Protective role of cyclooxygenase inhibitors in the adverse action of passive cigarette smoking on the initiation of experimental colitis in rats

The role of alpha7 nicotinic acetylcholine receptors in inflammatory bowel disease: involvement of different cellular pathways

INTRODUCTION

Autonomic imbalance plays a pivotal role in the pathophysiology of inflammatory bowel diseases (IBD). The central nervous system (CNS) cooperates dynamically with the immune system to regulate inflammation through humoral and neural pathways. In particular, acetylcholine (Ach), the main neurotransmitter in the vagus nerve, decreases the production of pro-inflammatory cytokines through a mechanism dependent on the α7 nicotinic Ach receptors (α7nAChRs). Areas covered: Here, we review the evidence for involvement of the cholinergic anti-inflammatory pathway (CAP) in IBD. We also elaborate the role of α7nAChRs and subsequent cellular pathways in CAP. Finally, we review potential therapeutic implications of modulators of these receptors. Expert opinion: Alpha7nAChR modulators possess both cognitive improving and anti-inflammatory properties. Although, these agents demonstrated therapeutic benefits in experimental models, their efficacy has not always been translated in clinical trials. Thus, development of more specific α7nAChR ligands as well as more experimental studies and better controlled trials, especially in the field of IBD, are encouraged for a progress in this field.

Combinatorial Intervention with Mesenchymal Stem Cells and Granulocyte Colony-Stimulating Factor in a Rat Model of Ulcerative Colitis

BACKGROUND

Bone marrow mesenchymal stem cells sometimes improve symptoms of inflammatory bowel disease.

AIM

To test the effects of combined granulocyte colony-stimulating factor (G-CSF) and MSC therapy in a rat model of ulcerative colitis (UC).

METHODS

Seventy-two rats with TNBS-induced UC were divided into control or treatment groups: control (no disease and no treatment), no treatment (model), 5-aminosalicylate (5-ASA) enema, or MSCs (labeled with BrdU) with (MSC/GCSF) or without (MSC) G-CSF, and G-CSF alone (GCSF). On days 14 and 28 post-treatment, macroscopic and histological appearances were assessed and the disease activity index (DAI) scored to evaluate the severity of disease. BrdU-labeled MSCs were identified by immunofluorescence to confirm transplantation and their location. The inflammatory profile of each group was evaluated by measuring expression of nuclear NF-κB p65, serum TNF-α, and IL-10 and by activity of mucosal myeloperoxidase (MPO).

RESULTS

Rats receiving MSC and G-CSF combination therapy had increased recruitment of MSCs to the colonic mucosa compared with rats receiving MSC transplantation alone. On day 28, the DAI, MPO activity, serum TNF-α and IL-10 levels, and NF-κB p65 expression in the combination therapy group were significantly lower compared to animals receiving no treatment, MSCs alone, or G-CSF alone (P < 0.05).

CONCLUSION

Intravenously transplanted MSCs migrate and distribute to the colon to effectively alleviate the symptoms of UC, while G-CSF enhances this effect via an anti-inflammatory effect and improvement in the pathologic features of UC. G-CSF may be a promising therapeutic regulator of MSCs that can improve therapeutic outcomes in patients with UC.

pH-sensitive nanoparticles of curcumin-celecoxib combination: evaluating drug synergy in ulcerative colitis model

Inflammatory bowel diseases, which largely comprise ulcerative colitis (UC) and Crohn's disease, are increasingly posing as a global threat because of the incompetence of the current therapy in the entire patient population. This necessitates the identification of alternative therapeutic molecules or their combinations, which may serve as effective first-line or maintenance therapeutics. In this quest, celecoxib, a selective cyclooxygenase-2 inhibiting nonsteroidal anti-inflammatory agent and curcumin, a natural antioxidant and anti-inflammatory agent, have both been found to be useful in alleviating UC. Furthermore, studies involving their combination have proved synergistic action of these two agents. In the current investigation, we have formulated pH-sensitive nanoparticles of curcumin-celecoxib combination as a potential therapy for UC. Synergistic action of the drug combination, delivery advantages of nanosized carriers, and pH-sensitive nature of the polymer were collectively hypothesized to reduce the overall toxicity and total dose of celecoxib and provide enhanced efficacy for mitigating UC. The hypothesis was confirmed in a UC model in rats, where pH-sensitive nanoparticles of the drug combination were found to be more efficacious than nanoparticles of either drugs or drug/s suspension. Further, the blank nanoparticles did not exhibit any therapeutic effect, thereby confirming efficacy of the drug combination for treating UC.

The effect of smoking on intestinal inflammation: what can be learned from animal models?

Epidemiological evidence demonstrates that smoking is the most important environmental risk factor in Crohn's disease while it positively interferes with the disease course of ulcerative colitis. However, the underlying mechanisms through which smoking exerts this divergent effect and affects pathogenesis of inflammatory bowel disease are largely unknown. Animal smoke models are good models to investigate the impact of cigarette smoke on intestinal physiology and inflammation. They enable one to explore the interaction of smoke components and the gut on cellular and molecular level, clarifying how smoking interferes with normal gut function and with disease course in inflammatory conditions. This review describes the currently used animal models for studying the impact of cigarette smoke on the intestinal tract. We first discuss the different methods for simulation of smoking. Furthermore, we focus on the effect of smoke exposure on normal gut physiology and immunology, on experimental (entero)colitis, and on inflammation-induced neoplasia. Based on this current knowledge, a hypothesis is formulated about the mechanisms through which cigarette smoke interferes with the gut in normal and pathological conditions.

Treatment of Suqingwan watered pill reduces colon injury induced by experimental colitis

ETHNOPHARMACOLOGICAL RELEVANCE

Sunqingwan watered pill (SWP) is a Chinese medicine compound, traditionally used in the treating UC symptoms like diarrhea, bloody and purulent stool, abdominal pain, etc. The present study aim to examine the effects of SWP on ulcerative colitis using the modern pharmacological models.

MATERIALS AND METHODS

To address this question, we used two experimental models of colitis, mice induced by dextran sulfate sodium (DSS) as well as rats induced by 2,4-dinitrochlorobenzene (DNCB). For the mice with DSS-induced colitis, the disease activity index (DAI) and colon histological injuries were observed. For the rat models with DNCB-induced colitis, DAI, levels of nitric oxide (NO) in serum, macroscopic and histological colon injury were investigated. Besides, we also introduced a usually used model of ear swelling induced by xylene in mice to reveal the effect of SWP on acute inflammation.

RESULT

In the mice with DSS-induced colitis and the rats with DNCB-induced colitis, SWP could significantly decreased the DAI scores, which meant the body weights of animals were recovered and the gross rectal bleeding reduced. Under the microscope, the histology of colon was obviously changed in SWP administration groups. In the rat models with DNCB-induced colitis, SWP also significantly attenuated macroscopic and colon histological injury. The colon scores in SWP groups in rats was obviously lower than those in the control and similarly the serum levels of NO in the treatment groups were significantly lower than that of control group except for low dosage group of SWP. SWP with the dosages of 1.755 and 3.510 g/kg could inhibit the degree of ear swelling significantly compared with the blank control group (p<0.01), showing it owned good anti-inflammatory activity after 14 days administration.

CONCLUSION

SWP is effective on treating UC, especially at the high dose and the mechanism may be related with adjusting the serum level of NO, inhibiting colonic mucosa damage and promoting ulcer repair.

Changes in atherosclerotic plaques induced by inhalation of diesel exhaust

OBJECTIVE

Exposure to particulate matter air pollution may be an independent risk factor for cardiovascular morbidity and mortality; however, the biological mechanisms are unclear. We hypothesize that exposure to diesel exhaust (DE), an important source of traffic-related particulate air pollution, promotes changes of atherosclerotic plaque component that may lead to plaque vulnerability.

METHODS AND RESULTS

30-week old ApoE knockout mice fed with regular chow inhaled DE (at 200 μg/m(3) of particulate) or filtered-air (control) for 7 weeks (6 h/day, 5 days/week) (12 mice/group). Total number of alveolar macrophages (p<0.01) and alveolar macrophages positive for particles (p<0.0001) were more than 8-fold higher after DE inhalation than the control. DE inhalation caused 1.5 to 3-fold increases in plaque lipid content (p<0.02), cellularity (p<0.02), foam cell formation (p<0.04), and smooth muscle cell content (p<0.05). The expression of oxidative stress markers, iNOS, CD36, and nitrotyrosine was significantly increased by 1.5 to 2-fold in plaques, with enhanced systemic lipid and DNA oxidation (p<0.02). Increased foam cells and the expression of iNOS (R(2)=0.72, p=0.0081) and CD36 (R(2)=0.49, p=0.015) in plaques were positively correlated with the magnitude of DE exposure.

CONCLUSIONS

Exposure to DE promotes changes in atherosclerotic plaques characteristic of unstable vulnerable plaques. Increased systemic and plaque oxidative stress markers suggest that these changes in plaques could be due to DE-induced oxidative stress.

Evidence for the complementary and synergistic effects of the three-alkaloid combination regimen containing berberine, hypaconitine and skimmianine on the ulcerative colitis rats induced by trinitrobenzene-sulfonic acid

Ulcerative colitis involves complicated etiology and presents diverse symptoms including intestine inflammation, bowel pain and diarrhea. Anti-inflammatory drugs are the mainstay in patient care, accompanied with antidiarrhea and analgesic agents used as symptomatic treatment. A classic traditional Chinese medicine formula, Fructus Mume pill (FMP), showed remarkable therapeutic efficacy in treating ulcerative colitis. However, since it contains many herbs and countless chemicals, the underlying mechanism is not clear. In this study, we selected three alkaloids from FMP, namely, berberine, hypaconitine and skimmianine to study the individual drug effect and compare these results with the BHS combination on: 1) The recovery of ulcerative colitis rats induced by trinitrobenzene-sulfonic acid. 2) Mice with xylene-induced acute exudative edema and acetic acid-induced writhing. 3) Gastrointestinal transit inhibition, and 4) the response of HT29 cells after treatment with lipopolysaccharide. We found that the compound hypaconitine showed a potent analgesic effect, while skimmianine acted as an antidiarrhea agent and the component berberine was the key agent exerting anti-inflammatory effect. However, since berberine killed the commensal bacteria and induced lipopolysaccharide release, it could at the same time aggravate colon inflammation. The three-alkaloid combination BHS produced complementary and synergistic effects in colon inflammation recovery, relieving acetic acid-induced bowel pain and xylene-induced acute exudative edema. BHS also decreased lipopolysaccharide production and enhanced the therapeutic efficacy. It is hoped that this study will lay the foundation to further dissect and understand the FMP formula to improve the treatment with simplified and well defined drug combinations for this dreadful disease.

The possible mechanisms of Fructus Mume pill in the treatment of colitis induced by 2,4,6-trinitrobenzene sulfonic acid in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Fructus Mume pill (FMP) has been used as a folk remedy for gastrointestinal diseases in China over thousands of years. FMP was approved for the treatment of gastrointestinal diseases in 2001 by the State Food and Drug Administration (SFDA) of China. Although FMP had significant efficacy for treatment of the patients with inflammatory bowel disease (IBD) in the clinic, the mechanism of action is still unclear.

AIM OF THE STUDY

In the present study, the effects and possible mechanism of FMP on colitis induced by 2,4,6-trinitrobenzene sulfonic acid (TNBS) were investigated.

MATERIALS AND METHODS

Fifty-four SD rats were divided into six groups. Nine rats for each group from three independent experiments were investigated for the effects of FMP.

RESULTS

FMP protected against diarrhea, colon weight increase, colonic accretion, ulceration and myeloperoxidase (MPO) activity elevation. The effects of FMP on recovery of colonic damage and restoration of the normal structures of colorectums were superior to dexamethasone (DEX). FMP promoted the restoration of abnormal cytokine secretion after TNBS treatment. FMP was effective in restoring the balance of intestinal bacteria population from the imbalance of G(+)/G(-) in rats with colitis.

CONCLUSIONS

The results indicated that FMP is effective in treatment of colitis in an experimental rat model. The possible mechanisms may be through down-regulation of Th1-polarized immune response and opsonic effect of intestinal commensal bacteria in this model system.

Cyclooxygenase-2, multidrug resistance 1, and breast cancer resistance protein gene polymorphisms and inflammatory bowel disease in the Danish population

OBJECTIVE

Crohn's disease (CD) and ulcerative colitis (UC) are characterized by an impaired mucosal defence to normal constituents of the intestinal flora and a dysregulated inflammatory response. The purpose of the study was to investigate whether single nucleotide polymorphisms (SNPs) in genes involved in these processes were associated with CD and UC.

MATERIAL AND METHODS

Allele frequencies of the cyclooxygenase 2 (COX-2/PTGS2/PGHS2) G-765C and breast cancer resistance protein (BCRP/ABCG2) C421A as well as allele and haplotype frequencies of multidrug resistance 1 (MDR1, ABCB1) SNPs G2677T/A, C3435T and G-rs3789243-A (intron 3) were assessed in a Danish case-control study comprising 373 CD and 541 UC patients and 796 healthy controls.

RESULTS

Carriers of the homozygous COX-2 and MDR1 intron 3 variant had a relatively high risk of CD, odds ratio (95% CI) (OR (95% CI))=2.86 ((1.34-5.88) p=0.006) and 1.39 ((0.99-1.92) p=0.054), respectively, and for UC of 2.63 ((1.33-5.26) p=0.005) and 1.28 ((0.96-1.51) p=0.093), respectively, assuming complete dominance. No association was found for BCRP or other MDR1 SNPs, or for selected MDR1 haplotypes. No effect-modification of smoking habit at the time of diagnosis was found.

CONCLUSIONS

An effect of the COX-2 polymorphism on both CD and UC was shown which is compatible with the presence of a recessive allele in linkage equilibrium with the SNP marker in the COX-2 gene. The polymorphism located in intron 3 of the MDR1 gene showed a weak association with CD, and a marginally suggestive association with UC.

The beneficial effect of Rheum tanguticum polysaccharide on protecting against diarrhea, colonic inflammation and ulceration in rats with TNBS-induced colitis: the role of macrophage mannose receptor in inflammation and immune response

Rhubarb has been used as a folk remedy for gastrointestinal disease in China for over two thousand years. In the present study, we evaluated the effect of Rheum tanguticum polysaccharide (RTP), a water soluble fraction extracted from rhubarb, on protection from inflammation and colonic damage in 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis in rats. RTP protected against diarrhea, colon weight increase, and ulceration induced by TNBS. It was at least as effective as dexamethasone (DEX). RTP significantly decreased myeloperoxidase (MPO) activity in the colonic mucosa. Oral administration of RTP was as effective as intraperitoneal (i.p.) injection on toxicity protection and MPO activity. To further investigate the possible underlying mechanism, we studied the role of mannose receptor (MR) in cytokine secretion, ligand binding and endocytosis of macrophages. The secretion of IFN-gamma was dramatically increased while IL-4 decreased in colitis compared to the control (normal rats), and RTP restored the condition similar to the control in vivo. The secretion of IFN-gamma by macrophages was induced by RTP and lipoarabinomannan (LAM) but not mannose in vitro. Mannose completely inhibited the effect of RTP, while RTP and LAM affected each other on IFN-gamma secretion. The MR-mediated ligand binding and endocytosis of macrophages were markedly decreased in colitis and RTP restored their function to near normal condition. The results indicated that RTP targeted MR and down-regulation of Th1-polarized immune response may be the possible mechanism for its attenuation of intestinal inflammation and damage. RTP may be useful for treatment of patients with inflammatory bowel disease.

Interaction of cigarette smoking with cyclooxygenase-2 on ulcerative colitis-associated neoplasia in mice

The interactions of cigarette smoking with COX-2 on colitis and colitis-associated adenoma formation were studied. Mice were induced with colitis and exposed to cigarette smoke (CS) and/or SC236 (a COX-2 inhibitor). Results indicated that CS did not alter acute colonic inflammation. Addition of SC236 abolished the induction of proliferation and oxidative damage by colitis. Chronic SC236 treatment abolished the promoting effect of CS on colonic adenoma formation, via suppression of COX-2- and VEGF-mediated proliferation and angiogenesis, and reversed bcl-2-mediated inhibition of apoptosis by CS. To conclude, COX-2 inhibitor could be an implication on cancer prevention in smokers with chronic colitis.

Rosiglitazone, a PPARgamma ligand, modulates signal transduction pathways during the development of acute TNBS-induced colitis in rats

Recent studies have shown that peroxisome proliferator-activated receptor gamma (PPARgamma), a highly nuclear receptor expressed in the colon, may participate in the control of inflammation, especially in regulating the production of immunomodulatory and inflammatory mediators, cellular proliferation and apoptosis. In order to delve into the anti-inflammatory mechanisms and signalling pathways of PPARgamma agonists, we have studied the effects of rosiglitazone, a PPARgamma agonist on the extent and severity of acute ulcerative colitis caused by intracolonic administration of 2,4,6-trinitribenzene sulfonic acid (TNBS) in rats. The inflammatory response was assessed by gross appearance, myeloperoxidase (MPO) activity, tumour necrosis factor alpha (TNF-alpha) levels and a histological study of the lesions. We determined prostaglandin E2 production as well as the cyclooxygenases (COX)-1 and -2 expressions by immunohistochemistry and Western blotting. The nuclear factor kappa (NF-kappaB) p65 and p38 mitogen-activated protein kinase (MAPK) expression levels were also measured by Western blotting. Finally, since PPARgamma agonists modulate apoptosis, we tried to clarify its effects under early acute inflammatory conditions. Inflammation following TNBS induction was characterized by increased colonic wall thickness, edema, diffuse inflammatory cells infiltration, necrosis reaching an ulcer index (UI) of 9.66+/-0.66 cm(2) and increased MPO activity and TNF-alpha colonic levels. Rosiglitazone treatment significantly reduced the morphological alteration associated with TNBS administration and the UI with the highest dose. In addition, the degree of neutrophil infiltration and the cytokine levels were significantly ameliorated. Rosiglitazone significantly reduced the rise in the prostaglandin (PG) E(2) generation compared with TNBS group. The COX-1 levels remained stable throughout the treatment in all groups. The COX-2 expression was elevated in TNBS group; however rosiglitazone administration reduced the COX-2 overexpression. A high expression of NF-kappaB p65 and p38 MAPK proteins appeared in colon mucosa from control TNBS-treated rats; nevertheless, PPARgamma agonist treatment drastically decreased them. There were no significant changes in apoptosis after rosiglitazone treatment when compared to TNBS group. In conclusion, rosiglitazone seems to modulate the acute colitis through NF-kappaB p65 and p38 MAPK signalling pathways.

The effects of selective cyclooxygenase-2 inhibitors, celecoxib and rofecoxib, on experimental colitis induced by acetic acid in rats

Several mediators may be involved in the pathogenesis of inflammatory bowel disease, as well as in experimental colitis. The present work was conducted to investigate the effects of the two selective cyclooxygenase-2 inhibitors, celecoxib and rofecoxib, on experimentally induced colitis in rats. Rectal instillation of acetic acid was used to induce the colitis. Acetic acid treatment caused haemorrhagic diarrhoea and weight loss in rats. Celecoxib (5 mg/kg) or rofecoxib (2.5 mg/kg), when given twice daily by the oral route, reduced the degree of haemorrhagic diarrhoea and the weight loss produced. In addition, they produced a significant reduction in the degree of colonic injury, the rise in myeloperoxidase (MPO) levels, total nitric oxide synthetase (NOS) activity, platelet-activating factor (PAF), histamine levels and prostaglandin E2 levels. In contrast, there was a significant increase in the levels of reduced glutathione (GSH). Thus, the findings of the present study provide evidence that selective cyclooxygenase-2 inhibitors may be beneficial in patients with inflammatory bowel disease.

Toxic effects of nonsteroidal antiinflammatory drugs on the small bowel, colon, and rectum

The gastrointestinal toxicity of conventional nonsteroidal antiinflammatory drugs (NSAIDs) is not confined to the stomach and proximal duodenum but extends also to the rest of the small bowel, colon, and rectum. Long-term NSAID therapy usually induces clinically silent enteropathy characterized by increased intestinal permeability and inflammation. Chronic occult bleeding and protein loss may result in iron-deficiency anemia and hypoalbuminemia. NSAIDs can also induce small bowel ulcers that infrequently lead to acute bleeding, perforation, or chronic scarring responsible for diaphragm-like strictures. At the colon and rectum, NSAID use can result in de novo lesions such as nonspecific colitis and rectitis, ulcers, and diaphragm-like strictures. NSAIDs have been implicated in the development of segmental ischemic colitis. In patients with diverticular disease, NSAID use increases the risk of severe diverticular infection and perforation. NSAIDs can trigger exacerbations of ulcerative colitis or Crohn's disease. With selective COX-2 inhibitors, the risk of gastrointestinal toxicity is reduced as compared to conventional NSAIDs but is not completely eliminated. Experimental studies suggest that long-term COX-2 inhibitor therapy may cause damage to the previously healthy small bowel. Similar to conventional NSAIDs, COX-2 inhibitors may be capable of triggering exacerbations of inflammatory bowel disease.

Inflammatory bowel disease and smoking: a review of epidemiology, pathophysiology, and therapeutic implications

The relationship between smoking behavior and inflammatory bowel disease (IBD) is complex. While Crohn's disease (CD) is associated with smoking and smoking has detrimental effects on the clinical course of the disease, ulcerative colitis (UC) is largely a disease of nonsmokers and former smokers. Furthermore, cigarette smoking may even result in a beneficial influence on the course of ulcerative colitis. The potential mechanisms involved in this dual relationship include changes in humoral and cellular immunity, cytokine and eicosanoid levels, gut motility, permeability, and blood flow, colonic mucus, and oxygen free radicals. Nicotine is assumed to be the active moiety. The differential therapeutic consequences comprise the cessation of smoking in CD and, so far, clinical trials using nicotine in different forms of application for UC. In this article, we review the relationship between cigarette smoking and IBD, considering epidemiological, pathogenetic, and clinical aspects.

Resveratrol, a polyphenol found in grapes, suppresses oxidative damage and stimulates apoptosis during early colonic inflammation in rats

Oxidative stress, neutrophil infiltration, proinflammatory cytokines and eicosanoid generation are clearly involved in the pathogenesis of intestinal bowel disease. Resveratrol, a polyphenolic compound found in grapes and wine, has been shown to have anti-inflammatory, antioxidant, antitumour and immunomodulatory activities, however, its effects on experimental colitis remain unknown. We have investigated the effects of resveratrol on the colon injury caused by intracolonic instillation of trinitrobenzenesulphonic acid (TNBS) in rats. We determined the production of prostaglandin (PG)E(2) and PGD(2) in colon mucosa and the expression of cyclo-oxygenases (COX)-1 and -2 immunohistochemically. The inflammatory response was assessed by histology and myeloperoxidase activity, as an index of neutrophil infiltration. Interleukin-1 beta production, histological and histochemical analysis of the lesions were also carried out. Finally, since resveratrol has been found to modulate apoptosis we intended to elucidate its effects on colonic mucosa under early acute inflammatory conditions. Resveratrol (5-10mg/kg/day) significantly reduced the degree of colonic injury, the index of neutrophil infiltration and the levels of the cytokine. Resveratrol did not revert the increased PGE(2) levels but produced a significant fall in the PGD(2) concentration. Compared with inflamed colon, no changes in staining for COX-1 were observed in colon of resveratrol and TNBS-treated rats. In contrast, COX-2 expression was decreased. Furthermore, resveratrol enhanced apoptosis compared with already high level induced by TNBS. In conclusion, resveratrol reduces the damage in experimentally induced colitis, alleviates the oxidative events and stimulates apoptosis.

Complications intestinales liées aux AINS

Chronic use of non-salicylate NSAIDs causes in most individuals an asymptomatic enteropathy involving the small bowel, particularly its distal part. This enteropathy is characterised by an increase in intestinal permeability and a mild mucosal inflammation. Hypoalbuminemia and iron deficiency may occur. In addition, non-salicylate NSAIDs may cause focal lesions of the small intestine. Ulcerations and ulcers, that can be accidentally discovered during an ileoscopy, may cause acute or chronic bleeding. Deep ulcers may provoke sudden peritonitis. Small bowel diaphragms are rare fibrotic lesions, specifically associated with the use of non-salicylate NSAIDs or salicylates (duodenal diaphragms only). NSAID use is not associated with a constant toxicity on colonic mucosa. NSAID-induced colonic ulcers and diaphragms are rare. In patients with colonic diverticulosis, NSAID intake is a risk factor for severe attacks of diverticulitis. Acute or chronic use of non-salicylate NSAIDs increases the risk for ischemic colitis and flare-ups of inflammatory bowel disease. De novo colitis caused by non-salicylate NSAIDs are rare. The definite diagnosis of this entity relies on the absence of recurrence of colitis in the 2-3 following years. Such a recurrence would lead to the post-hoc diagnosis of first attack of inflammatory bowel disease triggered by NSAID use. Experimental data suggest that selective COX-2 inhibitors do not alter constantly mucosa of the small intestine. Pilot epidemiological works suggest that severe intestinal lesions are less frequent in association with COX-2 inhibitor use than in association with conventional NSAIDs. However, COX-2 appears as playing a beneficial role in mucosal healing, and it seems that COX-2 inhibitors, like conventional NSAIDs, may trigger flare-ups of inflammatory bowel disease.

A mechanistic study of cigarette smoke and cyclooxygenase-2 on proliferation of gastric cancer cells

Cigarette smoke has been shown to cause gastric cancer. Overexpression of cyclooxygenase-2 (COX-2) is a common characteristic in gastric malignancy. The present study aimed to explore the correlation between cigarette smoke and COX-2 in the promotion of tumorigenesis in human gastric cancer cells (AGS). We further studied the action of COX-2 on other proto-oncogenes on gastric tumor growth. Results showed that chloroform extract (CE) and ethanol extract (EE) from cigarette smoke dose-dependently stimulated gastric cancer cell proliferation, which was accompanied with an activation of ornithine decarboxylase (ODC) activity, COX-2, and c-myc expressions. Both antisense of c-myc and alpha-difluoromethylornithine (DFMO, specific ODC inhibitor) inhibited cell proliferation without affecting COX-2 expression in response to cigarette smoke extracts (CSE). However, selective COX-2 inhibitor (SC-236) not only blocked the proliferative activity but also the ODC activity and c-myc protein expression by CSE in gastric cancer cells. Further, supplementation of exogenous prostaglandin (PG) E(2) reversed all the inhibitory actions of SC-236. Our results underline the importance of COX-2 in the cancer-promoting effect of CSE and its modulation on its downstream growth-related genes, such as c-myc and ODC in cancer cell proliferation. These results reveal that CSE-induced gastric carcinogenesis is via the COX-2/c-myc/ODC and PGE(2)-dependent pathway. Hence, selective COX-2 inhibitor could be an effective therapeutic agent for gastric cancer in smokers.

Lipoxins: pro-resolution lipid mediators in intestinal inflammation

Many inflammatory processes are self-limiting, suggesting the existence of endogenous anti-inflammatory mechanisms. Among the lipid mediators generated during cell-cell interactions are the lipoxins (LX, including LXA(4) and B(4)), a distinct class of lipoxygenase-derived eicosanoids. Aspirin acetylation of cyclooxygenase 2 also promotes the generation of a series of 15-epimers of LXA(4), known as aspirin-triggered lipoxins (ATL), that may account for some of the bioactivity profile of aspirin and possibly of nonsteroidal anti-inflammatory drugs. Native LX are rapidly inactivated in vivo, and stable analogs of LXA(4), LXB(4), and ATL have been synthesized that possess enhanced bioavailability and potency as anti-inflammatory eicosanoids. Here, we review current in vitro, ex vivo, and in vivo evidence supporting cytoprotective and proresolution roles for LX in intestinal inflammation. LXA(4), LXA(4) analogs, and ATL analogs inhibit neutrophil chemotaxis, adhesion to epithelium, and epithelial cell chemokine release. In addition, LX blunt TNF-alpha-stimulated inflammatory responses, cyclooxygenase product generation, and epithelial cell apoptosis and are cytoprotective for cytokine-activated colonic mucosa ex vivo. LX, ATL, and synthetic LX analogs have already been demonstrated to possess impressive antiinflammatory and proresolution efficacy in a range of experimental models of inflammation in vivo. Further elucidation of the role of LX in intestinal epithelial cell biology and immune function may yield novel therapeutic approaches in inflammatory bowel disease and possibly gastrointestinal cancer.

Selective inhibitors of cyclo-oxygenase-2 (COX-2) induce hypoalgesia in a rat paw model of inflammation

1. It is well-established that inhibitors of cyclo-oxygenase (COX) and hence of prostaglandin (PG) biosynthesis reverse inflammatory hyperalgesia and oedema in both human and animal models of inflammatory pain. 2. Paw oedema and hyperalgesia in rats were induced by injecting carrageenan (250 micro g paw(-1)) into a hindpaw. Both inflammatory responses were followed for 24 h after the injection, measuring hyperalgesia by decreased pain threshold in the paws and oedema by plethysmography. 3. Three selective inhibitors of cyclo-oxygenase-2 (COX-2), celecoxib, rofecoxib and SC 236, given systemically in a range of doses, before the inflammatory stimulus, abolished carrageenan-induced hyperalgesia with little reduction of oedema. These inhibitors also induced hypoalgesia, increasing nociceptive thresholds in the inflamed paw above normal, non-inflamed levels. This hypoalgesia was lost at the higher doses of the selective inhibitors, although hyperalgesia was still prevented. 4. In paws injected with saline only, celecoxib, given at the dose inducing the maximum hypoalgesia after carrageenan, did not alter the nociceptive thresholds. 5. Two non-selective inhibitors of COX-2, indomethacin and piroxicam, abolished hyperalgesia and reduced oedema but did not induce hypoalgesia. 6. Celecoxib given locally into the paw also abolished inflammatory hyperalgesia and induced hypoalgesia without reducing oedema. 7. We conclude that hypoalgesia is expressed only over a critical range of COX-2 inhibition and that concomitant inhibition of COX-1 prevents expression of hypoalgesia, although hyperalgesia is still prevented. 8 Our results suggest a novel anti-nociceptive pathway mediating hypoalgesia, involving COX-2 selectively and having a clear peripheral component. This peripheral component can be further explored for therapeutic purposes.