Role of eicosanoids as mediators of inflammation in inflammatory bowel disease

Involvement of Proinflammatory Arachidonic Acid (ARA) Derivatives in Crohn’s Disease (CD) and Ulcerative Colitis (UC)

Recently, an increase in the incidence of inflammatory bowel disease (IBD) has been observed, especially among children and adolescents. Currently, few studies focus on the differentiation of inflammation in IBD subunits, i.e., Crohn’s Disease (CD) and Ulcerative Colitis (UC). The aim of this study was to compare the concentrations of proinflammatory mediators of arachidonic acid (ARA) and linoleic acid (LA) in patients with CD (n = 34) and UC (n = 30), in order to identify differences in inflammation in both diseases and within the same entity, according to disease activity. Sixty-four adolescents with a mean age of 13.76 ± 2.69 and 14.15 ± 3.31, for CD and UC, respectively, were enrolled in the study. Biochemical analysis of ARA and LA derivatives was performed using a liquid chromatography. A trend was observed in the concentration of 15S-HETE (hydroxyeicosatetraenoic acids) in CD relative to UC. The active phase of both diseases showed a higher 15S-HETE concentration in active CD relative to active UC. Comparing patients with CD with active and inactive disease showed a trend of increased levels of thromboxane B2, leukotriene B4 and 9S-HODE (hydroxyoctadecadienoic acid) in the active versus the inactive disease. We also observed statistically significantly higher levels of 12S-HETE in inactive CD relative to active CD. In the UC group, on the other hand, statistically significantly higher levels of prostaglandin E2 and 16RS-HETE were observed in active UC relative to inactive UC. Moreover, significantly higher concentrations of LTX A4 5S, 6R were observed in inactive UC relative to the active phase. In conclusion, the present study indicated the activity of the 15-LOX pathway in CD. Further studies involving lipid mediators in patients with IBD may contribute to the development of new therapies for the treatment of IBD. The identification of differences in the course of inflammation may help to target therapy in CD and UC, and perhaps allow the introduction of an additional diagnostic marker between the two main IBD subtypes.

Clinical Pharmacokinetic and Pharmacodynamic Considerations in the Treatment of Inflammatory Bowel Disease

According to recent clinical consensus, pharmacotherapy of inflammatory bowel disease (IBD) is, or should be, personalized medicine. IBD treatment is complex, with highly different treatment classes and relatively few data on treatment strategy. Although thorough evidence-based international IBD guidelines currently exist, appropriate drug and dose choice remains challenging as many disease (disease type, location of disease, disease activity and course, extraintestinal manifestations, complications) and patient characteristics [(pharmaco-)genetic predisposition, response to previous medications, side-effect profile, necessary onset of response, convenience, concurrent therapy, adherence to (maintenance) therapy] are involved. Detailed pharmacological knowledge of the IBD drug arsenal is essential for choosing the right drug, in the right dose, in the right administration form, at the right time, for each individual patient. In this in-depth review, clinical pharmacodynamic and pharmacokinetic considerations are provided for tailoring treatment with the most common IBD drugs. Development (with consequent prospective validation) of easy-to-use treatment algorithms based on these considerations and new pharmacological data may facilitate optimal and effective IBD treatment, preferably corroborated by effectiveness and safety registries.

Molecular mechanism of plant stress hormone methyl jasmonate for its anti-inflammatory activity

Plant stress hormones (Phytohormones/PTH) are abundantly present in numerous vascular plants. Several classes of plant stress hormones like auxins (AU) & gibberellins (GA), cytokinins (CK), abscisic acid (ABA), ethylene (ET), salicylic acid (SA), jasmonates (JA), brassinosteroids (BR) and strigolactones are synthesized within specialized plant cells. Among them, jasmonate are prominent class of stress hormones involved in survival of plants in stressful conditions. Methyl jasmonate (MeJA) is ester of jasmonic acid is extensively studied for its potential clinical benefits. MeJA is used as an effective antimicrobial agent, food preservative, antioxidant in food and agricultural sectors. The clinical benefits of MeJA have been related to their prominent interactions with inflammatory NF-κB pathways, inhibition of enzymes, gene expression for synthesis of inflammatory mediators, signaling molecules, oxidative stress and modulation of pain perception/nociceptive responses. The objective of the present review is to provide an cohesive relation of MeJA in inflammation with reference to past and recent in-vivo and in-vitro investigations in broad perspectives.

Phytotherapies in inflammatory bowel disease

Inflammatory bowel disease (IBD) has been considered as a group of heterogeneous intestinal diseases that affects multiple organs outside of the gastrointestinal tract and is due to an uncontrolled inflammatory response mediated by the immune system. The IBD etiology has not been clearly defined, and it is considered as a multifactorial disease. Due to side effects of some conventional therapies, the consumption of complementary and alternative medicines, and in particular, the herbal therapy, more than before is increasing. Herbal therapy results for management of IBD by various mechanisms including leukotriene B4 inhibition, antioxidant activity, immune system regulation of nuclear factor-kappa B, as well as antiplatelet activity are favorable, and no unfortunate events have been yet reported. In this article, we aimed to review and report the herbal therapies established for management of human IBD or evaluated by animal IBD models. Their possible mechanisms of actions are also discussed.

Dietary protocatechuic acid ameliorates dextran sulphate sodium-induced ulcerative colitis and hepatotoxicity in rats

The present study investigated the antioxidant and anti-inflammatory effects of dietary protocatechuic acid (PCA), a simple hydrophilic phenolic compound commonly found in many edible vegetables, on dextran sulphate sodium (DSS)-induced ulcerative colitis and its associated hepatotoxicity in rats. PCA was administered orally at 10 mg kg(-1) to dextran sulphate sodium exposed rats for five days. The result revealed that administration of PCA significantly (p < 0.05) prevented the incidence of diarrhea and bleeding, the decrease in the body weight gain, shortening of colon length and the increase in colon mass index in DSS-treated rats. Furthermore, PCA prevented the increase in the plasma levels of pro-inflammatory cytokines, markers of liver toxicity and markedly suppressed the DSS-mediated elevation in colonic nitric oxide concentration and myeloperoxidase activity in the treated rats. Administration of PCA significantly protected against colonic and hepatic oxidative damage by increasing the antioxidant status and concomitantly decreased hydrogen peroxide and lipid peroxidation levels in the DSS-treated rats. Moreover, histological examinations confirmed PCA chemoprotection against colon and liver damage. Immunohistochemical analysis showed that PCA significantly inhibited cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) protein expression in the colon of DSS-treated rats. In conclusion, the effective chemoprotective role of PCA in colitis and the associated hepatotoxicity is related to its intrinsic anti-inflammatory and anti-oxidative properties.

Serum Fatty Acids Are Correlated with Inflammatory Cytokines in Ulcerative Colitis

Background and Aims

Ulcerative colitis (UC) is associated with increased dietary intake of fat and n-6 polyunsaturated fatty acids (PUFA). Modification of fat metabolism may alter inflammation and disease severity. Our aim was to assess differences in dietary and serum fatty acid levels between control and UC subjects and associations with disease activity and inflammatory cytokines.

Methods

Dietary histories, serum, and colonic tissue samples were prospectively collected from 137 UC subjects and 38 controls. Both histologic injury and the Mayo Disease Activity Index were assessed. Serum and tissue cytokines were measured by Luminex assay. Serum fatty acids were obtained by gas chromatography.

Results

UC subjects had increased total fat and oleic acid (OA) intake, but decreased arachidonic acid (AA) intake vs controls. In serum, there was less percent saturated fatty acid (SFA) and AA, with higher monounsaturated fatty acids (MUFA), linoleic acid, OA, eicosapentaenoic acid (EPA), and docosapentaenoic acid (DPA) in UC. Tissue cytokine levels were directly correlated with SFA and inversely correlated with PUFA, EPA, and DPA in UC subjects, but not controls. 5-aminosalicylic acid therapy blunted these associations.

Conclusions

In summary, we found differences in serum fatty acids in UC subjects that correlated with pro-inflammatory tissue cytokines. We propose that fatty acids may affect cytokine production and thus be immunomodulatory in UC.

Recent discoveries on absorption of dietary fat: Presence, synthesis, and metabolism of cytoplasmic lipid droplets within enterocytes

Dietary fat provides essential nutrients, contributes to energy balance, and regulates blood lipid concentrations. These functions are important to health, but can also become dysregulated and contribute to diseases such as obesity, diabetes, cardiovascular disease, and cancer. Within enterocytes, the digestive products of dietary fat are re-synthesized into triacylglycerol, which is either secreted on chylomicrons or stored within cytoplasmic lipid droplets (CLDs). CLDs were originally thought to be inert stores of neutral lipids, but are now recognized as dynamic organelles that function in multiple cellular processes in addition to lipid metabolism. This review will highlight recent discoveries related to dietary fat absorption with an emphasis on the presence, synthesis, and metabolism of CLDs within this process.

Botanical Drugs as an Emerging Strategy in Inflammatory Bowel Disease: A Review

Crohn's disease and ulcerative colitis are the two most common categories of inflammatory bowel disease (IBD), which are characterized by chronic inflammation of the intestine that comprises the patients' life quality and requires sustained pharmacological and surgical treatments. Since their aetiology is not completely understood, nonfully efficient drugs have been developed and those that show effectiveness are not devoid of quite important adverse effects that impair their long-term use. Therefore, many patients try with some botanical drugs, which are safe and efficient after many years of use. However, it is necessary to properly evaluate these therapies to consider a new strategy for human IBD. In this report we have reviewed the main botanical drugs that have been assessed in clinical trials in human IBD and the mechanisms and the active compounds proposed for their beneficial effects.

Leukotriene C4 increases the susceptibility of adult mice to Shiga toxin-producing Escherichia coli infection

Shiga toxin-producing Escherichia coli (STEC) is a food-borne pathogen that causes hemorrhagic colitis. Under some circumstances, Shiga toxin (Stx) produced within the intestinal tract enters the bloodstream, leading to systemic complications that may cause the potentially fatal hemolytic-uremic syndrome (HUS). Despite STEC human infection is characterized by acute inflammation of the colonic mucosa, little is known regarding the role of proinflammatory mediators like cysteine leukotrienes (cysLTs) in this pathology. Thus, the aim of this work was to analyze whether leukotriene C4 (LTC4) influences STEC pathogenesis in mice. We report that exogenous LTC4 pretreatment severely affected the outcome of STEC gastrointestinal infection. LTC4-pretreated (LTC4+) and STEC-infected (STEC+) mice showed an increased intestinal damage by histological studies, and a decreased survival compared to LTC4-non-pretreated (LTC4-) and STEC+ mice. LTC4+/STEC+ mice that died after the infection displayed neutrophilia and high urea levels, indicating that the cause of death was related to Stx2-toxicity. Despite the differences observed in the survival between LTC4+ and LTC4- mice after STEC infection, both groups showed the same survival after Stx2-intravenous inoculation. In addition, LTC4 pretreatment increased the permeability of mucosal intestinal barrier, as assessed by FITC-dextran absorption experiments. Altogether these results suggest that LTC4 detrimental effect on STEC infection is related to the increased passage of pathogenic factors to the bloodstream. Finally, we showed that STEC infection per se increases the endogenous LTC4 levels in the gut, suggesting that this inflammatory mediator plays a role in the pathogenicity of STEC infection in mice, mainly by disrupting the mucosal epithelial barrier.

Leukotriene D4-induced Caco-2 cell proliferation is mediated by prostaglandin E2 synthesis

Leukotriene D₄ (LTD₄) is a pro-inflammatory mediator formed from arachidonic acid through the action of 5-lipoxygenase (5-LOX). Its biological effects are mediated by at least two G-coupled plasmatic cysteinyl LT receptors (CysLT_1-2R). It has been reported an upregulation of the 5-LOX pathway in tumor tissue unlike in normal colon mucosa. Colon tumors generally have an increased expression of CysLT₁R and colon cancer patients with high expression levels of CysLT₁R have poor prognosis. We previously observed that the cyclooxygenase pathway is involved in the control of intestinal epithelial cancer cell growth through PGE₂ production. The aim of this study was therefore to assess the effect of LTD₄ binding with CysLT₁R on Caco-2 cell growth. We note a number of key findings from this research. We observed that at a concentration similar to that found under inflammatory conditions, LTD₄ was able to induce Caco-2 cell proliferation and DNA synthesis. Moreover, with the use of a specific receptor antagonist this study has demonstrated that the effect of LTD₄ is a result of its interaction with CystLT₁R. We also note the possible participation of the PLC-IP₃-Ca²⁺/DAG-PKC signaling pathways in cytosolic PLA₂ and [³H]AA release induced by LTD₄-CystLT₁R interaction. Finally, we found that the resulting activation of the AA cascade and the production of PGE₂ eicosanoid could be related to the activation of cell signaling pathways such as ERK and CREB. These findings will help facilitate our understanding of how inflammatory mediators can affect the survival and dissemination of intestinal carcinoma cells.

Serum concentrations of eicosanoids and lipids in dogs naturally infected with Babesia canis

Canine babesiosis is a tick-borne disease with world-wide significance caused by intraerythrocytic protozoa of the genus Babesia. The eicosanoids, as inflammatory mediators, are involved in the regulation of the immune response and inflammatory reaction. Metabolism of lipids is of great importance in babesiosis. In this study it was aimed to investigate the dynamics of serum concentration of prostaglandin E2 (PGE2), thromboxane B2 (TxB2), leukotriene B4 (LTB4), triglycerides, total cholesterol (Chol), HDL- and LDL-cholesterol in dogs naturally infected with Babesia canis and healthy dogs. Both groups were measured for all parameters on the admission day and on the first, second and seventh day of the disease. Dogs that were included in this study had systemic inflammatory response syndrome (SIRS) and multiple organ dysfunction syndrome (MODS). It was demonstrated that the level of LTB4, PGE2, TxB2 in dogs naturally infected with B. canis significantly changed during the disease. The level of LTB4 was significantly higher during the study, while the concentration of PGE2 was significantly higher second, third and seventh day of disease in relation with healthy dogs. The level of TxB2 was significantly lower at the beginning of the disease, but after seven days concentration was significantly higher. Both group of patients with SIRS and MODS had significantly higher level of LTB4. Substained high concentrations of PGE2 were observed in dogs with MODS after therapy but not in dogs with SIRS, and LTB4 followed a similar tendency. On the other hand, increases in TxB2 were only significant in dogs with SIRS. The lipid profile in naturally infected dogs with B. canis infection was significantly changed. Further studies are needed to assess the prognostic values of lipid mediators in dogs with B. canis infection, and the ability of these markers to predict the progress of SIRS and MODS.

Targets and candidate agents for type 2 diabetes treatment with computational bioinformatics approach

We sought to explore the molecular mechanism of type 2 diabetes (T2D) and identify potential drug targets and candidate agents for T2D treatment. The differentially expressed genes (DEGs) were assessed between human pancreatic islets with T2D and normal islets. The dysfunctional pathways, the potential transcription factor, and microRNA targets were analyzed by bioinformatics methods. Moreover, a group of bioactive small molecules were identified based on the connectivity map database. The pathways of Eicosanoid Synthesis, TGF-beta signaling pathway, Prostaglandin Synthesis and Regulation, and Integrated Pancreatic Cancer Pathway were found to be significantly dysregulated in the progression of T2D. The genes of ZADH2 (zinc binding alcohol dehydrogenase domain containing 2), BTBD3 (BTB (POZ) domain containing 3), Cul3-based ligases,  LTBP1 (latent-transforming growth factor beta binding protein 1), PDGFRA (alpha-type platelet-derived growth factor receptor), and FST (follistatin) were determined to be significant nodes regulated by potential transcription factors and microRNAs. Besides, two small molecules (sanguinarine and DL-thiorphan) were identified to be capable of reverse T2D. In the present study, a systematic understanding for the mechanism underlying T2D development was provided with biological informatics methods. The significant nodes and bioactive small molecules may be drug targets and candidate agents for T2D treatment.

CysLT(1)R antagonists inhibit tumor growth in a xenograft model of colon cancer

The expression of the inflammatory G-protein coupled receptor CysLT₁R has been shown to be upregulated in colon cancer patients and associated with poor prognosis. The present study investigated the correlation between CysLT₁R and colon cancer development in vivo using CysLT₁R antagonists (ZM198,615 or Montelukast) and the nude mouse xenograft model. Two drug administration regimens were established. The first regimen was established to investigate the importance of CysLT₁R in tumor initiation. Nude mice were inoculated with 50 µM CysLT₁R antagonist-pretreated HCT-116 colon cancer cells and received continued treatment (5 mg/kg/day, intraperitoneally). The second regimen aimed to address the role of CysLT₁R in tumor progression. Nude mice were inoculated with non-pretreated HCT-116 cells and did not receive CysLT₁R antagonist treatment until recordable tumor appearance. Both regimens resulted in significantly reduced tumor size, attributed to changes in proliferation and apoptosis as determined by reduced Ki-67 levels and increased levels of p21^WAF/Cip1 (P<0.01), cleaved caspase 3, and the caspase-cleaved product of cytokeratin 18. Decreased levels of VEGF (P<0.01) and reduced vessel size (P<0.05) were also observed, the latter only in the ZM198,615-pretreatment group. Furthermore, we performed a series of in vitro studies using the colon cancer cell line HCT-116 and CysLT₁R antagonists. In addition to significant reductions in cell proliferation, adhesion and colony formation, we observed induction of cell cycle arrest and apoptosis in a dose-dependent manner. The ability of Montelukast to inhibit growth of human colon cancer xenograft was further validated by using two additional colon cancer cell lines, SW-480 and HT-29. Our results demonstrate that CysLT₁R antagonists inhibit growth of colon cancer xenografts primarily by reducing proliferation and inducing apoptosis of the tumor cells.

Intestinal inflammation in TNBS sensitized rats as a model of chronic inflammatory bowel disease

An enteritis, based on a delayed-type hypersensitivity reaction, was induced in TNBS (2,4,4-trinitrobenzenesulphonic acid) sensitized rats by multiple intrajejunal challenge with TNBS via an implanted catheter. This treatment induced chronic inflammation of the distal small intestine characterized by intense hyperaemia, oedema and gut wall thickening as assessed by macroscopic scoring and weighing a defined part of the dissected intestine. Histologically, the inflammatory response included mucosal and submucosal cell infiltration by lymphocytes and histiocytes, transmural granulomatous inflammation with multinucleated cells and activated mesenteric lymph nodes. Ex vivo stimulated release of the inflammatory mediator LTB₄ in the dissected part of the intestine was increased following TNBS treatment. Drug treatment with sulphasalazine or 5-aminosalicylic acid improved the enteritis score and attenuated TNBS induced oedema formation and LTB₄ production. The applicability and relevance of this new model are discussed with respect to drug development and basic research of inflammatory bowel diseases.

The 5-lipoxygenase pathway is required for acute lung injury following hemorrhagic shock

The cellular and biochemical mechanisms leading to acute lung injury (ALI) and subsequent multiple organ failure are only partially understood. To study the potential role of eicosanoids, particularly leukotrienes, as possible mediators of ALI, we used a murine experimental model of ALI induced by hemorrhagic shock after blood removal via cardiac puncture. Neutrophil sequestration, as shown by immunofluorescence and protein leakage into the alveolar space were measured as markers of injury. We used liquid chromatography coupled to tandem mass spectrometry to unequivocally identify several eicosanoids in the bronchoalveolar lavage fluid of experimental animals. MK886, a specific inhibitor of the 5-lipoxygenase (5-LO) pathway, and transgenic mice deficient in 5-LO were used to determine the role of this enzymatic pathway in this model. Leukotriene B4 and leukotriene C4 were consistently elevated in shock-treated mice compared with sham-treated mice. MK886 attenuated neutrophil infiltration and protein extravasation induced by hemorrhagic shock. 5-Lipoxygenase-deficient mice showed reduced neutrophil infiltration and protein extravasation after shock treatment, indicating greatly reduced lung injury. These results support the hypothesis that 5-LO, most likely through the generation of leukotrienes, plays an important role in the pathogenesis of ALI induced by hemorrhagic shock in mice. This pathway could represent a new target for pharmacological intervention to reduce lung damage following severe primary injury.

Regulation of cysteinyl leukotriene receptor 2 expression--a potential anti-tumor mechanism

Background

The cysteinyl leukotrienes receptors (CysLTRs) are implicated in many different pathological conditions, such as inflammation and cancer. We have previously shown that colon cancer patients with high CysLT₁R and low CysLT₂R expression demonstrate poor prognosis. Therefore, we wanted to investigate ways for the transcriptional regulation of CysLT₂R, which still remains to be poorly understood.

Methodology/Principal Findings

We investigated the potential role of the anti-tumorigenic interferon α (IFN-α) and the mitogenic epidermal growth factor (EGF) on CysLT₂R regulation using non-transformed intestinal epithelial cell lines and colon cancer cells to elucidate the effects on the CysLT₂R expression and regulation. This was done using Western blot, qPCR, luciferase reporter assay and a colon cancer patient array. We found a binding site for the transcription factor IRF-7 in the putative promoter region of CysLT₂R. This site was involved in the IFN-α induced activity of the CysLT₂R luciferase reporter assay. In addition, IFN-α induced the activity of the differentiation marker alkaline phosphatase along with the expression of mucin-2, which protects the epithelial layer from damage. Interestingly, EGF suppressed both the expression and promoter activity of the CysLT₂R. E-boxes present in the CysLT₂R putative promoter region were involved in the suppressing effect. CysLT₂R signaling was able to suppress cell migration that was induced by EGF signaling.

Conclusions/Significance

The patient array showed that aggressive tumors generally expressed less IFN-α receptor and more EGFR. Interestingly, there was a negative correlation between CysLT₂R and EGFR expression. Our data strengthens the idea that there is a protective role against tumor progression for CysLT₂R and that it highlights new possibilities to regulate the CysLT₂R.

Leukotriene B4 mediates inflammation via TRPV1 in duct obstruction-induced pancreatitis in rats

OBJECTIVES

We tested the hypothesis that leukotriene B4 (LTB4) mediates pancreatic inflammation in rats via activation of the transient receptor potential vanilloid 1 (TRPV1).

METHODS

Leukotriene B4 or a vehicle was administered to adult rats via celiac axis injection after pretreatment with the TRPV1 antagonist, capsazepine, or vehicle, and the severity of subsequent pancreatitis was assessed by measuring pancreatic edema, myeloperoxidase (MPO) activity, and histological grading. In a second experiment, acute pancreatitis was induced by common pancreaticobiliary duct ligation. Six hours after surgery, pancreatic tissue levels of LTB4 were determined by enzyme-linked immunosorbent assay. Also, the effects of inhibition of LTB4 biosynthesis by pretreatment with the 5-lipoxygenase-activating peptide inhibitor, MK-886, were determined.

RESULTS

Celiac axis administration of LTB4 significantly increased pancreatic edema and MPO activity, and produced histological evidence of pancreatic edema, neutrophil infiltration, and necrosis. Capsazepine pretreatment significantly reduced all inflammatory parameters in LTB4-induced pancreatitis. Pancreatic tissue levels of LTB4 were significantly elevated in rats that underwent common pancreaticobiliary duct ligation compared with control rats. MK-886 pretreatment significantly inhibited pancreatic edema, histological damage, and pancreatic MPO concentrations.

CONCLUSIONS

Common pancreaticobiliary duct obstruction causes an increase in pancreatic LTB4 concentrations that in turn mediates activation of TRPV1 resulting in acute pancreatitis.

Blockade of LTB(4) /BLT(1) pathway improves CD8(+) T-cell-mediated colitis

BACKGROUND

Leukotriene B4 (LTB(4) ) has chemotactic properties for activated T cells expressing the high-affinity receptor BLT(1) . This study investigated whether the LTB(4) antagonist (CP-105,693), selective for BLT(1) receptor, could protect mice from colitis mediated by specific cytotoxic CD8(+) T lymphocytes (CTL).

METHODS

Virus-specific colitis was induced in C57Bl/6 mice transferred with lymphoid cells from P14 TcR Tg mice which are specific to class I GP33 peptide of LCMV. Mice were immunized with GP33-pulsed dendritic cells and colitis was elicited by intrarectal administration of the peptide. Colitis was evaluated by body weight loss and macroscopic and histological analysis of colon. In vivo priming of specific CD8(+) CTL was determined using interferon (IFN)-γ ELISPOT and in vivo CTL assays. In some experiments mice were treated with a selective LTB(4) receptor antagonist.

RESULTS

Immunization with GP33-pulsed dendritic cells (DCs) induced priming of specific CD8(+) CTL, as shown by the presence of IFN-γ-producing CD8(+) T cells in colon draining lymph nodes and in vivo CTL assays. Intrarectal challenge with GP33 induced severe colitis and recruitment of granzyme B(+) P14 CD8(+) cells in colon. Treatment with the specific LTB(4) receptor antagonist before elicitation of colitis reduced the severity of colitis and decreased the frequency of specific effectors.

CONCLUSIONS

Colitis can be induced by IFN-γ-producing cytotoxic CD8(+) CTL specific for viral antigen. Blockade of the LTB(4) /BLT(1) pathway by a selective BLT(1) receptor antagonist attenuates colitis by inhibiting CD8(+) effectors recruitment in colon. These data illustrate the therapeutic potential of LTB(4) receptor selective antagonists in protection from CD8(+) T-cell-mediated intestinal inflammation.

Ligand-induced tyrosine phosphorylation of cysteinyl leukotriene receptor 1 triggers internalization and signaling in intestinal epithelial cells

Background

Leukotriene D₄ (LTD₄) belongs to the bioactive lipid group known as eicosanoids and has implications in pathological processes such as inflammation and cancer. Leukotriene D₄ exerts its effects mainly through two different G-protein-coupled receptors, CysLT₁ and CysLT₂. The high affinity LTD₄ receptor CysLT₁R exhibits tumor-promoting properties by triggering cell proliferation, survival, and migration in intestinal epithelial cells. In addition, increased expression and nuclear localization of CysLT₁R correlates with a poorer prognosis for patients with colon cancer.

Methodology/Principal Findings

Using a proximity ligation assay and immunoprecipitation, this study showed that endogenous CysLT₁R formed heterodimers with its counter-receptor CysLT₂R under basal conditions and that LTD₄ triggers reduced dimerization of CysLTRs in intestinal epithelial cells. This effect was dependent upon a parallel LTD₄-induced increase in CysLT₁R tyrosine phosphorylation. Leukotriene D₄ also led to elevated internalization of CysLT₁Rs from the plasma membrane and a simultaneous increase at the nucleus. Using sucrose, a clathrin endocytic inhibitor, dominant-negative constructs, and siRNA against arrestin-3, we suggest that a clathrin-, arrestin-3, and Rab-5-dependent process mediated the internalization of CysLT₁R. Altering the CysLT₁R internalization process at either the clathrin or the arrestin-3 stage led to disruption of LTD₄-induced Erk1/2 activation and up-regulation of COX-2 mRNA levels.

Conclusions/Significance

Our data suggests that upon ligand activation, CysLT₁R is tyrosine-phosphorylated and released from heterodimers with CysLT₂R and, subsequently, internalizes from the plasma membrane to the nuclear membrane in a clathrin-, arrestin-3-, and Rab-5-dependent manner, thus, enabling Erk1/2 signaling and downstream transcription of the COX-2 gene.

Anti-inflammatory effects of freeze-dried black raspberry powder in ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory disease of the colonic mucosa that can dramatically increase the risk of colon cancers. In the present study, we evaluated the effects of a dietary intervention of freeze-dried black raspberries (BRB), a natural food product with antioxidant and anti-inflammatory bioactivities, on disease severity in an experimental mouse model of UC using 3% dextran sodium sulfate (DSS). C57BL/6J mice were fed either a control diet or a diet containing BRB (5 or 10%) for 7-14 days and then the extent of colonic injury was assessed. Dietary BRB markedly reduced DSS-induced acute injury to the colonic epithelium. This protection included better maintenance of body mass and reductions in colonic shortening and ulceration. BRB treatment, however, did not affect the levels of either plasma nitric oxide or colon malondialdehyde, biomarkers of oxidative stress that are otherwise increased by DSS-induced colonic injury. BRB treatment for up to 7 days suppressed tissue levels of several key pro-inflammatory cytokines, including tumor necrosis factor α and interleukin 1β. Further examination of the inflammatory response by western blot analysis revealed that 7 day BRB treatment reduced the levels of phospho-IκBα within the colonic tissue. Colonic cyclooxygenase 2 levels were also dramatically suppressed by BRB treatment, with a concomitant decrease in the plasma prostaglandin E₂ (276 versus 34 ng/ml). These findings demonstrate a potent anti-inflammatory effect of BRB during DSS-induced colonic injury, supporting its possible therapeutic or preventive role in the pathogenesis of UC and related neoplastic events.

Effect of resveratrol and quercetin in experimental infection by Salmonella enterica serovar Typhimurium

Flavonoids are phenolic compounds widely distributed in almost every plant and act as pharmacologically active constituents in many herbal medicines. They have multiple biological, pharmacological, and medicinal properties including anti-inflammatory and cytoprotective effects. In the present study, the experiments were performed to evaluate the effect of resveratrol and quercetin on proliferation, viability, nitric oxide (NO) production, and apoptosis in Salmonella enterica serovar Typhimurium-infected U937 cells and monocytes (MN). The results showed in a time- and dose-dependent manner that both resveratrol and quercetin reduced S. enterica serovar Typhimurium-induced NO production. In addition, the vegetable extracts resveratrol and quercetin inhibited cell viability and proliferation in S. enterica serovar Typhimurium-infected cells. S. enterica serovar Typhimurium-induced apoptosis was also blocked by resveratrol and quercetin. The results obtained indicate that flavonoids modulate the host response during salmonellosis by protecting the host cells from the toxic effects of bacterial infection and also by decreasing programmed cell death. Hence, these polyphenols can be considered potential candidates against S. enterica serovar Typhimurium-related gastric pathogenic processes, and further attention should be given to their application as a treatment for infectious diseases.

Clinical pharmacology of 5-ASA compounds in inflammatory bowel disease

Mesalamine has been the first-line of therapy in patients with inflammatory bowel disease (IBD) since the 1960s. This article serves as a review of the different 5-aminosalicylic acid compounds, release formulations, use and dosing in the treatment of IBD, in particular ulcerative colitis.

Adenosine: An immune modulator of inflammatory bowel diseases

Inflammatory bowel disease (IBD) is a common and lifelong disabling gastrointestinal disease. Emerging treatments are being developed to target inflammatory cytokines which initiate and perpetuate the immune response. Adenosine is an important modulator of inflammation and its anti-inflammatory effects have been well established in humans as well as in animal models. High extracellular adenosine suppresses and resolves chronic inflammation in IBD models. High extracellular adenosine levels could be achieved by enhanced adenosine absorption and increased de novo synthesis. Increased adenosine concentration leads to activation of the A2a receptor on the cell surface of immune and epithelial cells that would be a potential therapeutic target for chronic intestinal inflammation. Adenosine is transported via concentrative nucleoside transporter and equilibrative nucleoside transporter transporters that are localized in apical and basolateral membranes of intestinal epithelial cells, respectively. Increased extracellular adenosine levels activate the A2a receptor, which would reduce cytokines responsible for chronic inflammation.

Gene expression profiling in autoimmune diseases: Chronic inflammation or disease specific patterns?

A central issue in autoimmune disease is whether the underlying inflammation is a repeated stereotypical process or whether disease specific gene expression is involved. To shed light on this, we analysed whether genes previously found to be differentially regulated in rheumatoid arthritis (RA) patients and healthy individuals were specific for the arthritic process or likewise altered in other chronic inflammatory diseases such as chronic autoimmune thyroiditis (Hashimoto's thyroiditis, HT) and inflammatory bowel disease (IBD). Using qPCR for 18 RA-discriminative genes, there were no significant differences in peripheral blood mononuclear cell (MNC) gene expression patterns between 15 newly diagnosed HT patients and 15 matched healthy controls. However, the MNC expression levels of five genes were significantly upregulated in 25 IBD patients, compared to 18 matched healthy controls (CD14, FACL2, FCN1, RNASE2, VNN2). There was concordance in the directional change for all genes between IBD and RA patients, i.e. increased expression compared to controls. These data show that one third of the genes significantly upregulated in MNC from RA patients were upregulated in patients with other chronic immunoinflammatory diseases, but only if accompanied by pronounced systemic manifestations. This suggests that at least some of the genes activated in RA are predominantly or solely related to general and disease-nonspecific autoimmune processes.

Plasma lipids and inflammation in active inflammatory bowel diseases

BACKGROUND

Ulcerative colitis (UC) and Crohn's disease (CD) can cause metabolic and inflammatory alterations.

AIM

To evaluate the relationships between inflammatory parameters, plasma lipids and phospholipid fatty acid (FA) composition in patients with active UC and CD.

METHODS

Diet, the Harvey-Bradshaw Activity Index (HBAI), inflammatory parameters, lipoproteins and FA composition were assessed in 60 CD and 34 UC.

RESULTS

No differences in clinical parameters were observed in the two groups. Total cholesterol correlated inversely with the number of bowel movements in both groups and directly with BMI in UC. Arachidonic acid correlated inversely with HBAI in UC and total and HDL cholesterol were inversely related to C-reactive protein (CRP) in CD while HDL correlated with CRP in UC. Docosapentaenoic acid was the only polyunsaturated n-3 FA that was correlated to CRP in both groups. Total cholesterol was independently associated in the multiple regression analysis with the number of bowel movements and systemic inflammation.

CONCLUSIONS

Total and LDL cholesterol were lower in the active UC and CD than in the healthy subjects and were correlated with the systemic inflammatory status. Phospholipid FA composition was correlated to the systemic inflammatory status, but was unrelated to dietary intake and intestinal disease activity.

An increased expression of cysteinyl leukotriene 2 receptor in colorectal adenocarcinomas correlates with high differentiation

Increased levels of inflammatory mediators such as cysteinyl leukotrienes (CysLT) have been found in and around tumors. These data, along with our previous observation that the G-protein-coupled receptor CysLT(1)R, which signals survival and proliferation, is up-regulated in colon cancer, suggest an important role for CysLT(1)R in tumor development. The objective of this study was to examine the expression and function of the low-affinity CysLT2 receptor (CysLT2R) in colon cancer. We found lower expression levels of CysLT2R compared with CysLT(1)R in cancer cell lines as well as clinical tumor material. Interestingly, CysLT2R, like CysLT(1)R, was found to be one of few G-protein-coupled receptors that are located both at the plasma membrane and the nuclear membrane. No effect of CysLT2R signaling on cell proliferation was observed, nor was there a correlation between CysLT2R and different proliferation markers such as Ki-67 and cyclooxygenase-2 in the tumor material. Instead, we found that activation of this receptor in colon cancer cells led to cellular differentiation similar to the effects of butyrate treatment. In accordance with this finding, we found that reduced expression of CysLT2R in colon cancer was associated with poor prognosis. We report the novel finding that CysLT2R signaling leads to terminal differentiation of colon carcinoma cells and growth inhibition, and that its expression is relatively high in less malignant forms of colon cancer. These data suggest that the balance between these two receptors is important for tumor progression and disease outcome.

HETEs enhance IL-1-mediated COX-2 expression via augmentation of message stability in human colonic myofibroblasts

Proinflammatory cytokines and eicosanoids are central players in intestinal inflammation. IL-1, a key cytokine associated with intestinal mucosal inflammation, induces COX-2 expression in human colonic myofibroblasts (CMF) and increased prostaglandin E(2) secretion is associated with inflammatory bowel disease (IBD) and colorectal cancer (CRC). We have previously demonstrated that IL-1alpha-induced cyclooxygenase-2 (COX-2) expression is the result of NF-kappaB- and ERK-mediated transcription, as well as COX-2 message stabilization, which depends on p38, MAPKAPK-2 (MK-2) and human antigen R (HuR) RNA binding protein activation. Lipoxygenase (LOX)-derived hydroxyeicosatetraenoic acids (HETEs) are elevated in IBD and colonic adenomas and "cross talk" has been observed between the COX and LOX pathways. Since COX-2 expression is primarily in CMFs in colonic adenomas, we examined the impact of LOX metabolites, particularly HETEs, on IL-1alpha-induced COX-2 expression in human CMFs. Although 5(S)-, 12(R)-, and 15(S)-HETEs alone had little to no effect on COX-2 expression, they enhanced IL-1-mediated COX-2 expression 3.6 +/- 0.5-fold. Studies utilizing heterogeneous nuclear RNA amplification and 5,6-dichloro-beta-d-ribofuranosylbenzimidazole treatment were undertaken to measure COX-2 transcription and message stabilization, respectively. We found that HETEs enhanced IL-1-induced COX-2 mRNA levels in CMF as the result of increased p38, MK-2, and HuR activity, increasing message stability greater than that observed with IL-1 alone. Thus HETEs can act synergistically with IL-1alpha to induce COX-2 expression in human CMFs. HETEs may play a role in both colonic inflammation and in increasing the risk of CRC in IBD independently and via induction of COX-2-mediated prostaglandin secretion.

Optimization of assay conditions for leukotriene B4 synthesis by neutrophils or platelets isolated from peripheral blood of monogastric animals

Neutrophils are involved in inflammation through leukotriene (LT) production. The predominant proinflammatory leukotriene released from neutrophils is LTB4, which serves as a biological marker of inflammation. The purpose of this study was to optimize the conditions ex vivo for LTB4 production by neutrophils from horses and dogs, and platelets from chickens. Optimal production of LTB4 was characterized by incubation time (2.5, 5, 10, 15 or 20 min), temperature (25 or 37 degrees C), and calcium ionophore A23187 concentration (0.1, 1, 10 or 20 microM). Incubation longer than 2.5 min did not increase production of LTB4 in chickens or horses; in dogs, incubation for 2.5 and 10 min resulted in the highest concentrations of LTB4 (P<or=0.05). In all species, incubation at 37 degrees C resulted in optimal LTB4 production (P<or=0.05). Production of LTB4 was highest when neutrophils or platelets were stimulated with 20 microM calcium ionophore in all species (P<or=0.05). These results indicate that neutrophils isolated from horses and dogs, and platelets isolated from chickens, are capable of producing LTB4. Optimum conditions for LTB4 production are similar in all three species.

The role of leukotriene B4 in Clostridium difficile toxin A-induced ileitis in rats

BACKGROUND & AIMS

Clostridium difficile toxin A is a potent intestinal inflammatory agent that has been shown to act at least partially by neurogenic mechanisms involving activation of the transient receptor potential vanilloid 1 (TRPV1) (capsaicin) receptor. We tested the hypothesis that leukotriene B4 (LTB4) mediates the effects of toxin A via activation of the TRPV1 receptor.

METHODS

Isolated rat ileal segments were pretreated with pharmacologic agents before intraluminal injection of toxin A or LTB4. After 3 hours, the treated segments were removed and inflammation was assessed by luminal fluid accumulation, myeloperoxidase activity, and histology.

RESULTS

LTB4 caused ileitis similar to that caused by toxin A and antagonism of TRPV1 receptors but not LTB4 receptors inhibited LTB4-induced inflammation. LTB4 also stimulated TRPV1-mediated substance P release and pretreatment with a specific substance P-receptor antagonist blocked LTB4-induced substance P action and ileitis. Inhibition of the LTB4 biosynthetic enzyme 5-lipoxygenase inhibited toxin A-induced increases in ileal LTB4 levels and toxin A- but not LTB4-induced ileitis.

CONCLUSIONS

LTB4 mediates the inflammatory effects of toxin A via activation of TRPV1 receptors.

Role of Salmonella surface components in immunomodulation of inflammatory mediators

Salmonella enterica serovar Typhimurium and its surface components were assessed for their inflammatory potential by footpad oedema test using plethysmometer. Inflammation was found to be the highest when outer membrane proteins (OMPs) were used as inflammagen followed by lipid associated protein-lipopolysaccharide complex (LAP-LPS) and lipopolysaccharides (LPS). Inflammation produced by OMPs was found to be comparable to that by carrageenan (a known positive inflammagen). However, injection of L-histidine (an antioxidant) prior to administration of carrageenan or Salmonella enterica serovar Typhimurium inhibited the inflammation, which indicated the involvement of oxidants during inflammatory response. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and nitric oxide (NO) production by peritoneal macrophages from infected mice exhibited a significant increase as compared to those of the immunized mice. In contrast, glutathione production was found to be the maximum in the macrophages taken from OMPs-immunized mice followed by LAP-LPS and LPS alone. The biochemical studies correlated well with histopathological studies of intestinal tissue of animals from various groups. Based upon these parameters, inflammation seems to be modulated by OMPs and LAP-LPS, which may be because of the protein moieties present in the components. Hence, immunization with protein moieties having L-histidine or L-histidine-like structures may suggest an alternative to the potential therapeutic values of anti-inflammatory drugs. Thus the results of this study form the basis for evaluating these antigens (either alone or in combination with polysaccharides) for preventive intervention rather than therapeutic.

Disturbances in epithelial ionic secretion in different experimental models of colitis

This paper studies the disturbances in ionic secretion in the colon of rats with different models of acute and chronic colitis measured as changes in short-circuit current. The aim was to verify whether the reported inhibition of basal and stimulated secretion in the trinitrobenzene sulfonic acid and mytomicin C models are applicable to experimental colitis as such. All models showed remarkable similarity in ion transport as determined in Ussing chambers, with downregulated basal as well as carbachol evoked secretion. The EC(50) of carbachol was unchanged in all cases. Iodoacetamide and oxazolone colitis models were notable exceptions in that the dose response curves for carbachol were unaltered compared to controls. The reason is unclear but seems to be unrelated to either interferon gamma or interleukin 4 levels or to the severity of the inflammatory response.

A Novel Localization of the G-Protein-Coupled CysLT1 Receptor in the Nucleus of Colorectal Adenocarcinoma Cells

Searching for a link between inflammation and colon cancer, we have found that the inflammatory mediator leukotriene D4 (LTD4), via its receptor CysLT1, induces cyclooxygenase-2 expression, survival, and proliferation in intestinal epithelial cells. In conjunction with our previous observation that CysLT1 receptor expression is increased in colorectal adenocarcinomas, we here found an increased nuclear localization of the CysLT1 receptor in colorectal adenocarcinomas. This novel discovery of CysLT1 receptors in the nucleus was further analyzed. It was found to be located in the outer nuclear membrane in colon cancer cells and in the nontransformed epithelial cell line Int 407 cells by Western blot and electron microscopy. Cancer cells displayed higher amounts of the nuclear CysLT1 receptor, but prolonged LTD4 exposure induced its nuclear translocation in nontransformed cells. Truncation of a nuclear localization sequence abrogated this translocation as well as the LTD4-induced proliferative response. In accordance, nuclear CysLT1 receptors exhibited proliferative extracellular signal-regulated kinase 1/2 signaling. The significance of these experimental findings is supported by the observed correlation between the proliferative marker Ki-67 and nuclear CysLT1 receptor localization in colorectal adenocarcinomas. The present findings indicate that LTD4 cannot only be synthesized but also signal proliferation through nuclear CysLT1 receptors, stressing the importance of leukotrienes in inflammation-induced colon carcinogenesis.

Mesalamine delivery systems: do they really make much difference?

Sulfasalazine's role as the first-line of therapy in patients with inflammatory bowel disease has led to the development of other "designer" aminosalicylates, which eliminate the sulfa-moiety, and attempt to target the topically active mesalamine to the inflamed bowel. Olsalazine sodium and balsalazide disodium utilize the same azo-bond structure as sulfasalazine, requiring release of active mesalamine by colonic bacteria, and thus targeting these agents to the colon. Other mesalamine delivery systems use pH-dependant- or moisture-release to liberate the active mesalamine in both the large and small bowel. Direct application of mesalamine via enema or suppository is also effective in patients with distal colitis. The pharmacology and thus the undesirable drug absorption rates differ between drugs, although the clinical importance of these characteristics is debatable. Differences in release-systems, the impact of the fed and fasting state, and unique patient intolerances to individual agents demand an understanding of each of these products, and their application to patient therapy.

Linoleic acid, but not oleic acid, upregulates the production of interleukin-8 by human intestinal smooth muscle cells isolated from patients with Crohn's disease

BACKGROUND & AIMS

Crohn's disease is a chronic inflammatory bowel disease (IBD) of unknown etiology. In this study, we investigated the hypothesis that dietary fatty acids, linoleic acid (LA) and oleic acid (OA), could be involved in the inflammatory response through stimulation of the neutrophil chemokine, IL-8.

METHODS

Human intestinal smooth muscle (HISM) cells were isolated from normal patients and patients with Crohn's disease and cultured for 24h with LA or OA in the presence or absence of oxidative stress. The concentrations of IL-8 were measured in the media and cellular oxidative stress was quantitated by measurement of thiobarbituric acid reactive substances (TBARSs).

RESULTS

Spontaneous production of IL-8 was significantly higher in HISM cells isolated from Crohn's bowel compared to control bowel. LA caused a marked, nine-fold, increase in IL-8 secretion by Crohn's cells, an effect that could be simulated in normal HISM cells by co-incubation of LA with an oxidizing solution (Ox) composed of hypoxanthine+xanthine oxidase+FeSO(4) (OxLA). These effects were inhibited by vitamins C and E. Treatment of Crohn's cells with OxLA did not further increase IL-8 over that of LA alone. The effect of LA alone was not associated with an increase in cellular oxidative stress as quantitated by TBARSs. In contrast to the results with LA, treatment with OA or OxOA did not increase IL-8 in either normal or Crohn's cells. In addition, OA protected Crohn's cells from the increase in TBARSs induced by Ox. In contrast to IL-8, spontaneous production of monocyte chemotactic protein (MCP-1) was significantly lower in Crohn's HISM cells as compared to normal cells and exposure to OxLA did not increase its production.

CONCLUSIONS

LA, but not OA, increased the production of IL-8 by HISM cells. These results suggest that replacement of LA by OA in the diet of Crohn's patients and increased intake of a diet rich in antioxidants could be beneficial in decreasing inflammatory activity in Crohn's disease.

Inflammatory bowel disease and the eye

Inflammatory bowel disease includes Crohn's disease and ulcerative colitis, and is characterized by chronic inflammation of the intestines. The advances in understanding of the inflammatory process have resulted in improved treatment of inflammatory bowel disease. The systemic complications of inflammatory bowel disease involve many organs, eyes included. The ophthalmic complications are usually of inflammatory origin. Some of these complications, like scleritis, may reflect overall disease activity. Treatment of intestinal inflammation-either medical or surgical-usually helps resolution of ophthalmic complications. This review describes recent developments in the diagnosis and management of the inflammatory bowel disease and its ophthalmic complications.

Regulation of leukotriene-dependent induction of cyclooxygenase-2 and Bcl-2

Leukotrienes play an important pathophysiological role in chronic inflammatory states and, as previously shown, cause increased levels of cyclooxygenase-2 (COX-2) in intestinal epithelial cells. The anti-apoptotic protein Bcl-2 is also elevated by LTD(4) stimulation, and in colon cancer, so we studied the mechanisms of COX-2 and Bcl-2 regulation. We found that LTD(4) induced a 3-fold elevation of COX-2 transcription in Int 407 cells and a 2-fold equivalent in colon cancer cells, Caco-2. This was mediated through a pertussis toxin (PTX) sensitive G-protein and the MAP kinase Erk-1/2 pathway, and this was also shown to be the route to up-regulation of Bcl-2 by LTD(4). In good agreement with this, we detected a strong activation of Erk-1/2 that was further increased by COX-2 inhibition, pointing towards the existence of negative feedback regulation. Furthermore, COX-2 activity is responsible for the effects on Bcl-2, but this is not conveyed through the production of PGE(2).

Balsalazide is superior to mesalamine in the time to improvement of signs and symptoms of acute mild-to-moderate ulcerative colitis

OBJECTIVE

Balsalazide is a novel azo-bonded 5-aminosalicylic acid treatment for mild-to-moderate ulcerative colitis. The study objective was to compare symptomatic remission rates with balsalazide and mesalamine while controlling for extent of disease and time since diagnosis in patients with active, mild-to-moderate ulcerative colitis.

METHODS

A total of 173 patients with sigmoidoscopically verified ulcerative colitis were randomized to 8 wk of double-blind treatment with balsalazide 6.75 g/day or mesalamine 2.4 g/day. Both treatments provided 2.4 g/day of oral 5-aminosalicylic acid. Patients maintained symptom diaries throughout the treatment period.

RESULTS

Overall, 46% of balsalazide- and 44% of mesalamine-treated patients achieved symptomatic remission. Higher response rates were noted in newly diagnosed patients with < or = 40 cm of disease (68% vs 61%) than in recently relapsed patients with >40 cm of disease (36% vs 25%). The median time to symptomatic remission was 12 days shorter with balsalazide (25 days) than with mesalamine (37 days). Significantly more balsalazide patients showed sigmoidoscopic (p = 0.002), stool frequency (p = 0.006), rectal bleeding (p = 0.006), and physician's global assessment score (p = 0.013) improvement by 14 days than did mesalamine patients. Similar proportions of patients reported adverse events (54% vs 64%), which were most commonly related to the gastrointestinal and central and peripheral nervous systems.

CONCLUSIONS

Balsalazide is an effective and safe treatment for mild-to-moderate ulcerative colitis. Improvement of symptoms occurs considerably earlier with balsalazide than with mesalamine.

Altered lipid profile, lipoprotein composition, and oxidant and antioxidant status in pediatric Crohn disease

BACKGROUND

Growing evidence supports a role for peroxidation in the pathogenesis of Crohn disease (CD). The activation of inflammatory cells, the release of their mediators, and the excessive production of free radicals may affect circulating lipids.

OBJECTIVE

We examined the lipid profile, lipoprotein composition, and oxidant-antioxidant status of children with CD.

DESIGN

We studied 22 pediatric CD patients and 10 healthy control subjects.

RESULTS

The proportion of saturated and monounsaturated fatty acids in plasma of CD patients was higher but that of polyunsaturated fatty acids was lower than in control subjects. This resulted in higher ratios in CD patients of palmitoleic acid to linoleic acid (P < 0. 05) and of eicosatrienoic acid to arachidonic acid (P < 0.04), 2 established indexes of essential fatty acid deficiency. Hypocholesterolemia was noted in CD patients as a result of lower LDL-cholesterol concentrations than in control subjects (P < 0.02). Plasma apolipoproteins B (P < 0.02) and A-I (P < 0.02) were also lower in CD patients, whereas plasma triacylglycerols were higher (P < 0.005). Lipoprotein composition was altered in CD patients, with relative triacylglycerol depletion and protein enrichment in VLDL. In contrast, intermediate-density lipoprotein of CD patients was characterized by an increased percentage of triacylglycerol and protein (P < 0.005) and a reduced proportion of phospholipids (P < 0. 01). Additional abnormalities were observed in the chemical distribution of HDL(2) and HDL(3) moieties. Lipid peroxidation was documented by higher plasma malondialdehyde concentrations in CD patients (P < 0.05), accompanied by lower retinol concentrations (P < 0.02).

CONCLUSION

Disturbances in the lipid profile, in lipoprotein concentrations and composition, and in oxidant-antioxidant status occur in CD patients.

Inhibition of cytoplasmic phospholipase A2 expression by glucocorticoids in rat intestinal epithelial cells

BACKGROUND & AIMS

Glucocorticoids are the most potent and widely accepted anti-inflammatory agents in the treatment of pathological conditions of the gastrointestinal tract in part by inhibiting the synthesis of proinflammatory prostanoids and leukotrienes. Multiple forms of phospholipase A2 may be associated with the production of these metabolites; this study focused on the molecular mechanism(s) by which glucocorticoids control expression of the arachidonyl-selective, cytosolic phospholipase A2 (cPLA2) in intestinal cells.

METHODS

Northern analysis, a transcriptional assay, and enzymatic evaluation were used to access expression of the cPLA2 gene in rat small intestinal epithelial and mouse fibroblast cell lines treated with dexamethasone.

RESULTS

Basal cPLA2 messenger RNA (mRNA) expression was repressed 75% in the presence of dexamethasone with a concomitant decrease in enzymatic activity. Nuclear runoff assays showed a marked decline in de novo cPLA2 RNA synthesis, implicating a transcriptional mechanism associated with the dexamethasone-mediated suppression of cPLA2. Induced expression of cPLA2 mRNA by several proinflammatory cytokines was blocked by cotreatment with dexamethasone.

CONCLUSIONS

Glucocorticoids are capable of markedly altering basal and cytokine-stimulated cPLA2 gene expression in intestinal epithelial cells, leading to a reduction in arachidonate pools in these cells. Dexamethasone-dependent inhibition occurs through a direct reduction of de novo cPLA2 gene transcription.

Effects of 1-chloro-2,4,6-trinitrobenzene on 5-lipoxygenase activity and cellular leukotriene synthesis

5-Lipoxygenase (EC 1.13.11.34) is the key enzyme in the regulation of leukotriene synthesis. Here, the effects of various substituted nitrobenzene compounds on 5-lipoxygenase activity and the formation of leukotriene B4 (LTB4) were studied in polymorphonuclear leukocytes (PMNL), B lymphocytes, and human whole blood. 1-Chloro-2,4,6-trinitrobenzene (TNCB) was found to inhibit calcium ionophore A23187-induced leukotriene synthesis in PMNL in a biphasic manner. Thus, 1.0 microM TNCB caused 50% inhibition of LTB4 formation, but only 16% inhibition was found at 10 times higher concentration. In contrast, this higher concentration of TNCB activated the synthesis of LTB4 when PMNL were stimulated with arachidonic acid alone, demonstrating that TNCB can exert both stimulatory and inhibitory effects on leukotriene synthesis depending on the experimental conditions. The inhibitory effect of 1.0 microM TNCB on ionophore A23187-induced leukotriene synthesis could be circumvented by addition of exogenous arachidonic acid. At high concentrations of TNCB (25-100 microM), the drug blocked ionophore A23187-induced leukotriene synthesis. TNCB also inhibited LTB4 formation in B lymphocytes, as well as in human whole blood. The activity of recombinant 5-lipoxygenase was inhibited by TNCB, and reduced glutathione or beta-mercaptoethanol counteracted this inhibition. This suggests that TNCB might inhibit 5-lipoxygenase by alkylating thiol groups. TNCB possessed a high specificity for 5-lipoxygenase with only modest inhibitory effects on 12-lipoxygenase (EC 1.13.11.31), 15-lipoxygenase (EC 1.13.11.12), and phospholipase A2 (EC 3.1.1.4) activities. Taken together, these results show that TNCB can both specifically inhibit and stimulate leukotriene formation and might be useful in further studies on the regulation of 5-lipoxygenase.

Production of arachidonic acid metabolites by the colon adenocarcinoma cell line HT29 cl.19A and their effect on chloride secretion

Eicosanoids were found in large amounts in the colonic mucosa of patients suffering from inflammatory bowel diseases and colonic adenocarcinoma. The aim of this study was to evaluate the role of the intestinal epithelial cells in the arachidonic acid metabolism and their functional response to certain eicosanoids. We used the human adenocarcinoma epithelial cell line HT29 cl.19A cell, which is an in vitro model of colon carcinoma and ion transport. These cells were found to express 5- and 15-lipoxygenase, leukotriene A4 hydrolase and cyclooxygenase-1 and -2 mRNAs. We observed an arachidonic acid metabolism via 5-lipoxygenase pathway despite the lack of FLAP mRNA expression and that certain eicosanoids such as hydroperoxy- and hydroxyeicosatetraenoic acids stimulate chloride secretion.

Phospholipase A2 activating protein and idiopathic inflammatory bowel disease

BACKGROUND

Crohn's disease and ulcerative colitis are idiopathic inflammatory bowel diseases (IBD) involving synthesis of eicosanoids from arachidonic acid (AA), which is released from membrane phospholipids by phospholipase A2 (PLA2). A potentially important regulator of the production of these mediators is a protein activator of PLA2, referred to as PLA2 activating protein (PLAP).

AIMS

The purpose of this investigation was to discover if PLAP values might be increased in the inflamed intestinal tissue of patients with IBD and in intestinal tissue of mice with colitis.

PATIENTS

Biopsy specimens were taken from patients with ulcerative colitis and Crohn's disease undergoing diagnostic colonoscopy, and normal colonic mucosa was obtained from patients without IBD after surgical resection.

METHODS

Immunocytochemistry with affinity purified antibodies to PLAP synthetic peptides was used to locate PLAP antigen in sections of intestinal biopsy specimens from IBD patients compared with that of normal intestinal tissue. Northern blot analysis with a murine [32P] labelled plap cDNA probe was performed on RNA extracted from the colons of mice fed dextran sulphate sodium (DSS) and cultured HT-29 cells exposed to lipopolysaccharide (LPS).

RESULTS

PLAP antigen was localised predominantly within monocytes and granulocytes in intestinal tissue sections from IBD patients, and additional deposition of extracellular PLAP antigen was associated with blood vessels and oedema fluid in the inflamed tissues. In contrast, tissue sections from normal human intestine were devoid of PLAP reactive antigen, except for some weak cytoplasmic reaction of luminal intestinal epithelial cells. Similarly, colonic tissue from DSS treated mice contained an increased amount of PLAP antigen compared with controls. The stroma of the lamina propria of the colonic mucosa from the DSS treated mice reacted intensely with antibodies to PLAP synthetic peptides, while no reaction was observed with control mouse colons. These data were supported by northern analysis which showed that PLAP mRNA was increased in the colons of DSS treated mice and cultured HT-29 cells exposed to LPS.

CONCLUSIONS

As PLAP values were increased in the intestinal mucosa of IBD patients and mice with colitis, as well as in LPS treated cultured HT-29 cells, a role was postulated for PLAP in increasing PLA2 activity, which leads to the increased synthesis of eicosanoids in intestinal tissues of patients with these inflammatory diseases.

Omega-3 fatty acids and low carbohydrate diet for maintenance of remission in Crohn's disease. A randomized controlled multicenter trial. Study Group Members (German Crohn's Disease Study Group)

BACKGROUND

There is no established therapy for maintaining remission in patients with Crohn's disease. Following different suggestions from the literature, two potential interventions for maintaining remission were tested against placebo, using either 5 g/day of a highly concentrated omega-3 fatty acid compound or a carbohydrate-reduced diet (84 g/day).

METHODS

A total of 204 patients were recruited after they had had an acute relapse. After remission (CDAI < or = 150) was attained with steroid therapy, patients were randomized to receive either omega-3 fatty acids (n = 70), placebo (n = 65), or diet (n = 69). Low-dose prednisolone was given to all patients for the first 8 weeks of intervention. CDAI and an acute-phase protein (CRP) were used as criteria for a relapse.

RESULTS

The proportion of patients without relapse within a year were similar in the placebo and active treatment group (intention-to-treat analysis: placebo, 30%; active treatment, 30%; protocol-adhering patients, 29% versus 28%). Patients did gain benefit (53%; p = 0.023) for as long as they maintained the diet. However, intention-to-treat analysis (diet group, 40%) did not show a noticeable difference when compared with placebo.

CONCLUSIONS

Omega-3 fatty acids did not show an effect on extending the remission in Crohn's disease. For the diet patients the question remains whether the noncompliant patients dropped out early because they sensed a relapse approaching or whether their condition deteriorated because they failed to comply with the diet.

Presence of immunocytes and sulfidopeptide leukotrienes in the inflamed guinea pig distal colon

This study examined whether the immunocyte recruitment associated with a mild inflammatory state induced by acetic acid would produce detectable sulfidopeptide leukotriene (LT) levels from colonic tissues or in dialysates. Histological examination and measurements of peroxidase activities of inflamed tissues indicated edema, hyperplasia and neutrophil infiltration. Significant elevated LTB4 and prostaglandin E2(PGE2) levels were found but only slight elevations in sulfidopeptide LTs occurred. A slight elevation in eosinophil peroxidase indicated that eosinophil infiltration also occurred. The increase in sulfidopeptide LT levels appeared insufficient by itself to alter secretory responses in the distal colon. However, combined with other immunocyte products such as PGs, the sulfidopeptide LTs may influence the symptomology of inflammatory bowel disease.

Eicosanoids and inflammatory bowel disease

IBD is a disease of unknown cause that involves an amplification of the inflammatory response in the intestinal mucosa. Although not the only offending agents leading to the disease, eicosanoids, the collective group of AA metabolites, may a significant role in the pathogenesis of IBD. This article reviewed the biochemical pathways of eicosanoid formation and the clinical relevance of eicosanoids to IBD. Potential strategies designed to interfere with various aspects of AA metabolism were also outlined. Further clinical trials of newer compounds may soon prove them effective in the management of IBD.