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RBL-2H3 Cells (rbl-2h3 + cell)
Selected AbstractsChemInform Abstract: Synthesis of 3-Substituted Isocoumarins and Their Inhibitory Effects on Degranulation of RBL-2H3 Cells Induced by Antigen.CHEMINFORM, Issue 9 2009Ai Kurume Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Phospholipase,C, negatively regulates Rac/Cdc42 activation in antigen-stimulated mast cellsEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 1 2007Mirvat El-Sibai M.D. Abstract The Rho GTPases Rac and Cdc42 play a central role in the regulation of secretory and cytoskeletal responses in antigen-stimulated mast cells. In this study, we examine the kinetics and mechanism of Rac and Cdc42 activation in the rat basophilic leukemia RBL-2H3 cells. The activation kinetics of both Rac and Cdc42 show a biphasic profile, consisting of an early transient peak at 1,min and a late sustained activation phase at 20,40,min. The inhibition of phospholipase,C (PLC), causes a twofold increase in Rac and Cdc42 activation that coincides with a dramatic production of atypical filopodia-like structures. Inhibition of protein kinase,C using bisindolylmaleimide mimics the effect of PLC, inhibition on Rac activation, but not on Cdc42 activation. In contrast, depletion of intracellular calcium leads to a complete inhibition of the early activation peak of both Rac and Cdc42, without significant effects on the late sustained activation. These data suggest that PLC, is involved in a negative feedback loop that leads to the inhibition of Rac and Cdc42. They also suggest that the presence of intracellular calcium is a prerequisite for both Rac and Cdc42 activation. [source] The use of membrane translocating peptides to identify sites of interaction between the C5a receptor and downstream effector proteinsIMMUNOLOGY, Issue 4 2004Graham A. Auger Summary The complement fragment C5a is a potent leucocyte chemoattractant and activator, mediating its effects through a G-protein-coupled receptor. Whilst the C-terminal domain of this receptor has been shown to be essential for receptor desensitization and internalization, it is not known which domains couple to the receptor's heterotrimeric G proteins. In this report we have used a membrane translocating sequence (MTS) to examine the effects of the four intracellular domains of the human C5a receptor (C5aR) on the receptor's signalling via G,i family heterotrimeric G proteins in intact RBL-2H3 cells. The results indicate that all of the intracellular domains couple to downstream signalling, with the proximal region of the C terminus being a major binding site and intracellular loop 3 playing a role in G protein activation or receptor desensitization. [source] Antiallergic Activities of Pigmented Rice Bran Extracts in Cell AssaysJOURNAL OF FOOD SCIENCE, Issue 9 2007Sun Phil Choi ABSTRACT:, Using a panel of chemical, biochemical, and cell assays, we determined inhibitory effects of extracts of the pigmented black rice brans on in vitro allergic reactions. Ethanol-water (70% v/v) extracts from 5 pigmented brans were found to be more effective than an extract from a nonpigmented rice cultivar in suppressing the release of histamine and ,-hexosaminidase from basophilic RBL-2H3 cells stimulated with both Ionophore A23187 and immunoglobulin E (IgE)-antigen complexes. Suppression was also obtained with A23187-stimulated rat peritoneal mast cells. The extent of inhibition of these 2 markers of the immune response was accompanied by an influx of calcium ions. The inhibition of the immune process by the pigmented brans was confirmed by the observed modulation of the proinflammatory cytokine gene expressions and cytokine release, as indicated by the reduction in tumor necrosis factor (TNF)-,, interleukin (IL)-1,, IL-4, and IL-6 mRNA expressions determined with the reverse transcription-polymerase chain reaction (RT-PCR). Reduction of TNF-,, IL-1,, and IL-6 protein release from both the cultured cell line and peritoneal cells was further confirmed by enzyme-linked immunoadsorbent assays. Rice bran from the LK1-3-6-12-1-1 cultivar was the most effective inhibitor in all assays. This particular rice variety merits further evaluation as part of a human diet to ascertain its potential to protect against allergic diseases such as hay fever and asthma. [source] Mechanisms for recycling and biosynthesis of endogenous cannabinoids anandamide and 2-arachidonylglycerolJOURNAL OF NEUROCHEMISTRY, Issue 4 2008Ekaterina A. Placzek Abstract The mechanisms of endogenous cannabinoid biosynthesis are not completely understood. We hypothesized that anandamide could be recycled by the cell to form new endocannabinoid molecules and released into the extracellular space. We determined that new endocannabinoids derived from exogenous anandamide or arachidonic acid were synthesized and released from RBL-2H3 cells in response to ionomycin. Treatment of RBL-2H3 cells with nystatin and progesterone, agents that disrupt organization of lipid raft/caveolae, resulted in the attenuation of anandamide and 2-arachidonyl glycerol synthesis and/or release in response to stimulation with ionomycin suggesting a role for these membrane microdomains in endocannabinoid biosynthesis. Furthermore, anandamide synthesis may be independent of N -acyl phosphatidylethanolamine phospholipase D as expression of the enzyme was not detected in RBL-2H3 cells. We also established that extracellular calcium is necessary for endocannabinoid biosynthesis because release of intracellular calcium stores alone does not promote endocannabinoid biosynthesis. Next, we examined the role of calcium as a ,switch' to activate the synthesis of anandamide and simultaneously reduce uptake. Indeed, [3H] anandamide uptake was reduced in the presence of calcium. Our findings suggest a mechanism indicative of calcium-modulated activation of anandamide synthesis and simultaneous termination of uptake. [source] Real-time cellular uptake of serotonin using fluorescence lifetime imaging with two-photon excitationMICROSCOPY RESEARCH AND TECHNIQUE, Issue 4 2008Stanley Walter Botchway Abstract The real-time uptake of serotonin, a neurotransmitter, by rat leukemia mast cell line RBL-2H3 and 5-hydroxytryptophan by Chinese hamster V79 cells has been studied by fluorescence lifetime imaging microscopy (FLIM), monitoring ultraviolet (340 nm) fluorescence induced by two-photon subpicosecond 630 nm excitation. Comparison with two-photon excitation with 590 nm photons or by three-photon excitation at 740 nm shows that the use of 630 nm excitation provides optimal signal intensity and lowered background from auto-fluorescence of other cellular components. In intact cells, we observe using FLIM three distinct fluorescence lifetimes of serotonin and 5-hydroxytryptophan according to location. The normal fluorescence lifetimes of both serotonin (3.8 ns) and 5-hydroxytryptophan (3.5 ns) in solution are reduced to ,2.5 ns immediately on uptake into the cell cytosol. The lifetime of internalized serotonin in RBL-2H3 cells is further reduced to ,2.0 ns when stored within secretory vesicles. Microsc. Res. Tech., 2008. © 2007 Wiley-Liss, Inc. [source] Inhibition by troglitazone of the antigen-induced production of leukotrienes in immunoglobulin E-sensitized RBL-2H3 cellsBRITISH JOURNAL OF PHARMACOLOGY, Issue 2 2000Masamichi Yamashita The effect of troglitazone, an anti-diabetic drug with insulin-sensitizing action, on antigen-induced production of leukotriene (LT) B4, C4 and E4 and prostaglandin D2 (PGD2) was examined in dinitrophenol (DNP)-specific immunoglobulin E (IgE)-sensitized RBL-2H3 mast cells following stimulation by the antigen, DNP-conjugated human serum albumin. Levels of LTB4, C4 and E4 and PGD2 in the conditioned medium were enzyme-immunoassayed. Troglitazone inhibited the antigen-induced production of LTB4, C4 and E4 and the potency of the inhibition was comparable to that of zileuton, a specific inhibitor of 5-lipoxygenase (5-LOX) and a clinically used anti-asthmatic drug. Neither troglitazone nor zileuton affected antigen-induced production of PGD2, arachidonic acid release from membrane phospholipids and degranulation. Troglitazone inhibited LTB4 production by the supernatant fraction of RBL-2H3 cell lysate with similar potency to zileuton, suggesting that troglitazone inhibits LT production by direct inhibition of 5-LOX activity. Furthermore, it was shown that troglitazone as well as zileuton inhibited LTB4 production in A23187-stimulated rat peritoneal neutrophils. These findings suggest that troglitazone inhibits antigen-induced LT production in the IgE-sensitized RBL-2H3 cells and A23187-stimulated rat peritoneal neutrophils by direct inhibition of 5-LOX activity. British Journal of Pharmacology (2000) 129, 367,373; doi:10.1038/sj.bjp.0703044 [source] Blockade of superoxide generation prevents high-affinity immunoglobulin E receptor-mediated release of allergic mediators by rat mast cell line and human basophilsCLINICAL & EXPERIMENTAL ALLERGY, Issue 4 2002T. Yoshimaru Summary Background Previous studies have shown that rat peritoneal mast cells and mast cell model rat basophilic leukaemia (RBL-2H3) cells generate intracellular reactive oxygen species (ROS) in response to antigen challenge. However, the physiological significance of the burst of ROS is poorly understood. Objective The present study was undertaken to investigate the role of superoxide anion in mediator release in rat and human cell systems. Methods RBL-2H3 cells were directly stimulated with anti-rat Fc,RI ,-subunit monoclonal antibody (mAb). For the analysis of human cell system, leucocytes were isolated by dextran sedimentation from healthy volunteers or from patients, and challenged either with anti-human Fc,RI mAb or with the relevant antigens. Superoxide generation was determined by chemiluminescence-based methods. The releases of histamine and leukotrienes (LT)s were determined by enzyme-linked immunosorben assay (ELISA). Results Cross-linking of Fc,RI on RBL-2H3 cells or on human leucocytes from healthy donors by the anti-Fc,RI mAb resulted in a rapid generation of superoxide anion, as determined by chemiluminescence using superoxide-specific probes. Similarly, leucocytes from patients generated superoxide anion in response to the challenge with the relevant allergen but not with the irrelevant allergen. Furthermore, diphenyleneiodonium (DPI), a well-known inhibitor of flavoenzymes suppressed the superoxide generation and the release of histamine and LTC4 induced by the anti-Fc,RI mAb or by allergen in parallel. Conclusion These results indicate that both RBL-2H3 cells and human basophils generate superoxide anion upon Fc,RI cross-linking either by antibody or by allergen challenge and that blockade of the generation prevents the release of allergic mediators. The findings strongly support the role of superoxide generation in the activation of mast cells and basophils under both physiological and pathological conditions. The findings suggest that drugs regulating the superoxide generation have potential therapeutic use for allergic disorders. [source] | |||||||||||||