Review article: thromboxanes in inflammatory bowel disease--pathogenic and therapeutic implications

Ginsenoside Rk3 Ameliorates Obesity-Induced Colitis by Modulating Lipid Metabolism in C57BL/6 Mice

Lipid metabolism is closely related to obesity and its complications. Our previous study found that ginsenoside Rk3 (Rk3), a natural bioactive substance derived from ginseng, can effectively alleviate obesity-induced colitis, while its impact on the improvement of the lipid metabolism disorder remains unclear. Here, we demonstrated that Rk3 significantly alleviated inflammation, oxidative stress, and lipid dysregulation in high-fat diet-induced colitis C57BL/6 mice. The potential mechanism by which Rk3 mitigated colon inflammation in the context of obesity may involve the modulation of polyunsaturated fatty acid metabolism with specific attention to n-6 fatty acids, linoleic acid, and arachidonic acid. Rk3 intervention markedly reduced the production of pro-inflammatory factors (PGE2, PGD2, TXB2, HETE, and HODE) by inhibiting cyclooxygenase and lipoxygenase pathways, while enhancing the production of anti-inflammatory factors (EET and diHOME) via cytochrome P450 pathways. Our findings suggest that Rk3 is a potential anti-inflammatory natural drug that can improve obesity-induced intestinal inflammation by regulating lipid metabolism.

Simultaneous Quantitation of Lipid Biomarkers for Inflammatory Bowel Disease Using LC-MS/MS

Eicosanoids are key mediators and regulators of inflammation and oxidative stress that are often used as biomarkers for severity and therapeutic responses in various diseases. We here report a highly sensitive LC-MS/MS method for the simultaneous quantification of at least 66 key eicosanoids in a widely used murine model of colitis. Chromatographic separation was achieved with Shim-Pack XR-ODSIII, 150 × 2.00 mm, 2.2 µm. The mobile phase was operated in gradient conditions and consisted of acetonitrile and 0.1% acetic acid in water with a total flow of 0.37 mL/min. This method is sensitive, with a limit of quantification ranging from 0.01 to 1 ng/mL for the various analytes, has a large dynamic range (200 ng/mL), and a total run time of 25 min. The inter- and intraday accuracy (85-115%), precision (≥85%), and recovery (40-90%) met the acceptance criteria per the US Food and Drug Administration guidelines. This method was successfully applied to evaluate eicosanoid metabolites in mice subjected to colitis versus untreated, healthy control mice. In summary, we developed a highly sensitive and fast LC-MS/MS method that can be used to identify biomarkers for inflammation and potentially help in prognosis of the disease in inflammatory bowel disease (IBD) patients, including the response to therapy.

Fecal Microbiota Transplantation Controls Murine Chronic Intestinal Inflammation by Modulating Immune Cell Functions and Gut Microbiota Composition

Different gastrointestinal disorders, including inflammatory bowel diseases (IBD), have been linked to alterations of the gut microbiota composition, namely dysbiosis. Fecal microbiota transplantation (FMT) is considered an encouraging therapeutic approach for ulcerative colitis patients, mostly as a consequence of normobiosis restoration. We recently showed that therapeutic effects of FMT during acute experimental colitis are linked to functional modulation of the mucosal immune system and of the gut microbiota composition. Here we analysed the effects of therapeutic FMT administration during chronic experimental colitis, a condition more similar to that of IBD patients, on immune-mediated mucosal inflammatory pathways. Mucus and feces from normobiotic donors were orally administered to mice with established chronic Dextran Sodium Sulphate (DSS)-induced colitis. Immunophenotypes and functions of infiltrating colonic immune cells were evaluated by cytofluorimetric analysis. Compositional differences in the intestinal microbiome were analyzed by 16S rRNA sequencing. Therapeutic FMT in mice undergoing chronic intestinal inflammation was capable to decrease colonic inflammation by modulating the expression of pro-inflammatory genes, antimicrobial peptides, and mucins. Innate and adaptive mucosal immune cells manifested a reduced pro-inflammatory profile in FMT-treated mice. Finally, restoration of a normobiotic core ecology contributed to the resolution of inflammation. Thus, FMT is capable of controlling chronic intestinal experimental colitis by inducing a concerted activation of anti-inflammatory immune pathways, mechanistically supporting the positive results of FMT treatment reported in ulcerative colitis patients.

Immuno-PET of Innate Immune Markers CD11b and IL-1β Detects Inflammation in Murine Colitis

Inflammatory bowel disease (IBD) is a chronic relapsing and remitting inflammatory disease of the gastrointestinal tract. The diagnosis and monitoring of IBD are reliant on endoscopy, which is invasive and does not provide information on specific mediators. Symptom flare in IBD is associated with increased activation of innate immune pathways. Immuno-PET approaches have previously demonstrated the ability to detect colitis; however, a direct comparison of antibodies targeted to innate immune mediators and cells has not been done. We aimed to compare immuno-PET of antibodies to IL-1β and CD11b against standard ¹⁸F-FDG and MRI approaches to detect colonic inflammation. Methods: Colonic concentrations of IL-1β and myeloperoxidase were determined by ELISA, and colonic infiltration by CD11b-positive CD3-negative innate immune cells was determined by flow cytometry and compared between healthy and dextran sodium sulphate-treated colitic mice. PET of ⁸⁹Zr-lα-IL-1β, ⁸⁹Zr-α-CD11b, and ¹⁸F-FDG was compared by volume-of-interest analysis and with MRI by region-of-interest analysis. Imaging results were confirmed by ex vivo biodistribution analysis. Results: Colonic inflammation was associated with impaired colonic epithelial barrier permeability, increased colonic IL-1β and myeloperoxidase concentrations, and increased CD11b-positive CD3-negative innate immune cell infiltration into the colon. ⁸⁹Zr-α-IL-1β and ⁸⁹Zr-α-CD11b immuno-PET detected colonic inflammation, as did ¹⁸F-FDG, and all PET tracers were more sensitive than MRI. Although ¹⁸F-FDG volumes of interest correlated with colitis severity and a strong trend was observed with ⁸⁹Zr-α-IL-1β, no correlation was observed for ⁸⁹Zr-α-CD11b or MRI. ⁸⁹Zr-α-IL-1β was distributed mainly to the gastrointestinal tract, whereas ⁸⁹Zr-α-CD11b was distributed to more tissue types. Conclusion: Immuno-PET using antibodies directed to innate immune markers detected colonic inflammation, with ⁸⁹Zr-α-IL-1β providing a more tissue-specific signal than ⁸⁹Zr-α-CD11b. Development of these technologies for human subjects will potentially provide a less invasive approach than endoscopy for diagnosing and monitoring IBD.

Eicosanoid receptors: Targets for the treatment of disrupted intestinal epithelial homeostasis

The importance of cyclooxygenase and lipoxygenase pathways and the consequent eicosanoid synthesis in the physiology and pathophysiology of the intestinal epithelium is currently being established. Each eicosanoid (prostanoid, leukotriene, hydroxyeicosatetraenoic acid) preferentially recognizes one or more receptors coupled to one or more signal-transduction processes. This overview focuses on the role of eicosanoid receptors in the maintenance of intestinal epithelium physiology through the control of proliferation/differentiation/apoptosis processes. Furthermore, it is reported that the role of these receptors on the regulation of the barrier function of the intestinal epithelium have arisen through the regulation of absorption/secretion processes, tight-junction state and the control of the intestinal immune response. Also, this review considers the implication of AA cascade in the disruption of epithelial homeostasis during inflammatory bowel diseases and colorectal cancer as well as the therapeutic values and potential of the eicosanoid receptors as novel targets for the treatments of the pathologies above mentioned.

Ingestion of (n-3) fatty acids augments basal and platelet activating factor-induced permeability to dextran in the rat mesenteric vascular bed

Loss of intestinal barrier function and subsequent edema formation remains a serious clinical problem leading to hypoperfusion, anastomotic leakage, bacterial translocation, and inflammatory mediator liberation. The inflammatory mediator platelet activating factor (PAF) promotes eicosanoid-mediated edema formation and vasoconstriction. Fish oil-derived (n-3) fatty acids (FA) favor the production of less injurious eicosanoids but may also increase intestinal paracellular permeability. We hypothesized that dietary (n-3) FA would ameliorate PAF-induced vasoconstriction and enhance vascular leakage of dextran tracers. Rats were fed either an (n-3) FA-rich diet (EPA-rich diet; 4.0 g/kg EPA, 2.8 g/kg DHA) or a control diet (CON diet; 0.0 g/kg EPA and DHA) for 3 wk. Subsequently, isolated and perfused small intestines were stimulated with PAF and arterial pressure and the translocation of fluid and macromolecules from the vasculature to lumen and lymphatics were analyzed. In intestines of rats fed the EPA-rich diet, intestinal phospholipids contained up to 470% more EPA and DHA at the expense of arachidonic acid (AA). The PAF-induced increase in arterial pressure was not affected by the EPA-rich diet. However, PAF-induced fluid loss from the vascular perfusate was higher in intestines of rats fed the EPA-rich diet. This was accompanied by a greater basal loss of dextran from the vascular perfusate and a higher PAF-induced transfer of dextran from the vasculature to the lumen (P = 0.058) and lymphatics. Our data suggest that augmented intestinal barrier permeability to fluid and macromolecules is a possible side effect of (n-3) FA-rich diet supplementation.

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.

Hypoxia and metabolic factors that influence inflammatory bowel disease pathogenesis

The gastrointestinal epithelium is anatomically positioned to provide a selective barrier between the anaerobic lumen and lamina propria, which has a high rate of metabolism. Supported by a complex vasculature, this important barrier is affected by reduced blood flow and resultant tissue hypoxia, particularly during the severe metabolic shifts associated with active inflammation in individuals with inflammatory bowel disease. Activation of hypoxia-inducible factor (HIF) under these conditions promotes resolution of inflammation in mouse models of disease. Protective influences of HIF are attributed, in part, to the complex regulation of barrier protection with the intestinal mucosa. Reagents that activate HIF, via inhibition of the prolyl hydroxylase enzymes, might be developed to induce hypoxia-mediated resolution in patients with intestinal mucosal inflammatory disease.

An association between dietary arachidonic acid, measured in adipose tissue, and ulcerative colitis

BACKGROUND & AIMS

Dietary arachidonic acid, an n-6 polyunsaturated fatty acid (n-6 PUFA), might be involved in the etiology of ulcerative colitis (UC). We performed a prospective cohort study to determine whether high levels of arachidonic acid in adipose tissue samples (which reflects dietary intake) are associated with UC.

METHODS

We analyzed data collected from 57,053 men and women in the EPIC-Denmark Prospective Cohort Study from 1993 to 1997. Adipose tissue biopsy samples were collected from gluteal regions at the beginning of the study, the cohort was monitored over subsequent years, and participants who developed UC were identified. A subcohort of 2510 randomly selected participants were used as controls. Concentrations of arachidonic acid were measured in adipose tissue samples. In the analysis, arachidonic acid levels were divided into quartiles; relative risks (RR) were calculated and adjusted for smoking, use of aspirin and nonsteroidal anti-inflammatory drugs, and levels of n-3 PUFAs.

RESULTS

A total of 34 subjects (56% men) developed incident UC at a median age of 58.8 years (range, 50.0-69.0 years). Those in the highest quartile for arachidonic acid concentrations in adipose tissue had an RR for UC of 4.16 (95% confidence interval [CI]: 1.56-11.04); a trend per 0.1% increase in arachidonic acid of 1.77 in RR was observed (95% CI: 1.38-2.27). The fraction attributed the highest levels of arachidonic acid was 40.3%.

CONCLUSIONS

Individuals with the highest relative concentrations of arachidonic acid in adipose tissue have a significantly greater risk of developing UC. Dietary modifications might therefore prevent UC or reduce disease symptoms.

Prostanoid receptor antagonists: development strategies and therapeutic applications

Identification of the primary products of cyclo-oxygenase (COX)/prostaglandin synthase(s), which occurred between 1958 and 1976, was followed by a classification system for prostanoid receptors (DP, EP(1), EP(2) ...) based mainly on the pharmacological actions of natural and synthetic agonists and a few antagonists. The design of potent selective antagonists was rapid for certain prostanoid receptors (EP(1), TP), slow for others (FP, IP) and has yet to be achieved in certain cases (EP(2)). While some antagonists are structurally related to the natural agonist, most recent compounds are 'non-prostanoid' (often acyl-sulphonamides) and have emerged from high-throughput screening of compound libraries, made possible by the development of (functional) assays involving single recombinant prostanoid receptors. Selective antagonists have been crucial to defining the roles of PGD(2) (acting on DP(1) and DP(2) receptors) and PGE(2) (on EP(1) and EP(4) receptors) in various inflammatory conditions; there are clear opportunities for therapeutic intervention. The vast endeavour on TP (thromboxane) antagonists is considered in relation to their limited pharmaceutical success in the cardiovascular area. Correspondingly, the clinical utility of IP (prostacyclin) antagonists is assessed in relation to the cloud hanging over the long-term safety of selective COX-2 inhibitors. Aspirin apart, COX inhibitors broadly suppress all prostanoid pathways, while high selectivity has been a major goal in receptor antagonist development; more targeted therapy may require an intermediate position with defined antagonist selectivity profiles. This review is intended to provide overviews of each antagonist class (including prostamide antagonists), covering major development strategies and current and potential clinical usage.

Genomic expression profiling of peripheral blood leukocytes of pigs infected with highly virulent classical swine fever virus strain Shimen

Classical swine fever (CSF), caused by a virus of the same name (CSFV), is a highly contagious swine pyrexic disease featuring extensive haemorrhagic lesions and leukopenia, but little is known about the molecular mechanisms of its pathogenesis. To gain insight into the interaction between the virus and host cells, microarray analyses were performed to detect alterations in genomic expression of pig peripheral blood leukocytes (PBLs) following CSFV infection. Three healthy pigs were inoculated with a lethal dose of highly virulent CSFV strain Shimen. PBLs were isolated at the onset of typical clinical signs and total RNA was subjected to microarray analyses with Affymetrix Porcine Genome Array GeneChips. Of all 20 201 pig genes arrayed in the chip, 1745 showed altered expression (up- or downregulation) after infection. These were classified into eight functional groups, relating to cell proliferation (3.6 %), immune response (2.1 %), apoptosis (1.4 %), kinase activity (1.4 %), signal transduction (1.4 %), transcription (0.7 %), receptor activity (0.7 %) and cytokines/chemokines (0.4 %). The remaining 88.3 % of genes had unknown functions. Alterations in genomic expression were confirmed by real-time RT-PCR of selected cellular genes and Western blotting of annexin 2, a cellular protein relating to virus infection. The observed expression changes of numerous genes involved in immune and inflammatory responses and in the apoptosis process indicate that CSFV has developed sophisticated mechanisms to cause leukopenia in infected pigs. These data provide a basis for exploring the molecular pathogenesis of CSFV infection through an understanding of the interaction between viral and cellular components.

Benefit of nicorandil using an immunologic murine model of experimental colitis

Inflammatory bowel disease (IBD) is a chronic inflammatory condition with an unknown etiology. Nicorandil, a potassium channel opener, has been used for many years for the treatment of angina. Recently, it has been shown that nicorandil possesses some novel traits such as anti-apoptotic, gastroprotective, free radical scavenging, and anti-inflammatory properties. Therefore, we set out to examine the possible beneficial effect of nicorandil in a rat model of IBD. Colitis was induced by rectal administration of 2,4,6-trintrobenzene sulphonic acid (TNBS) into rats. Groups of animals used in this study were sham, control, and exposure to dexamethasone, nicorandil, glibenclamid (a pure adenosine triphosphate sensitive potassium channel (KATP) blocker), or nicorandil plus glibenclamid. Drugs were administered by gavage and animals were sacrificed after 7 days. Biochemical markers, including TNF-α and IL-1β, ferric reducing/antioxidant power (FRAP), myeloperoxidase (MPO) activity and thiobarbitoric acid-reactive substance (TBARS), were measured in the homogenate of colonic tissue. Results indicate that nicorandil significantly reduces macroscopic and histological damage induced by TNBS. Nicorandil diminishes MPO activity and levels of TBARS, TNF-∢, and IL-1β in damaged colonic tissue with a concomitant increase in FRAP value (P<0.01). These effects were not reversed by coadministration of glibenclamide. In conclusion, nicorandil is able to ameliorate experimental IBD with a dose in which it does not show any anti-hypertensive effect, and the mechanism of which is partially or totally independent from KATP channels. It is hypothesized that nitric oxide donation and free-radical scavenging properties of nicorandil upregulate endothelial nitric oxide synthase may be responsible for this phenomenon. These findings suggest that nicorandil can be useful in treatment of IBD, although further investigations are needed to elucidate the mechanisms involved.

NV-52

NV-52, a synthetic flavonoid derivative, is a selective thromboxane synthase (TXS) inhibitor that is being developed as a treatment for inflammatory bowel disease. NV-52 selectively inhibits TXS in vitro in physiological relevant concentrations, causing a reduction in thromboxane B(2) of </= 40% in association with an increase in prostaglandin E(2). NV-52 is effective in suppressing colonic inflammation in a murine model of inflammatory bowel disease. NV-52 has not demonstrated any toxicity in in vitro and animal toxicological studies, and has been administered to normal volunteers in a Phase I clinical trial without detectable adverse effects. NV-52 is well absorbed and a single dose of 400 mg p.o. produced a plasma concentration that is comparable with the concentrations that have been shown to produce significant TXS inhibition in vitro.

The intestinal microvasculature as a therapeutic target in inflammatory bowel disease

Chronic inflammation is a complex biologic process which involves immune as well as non-immune cells including the microvasculature and its endothelial lining. Growing evidence suggests that the microvasculature plays an integral role in the pathophysiology of inflammatory bowel disease (IBD; Crohn's disease and ulcerative colitis). The microvasculature contributes to chronic inflammation through altered leukocyte recruitment, impaired perfusion, and angiogenesis leading to tissue remodeling. These diverse areas of IBD microvascular biology represent therapeutic targets that are currently undergoing investigation.

The potential interactions between polyunsaturated fatty acids and colonic inflammatory processes

n-3 Polyunsaturated fatty acids (PUFAs) are recognized as having an anti-inflammatory effect, which is initiated and propagated via a number of mechanisms involving the cells of the immune system. These include: eicosanoid profiles, membrane fluidity and lipid rafts, signal transduction, gene expression and antigen presentation. The wide-range of mechanisms of action of n-3 PUFAs offer a number of potential therapeutic tools with which to treat inflammatory diseases. In this review we discuss the molecular, animal model and clinical evidence for manipulation of the immune profile by n-3 PUFAs with respect to inflammatory bowel disease. In addition to providing a potential therapy for inflammatory bowel disease there is also recent evidence that abnormalities in fatty acid profiles, both in the plasma phospholipid membrane and in perinodal adipose tissue, may be a key component in the multi-factorial aetiology of inflammatory bowel disease. Such abnormalities are likely to be the result of a genetic susceptibility to the changing ratios of n-3 : n-6 fatty acids in the western diet. Evidence that the fatty acid components of perinodal adipose are fuelling the pro- or anti-inflammatory bias of the immune response is also reviewed.

Paradox of simultaneous intestinal ischaemia and hyperaemia in inflammatory bowel disease

This review has focused on evidence regarding intestinal perfusion of inflammatory bowel disease (IBD). Basic investigation has defined an altered microvascular anatomy in the affected IBD bowel, which corresponds with diminished mucosal perfusion in the setting of chronic, long-standing inflammation. Diminished perfusion is linked to impaired wound healing, and may contribute to the continued refractory mucosal damage, which characterizes IBD. Alterations in vascular anatomy and physiology in IBD suggests additional possible mechanisms by which micro-vessels may contribute to the initiation and perpetuation of IBD. This begs the following questions: will angiogenesis within the gut lead to sustained inflammation, does the growing vasculature generate factors that transform the surrounding tissue and does angiogenesis generate vascular anastomosis within the gut, with shunting of blood away from the mucosal surface, impairment of metabolism and potentiation of gut damage? Further studies are required to define the mechanisms that underlie the vascular dysfunction and its role in pathophysiology of IBD.

Cyclic AMP-dependent Cl- secretion induced by thromboxane A2 in isolated human colon

Increased release of thromboxane A(2) (TXA(2)) has been shown to be involved in inflammatory bowel diseases. In the present study, we have investigated the effect of a stable TXA(2) analogue (STA(2)) on the electrical parameters in isolated human colonic mucosa. In the human mucosa set between Ussing chambers, STA(2) stimulated Cl- secretion in a concentration-dependent manner with an EC(50) of 0.06 microm. The STA(2)-induced Cl- secretion was significantly inhibited by ONO-3708 (10 microm), a specific TXA(2) receptor antagonist. The effect of STA(2) (0.3 microm) was independent of the colonic segment from which the tissue was obtained, from caecum to rectum. Chromanol 293B, an inhibitor of the cAMP-dependent KvLQT1 channel, attenuated the STA(2)-induced Cl- secretion in the human colonic mucosa (IC(50) value 1.18 microm). We found that KvLQT1 mRNA and protein were expressed in all the tested segments of the human colon. The STA(2)-induced Cl- secretion was significantly inhibited by 8-bromo-2'-monobutyryladenosine-3',5'-cyclic monophosphorothioate (50 microm), a membrane-permeant cAMP antagonist. STA(2) (0.3 microm) significantly increased the intracellular cAMP levels and the short-circuit current via TXA(2) receptor in a human colonic cell line. These results suggest that the TXA(2)-induced Cl- secretion in the colon is mediated via the cAMP pathway in addition to the Ca(2+)-calmodulin pathway which was previously reported.

Alternative immunomodulators

There is now a large number of potential immunomodulatory agents that may be of value in inflammatory bowel disease. The newer immunosuppressants, such as tacrolimus and mycophenolate, probably offer little more than providing comparable alternatives to more established agents, and fish oil and other eicosanoid modulators are probably not especially potent if effective. The biological agents, however, bring a more novel and potentially powerful approach. Natalizumab, and targeted mucosal delivery of interleukin-10 already show considerable promise.

N-3 fatty acids for the treatment of inflammatory bowel diseases

The aim of the present paper is to briefly review the literature relating to clinical studies of the use of polyunsaturated long-chain fatty acids in the treatment of inflammatory bowel diseases (IBD) such as ulcerative colitis and Crohn's disease. The reasons for the discrepancies in the findings could be related to the different study designs, different treatments, overlapping of treatment effects, as well as the variety of treatment formulations and doses used, which have led to results that are, in certain instances, very difficult to explain. Emphasis on a treatment formulation which reduces the incidence of side effects, together with careful selection of patients and experimental design, seems to be associated with benefits, and these studies point to the therapeutic potential for these lipids in the therapy of IBD. It is possible that these fatty acids act by reducing low-grade active inflammation rather than by preventing reinitiation of the inflammatory process from a truly quiescent state. Whether this treatment is applicable to all IBD patients has not been fully elucidated. Nevertheless, taken together, all these studies suggest the effectiveness of these new therapeutic approaches, not only when conventional treatment fails or when it is not possible to treat chronically, but also, in some instances, as first choice.

E3040 sulphate, a novel thromboxane synthase inhibitor, blocks the Cl- secretion induced by platelet-activating factor in isolated rat colon

1. E3040 (6-hydroxy-5,7-dimethyl-2-methylamino-4-(3-pyridylmethyl)benzothiazole), is a novel dual inhibitor of 5-lipoxygenase (5-LOX) and thromboxane synthase (Tx synthase). Here, we examined the effects of E3040 sulphate, a sulphate conjugate of E3040, on these enzyme activities in cell-free systems and on the thromboxane A2 (TxA2)-mediated Cl- secretion induced by platelet-activating factor (PAF) in isolated rat colons. 2. E3040 sulphate inhibited Tx synthase activity in a concentration-dependent manner (IC50=0.013 microM), whereas it induced little effects on 5-LOX and cyclo-oxygenase activities (IC50>100 microM) with the cell-free enzyme assay. 3. With isolated rat colonic mucosa, E3040 sulphate in a concentration-dependent manner (IC50=1.8 microM) inhibited the Cl- secretion induced by 10 microM PAF. On the other hand, E3040 sulphate (30 microM) induced no effect on the prostaglandin E2 (0.5 microM)- and leukotriene D4 (1 microM)-induced Cl- secretion in the colon. 4. PAF (10 microM) increased a release of TxB2, a stable metabolite of TxA2, from the colonic mucosa. This increase was significantly inhibited by subsequent addition of E3040 sulphate (30 microM). 5. Probenecid (100 microM), an inhibitor of organic anion transporter, abolished the inhibitory effect of E3040 sulphate on the PAF-induced Cl- secretion. Another inhibitor, sulphobromophthalein (30 microM) partially but significantly attenuated the effect of E3040 sulphate. p-aminohippuric acid (1 mM) had no effect. 6. These findings suggest that E3040 sulphate is a novel Tx synthase inhibitor, and that E3040 sulphate taken up into the colonic cells by organic anion transporters inhibits the PAF-induced Cl- secretion by blocking a release of TxA2.

Efficacy and safety of oral ridogrel in the treatment of ulcerative colitis: two multicentre, randomized, double-blind studies

BACKGROUND

Ridogrel at low doses inhibits thromboxane synthase. Oral ridogrel, from 5 mg once daily to 150 mg twice daily, improves the endoscopic appearance of colonic mucosa and clinical manifestations in mild to moderate ulcerative colitis.

AIM

One US trial and one international trial were conducted to determine the effect of ridogrel on mild to severe active ulcerative colitis.

METHODS

Two 12-week, double-blind, randomized, parallel-group trials were conducted. A US trial compared 0.5 mg, 2.5 mg and 5 mg of ridogrel once daily with placebo. An international trial compared 0.5 mg of ridogrel once daily with 2.5 mg and 5.0 mg of ridogrel once daily and 800 mg of mesalazine (known as mesalamine in the USA) three times daily. The primary efficacy outcome measure was the rate of complete remission.

RESULTS

In the US trial, complete remission was achieved in 20.8% of patients in the 0.5 mg ridogrel group, 17.9% in the 2.5 mg ridogrel group, 20.6% in the 5.0 mg ridogrel group and 13.6% in the placebo group. In the international trial, 14.4% of patients in the 0.5 mg ridogrel group, 19.6% in the 2.5 mg ridogrel group, 19.4% in the 5.0 mg ridogrel group and 16.4% in the mesalazine group experienced complete remission. In the international trial, rates of complete remission at the end-point were greater in the 2.5 mg and 5.0 mg ridogrel groups than in the 0.5 mg ridogrel group, but the differences were not statistically significant. In the US trial, rates of complete remission at the end-point were greater in the 2.5 mg and 5.0 mg ridogrel groups than in the placebo group, but the differences were not statistically significant. Approximately 30% of the patients in each group discontinued treatment before the 12-week end-point owing to a lack of therapeutic response. All doses of ridogrel were well tolerated and comparable with placebo or mesalazine in terms of safety.

CONCLUSIONS

No significant differences in the primary efficacy outcome measure were found between either the 2.5 mg or the 5.0 mg dose of ridogrel and placebo in the US trial and between either the 2.5 mg or the 5.0 mg dose of ridogrel and the 0.5 mg dose of ridogrel, a surrogate dose for placebo, in the international trial. There was no clear indication in either trial of an effective dose of ridogrel in the treatment of ulcerative colitis.

Vascular responses to endothelin-1, angiotensin-II, and U46619 in glycerol-induced acute renal failure

Angiotensin II and endothelin-1, major endogenous vasoconstrictors in acute renal failure (ARF), can modulate the effects of each other. This study aimed to evaluate the interaction between these vasoconstrictors in glycerol-induced ARF by evaluating their effects in the isolated perfused kidney in the presence of their respective antagonists. In ARF, angiotensin II (2.5-25 ng) caused an increase in perfusion pressure. Saralasin, 1 microM, a nonselective angiotensin receptor antagonist, reduced these responses by 61+/- 6% (p < 0.05). Surprisingly, SQ29548, 1 microM, a selective PGH2 /thromboxane A2 receptor blocker, also reduced angiotensin II responses (62 +/- 4%; p < 0.05). BQ610 1 microM, an ETA -selective receptor antagonist, was without effect, but BQ788 1 microM, an ETB -selective antagonist, attenuated the response by 70 +/- 4% (p < 0.05). In ARF, in contrast to angiotensin II, vasoconstriction by endothelin-1 (5-25 ng) was diminished. Saralasin further attenuated endothelin-1 response by 65 +/- 2% (p < 0.05), whereas SQ29548 was without effect. BQ788 reduced the responses by 67 +/- 7% (p < 0.05), whereas BQ610 was without effect (42 +/- 30%; p > 0.05). BQ610 and BQ788 combination further reduced vasoconstriction by 89 +/- 3% (p < 0.05). Responses to U46619 were not changed in ARF. However, saralasin and BQ788, but not BQ610, attenuated its vasoconstrictor action. We conclude that vascular responses in ARF may be attributed to enhanced responses to angiotensin II through activation of ETB and/or PGH2 /thromboxane A2 receptors. We also suggest that the vasoconstrictor response to endothelin-1 in ARF is predominantly ETB receptor-mediated.

Lack of efficacy of ridogrel, a thromboxane synthase inhibitor, in a placebo-controlled, double-blind, multi-centre clinical trial in active Crohn's disease

BACKGROUND

Thromboxanes are produced in excess and platelets are activated in active Crohn's disease. Preliminary reports have suggested that ridogrel, a dual thromboxane synthase inhibitor and receptor antagonist, may have therapeutic benefit in patients with inflammatory bowel disease.

AIMS

To investigate the efficacy of ridogrel in patients with active Crohn's disease.

PATIENTS AND METHODS

This was an international, multicentre, randomized, double-blind, placebo-controlled trial of 5 mg/day oral ridogrel for 12 weeks in 85 patients with moderately active Crohn's disease. Sixty patients were randomized to receive ridogrel, and 25 to placebo. The Crohn's disease activity index (CDAI) was used to assess disease activity: remission was defined as a CDAI < 150. Changes in clinical condition, as assessed by the Harvey-Bradshaw index, global evaluation by the investigator and the patient, and blood measures of inflammation, were used as secondary outcomes.

RESULTS

The patients' mean (s.d.) CDAI at recruitment was 277 (68) in the ridogrel treated group and 265 (70) in the placebo group. At their final assessment, 20 out of 60 (35%) patients who had been given ridogrel in an intention-to-treat analysis and seven out of 25 (28%) patients given placebo were in remission (no significant difference). No significant differences in Harvey- Bradshaw index or global evaluation were noted between patients given ridogrel and those given placebo. Adverse events were similar in both groups.

CONCLUSION

A 5-mg dose of oral ridogrel was not more effective than placebo in inducing remission in patients with moderately active Crohn's disease. If thromboxane synthesis and platelet function are to be targeted for the treatment of Crohn's disease, more potent agents require development and assessment.

Ridogrel enemas in distal ulcerative colitis

OBJECTIVE

To evaluate the effect of Ridogrel enemas (Janssen Research Foundation, Beerse, Belgium) on disease activity and mucosal inflammatory mediators in patients with active left-sided ulcerative colitis.

DESIGN AND METHODS

Eleven patients with active left-sided ulcerative colitis were evaluated in an open non-placebo-controlled pilot study. All patients were treated with Ridogrel enemas (300 mg/40 ml once daily) over four weeks. A disease activity score based on clinical, endoscopic and histological criteria was obtained before and after treatment with Ridogrel. The concentrations of thromboxane B2 (TxB2), prostaglandin E2 (PGE2), interleukin-6 (IL-6) and tumour necrosis factor alpha (TNF-alpha) were measured in mucosal biopsies before and after treatment.

RESULTS

One patient discontinued treatment because of progression of disease, the other ten patients tolerated the Ridogrel enemas well. Mucosal TxB2 concentration decreased significantly in all patients. The mucosal concentrations of the other inflammatory mediators (PGE2, IL-6 and TNF-alpha) were unaltered. The disease score decreased in five patients. However, clinical improvement was not always associated with a decrease in endoscopic and/or histological scores.

CONCLUSIONS

This pilot study shows that Ridogrel enemas selectively reduce mucosal TxB2 concentration.

Recent advances in inflammatory bowel disease

The last decade has seen tremendous advances in our knowledge, which has led to genuine improvements in our understanding of the pathogenesis and management of inflammatory bowel disease (IBD). The combined power of cellular and molecular biology has begun to unveil the enigmas of IBD, and, consequently, substantial gains have been made in the treatment of IBD. Refinements in drug formulation have provided the ability to target distinct sites of delivery, while enhancing the safety and efficacy of older agents. Simultaneous progress in biotechnology has fostered the development of new agents that strategically target pivotal processes in disease pathogenesis. This article addresses our current understanding of the pathogenesis of IBD, including the latest developments in animal models and covers agents currently used in the treatment of IBD as well as emerging therapies.

Regulation of intestinal regeneration: new insights

Intestinal regeneration is the process by which intestinal injury penetrating deep to the lamina propria heals. The regenerative process involves epithelial cell migration and proliferation, changes in cellular function, adaptation of subepithelial tissues, and contraction of the injured area. This requires interaction of multiple cell types. While many observations have been made about the process of regeneration, its regulation is not well understood. Previous studies, performed primarily in a serosal patch model, have identified many potential regulatory factors. These include location and size of the injury, other associated injury, e.g., resection, and a variety of agents that influence one or more of the primary processes involved. Epidermal growth factor (EGF), in particular, appears to play a role in many aspects of regeneration. Recent advances in the understanding of intestinal growth regulation have provided new insights into the regulation of intestinal regeneration. Developmental studies in genetically manipulated mice suggest a role for gene products not previously implicated in regeneration. The importance of apoptosis in growth regulation has recently been emphasized. Mesenchymal-epithelial interactions have gained greater appreciation. Finally, it has become clear that immune cells and cytokines are important factors in this process. Transforming growth factor-beta (TGFbeta) has been implicated as another important regulator of several of the processes involved in intestinal regulation. Improved understanding of the regulation of intestinal regeneration will lead to new therapeutic approaches to stimulate intestinal healing in the clinical setting.

Thromboxane A(2)-mediated Cl(-) secretion induced by platelet-activating factor in isolated rat colon

Thromboxane A(2) is a novel endogenous secretagogue of Cl(-) secretion in the distal colon. Here, we examined if the Cl(-) secretion caused by platelet-activating factor (PAF; 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is mediated by thromboxane A(2) production using isolated mucosae of the rat colon. Furosemide (100 microM) and 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB; 300 microM) completely inhibited PAF (10 microM)-induced increase in short-circuit current (Isc) across the mucosa, indicating that PAF caused a Cl(-) secretion in the rat colon. A selective thromboxane A(2) receptor antagonist (sodium(E)-11-[2-(5, 6-dimethyl-1-benzimidazolyl)-ethylidene]-6,11-dihydrobenz[b, e]oxepine-2-carboxylate monohydrate; KW-3635), and a selective thromboxane synthase inhibitor (sodium 4-[alpha-hydroxy-5-(1-imidazolyl)-2-methylbenzyl]-3, 5-dimethylbenzoate dihydrate; Y-20811) inhibited the PAF-induced Cl(-) current in a concentration-dependent manner. The IC(50) values of KW-3635 and Y-20811 were 2.1 and 0.5 microM, respectively. 30 microM KW-3635 and 1 microM Y-20811 inhibited the PAF response by 92% and 83%, respectively. These inhibitors did not affect the prostaglandin E(2)-induced increase in Isc. A 5-lipoxygenase-activating protein inhibitor (3-[1-(p-chlorobenzyl)-5-(isopropyl)-3-t-butylthioindol-2-yl]-2, 2-dimethyl-propanoic acid sodium; MK-886) (5 microM) did not affect the PAF-induced Cl(-) current. The present study suggests that the PAF-induced Cl(-) secretion in the rat colonic mucosa is mainly mediated by a release of thromboxane A(2).

Ridogrel, a dual thromboxane synthase inhibitor and receptor antagonist: anti-inflammatory profile in inflammatory bowel disease

BACKGROUND

Thromboxanes, prostaglandins, reactive oxygen metabolites and pro-inflammatory cytokines are produced in excess in inflammatory bowel disease. Preliminary reports suggest that ridogrel, a thromboxane synthesis inhibitor and receptor blocker, may have therapeutic benefits in ulcerative colitis.

AIMS

To investigate the anti-inflammatory profile of ridogrel.

METHODS

The effects of ridogrel on the production of eicosanoids, reactive oxygen metabolites and cytokines by cultured inflamed colorectal mucosal biopsies were made using ELISA and chemiluminescence, reactive oxygen metabolite generation in a cell-free system, and platelet activation using flow cytometry. The effects of oral ridogrel on mucosal release of eicosanoids in two patients with active ulcerative colitis were assessed using rectal dialysis.

RESULTS

Ridogrel significantly reduced the release of thromboxane B2, but not prostaglandin E2 or tumour necrosis factor-alpha, from biopsies (P < 0.01 for 10 microM ridogrel). Ridogrel showed no direct antioxidant activity but significantly reduced reactive oxygen metabolite production from cultured biopsies (P < 0.01 for 10 microM ridogrel). Platelet activation in vitro was inhibited by ridogrel (P </= 0.05 for >/= 10 microM ridogrel). Mean rectal mucosal thromboxane B2 release was reduced to 86% of pre-treatment levels in two patients treated with oral ridogrel.

CONCLUSIONS

Its inhibition of mucosal production of thromboxane B2, reactive oxygen metabolites, and of platelet activation, suggests that ridogrel could have a therapeutic role in inflammatory bowel disease.

Eicosanoids and the large intestine

During the past three decades, many studies have been conducted to determine the precise role of eicosanoids in colorectal physiology and pathophysiology. This research has increased our understanding of bioactive lipid signaling, and may contribute to the development of more effective therapeutic modalities for digestive diseases in the future. The purpose of this report is to provide a brief overview of the role of eicosanoids in the colon and rectum. This information has been organized according to both functional and disease-related categories. The role of eicosanoids in colonic secretion, motility, inflammatory bowel disease, and colorectal neoplasia will be discussed.

Polyunsaturated fatty acids and inflammatory bowel disease

The rationale for supplementation with n-3 fatty acids to promote the health of the gastrointestinal tract lies in the antiinflammatory effects of these lipid compounds. The first evidence of the importance of dietary intake of n-3 polyunsaturated fatty acids was derived from epidemiologic observations of the low incidence of inflammatory bowel disease in Eskimos. The aim of this paper was to briefly review the literature on the use of n-3 fatty acids in inflammatory bowel disease (ulcerative colitis and Crohn disease), the results of which are controversial. The discrepancies between studies may reside in the different study designs used as well as in the various formulations and dosages used, some of which may lead to a high incidence of side effects. Choosing a formulation that lowers the incidence of side effects, selecting patients carefully, and paying strict attention to experimental design are critical when investigating further the therapeutic potential of these lipids in inflammatory bowel disease.

ANG II- and TxA(2)-induced mesenteric vasoconstriction in rats is mediated by separate cell signaling pathways

Studies in vitro have demonstrated that vasoconstrictor agents increase intracellular Ca(2+) and activate protein kinase C (PKC) to elevate vascular tone. The aim of the present study was to determine the importance of these signaling pathways for angiotensin II (ANG II) and thromboxane A(2) (TxA(2)) in regulating mesenteric blood flow (MBF) in vivo. In anesthetized rats increasing doses of ANG II or the TxA(2) agonist U-46619 were administered into the superior mesenteric artery to reduce MBF. Intra-arterial infusion of inhibitors served to examine the contribution of different pathways: 8-(diethylamino)octyl 3,4,5-trimethoxybenoate hydrochloride (TMB-8) to inhibit intracellular Ca(2+) release, nifedipine to block transmembrane Ca(2+) influx through the L-type Ca(2+) channel, and staurosporine to inhibit PKC. Each of the inhibitors attenuated ANG II-induced reductions in MBF, and all dose-response curves were shifted to the right to an approximately threefold higher ANG II dose. Combinations of the inhibitors revealed that their effects were additive; together they abolished the vasoconstrictor action of ANG II completely. In contrast, the dose-response curve for U-46619 was not affected by any of the inhibitors infused either separately or together. The results demonstrate that a rise in intracellular Ca(2+) and activation of PKC are major mediators of the vasoconstrictor effect of ANG II in mesenteric circulation, but they play a subordinate role, if any, for the effects of TxA(2). Because TxA(2) plays a major role only under pathological conditions, the uncontrolled vasoconstriction appears to be associated with the recruitment of novel signal transduction pathways.

Interventional nutrition for gastrointestinal disease

Nutritional intervention plays a key role in the successful management of gastrointestinal disease. This article focuses on several novel areas of nutritional intervention that are becoming increasingly important in gastrointestinal disease, including short-chain fatty acids, omega-3 polyunsaturated fatty acids and glutamine. Short-chain fatty acids are the principal end-products of bacterial fermentation of dietary fibers and have profound effects on normal intestinal cell metabolism and proliferation. Short-chain fatty acids have the potential to improve overall intestinal health, stimulate intestinal healing, and decrease intestinal inflammation. Omega-3 fatty acids, from dietary sources or supplements, may also be useful in decreasing intestinal inflammation and in preventing intestinal cancer. Finally, glutamine also may play an important role in the nutritional management of gastrointestinal disease.

Nutritional issues in inflammatory bowel disease

Malnutrition is a very common problem in patients with chronic inflammatory bowel diseases. This article discusses the incidence, causes, and clinical consequences of malnutrition in these patient groups. The role of nutritional support administered enterally or parenterally either as primary or adjunctive therapy is highlighted, based on past and more recent controlled studies. Additional attention is given to the roles of glutamine, short-chain fatty acids, fish oil, and alternative nutritional therapy.

Adjuvant post-operative therapy

About 90% of patients with Crohn's disease require surgery at some time in their lives but the clinical recurrence rate after surgery is about 50% within 5 years, with 50% requiring further surgery within 10 years. Endoscopic evidence of relapse can be found in 75% within 12 weeks of resection. There is therefore a major problem to be solved. The solution is less clear. Retrospective studies suggest that smoking is a major factor determining a poor prognosis after surgery and it is most important that patients are encouraged to stop. There is strong evidence linking diet with Crohn's disease but the mechanism and nature of this link remains unclear. A low total fat intake, possibly supplemented with eudragitcoated n-3 fatty acid (fish oil) looks reasonable on current evidence but not proven. Mesalazine and metronidazole are the drugs for which most supportive evidence is available. The individual trials of mesalazine have generally proved inconclusive and meta-analyses have been needed to demonstrate a significant beneficial effect (approximately halving the relapse rate at 1 year). More recent large controlled studies performed after the meta-analyses however have again proved negative and the benefit is probably more modest than the meta-analyses suggested. Metronidazole, 20 mg/day for the first 3 months after surgery, has been shown to reduce relapse by just over one-third with a beneficial effect that was surprisingly sustained throughout a 3 year follow-up period. Peripheral neuropathy is a problem and further studies are needed at lower dosage. Azathioprine, 1.5-2 mg/kg/day is effective as maintenance therapy but there is insufficient evidence to recommend its routine post-operative use, moreover it takes up to 3 months to have an effect. Although budesonide has been shown to delay the time to relapse in non-operated patients it, like other corticosteroids, has been shown to be no better than placebo when maintenance is assessed according to the proportion of patients who remain relapse-free after 1 year. Patients undergoing operation for Crohn's disease should therefore be strongly advised to stop smoking. A 3 month course of oral metronidazole plus continued maintenance with oral mesalazine can be justified on current evidence but further studies are needed.

Pathogenesis of Crohn's disease

In the absence of a single initiating aetiological factor, most workers envisage Crohn's disease as the manifestation of poorly regulated immune and inflammatory processes within the gut wall. Initially these responses may arise as a response to common antigens associated with the gut--bacterial products being amongst the most obvious candidates. In genetically predisposed individuals there is overexpression both of local immune response mechanisms in the gut wall (T-cells, B-cells and macrophages) and of systemic inflammatory cells (predominantly polymorphonuclear leukocytes), which are attracted into the inflamed gut through activation of adhesion molecules on the vascular endothelium. As a consequence a large number of pro-inflammatory processes are expressed in the gut wall, inadequately checked by the normal counter-inflammatory processes that should serve to limit inflammation. Defining the relative importance of the individual processes, and identifying critical steps that could be inhibited or enhanced for therapeutic purposes, is a major challenge of Crohn's disease research.

Localization and quantification of TXB2 in human healthy and inflammatory gingival mucosa

We conducted a study to localize and quantify the thromboxane B2 (TXB2) in human gingival tissue obtained from clinically healthy sites and patients with gingivitis and periodontitis. Human gingival samples were assayed for TXB2 by immunofluorescence on slides and enzyme-immunoassay (EIA). We found that concentrations of TXB2 in gingivitis sites are at mean 10-fold higher than in the healthy sites and histologically show a consistently intracytoplasmic staining with a significant increase in gingivitis. This argues in favour of a local production of TXB2. Concentrations of TXB2 at periodontitis sites are only 3-fold higher than in healthy sites and histologically show a stronger staining as for the gingivitis sections, with principally an extracellular localization. Thus, TXB2 could be released in large quantities in the crevicular fluid when the periodontitis stage has reached. These data suggest that the epithelial cells of the gingival tissue are involved in synthesis and secretion of TXB2, which occurred during the development of gingival inflammation.

Thromboxane A2, released by the anti-tumour drug irinotecan, is a novel stimulator of Cl- secretion in isolated rat colon

1. A camptothecin derivative, irinotecan (Cpt-11), is a topoisomerase I inhibitor and has a strong activity against a broad range of human cancer. One of the side-effects of this drug is diarrhoea. Here, we tried to determine the mediator of the irinotecan-induced Cl- secretion which may underlie this diarrhoea, using isolated mucosae of rat distal colon. 2. Irinotecan increased Cl- secretory current in a concentration-dependent manner across the mucosa, set between Ussing chambers. Thromboxane A2 (TXA2) has not been reported to date as a physiological stimulant of Cl- secretion in the distal colon. However, the major part of the present irinotecan-induced current was inhibited by selective thromboxane A2 receptor antagonists (KW-3635 and ONO-3708), and a selective thromboxane synthase inhibitor (Y-20811). In fact, we found that irinotecan stimulated the release of TXA2 in a concentration-dependent manner from the isolated mucosa into the bathing solutions. 3. Furthermore, 9,11-epithio-11,12-methano-thromboxane A2 (STA2), a stable analogue of TXA2, induced Cl- secretion, which was almost completely inhibited by the TXA2 receptor antagonists. 4. In single cells of isolated crypts, STA2 depolarized the cell and increased the membrane conductance, indicating that STA2 opened the apical Cl- channel of the crypt cells. 5. We conclude, therefore, that the irinotecan-induced endogenous TXA2 is a novel stimulant of the Cl- secretion from the crypt cells of distal colon.

Effect of an enteric-coated fish-oil preparation on relapses in Crohn's disease

BACKGROUND

Patients with Crohn's disease may have periods of remission, interrupted by relapses. Because fish oil has antiinflammatory actions, it could reduce the frequency of relapses, but it is often poorly tolerated because of its unpleasant taste and gastrointestinal side effects.

METHODS

We performed a one-year, double-blind, placebo-controlled study to investigate the effects of a new fish-oil preparation in the maintenance of remission in 78 patients with Crohn's disease who had a high risk of relapse. The patients received either nine fish-oil capsules containing a total of 2.7 g of n-3 fatty acids or nine placebo capsules daily. A special coating protected the capsules against gastric acidity for at least 30 minutes.

RESULTS

Among the 39 patients in the fish-oil group, 11 (28 percent) had relapses, 4 dropped out because of diarrhea, and 1 withdrew for other reasons. In contrast, among the 39 patients in the placebo group, 27 (69 percent) had relapses, 1 dropped out because of diarrhea, and 1 withdrew for other reasons (difference in relapse rate, 41 percentage points; 95 percent confidence interval, 21 to 61; P < 0.001). After one year, 23 patients (59 percent) in the fish-oil group remained in remission, as compared with 10 (26 percent) in the placebo group (P = 0.003). Logistic-regression analysis indicated that only fish oil and not sex, age, previous surgery, duration of disease, or smoking status affected the likelihood of relapse (odds ratio for the placebo group as compared with the fish-oil group, 4.2; 95 percent confidence interval, 1.6 to 10.7).

CONCLUSIONS

In patients with Crohn's disease in remission, a novel enteric-coated fish-oil preparation is effective in reducing the rate of relapse.

Mediators of inflammation in chronic inflammatory bowel disease

A distinguishing feature of inflammatory bowel disease (IBD) is its apparently spontaneous, chronic relapsing course. Despite extensive research over several decades the etiology of IBD remains unknown, but evidence has accumulated to suggest that the mucosal inflammatory response may be caused by (i) a defective mucosal barrier function resulting in an abnormally increased exposure to luminal antigens and toxins, (ii) an appropriate immunologic response to an unusual infection, antigen or toxin, or (iii) an inappropriate immunological response to ubiquitous antigens or stimuli. In recent years, the identification of established and potential mediators of inflammation has expanded to include eicosanoids, platelet activating factor, biogenic amines, kinins, complement-derived peptides, chemotactic peptides, cytokines, neuropeptides, and reactive metabolites of oxygen and nitrogen. Thus, the study of the inflammatory process has become ever more complex. Until the predisposing and trigger factors have been identified the achievement of a more rational and effective approach to therapy in IBD relies on interruption of the mechanisms responsible for excess mediator formation. As summarized in this review on the role of soluble mediators of inflammation, several Danish gastroenterologists have been profoundly engaged in basic and clinical research in the past 25 years to place some pieces of the confusing puzzle of IBD.

Review of the biology of Quercetin and related bioflavonoids

The French paradox is a dietary anomaly which has focused attention on the Mediterranean diet. Epidemiological studies revealed that this diet, replete in flavonoid-rich foods (Allium and Brassica vegetables, and red wine), correlated with the increased longevity and decreased incidence of cardiovascular disease seen in these populations. The most frequently studied flavonoid, quercetin, has been shown to have biological properties consistent with its sparing effect on the cardiovascular system. Quercetin and other flavonoids have been shown to modify eicosanoid biosynthesis (antiprostanoid and anti-inflammatory responses), protect low-density lipoprotein from oxidation (prevent atherosclerotic plaque formation), prevent platelet aggregation (antithrombic effects), and promote relaxation of cardiovascular smooth muscle (antihypertensive, antiarrhythmic effects). In addition, flavonoids have been shown to have antiviral and carcinostatic properties. However, flavonoids are poorly absorbed from the gut and are subject to degradation by intestinal micro-organisms. The amount of quercetin that remains biologically available may not be of sufficient concentration, theoretically, to explain the beneficial effects seen with the Mediterranean diet. The role of flavonoids may transcend their presence in food. The activity of flavonoids as inhibitors of reverse transcriptase suggests a place for these compounds in the control of retrovirus infections, such as acquired immunodeficiency syndrome (AIDS). In addition to specific effects, the broad-modulating effects of flavonoids as antioxidants, inhibitors of ubiquitous enzymes (ornithine carboxylase, protein kinase, calmodulin), and promoters of vasodilatation and platelet disaggregation can serve as starting material for drug development programmes.

Eicosanoids and the gastrointestinal tract

Determining the role of eicosanoids in gastrointestinal physiology and pathophysiology has been an active area of investigation over the past 20 years. The landmark discovery of prostaglandin endoperoxide synthase and other enzymes involved in the production of arachidonic acid products (lipoxygenases and epoxygenases) ushered in a new era of research. The goal of this review is to distill a large body of work pertaining to studies of eicosanoids in the gastrointestinal tract. This review has been organized according both to functional (secretion and motility) and disease-related (inflammation, mucosal injury, and neoplasia) effects. The aim of this article is to present a clear summary of this area of gastroenterology so that future research can be directed in a logical and productive manner.

Intense nutritional support in inflammatory bowel disease

The value of intense nutritional support in inflammatory bowel disease is still debated. Claims have been made that total enteral nutrition is as effective as total parental nutrition. In this review, the use of parenteral and enteral nutritional support as primary therapy in patients with inflammatory bowel disease has been critically evaluated. Most studies have been uncontrolled and nonrandomized with short-term follow-up. The literature does suggest, however, that intense nutritional support may have an adjunctive role to drug therapy in achieving remission in Crohn's disease, especially in corticosteroid-refractory patients. Nutritional support has a lesser role in chronic ulcerative colitis, except for assistance in pre- and postoperative management. The data do not support one variety of nutritional support over another, although enteral support should be used if possible, as it is less costly and potentially less complicated.