Niacin ameliorates ulcerative colitis via prostaglandin D2-mediated D prostanoid receptor 1 activation.

Niacin, as an antidyslipidemic drug, elicits a strong flushing response by release of prostaglandin (PG) D2 However, whether niacin is beneficial for inflammatory bowel disease (IBD) remains unclear. Here, we observed niacin administration-enhanced PGD2 production in colon tissues in dextran sulfate sodium (DSS)-challenged mice, and protected mice against DSS or 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis in D prostanoid receptor 1 (DP1)-dependent manner. Specific ablation of DP1 receptor in vascular endothelial cells, colonic epithelium, and myeloid cells augmented DSS/TNBS-induced colitis in mice through increasing vascular permeability, promoting apoptosis of epithelial cells, and stimulating pro-inflammatory cytokine secretion of macrophages, respectively. Niacin treatment improved vascular permeability, reduced apoptotic epithelial cells, promoted epithelial cell update, and suppressed pro-inflammatory gene expression of macrophages. Moreover, treatment with niacin-containing retention enema effectively promoted UC clinical remission and mucosal healing in patients with moderately active disease. Therefore, niacin displayed multiple beneficial effects on DSS/TNBS-induced colitis in mice by activation of PGD2/DP1 axis. The potential efficacy of niacin in management of IBD warrants further investigation.

Optimizing of the basophil activation test: Comparison of different basophil identification markers.

BACKGROUND: Flowcytometric identification of basophils is a prerequisite for measuring activation of basophils with IgE-dependent or IgE-independent stimuli. Aim of this study was to compare different marker combinations in a simultaneous multicolor flowcytometric measurement. METHODS: Ten patients with a grass pollen allergy and three controls were included in the study. Basophilic cells were gated by using anti-CCR3, anti-IgE, anti-CRTH2, anti-CD203c, and anti-CD3. Cells were activated by a monoclonal anti-FcεRI antibody, N-formyl-methionyl-leucyl-phenylalanine (fMLP), and the allergen extract Phleum pratense. The activation marker anti-CD63 was used. RESULTS: The highest relative number of basophils was found with anti-CCR3+ cells, anti-IgE+ and anti-IgE+ /anti-CD203c+ cells, the lowest with CRTH2+/CD203c+/CD3- cells. A very good and good concordance of CCR3+ cells was seen with CCR3+/CD3- cells and CRTH2+/CD203c+/CD3- cells in all experiments. The contamination of the CCR3+ population with CD3+ cells and the contamination of the IgE+-population with CCR3- cells and CD203- cells were the lowest compared to all other marker combinations. CONCLUSIONS: As the highest relative number of basophils was identified by anti-CCR3 followed by the anti-IgE and anti-IgE/antiCD203c positive population in most cases, these markers can generally be recommended for identification of basophils. If a basophil population with very high purity is needed, anti-IgE should be chosen.

Efficacy of the oral chemoattractant receptor homologous molecule on TH2 cells antagonist BI 671800 in patients with seasonal allergic rhinitis.

BACKGROUND: The inflammatory response in patients with seasonal allergic rhinitis (SAR) is partly mediated by the prostaglandin D2 receptor chemoattractant receptor homologous molecule on T(H)2 cells (CRTH2). OBJECTIVE: We sought to investigate the efficacy and safety of the oral CRTH2 antagonist BI 671800 (50, 200, and 400 mg twice daily), fluticasone propionate nasal spray (200 µg once daily), or oral montelukast (10 mg once daily) administered for 2 weeks in patients with SAR. METHODS: In this randomized, double-blind, placebo-controlled, partial-crossover study, participants aged 18 to 65 years with a positive skin prick test to Dactylis glomerata pollen were exposed to out-of-season allergen in the environmental challenge chamber for 6 hours. The primary efficacy variable was the total nasal symptom score assessed as the area under the curve (AUC)(0-6h). RESULTS: In total, 146 patients (63.7% male; mean age, 36.1 years) were randomized. The adjusted mean total nasal symptom score AUC(0-6h) was significantly reduced versus placebo with 200 mg of BI 671800 (absolute difference, -0.85; percentage difference, -17%; P = .0026), montelukast (absolute difference, -0.74; percentage difference, -15%; P = .0115), and fluticasone propionate (absolute difference, -1.64; percentage difference, -33%; P < .0001). Compared with placebo, BI 671800 significantly reduced nasal eosinophil values (P < .05 for all doses), significantly inhibited nasal inflammatory cytokine levels (IL-4 and eotaxin, P < .05; 200 mg twice daily), and induced a dose-related reduction in ex vivo prostaglandin D2-mediated eosinophil shape change. CONCLUSION: Two hundred milligrams of BI 671800 twice daily demonstrated efficacy in treating SAR symptoms induced by environmental challenge chamber allergen exposure and had a favorable safety profile.

CRTH2-dependent, STAT6-independent induction of cedar pollen dermatitis.

BACKGROUND: Airborne contact dermatitis to cedar pollen is a recently identified disease that generally affects individuals with cedar pollinosis of the nasal and/or ocular symptoms, as well as some patients with atopic dermatitis. OBJECTIVE: To elucidate the pathological mechanisms of cedar pollen dermatitis. METHODS: We established a mouse model of cedar pollen dermatitis by epicutaneous sensitization with Japanese cedar pollen antigen (Ag). RESULTS: Histologically, there was marked dermal cellular infiltrate, including eosinophils and mast cells, with epidermal thickening. The induction of dermatitis was accompanied by production of cedar pollen-specific IgE. In the lesional skin, IL-13, IL-18, eotaxin/chemokine (C-C motif) ligand (CCL) 11, regulated upon activation, normal T cell expressed and secreted/CCL5, macrophage-derived chemokine/CCL22 and thymus and activation-regulated chemokine/CCL17, but not IL-4 and IFN-gamma, were produced. Mast cell-deficient WBB6F1-W/W(v) mice failed to develop cedar pollen dermatitis, although regional lymph node cells proliferated in response to Cryptomeria japonica (Cry j) 1 and Cry j2 Ags in vitro. Surprisingly, the induction of dermatitis was independent of STAT6/IgE. In contrast, mice deficient in CRTH2, a receptor for prostaglandin D2 (PGD2), showed diminished inflammation. Consistent with this, ramatroban, a CRTH2 antagonist, significantly inhibited inflammatory cell infiltration. CONCLUSION: These data suggest that PGD2-CRTH2 signalling contributes to inflammation in cedar pollen dermatitis, and unlike cedar pollinosis of the nasal mucosa, STAT6 is not a therapeutic target for treatment.

Fatty acids and immune responses--a new perspective in searching for clues to mechanism.

Dietary essential fatty acids are the precursors for eicosanoids. Among the eicosanoids derived from arachidonic acid, prostaglandin (PG) E2 is known to possess immunosuppressive actions. Thus, it has been a prevailing hypothesis that the immuno-modulatory roles of dietary fatty acids are mediated at least in part through the alteration of PG biosynthesis. PGs exert their biological effects through their cognate receptors. There are four subtypes of PGE receptors (EP1, EP2, EP3, and EP4) so far identified. Although the association of EP receptors with G proteins coupled to adenylate cyclase and the mobilization of intracellular calcium are well documented, downstream signaling pathways for these receptors are virtually unknown. Identification of downstream signaling pathways for each subtype of EP receptors and target genes regulated by the activation of the receptor will help with our understanding of the mechanism by which dietary fatty acids affect immune responses through the modulation of PGE2 biosynthesis. Emerging evidence suggests that fatty acids can additionally act as second messengers, regulators of signal transducing molecules or transcription factors. Acylation with long-chain fatty acids can occur on a variety of signaling molecules and can affect their membrane translocation and functions. Dietary fatty acids can alter functional properties of lipid mediators by changing the composition of acyl moieties of these molecules. Evidence accumulated recently indicates that long-chain unsaturated fatty acids and their metabolites bind and activate peroxisome proliferator-activated receptors (PPARs). PPARs are nuclear hormone receptors and transcription factors that regulate the expression of broad arrays of genes involved not only in lipid and glucose metabolism, but also in immune and inflammatory responses. PPARs may therefore be important cellular targets that mediate modulation of immune responses by dietary fatty acids. Together, it becomes clear now that multiple steps in various receptor-mediated signaling pathways can be modulated by dietary fatty acids. It will be a challenging task to quantitatively determine how different fatty acids alter functional properties of multitude of signaling components and final cellular responses. Elucidating the mechanism of actions of fatty acids on receptor-mediated signaling pathways in immuno-competent cells will provide a new insight for understanding the immuno-modulatory roles of dietary fatty acids.