may be due to inhibition of COX-2-dependent pathways that are proceeding at low rates. This hypothesis is consistent with the similar pharmacological effects of paracetamol and the selective COX-2 inhibitors. COX-3, a splice variant of COX-1, has been suggested to be the site of action of paracetamol, but genomic and kinetic analysis indicates that this selective interaction is unlikely to be clinically relevant. There is considerable evidence that the analgesic effect of paracetamol is central and is due to activation of descending serotonergic pathways, but its primary site of action may still be inhibition of PG synthesis. The action of paracetamol at a molecular level is unclear but could be related to the production of reactive metabolites by the peroxidase function of COX-2, which could deplete glutathione, a cofactor of enzymes such as PGE synthase.

Role of Ca2+-independent phospholipase A2 and n-3 polyunsaturated fatty acid docosahexaenoic acid in prostanoid production in brain: perspectives for protection in neuroinflammation

Various diseases of the central nervous system are characterized by induction of inflammatory events, which involve formation of prostaglandins. Production of prostaglandins is regulated by activity of phospholipases A(2) and cyclooxygenases. These enzymes release the prostaglandin precursor, the n-6 polyunsaturated fatty acid, arachidonic acid and oxidize it into prostaglandin H(2). Docosahexaenoic acid, which belongs to the n-3 class of polyunsaturated fatty acids, was shown to reduce production of prostaglandins after in vivo and in vitro administration. Nevertheless, the fact that in brain tissue cellular phospholipids naturally have a uniquely high content of docosahexaenoic acid was ignored so far in studies of prostaglandin formation in brain tissue. We consider the following possibilities: docosahexaenoic acid might attenuate production of prostaglandins by direct inhibition of cyclooxygenases. Such inhibition was found with the isolated enzyme. Another possibility, which has been already shown is reduction of expression of inducible cyclooxygenase-2. Additionally, we propose that docosahexaenoic acid could influence intracellular Ca(2+) signaling, which results in changes of activity of Ca(2+)-dependent phospholipase A(2), hence reducing the amount of arachidonic acid available for prostaglandin production. Astrocytes, the main type of glial cells in the brain control the release of arachidonic acid, docosahexaenoic acid and the formation of prostaglandins. Our recently obtained data revealed that the release of arachidonic and docosahexaenoic acids in astrocytes is controlled by different isoforms of phospholipase A(2), i.e. Ca(2+)-dependent phospholipase A(2) and Ca(2+)-independent phospholipase A(2), respectively. Moreover, the release of arachidonic and docosahexaenoic acids is differently regulated through Ca(2+)- and cAMP-dependent signal transduction pathways. Based on analysis of the current literature and our own data we put forward the hypothesis that Ca(2+)-independent phospholipase A(2) and docosahexaenoic acid are promising targets for treatment of inflammatory related disorders in brain. We suggest that Ca(2+)-independent phospholipase A(2) and docosahexaenoic acid might be crucially involved in brain-specific regulation of prostaglandins.

Changes in upper gastrointestinal physiology with age

Diseases of the upper gastrointestinal tract such as peptic ulceration and gastric cancer become more common and more severe with advancing age. In the normal stomach and duodenum, there is a balance between mucosal protective mechanisms and endogenous (gastric acid and pepsin) and exogenous aggressive factors. The high incidence of gastrointestinal pathology seen in older age groups is not related to increase in the secretion of endogenous aggressive factors. Recent work suggests that gastrointestinal mucosal protective mechanisms are impaired with age. The roles in the gastrointestinal tract of molecules that have been implicated in mucosal repair, such as trefoil peptides and matrix components, are beginning to be elucidated and their study in older people is essential to ensure appropriate, efficient, cost-effective management of gastric pathology in the elderly. Strategies to improve the management of upper gastrointestinal diseases in older people will reduce mortality and improve quality of life.

Cyclooxygenase Isozymes: The Biology of Prostaglandin Synthesis and Inhibition

Nonsteroidal anti-inflammatory drugs (NSAIDs) represent one of the most highly utilized classes of pharmaceutical agents in medicine. All NSAIDs act through inhibiting prostaglandin synthesis, a catalytic activity possessed by two distinct cyclooxygenase (COX) isozymes encoded by separate genes. The discovery of COX-2 launched a new era in NSAID pharmacology, resulting in the synthesis, marketing, and widespread use of COX-2 selective drugs. These pharmaceutical agents have quickly become established as important therapeutic medications with potentially fewer side effects than traditional NSAIDs. Additionally, characterization of the two COX isozymes is allowing the discrimination of the roles each play in physiological processes such as homeostatic maintenance of the gastrointestinal tract, renal function, blood clotting, embryonic implantation, parturition, pain, and fever. Of particular importance has been the investigation of COX-1 and -2 isozymic functions in cancer, dysregulation of inflammation, and Alzheimer's disease. More recently, additional heterogeneity in COX-related proteins has been described, with the finding of variants of COX-1 and COX-2 enzymes. These variants may function in tissue-specific physiological and pathophysiological processes and may represent important new targets for drug therapy.

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

OBJECTIVE

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

ANIMALS

24 horses.

PROCEDURE

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

RESULTS

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

CONCLUSIONS AND CLINICAL RELEVANCE

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

Inhibition of rat mammary gland carcinogenesis by simultaneous targeting of cyclooxygenase-2 and peroxisome proliferator-activated receptor gamma

We examined the effect of celecoxib, a cyclooxygenase-2 (COX-2) inhibitor, and N-(9-fluorenyl-methyloxycarbonyl)-L-leucine (F-L-Leu), a peroxisome proliferator-activated receptor gamma (PPAR gamma) agonist, separately and combined, on the development of methylnitrosourea (MNU)-induced rat mammary gland carcinogenesis. Celecoxib and F-L-Leu significantly reduced tumor incidence and multiplicity (P < 0.05). Combining both agents exerted higher (synergistic) cancer inhibition than separate treatments (P < 0.05). The effects of the test drugs on COX-2 and PPAR gamma expression and on the synthesis of prostaglandin E(2) (PGE(2)) and 15-deoxy-Delta(12,14)-PGJ(2) (15d-PGJ(2)) were examined in rat mammary normal (MNU-untreated), uninvolved, and tumor (MNU-treated) tissues. Celecoxib and F-L-Leu, separately, inhibited COX-2 and up-regulated PPAR gamma expression. These effects were paralleled by inhibition of PGE(2) synthesis and up-regulation of 15d-PGJ(2). Combined treatment resulted in higher alterations in COX-2 and PPAR gamma transcripts and PG synthesis compared with separate administrations. The effect of the test agents on Bcl(2), BAX, and protein kinase C alpha expression levels were examined in the rat mammary gland and the pro-(BAX:Bcl(2)) and anti-[PKC alpha*(Bcl(2)/BAX)] apoptotic ratios were evaluated. Each drug increased the proapoptotic ratio by 2- to 7-fold and reduced the antiapoptotic ratio by 2- to >8-fold in all tissues. Combined treatment, however, resulted in >9- to 14-fold up-regulation in the proapoptotic processes and 15- to >30-fold down-regulation in the antiapoptotic ones. Analyses were also carried out on the drug-induced modulation of cell cycle regulators and proliferation markers (cyclin-dependent kinase 1 and proliferating cell nuclear antigen). F-L-Leu and celecoxib each reduced the cyclin-dependent kinase 1 and proliferating cell nuclear antigen expression in the tumor. Higher down-regulation was attained in all tissues by combined treatment where cyclin-dependent kinase 1 and proliferating cell nuclear antigen almost retained the expression levels observed in the normal glands. In conclusion, simultaneous targeting of COX-2 and PPAR gamma may inhibit mammary cancer development more effectively than targeting each molecule alone. COX-2 inhibitors and PPAR gamma agonists coordinately mediate their anticancer effect via both COX-dependent (inhibition of COX-2, activation of PPAR gamma, and modulation PG synthesis) and COX-independent (induction of proapoptotic factors and inhibition of cell proliferation) pathways.

Review article: the ageing bowel and intolerance to aspirin

Aspirin has a role in the prevention of cardiovascular and cerebrovascular disease, Alzheimer's dementia and several cancers. Encouraging all 50 year olds to take low-dose aspirin doubles their chances of living a healthy life into their nineties. The widespread use of aspirin, however, is limited as many older subjects are currently unable to take aspirin because of gastrointestinal side-effects. This review explores why gastrointestinal events occur with aspirin use and how a net benefit from prophylactic aspirin might be achieved in older subjects. It is suggested that, by understanding the age-related changes in upper gastrointestinal physiology and the mechanisms by which aspirin leads to the risk reductions associated with its use, it may be possible to direct interventions to improve tolerability in older subjects. This would allow greater numbers of older subjects to gain the benefits associated with aspirin use.

Comparison of the properties of prostaglandin H synthase-1 and -2

Biosynthesis of prostanoid lipid signaling agents from arachidonic acid begins with prostaglandin H synthase (PGHS), a hemoprotein in the myeloperoxidase family. Vertebrates from humans to fish have two principal isoforms of PGHS, termed PGHS-1 and-2. These two isoforms are structurally quite similar, but they have very different pathophysiological roles and are regulated very differently at the level of catalysis. The focus of this review is on the structural and biochemical distinctions between PGHS-1 and-2, and how these differences relate to the functional divergence between the two isoforms.

Pre-mRNA splicing modulations in senescence

Aging and associated diseases involve multilevel changes in the complex phenomenon of alternative splicing. Here, we review the potential genomic and environmental origins of such changes and discuss the research implications of these findings.