Role of cytokines and platelet-activating factor in inflammatory bowel disease. Implications for therapy

[Platelet-activating Factor (PAF) in Urinary Bladder Smooth Muscle (UBSM): Its Novel Role as a Potential Inducer of Detrusor Overactivity and the Mechanisms Underlying Its Effects in Enhancing UBSM Mechanical Activities]

Platelet-activating factor (PAF), a phospholipid mediator, was discovered in 1972 as an inducer of platelet aggregation. Subsequent studies have revealed that PAF has a variety of biological functions, such as its role as a potent proinflammatory mediator. Additionally, PAF regulates the contractile functions of various types of smooth muscle (SM), such as the (1) endothelium-dependent relaxation of vascular SM; (2) contraction and epithelium-dependent relaxation of airway SM; (3) contraction of gastrointestinal SM; and (4) contraction of uterine SM, which occurs more strongly in pregnant females. PAF is produced in platelets, monocytes, neutrophils, and macrophages, which are cells related to thrombus formation and inflammation/immune responses. Furthermore, PAF is produced in various other cells throughout the body. Interestingly, recent studies have focused on the urinary bladder (UB) as a PAF-producing organ since the accumulation of this phospholipid is enhanced in patients with bladder cancer and interstitial cystitis/bladder pain syndrome, especially those who smoke. Therefore, in UB tissue, PAF may play a substantial role as an inducer or enhancer of cancers and inflammatory diseases. However, the effects of PAF on the immediate mechanical activities of UBSM have not been investigated to date. In this regard, we recently discovered that PAF strongly enhances mechanical activities (muscle tone and spontaneous contractile activity) in UBSM tissues isolated from guinea pigs and mice. In this review article, we present our data on these PAF effects together with the possible underlying mechanisms. We also discuss the potential pathophysiological roles of this phospholipid in UB diseases and disorders.

Metabolomics as a Promising Resource Identifying Potential Biomarkers for Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a relapsing chronic disorder of the gastrointestinal tract characterized by disruption of epithelial barrier function and excessive immune response to gut microbiota. The lack of biomarkers providing early diagnosis or defining the status of the pathology difficulties an accurate assessment of the disease. Given the different metabolomic profiles observed in IBD patients, metabolomics may reveal prime candidates to be studied, which may help in understanding the pathology and identifying novel therapeutic targets. In this review, we summarize the most current advances describing the promising metabolites such as lipids or amino acids found through untargeted metabolomics from serum, faecal, urine and biopsy samples.

Cardiotoxicity during invasive pneumococcal disease

Streptococcus pneumoniae is the leading cause of community-acquired pneumonia and sepsis, with adult hospitalization linked to approximately 19% incidence of an adverse cardiac event (e.g., heart failure, arrhythmia, infarction). Herein, we review the specific host-pathogen interactions that contribute to cardiac dysfunction during invasive pneumococcal disease: (1) cell wall-mediated inhibition of cardiomyocyte contractility; (2) the new observation that S. pneumoniae is capable of translocation into the myocardium and within the heart, forming discrete, nonpurulent, microscopic lesions that are filled with pneumococci; and (3) the bacterial virulence determinants, pneumolysin and hydrogen peroxide, that are most likely responsible for cardiomyocyte cell death. Pneumococcal invasion of heart tissue is dependent on the bacterial adhesin choline-binding protein A that binds to laminin receptor on vascular endothelial cells and binding of phosphorylcholine residues on pneumococcal cell wall to platelet-activating factor receptor. These are the same interactions responsible for pneumococcal translocation across the blood-brain barrier during the development of meningitis. We discuss these interactions and how their neutralization, either with antibody or therapeutic agents that modulate platelet-activating factor receptor expression, may confer protection against cardiac damage and meningitis. Considerable collagen deposition was observed in hearts of mice that had recovered from invasive pneumococcal disease. We discuss the possibility that cardiac scar formation after severe pneumococcal infection may explain why individuals who are hospitalized for pneumonia are at greater risk for sudden death up to 1 year after infection.

Anti-ulcerogenic effect of methanolic extracts from Enicosanthellum pulchrum (King) Heusden against ethanol-induced acute gastric lesion in animal models

A natural source of medicine, Enicosanthellum pulchrum is a tropical plant which belongs to the family Annonaceae. In this study, methanol extract from the leaves and stems of this species was evaluated for its gastroprotective potential against mucosal lesions induced by ethanol in rats. Seven groups of rats were assigned, groups 1 and 2 were given Tween 20 (10% v/v) orally. Group 3 was administered omeprazole 20 mg/kg (10% Tween 20) whilst the remaining groups received the leaf and stem extracts at doses of 150 and 300 mg/kg, respectively. After an additional hour, the rats in groups 2-7 received ethanol (95% v/v; 8 mL/kg) orally while group 1 received Tween 20 (10% v/v) instead. Rats were sacrificed after 1 h and their stomachs subjected to further studies. Macroscopically and histologically, group 2 rats showed extremely severe disruption of the gastric mucosa compared to rats pre-treated with the E. pulchrum extracts based on the ulcer index, where remarkable protection was noticed. Meanwhile, a significant percentage of inhibition was shown with the stem extract at 62% (150 mg/kg) and 65% (300 mg/kg), whilst the percentage with the leaf extract at doses of 150 and 300 mg/kg was 63% and 75%, respectively. An increase in mucus content, nitric oxide, glutathione, prostaglandin E2, superoxide dismutase, protein and catalase, and a decrease in malondialdehyde level compared to group 2 were also obtained. Furthermore, immunohistochemical staining of groups 4-7 exhibited down-regulation of Bax and up-regulation of Hsp70 proteins. The methanol extract from the leaves and the stems showed notable gastroprotective potential against ethanol.

Safety and activity of dersalazine sodium in patients with mild-to-moderate active colitis: double-blind randomized proof of concept study

BACKGROUND

Dersalazine sodium is an inhibitor of platelet activator factor with potential efficacy in patients with ulcerative colitis through an alternative mechanism of action. The study was a first proof of clinical safety and activity of dersalazine sodium in patients with ulcerative colitis.

METHODS

A double-blind study of randomized patients with ulcerative colitis (Mayo score ≥ 5 and ≤ 10, including a sigmoidoscopy subscore ≥ 2) to dersalazine sodium 1200 mg/12 h, mesalazine 1200 mg/12 h, or placebo for 4 weeks. Mayo scores were calculated on week 2 (partial Mayo) and week 4 (full Mayo). All patients received open-label mesalazine for 4 additional weeks, and a final visit was done at week 8.

RESULTS

The study included 34 patients (13 dersalazine sodium, 10 mesalazine, and 11 placebo). Clinical remission was observed in 46.2% patients treated with dersalazine sodium versus 12.5% in mesalazine and 10% in placebo after 4 weeks of treatment. Colon biopsies showed significantly decreased expression of inflammatory genes in dersalazine sodium patients. Adverse events at least possibly related to treatment were observed in 23%, 12.5%, and 7.6% of patients receiving dersalazine sodium, mesalazine, and placebo, respectively; no serious adverse reactions were reported. Increased liver enzymes were reported in 2/13 patients receiving dersalazine sodium, with normal bilirubin levels; both returned to normal values on treatment interruption.

CONCLUSIONS

Studies in wider populations are needed to confirm the clinical activity of dersalazine sodium. Weekly measurements of liver function tests may be necessary for early detection of adverse events.

Serum metabolic profiling in inflammatory bowel disease

BACKGROUND

The inflammatory bowel diseases (IBD), Crohn's disease (CD), and ulcerative colitis (UC), are chronic inflammatory conditions of the gastrointestinal tract whose pathogenesis is not completely understood. (1)H nuclear magnetic resonance (NMR) spectroscopy of serum generates comprehensive metabolic profiles, reflecting systemic metabolism, which may be altered in disease states.

AIM

The aim of this study was to use (1)H NMR-based serum metabolic profiling in the investigation of CD patients, UC patients, and controls, potentially to provide insights into disordered metabolism in IBD, and into underlying mechanisms of disease.

METHODS

Serum metabolic profiles were acquired from 67 individuals (24 CD patients, 20 UC patients, and 23 healthy controls). The multivariate pattern-recognition techniques of principal components analysis (PCA) and partial least squares discriminant analysis with orthogonal signal correction (OSC-PLS-DA) were used to investigate differences between cohorts.

RESULTS

OSC-PLS-DA distinguished CD and UC cohorts with significant predictive accuracy, highlighting differences in lipid and choline metabolism. Metabolic profiles of both CD and UC cohorts, and the combined IBD cohort, differed significantly from controls: metabolites of importance in the OSC-PLS-DA models included lipoproteins (especially HDL cholesterol), choline, N-acetylglycoprotein, and amino acids.

CONCLUSIONS

(1)H NMR-based metabolic profiling has identified distinct differences in serum metabolic phenotype between CD and UC patients, as well as between IBD patients and controls.

Physiological functions and clinical implications of sphingolipids in the gut

Studies of sphingolipids have become one of the most rapidly advancing fields in the last two decades. These highly diverse lipids have been known to have multiple physiological functions and clinical implications in several diseases, including tumorigenesis, inflammation, atherosclerosis and neural degenerative diseases. Unlike other organs, sphingolipids in the intestinal tract are present not only as lipid constituents in the cells but also as dietary compositions for digestion in the lumen. The present review focuses on the presence of sphingolipids and their catalytic enzymes in the gut; the metabolism and the signaling effects of the metabolites and their impacts on barrier functions, cholesterol absorption, inflammatory diseases and tumor development in the gut.

Increased levels of homocysteine in patients with ulcerative colitis

AIM: To investigate serum levels of homocysteine (Hcys) and the risk that altered levels carry for thrombosis development in ulcerative colitis (UC) patients.

METHODS: 55 UC patients and 45 healthy adults were included. Hcys, vitamin B12 and folic acid levels were measured in both groups. Clinical history and thromboembolic events were investigated.

RESULTS: The average Hcys level in the UC patients was 13.3 ± 1.93 μmmol/L (range 4.60-87) and was higher than the average Hcys level of the control group which was 11.2 ± 3.58 μmmol/L (range 4.00-20.8) (P < 0.001). Vitamin B12 and folic acid average values were also lower in the UC group (P < 0.001). When multivariate regression analysis was performed, it was seen that folic acid deficiency was the only risk factor for hyperhomocysteinemia. Frequencies of thromboembolic complications were not statistically significantly different in UC and control groups. When those with and without a thrombosis history in the UC group were compared according to Hcys levels, it was seen that there were no statistically significant differences. A negative linear relationship was found between folic acid levels and Hcys.

CONCLUSION: We could not find any correlations between Hcys levels and history of prior thromboembolic events.

Expression of alkaline sphingomyelinase in yeast cells and anti-inflammatory effects of the expressed enzyme in a rat colitis model

Alkaline sphingomyelinase (Alk-SMase) is a key enzyme in the intestinal tract for digestion of dietary sphingomyelin (SM), which generates lipid messengers with cell-cycle regulating effects. The enzyme is significantly decreased in ulcerative colitis and colon cancer. Based on this information, we wanted to investigate whether the enzyme had preventive effects against murine colitis. We report herein a method to express a biologically active Alk-SMase from Pichia pastoris yeast cells. By using the expressed enzyme to treat a rat colitis model induced by dextran sulfate sodium, we found that intrarectal instillation of Alk-SMase once daily for 1 week significantly reduced the inflammation score and protected the colonic epithelium from inflammatory destruction. We found a tendency for decreased tumor necrosis factor (TNF)-alpha expression in the Alk-SMase-treated group. This study, for the first time, provides a method to produce the enzyme and shows the potential applicability of the enzyme in the treatment of inflammatory bowel diseases.

Reduced intracellular T-helper 1 interferon-gamma in blood of newly diagnosed children with Crohn's disease and age-related changes in Th1/Th2 cytokine profiles

Abnormal cytokine production by T-helper 1 (Th1)/T-helper 2 (Th2) lymphocytes has been implicated in the pathogenesis of inflammatory bowel disease (IBD). Few studies have examined Th1/Th2 cytokine status in pediatric IBD patients, and results have been inconsistent. We used flow cytometric detection of intracellular IFN-gamma/IL-4 cytokine production to investigate CD4+, Th1, and Th2 cells in the peripheral blood of children with untreated, newly diagnosed Crohn's disease (CD) (n = 23) and matched healthy controls (n = 49). Th1 cytokine levels were lower in CD patients compared with controls (p = 0.006) and strongly correlated with levels of albumin and hematocrit (r = 0.51, p = 0.007 and r = 0.35, p = 0.052, respectively). An age-dependent increase in Th1 cells was observed (p < 0.0005); however, no correlation was found between age, clinical end points, %CD4+, or Th2 cell numbers. In conclusion, the Th1 cytokine levels in blood are lower in early onset CD patients than in healthy children and are directly associated with disease-related clinical parameters. In future studies of pediatric IBD patients, it will be critical to consider the effect of age and disease progression on cytokine status in intestinal mucosa and peripheral blood.

Immune dysfunction in inflammatory bowel disease

Ulcerative colitis (UC) and Crohn's disease (CD) are idiopathic inflammatory bowel diseases (IBDs) that are characterized by chronic periods of exacerbation and remission. Research into the immunopathogenesis of IBD adds support to the theory that the disease results from a dysfunctional regulation of the immune system that leads to the polarization of intestinal immune cells toward a Th1 (T helper) response. The immunologic factors that mediate alterations in intestinal homeostasis and the development of intestinal mucosal inflammation have been at the forefront of IBD research. Cytokines, which are important regulators of leukocyte trafficking and apoptotic cell death, have emerged as essential immune molecules in the pathogenesis of IBD. In this study, recent advances in the understanding of the dynamism of cytokines and the consequences for mucosal immunity and inflammation in IBD are discussed. Furthermore, this study highlights the potential use of cytokines, anti-cytokine antibodies, and cytokine-related biologic therapies as novel targets for the treatment of IBD.

Use of herbal preparations in the treatment of oxidant-mediated inflammatory disorders

Complementary and alternative medicine (CAM) use has increased in popularity in recent years and herbal therapy alone is now a billion dollar market. For centuries herbs have been used as food and for medicinal purposes. Various herbs have been identified as possessing anti-inflammatory and antioxidative properties, and they are currently being used to treat inflammatory disorders as well as those caused by reactive oxygen species (ROS). Asthma, Alzheimer's disease, inflammatory bowel disease (IBD), rheumatoid arthritis (RA), and atherogenesis are all disorders where inflammation and ROS are involved in their pathogenesis. This review examines the pathogenesis of the above mentioned ROS-mediated inflammatory disorders, as well as discusses the antioxidant and anti-inflammatory mechanisms of various herbs and the clinical trials where herbs have been used to treat these disorders.

Intestinal alkaline sphingomyelinase hydrolyses and inactivates platelet-activating factor by a phospholipase C activity

Alkaline sphingomyelinase (alk-SMase) is a new member of the NPP (nucleotide pyrophosphatase/phosphodiesterase) family that hydrolyses SM (sphingomyelin) to generate ceramide in the intestinal tract. The enzyme may protect the intestinal mucosa from inflammation and tumorigenesis. PAF (platelet-activating factor) is a pro-inflammatory phospholipid involved in pathogenesis of inflammatory bowel diseases. We examined whether alk-SMase can hydrolyse and inactivate PAF. [3H]Octadecyl-labelled PAF was incubated with purified rat intestinal alk-SMase or recombinant human alk-SMase expressed in COS-7 cells. The hydrolytic products were assayed with TLC and MS. We found that alkSMase cleaved the phosphocholine head group from PAF and generated 1-O-alkyl-2-acetyl-sn-glycerol. Differing from the activity against SM, the activity against PAF was optimal at pH 7.5, inhibited by EDTA and stimulated by 0.1-0.25 mM Zn2+. The activity was abolished by site mutation of the predicted metal-binding sites that are conserved in all NPP members. Similar to the activity against SM, the activity against PAF was dependent on bile salt, particularly taurocholate and taurochenodeoxycholate. The V(max) for PAF hydrolysis was 374 mumol x h(-1) x (mg of protein)(-1). The hydrolysis of PAF and SM could be inhibited by the presence of SM and PAF respectively, the inhibition of PAF hydrolysis by SM being stronger. The PAF-induced MAPK (mitogen-activated protein kinase) activation and IL-8 (interleukin 8) release in HT-29 cells, and chemotaxis in leucocytes were abolished by alk-SMase treatment. In conclusion, alk-SMase hydrolyses and inactivates PAF by a phospholipase C activity. The finding reveals a novel function, by which alk-SMase may counteract the development of intestinal inflammation and colon cancer.

Hyperbaric oxygen enhances the efficiency of 5-aminosalicylic acid in acetic acid-induced colitis in rats

The aim of this study was to assess the efficiency of hyperbaric oxygen alone and in combination with 5-aminosalicylic acid in the acetic acid-induced colitis model, a well-known experimental model of inflammatory bowel disease in rats. Rats were randomly divided into five groups. In the noncolitis control group, rats were given isotonic saline, while in the other groups rats were treated by intracolonic administration of 4% acetic acid. In group 2, the untreated control group, no additional therapy was applied. In groups 3, 4, and 5 hyperbaric oxygen, 5-aminosalicylic acid. and 5-aminosalicylic acid + hyperbaric oxygen therapies were applied, respectively. Administration of acetic acid caused an inflammatory response in all animals. Histopathologic score was significantly higher in group 2 than in any other group. 5-Aminosalicylic acid and hyperbaric oxygen significantly decreased the histopathologic score (P < 0.05). Myeloperoxidase activity was also reduced significantly by 5-aminosalicylic acid (P < 0.05) but not by hyperbaric oxygen. The most prominent ameliorative effect, however, was seen in group 5 and the histopathologic score and myeloperoxidase activity were significantly lower than in groups 3 (P < 0.05) and 4 (P < 0.001). Hydroxyproline level also increased significantly in group 5, but not in groups 3 and 4 (P < 0.001). These findings indicate that hyperbaric oxygen therapy is effective in reducing the extent of colitis induced by acetic acid, although it is not as potent as 5-aminosalicylic acid. The combination of hyperbaric oxygen and 5-aminosalicylic acid, however, led to a much more prominent reduction in the severity of colitis. Hyperbaric oxygen may have a promising place in the treatment of inflammatory bowel disease.

Favorable response to subcutaneous administration of infliximab in rats with experimental colitis

AIM

To investigate the influence of infliximab (Remicade) on experimental colitis produced by 2,4,6,trinitrobenzene sulfonic acid (TNBS) in rats.

METHODS

Thirty-six Wistar rats were allocated into four groups (three groups of six animals each and a fourth of 12 animals). Six more healthy animals served as normal controls (Group 5). Group 1: colitis was induced by intracolonic installation of 25 mg of TNBS dissolved in 0.25 mL of 50% ethanol and infliximab was subcutaneously administered at a dose of 5 mg/kg BW; Group 2: colitis was induced and infliximab was subcutaneously administered at a dose of 10 mg/kg BW; Group 3: colitis was induced and infliximab was subcutaneously administered at a dose of 15 mg/kg BW; Group 4: colitis was induced without treatment with infliximab. Infliximab was administered on d 2-6. On the 7(th) d, all animals were killed. The colon was fixed in 10% buffered formalin and examined by light microscopy for the presence and activity of colitis and the extent of tissue damage. Tumor necrosis factor-alpha (TNF-alpha) and malondialdehyde (MDA) were also measured.

RESULTS

Significant differences concerning the presence of reparable lesions and the extent of bowel mucosa without active inflammation in all groups of animals treated with infliximab compared with controls were found. Significant reduction of the tissue levels of TNF-alpha in all groups of treated animals as compared with the untreated ones was found (0.47+/-0.44, 1.09+/-0.86, 0.43+/-0.31 vs 18.73+/-10.53 respectively). Significant reduction in the tissue levels of MDA was noticed in group 1 as compared to group 4, as well as between groups 2 and 4.

CONCLUSION

Subcutaneous administration of infliximab reduces the inflammatory activity as well as tissue TNF-alpha and MDA levels in chemical colitis in rats. Infliximab at a dose of 5 mg/kg BW achieves better histological results and produces higher reduction of the levels of TNF-alpha than at a dose of 10 mg/kg BW. Infliximab at a dose of 5 mg/kg BW produces higher reduction of tissue MDA levels than at a dose of 15 mg/kg BW.

Hyperhomocysteinemia in ulcerative colitis is related to folate levels

AIM: To study the prevalence and clinical significance of hyperhomocysteinemia (hHcys), an independent factor for arterial and venous thrombosis, in a group of patients with ulcerative colitis (UC).

METHODS: Fasting homocysteine (Hcys), folate, and vitamin B12 serum levels were measured in 40 UC patients and 50 healthy controls. Clinical data regarding UC were gathered.

RESULTS: Median serum Hcys levels in UC patients were similar to those in controls (12.26 µmol/L vs 12.32 µmol/L), but the prevalence of hHcys was higher in UC patients than in controls (30% vs 10%, P = 0.028). UC significantly increased the risk of hHcys (adjusted odds ratio: 4.125; 95%CI: 1.26-13.44). Multivariate regression analysis showed that male sex, folate and vitamin B12 deficiency or lower serum values were significant independent predictors of higher Hcys levels in UC patients (r² = 0.4; P<0.001).

CONCLUSION: hHcys is common in UC patients and it is related to folate and vitamin B12 deficiency or lower serum values. It would be reasonable for patients with UC to receive folate and vitamin B complex supplements as a prophylactic measure.

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.

Beneficial effect of a novel non-steroidal anti-inflammatory agent with basic character and antioxidant properties on experimental colitis in rats

Ulcerative colitis is a chronic disorder of unknown etiology. Conservative treatment remains empirical, even today. The aim of this study was to test the efficacy of a novel non-steroidal anti-inflammatory agent [5-(2-hydroxy-ethylamino)-1-cyclohexyl-2-pentanone] (compound A), with basic character and antioxidant properties on an experimental model of ulcerative colitis in rats. The effect of this compound was compared with that of methylprednisolone on the histological abnormalities and serum levels of tumor necrosis factor-alpha (TNF-alpha) in experimental colitis produced by 2,4,6-trinitrobenzenesulfonic acid (TNB). A total number of 24 rats were randomly assigned to one of four groups of six rats each. Group 1: colitis without treatment (disease control), group 2: normal animals (control), group 3: induction of experimental colitis treated with methylprednisolone (5.3 x 10(-3) mmol/kg i.v. every day for 7 days) and group 4: induction of experimental colitis plus administration of compound A (0.6 mmol/kg i.v. every day for 7 days). The administration of compound A resulted in a statistically significant reduction of the extent of tissue damage and of certain histological features (edema, inflammatory infiltration) (P<0.05). Compound A also resulted in a statistically significant reduction of the levels of serum TNF-alpha, compared to those of controls (P<0.005). The beneficial effect of this compound was probably due to the combination, on a single molecule, of anti-inflammatory and antioxidant properties as well as to its basic character. The reduction of the serum TNF-alpha levels could be one of the possible mechanism(s) of action of the compound. Further studies are necessary to establish the direct mechanism of action(s) of the drug and to evaluate its long-term efficacy and safety.

Coagulation factor XIII and markers of thrombin generation and fibrinolysis in patients with inflammatory bowel disease

OBJECTIVE

To relate factor XIII levels and other prothrombotic markers to inflammatory bowel disease and investigate the frequency of valine34leucine and its effect on factor XIII cross-linking activity in patients with inflammatory bowel disease.

DESIGN

Fifty patients with active inflammatory bowel disease but no venous thromboembolism (32 with ulcerative colitis, 18 with Crohn's disease), 50 patients with inactive inflammatory bowel disease but no venous thromboembolism (32 with ulcerative colitis, 18 with Crohn's disease), two age- and gender-matched healthy control groups of 100 subjects each were recruited. To further explore the relationship between valine34leucine and inflammatory bowel disease, 21 patients with the disease (13 with ulcerative colitis and eight with Crohn's disease) and venous thromoembolism (male to female ratio = 7 : 14, median age 59.5 years (range, 19-80 years)) were recruited. Two hundred and fifteen control subjects (M : F = 121 : 94, median age 62 years (28-74 years)), with venous thromboembolism (119 with deep venous thrombosis, and 96 with pulmonary embolism) were drawn from the same geographical area as the patients.

METHODS

Factor XIII A, B-subunit antigen and A2B2 tetramer levels were measured using an in-house sandwich enzyme-linked immunoassay method.

RESULTS

Factor XIII A2B2 tetramer and the A-subunit were significantly decreased in patients with active inflammatory bowel disease compared with controls (59% vs 95%, P < 0.0001 and 75% vs 102%, P < 0.0001, respectively), but not between the inactive inflammatory bowel disease group and controls. The D-dimer and prothrombin 1+2 fragment levels in patients with active inflammatory bowel disease were raised compared with controls (178 (152) vs 109 (84), P = 0.0007 and 82 (43) vs 55 (28), P = 0.0001, respectively). The factor XIII B-subunit and factor XIII cross-linking activity were not significantly different between patients with active or inactive inflammatory bowel disease and controls. There was no significant difference in genotype distribution in inflammatory bowel disease patients with or without venous thromboembolism and respective control subjects. Levels of tissue plasminogen activator antigen were significantly increased in patients with active inflammatory bowel disease when compared to inactive inflammatory bowel disease and controls (8.9 (3.7) vs 6.7 (3.4) vs 6.9 (3.4), P < 0.001).

CONCLUSIONS

Active inflammatory bowel disease is associated with activation of coagulation. Factor XIII A and A2B2 tetramer levels were markedly decreased in active inflammatory bowel disease. Variations in the level of factor XIII in patients with inflammatory bowel disease could be multifactorial and in part may result from the increased formation of microthrombi and accelerated turnover of the factor XIII. We found no evidence of association of factor XIII valine34leucine polymorphism and inflammatory bowel disease.

Novel azo derivatives as prodrugs of 5-aminosalicylic acid and amino derivatives with potent platelet activating factor antagonist activity

This paper describes the synthesis of a series of azo compounds able to deliver 5-aminosalicylic acid (5-ASA) and a potent platelet activating factor (PAF) antagonist in a colon-specific manner for the purpose of treating ulcerative colitis. We found it possible to add an amino group on the aromatic moiety of our reported 1-[(1-acyl-4-piperidyl)methyl]-1H-2-methylimidazo[4,5-c]pyridine derivatives or on British Biotech compounds BB-882 and BB-823 maintaining a high level of activity as PAF antagonist. A selected compound UR-12715 (49c) showed an IC(50) of 8 nM in the in vitro PAF-induced aggregation assay, and an ID(50) of 29 microg/kg in the in vivo PAF-induced hypotension test in normotensive rats. Through attachment of 49c to the 5-ASA via azo functionality we obtained UR-12746 (70). Pharmacokinetics experiments with [14C]-70 allow us to reach the following conclusions, critical in the design of these new prodrugs of 5-ASA. Neither the whole molecule 70 nor the carrier 49c were absorbed after oral administration of [14C]-70 in rat as was demonstrated by the absence of plasma levels of radioactivity and the high recovery of it in feces. Effective cleavage of azo bond (84%) by microflora in the colon is achieved. These facts ensure high topical concentrations of 5-ASA and 49c in the colon. Additionally, 70 exhibited a potent anticolitic effect in the trinitrobenzenesulfonic acid-induced colitis model in the rat. This profile suggests that UR-12746 (70) provides an attractive new approach to the treatment of ulcerative colitis.

Platelet-activating factor and endotoxin activate CCAAT/enhancer binding protein in rat small intestine

The transcription factor family CCAAT/enhancer binding proteins (C/EBP) is involved in inflammation via the regulation of the gene expression of various pro-inflammatory cytokines and proteins. PAF and endotoxin (lipopolysaccharide, LPS) are known agents causing intestinal inflammation and injury. In this study, we examined the binding activity of C/EBP isoforms in rat small intestine in response to PAF (1.5 microg kg(-1), i.v.) or LPS (5 mg kg(-1), i.v.). We found that C/EBP is constitutively active in normal small intestine, mainly as C/EBP-alpha and beta (C/EBP-beta>alpha). Both C/EBP-alpha and beta are localized in the intestinal epithelial cells: C/EBP-alpha mainly in the crypts, and C/EBP-beta in both villi and crypts, as well as in some lamina propria cells. Only minute amounts of C/EBP-delta were found. PAF rapidly upregulates the binding activity of C/EBP-alpha and beta within 30 min. The increase in C/EBP-alpha is prominent in the crypt cells, whereas the change of C/EBP-beta is more widespread. LPS also increases the binding activity of C/EBP-alpha and beta, and the response is slower than PAF. PAF synergizes with LPS to markedly activate all three subunits. The increase in C/EBP-alpha is transient, whereas the other two have a sustained elevation until 120 min. After challenge with PAF (but not LPS), small amounts of nuclear factor -kappaB (NF-kappaB) p50 and p65 subunits are found in the C/EBP-DNA binding complex, indicating cross-dimerization of the two transcription families. Pretreatment of rats with pyrrolidine dithiocarbamate (PDTC) suppresses LPS-, but not PAF-, induced NF-kappaB and C/EBP binding activity, and significantly increases the C/EBP-delta subunit in LPS- or PAF-induced C/EBP complex. These results suggest that PAF and LPS activate intestinal C/EBP in vivo, probably via different pathways.

Intestinal anti-inflammatory activity of UR-12746, a novel 5-ASA conjugate, on acute and chronic experimental colitis in the rat

The present study was undertaken to investigate the intestinal anti-inflammatory effects of UR-12746 on the acute and chronic stages of a trinitrobenzene sulphonic acid (TNBS) experimental model of inflammatory bowel disease (IBD) in the rat. UR-12746 is a novel, locally-acting compound which combines, through an azo bond, 5-aminosalicylic (5-ASA) and UR-12715, a potent platelet activating factor (PAF)-antagonist. UR-12746 oral pretreatment of colitic rats (50 and 100 mg kg(-1)) reduced acute colonic damage when evaluated 2 days after colonic insult. Postreatment for 4 weeks with UR-12746 (50 and 100 mg kg(-1)) resulted in a faster recovery of the damaged colonic mucosa, which was macroscopically significant from the third week. The intestinal anti-inflammatory effect of UR-12746 was associated with a decrease in leukocyte infiltration in the colonic mucosa, which was evidenced both biochemically, by a reduction in myeloperoxidase activity, and histologically, by a lower leukocyte count after morphometric analysis. This effect was higher than that seen with sulphasalazine, when assayed at the same doses and in the same experimental conditions. Several mechanisms can be involved in the beneficial effects showed by UR-12746: inhibition of leukotriene B(4) synthesis in the inflamed colon, improvement of the altered colonic oxidative status, and reduction of colonic interleukin-1beta production. The results suggest that the intestinal anti-inflammatory activity of UR-12746 can be attributed to the additive effects exerted by 5-ASA and UR-12715, the PAF antagonist compound, that are released in the colonic lumen after reduction of the azo bond by the intestinal bacteria.

Proliferative response of different human osteoblast-like cell models to proinflammatory cytokines

Children with inflammatory bowel disease are known to be at risk of osteopenia. The cause of this osteopenia is likely to be multifactorial, but the inflammatory process with its characteristic overproduction of cytokines has been implicated. To investigate this possible contribution of the disease activity to the development of osteopenia, we performed in vitro assays of the proliferation of osteoblast-like cells of differing origins in response to the inflammatory cytokines tumor necrosis factor-alpha and IL-1/beta. Osteoblast-like cells derived from pediatric bone explants, adherent stromal cells derived from bone marrow (osteoprogenitors), MG-63 osteosarcoma cells, and SV-40 virally transformed osteoprogenitor cells (HCC1) were studied. Tumor necrosis factor-alpha stimulated the proliferation of cells in primary cultures (i.e. from explants and marrow samples) in a linear, dose-dependent manner. In contrast, inhibition of proliferation was observed with the established cell lines (MG-63 and HCC1). IL-1beta stimulated proliferation of all cells apart from the immortalized human bone marrow cell line, HCC1, in which case potent inhibition was observed. We conclude that proinflammatory cytokines are potent regulators of osteoblast-like cell proliferation, and that the responses are specific to cell type. The opposite results obtained with established cell lines compared with the primary cultures suggest that careful consideration should be given to choosing the most suitable cell line for in vitro studies relating to in vivo mechanisms predisposing to osteopenia.

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).

Study of the mechanisms of acupuncture and moxibustion treatment for ulcerative colitis rats in view of the gene expression of cytokines

AIM: To observe the effect of acupuncture and moxibustion on the expression of IL-1β and IL-6 mRNA in ulcerative colitis rats.

METHODS: The SD rat ulcerative colitis model was created by immunological method associated with local stimulation. Colonic mucosa was prepared from human fresh surgical colonic specimens, homogenized by adding appropriate amount of normal saline and centrifuged at 3000 r/min. The supernatant was collected for measurement of protein conentration and then mixed with Freund adjuvant. This antigen fluid was first injected into the plantae of the model group rats, and then into their plantae, dorsa, inguina and abdominal cavities (no Freund adjuvant for the last injection) again on the 10th, 17th, 24th and 31st day. When a certain titer of serum anti-colonic anti body was reached, 2% formalin and antigen fluid ( no Freund adjuvant ) were administered separately by enema. The ulcerative colitis rat model was thus set up. The animals were randomly divided into four groups: model control group ( MC, n = 8 ), electro-acupuncture group (EA, n = 8), herbs-partition moxibustion group (HPM 8), normal control group ( NC, n = 8 ). HPM: Moxa cones made of refined mugwort floss were placed on the medicinal pad (medicinal pad dispensing: Radix Aconiti praeparata, cortex Cinnamomi, etc) for Qihai (RN 6) and Tianshu (S T 25, bilateral) and ignited. Two moxa cones were used for each acupoint once a day and 14 times in all. EA: Tianshu (bilateral) and Qihai were stimulated by the intermittent pulse with 2 Hz frequency, 4mA intensity for 20 min once a day and 14 times in all. After treatment, rats of all four groups were killed simultaneously. The spleen was separated and the distal colon was dissected. Total tissue RNA was isolated by the guanidinium thiocyanate phenol-chloroform extraction method. RT-PCR technique was used to study the expression of IL-1β and IL-6 mRNA.

RESULTS: IL-1β and IL-6 mRNAs were not detected in the spleen and colonic mucosa of the NC rats, whereas they were significantly expressed in that of the MC rats. IL-1β and IL-6 mRNAs we re markedly lower in the EA and HPM rats than that in MC rats. There was no significant difference between the levels of IL-1β and IL-6 mRNAs in the EA and HPM rats. The expressions of IL-1β and IL-6 mRNAs were nearly the same in the spleen and colon of all groups.

CONCLUSION: Acupuncture and moxibustion greatly inhibited the expression of IL-1β and IL-6 mRNA in the experimental ulcerative colitis rats.

Combined treatment with endothelin- and PAF-antagonists reduces posttransplant lung ischemia/reperfusion injury

BACKGROUND

Pathophysiologic changes of posttransplant lung ischemia/reperfusion injury are mediated by redundant cellular and humoral mechanisms. We investigated the protective effect of combined administration of platelet activating factor (PAF) and endothelin (ET) antagonists after prolonged ischemia in a small animal lung transplantation model.

METHODS

Orthotopic left lung transplantation was performed after 20 hours cold ischemia in male Fischer (F344) rats weighing 200-250 g. Group I served as control. In Group II, donors received 1 mg/kg body weight of the endothelin antagonist TAK-044, and recipients 2 mg/kg. Group III was treated with the PAF antagonist TCV-309 (donor: 50 microg/kg; recipient: 100 microg/kg) (Takeda Chemicals Ltd.). Group IV received a combined treatment with both substances at the same dosage. Twenty-four hours after reperfusion, the native contralateral lung was occluded to assess gas exchange of the graft only, and 5 minutes later the thoracic aorta was punctured for arterial blood gas analysis (n = 5). In other animals (n = 5), lung tissue was frozen 24 hours after reperfusion and assessed for myeloperoxidase activity (MPO) and thiobarbituric acid reactive substances.

RESULTS

Combined inhibition of PAF and ET-1 at the receptor level resulted in significantly improved graft function as compared to controls (Group I), and to groups treated with either TAK-044 or TCV-309. This was determined by a higher arterial oxygen content (112 +/- 9 mmHg, p = .00061 vs control, 48 +/- 5 mmHg), reduced MPO activity (0.35 +/- 0.02 deltaOD/mg/min, p = .000002 vs control, 1.1 +/- 0.1 deltaOD/mg/min) and reduced lipid peroxidation (59.5 +/- 2.5 pmol/g, p = .011 vs control, 78.5 +/- 4.1 pmol/g). The improvement of arterial oxygen (Group II 77 +/- 10 mmHg, p = .027 vs control; Group III 84 +/- 8 mmHg, p = .0081 vs control) and reduction of MPO activity (Group II 0.85 +/- 0.061 deltaOD/mg/min, p = .017; Group III 0.92 +/- 0.079 deltaOD/mg/min, p = .058) in groups treated with either a PAF antagonist or an ET antagonist was significantly less than in Group IV.

CONCLUSIONS

Combined donor and recipient treatment with an ET antagonist and a PAF antagonist results in superior posttransplant graft function 24 hours after reperfusion, suggesting a synergistic role of ET-1 and PAF in the mediation of reperfusion injury in this model. Single treatment with either of the antagonists revealed only a slight improvement compared to untreated controls.

The influence of cigarette smoking on cytokine levels in patients with inflammatory bowel disease

Anecdotal reports suggest that smoking may be beneficial for patients with inflammatory bowel disease (IBD) as nicotine may act through inflammatory mediators within the colonic mucosa. Furthermore, there is increasing evidence that cytokines play a pathologic role in IBD. Our aim was to determine the effects of cigarette smoking on cytokine levels in the colonic mucosa of patients with and without IBD. Mucosal biopsies were obtained from 10 patients with Crohn's disease (CD), 10 with ulcerative colitis (UC), and 10 healthy controls. Five of 10 patients in each of the three groups were smokers and five were nonsmokers. Concentrations of interleukin (IL)-1beta, IL-2, IL-6, and IL-8 were determined using enzyme-linked immunosorbent assay (ELISA). Cytokine levels of smokers were compared with nonsmokers in each group and with controls. Results were analyzed using the Mann-Whitney test; significance was set at p<0.05. The concentration of IL-8 was significantly higher in healthy controls who smoke compared with nonsmokers and significantly reduced in smokers with CD compared with nonsmokers with CD. Moreover, concentrations of IL-1beta and IL-8 were significantly reduced in smokers with UC compared with nonsmokers with UC. Smokers had significantly elevated levels of IL-8 in the colonic mucosa. Smokers with IBD had a significant reduction in cytokine levels; specifically, IL-1beta and IL-8 for patients with UC and IL-8 for patients with CD. Further studies are warranted to determine if this reduction in cytokine levels is histologically and clinically significant.

The factor V Leiden mutation increases the risk of venous thrombosis in patients with inflammatory bowel disease

BACKGROUND & AIMS

Thromboembolic disease is a significant cause of morbidity and mortality in patients with inflammatory bowel disease (IBD). The aim of this study was to determine the incidence and possible association of the factor V Leiden mutation with the development of thrombosis in patients with IBD.

METHODS

This retrospective study included 11 patients with IBD and arterial or venous thrombosis and 51 patients with IBD and no history of thrombosis who were matched for age, sex, ethnic/racial origin, and type of IBD (controls). The presence of the factor V Leiden mutation was determined by coagulation assay and confirmed by a polymerase chain reaction method.

RESULTS

Four of 11 IBD patients (36%) with thrombosis and 2 of 51 IBD controls (4%) were heterozygotes for the factor V Leiden mutation (relative risk, 14.00; 95% confidence interval, 1.55-169.25; P = 0.009, Fisher exact test). All thrombotic events in the patients with activated protein C resistance were venous with a calculated prevalence of 50% (4 of 8 patients) and a relative risk of venous thrombosis in IBD patients with factor V Leiden of 23 (95% confidence interval, 2-294; P = 0.005).

CONCLUSIONS

In patients with IBD, inheritance of the factor V Leiden mutation results in a significant increased risk of venous thrombosis.

The GM2 activator protein, its roles as a co-factor in GM2 hydrolysis and as a general glycolipid transport protein

Although there is only one documented function carried out by the GM2 activator protein in the lysosome, new information suggests that other less obvious roles may also be played by this protein in vivo. This information includes data demonstrating that the GM2 activator is a secretory, as well as a lysosomal protein, and that cells possess a carbohydrate-independent mechanism to re-capture the activator, with or without bound lipid, from the extracellular fluid. Additionally the GM2 activator has been shown to bind, solubilize and transport a broad spectrum of lipid molecules, such as glycolipids, gangliosides and at least one phosphoacylglycerol, between liposomes. At pH 7 the GM2 activator's rate of lipid transport is reduced by only 50% from its maximum rate which is achieved at approx. pH 5, suggesting that the GM2 activator may serve as a general intra- and/or inter-cellular lipid transport protein in vivo. Since the late 1970s the lysosomal form of the GM2 activator has been known to act as a substrate-specific co-factor for the hydrolysis of GM2 ganglioside by beta-hexosaminidase A. Gangliosides are a class of negatively charged glycolipids particularly abundant in neuronal cells which have been linked to numerous in vivo functions, such as memory formation and signal transduction events. Deficiency of the GM2 activator protein results in the storage of GM2 ganglioside and severe neurological disease, the AB-variant form of GM2 gangliosidosis, usually culminating in death before the age of 4 years. The exact mode-of-action of the GM2 activator in its role as a co-factor, and its specificity for various glycolipids are currently matters of debate in the literature.

Serum leptin in children and young adults with inflammatory bowel disease

BACKGROUND

Pediatric inflammatory bowel disease is often associated with growth failure and inadequate energy intake. Although several circulating cytokines are known to be elevated in inflammatory bowel disease, the mechanism for the related anorexia has not been described. Leptin is a newly recognized circulating protein that is an important regulator of appetite and energy metabolism; leptin levels are elevated in several animal models of inflammation. This study was conducted to determine whether serum leptin levels are elevated in young patients with inflammatory bowel disease.

METHODS

One hundred twelve children and young adults with Crohn's disease or ulcerative colitis were studied prospectively. Forty-two patients with other gastrointestinal illnesses were used as control subjects. Height, weight, erythrocyte sedimentation rate, serum albumin concentration, and clinical information were collected prospectively, and leptin was measured by radioimmunoassay of stored serum.

RESULTS

No significant differences in leptin levels were found among disease groups or control subjects. Body mass index and gender were the only independent predictors of serum leptin in all groups examined. Disease activity varied inversely with serum leptin in patients with Crohn's disease, but these differences were explained entirely by variations in body mass index.

CONCLUSIONS

The determinants of serum leptin were the same in young patients with inflammatory bowel disease as in normal populations, indicating that alterations in leptin levels are unlikely to mediate the anorexia and growth failure associated with this disease.

Investigation of the effects of platelet-activating factor (PAF) on ion transport and prostaglandin synthesis in human colonic mucosa in vitro

1 We have investigated the effects of platelet-activating factor (PAF), an endogenous mediator of inflammation, on ion transport and prostaglandin synthesis in the human isolated colon. 2 Application of PAF to the serosal surface of human colonic mucosa induced a marked, concentration-dependent increase in ion transport. Mucosal application was without effect. 3 The secretory response to PAF was significantly inhibited by prior application of a specific PAF receptor antagonist WEB 2170, indicating that the response is dependent on PAF receptor activation. 4 The response to PAF was attenuated by prior application of indomethacin or piroxicam, implicating products of the cyclo-oxygenase pathway in the response. 5 The response to PAF was attenuated by the loop diuretic bumetanide, indicating an involvement of chloride ion secretion in the response. 6 Addition of PAF to the serosal surface induced a significant increase in serosal prostaglandin E2 (PGE2), but not 6-oxo-PGF1alpha release. There was no effect on mucosal application of PAF. 7 In summary, we have shown that PAF is a potent secretagogue in isolated preparations of human colon and that the response is dependent on a specific PAF receptor, cyclo-oxygenase products and bumetanide-sensitive chloride ion transport.

Platelet-activating factor (PAF) up-regulates plasma and tissue PAF-acetylhydrolase activity in the rat: effect of cycloheximide

Platelet-activating factor (PAF) is a proinflammatory phospholipid mediator implicated in necrotizing enterocolitis. Regulation of PAF-acetylhydrolase (AH), the enzyme degrading PAF, is poorly understood. In this study we found that administration of a dose of PAF (1.5 microg/kg, i.v.), which does not cause gross intestinal injury, increased plasma and intestinal PAF-AH in the rat. Cycloheximide (CHX, 5 mg/kg, i.v.) reduced the activity of plasma (but not intestinal tissue) AH in control, as well as in PAF-injected rats, and aggravated systemic inflammation and tissue injury in the latter. The intestinal necrosis induced by PAF and CHX was ameliorated by posttreatment with WEB2170 (a PAF antagonist), indicating a role of endogenous PAF in mediating injury. Both WEB2170 and anti-TNF antibody reduced PAF-induced AH activity in intestinal tissue, but not in the plasma. Allopurinol largely prevented the injury induced by PAF and CHX, but had no effect on the up-regulation of AH. We conclude: 1) de novo protein synthesis is required to maintain physiologic AH level in the plasma; 2) PAF up-regulates plasma and intestinal AH activity; 3) CHX enhances the injurious effect of PAF; 4) endogenous PAF and TNF also play a role in the up-regulation of intestinal AH; the former probably mediating the intestinal injury by PAF; and 5) reactive oxygen species may mediate the injurious effect of PAF plus CHX, but do not contribute to the regulation of AH by PAF.

The effect of trinitrobenzene sulfonic acid on gut-derived smooth muscle cell arachidonic acid metabolism: role of endogenous prostanoids

The contribution of smooth muscle cells as a potential source of eicosanoid production during inflammatory states remains to be elucidated. We investigated the effect of trinitrobenzene sulfonic acid (TNB), a known pro-inflammatory agent, on jejunal smooth muscle cell eicosanoid production. Human gut-derived smooth muscle cells (HISM) were incubated with TNB for 1 hour. Additionally, some cells were preincubated with either dimethylthiourea, or indomethacin for 1 hour before exposure to identical concentrations of TNB. Incubation with TNB led to significant increases in PGE₂ and 6-keto PGF-1_α release, but not leukotriene B₄ release; responses which were both inhibited by dimethylthiourea and indomethacin treatment. Our results suggest that gutderived smooth muscle cells may represent an important source of proinflammatory prostanoids but not leukotrienes during inflammatory states of the intestine. The inhibition of prostanoid activity by thiourea may be mediated by suppression of cyclooxygenase activity in this cell line.