Cooperative and redundant signaling of leukotriene B4 and leukotriene D4 in human monocytes
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ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE24869 | GEO | 2011/09/21
SECONDARY ACCESSION(S): PRJNA132125
REPOSITORIES: GEO
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Project description:LTB4, 50 nmol/L for 30 minutes, induced expression of 27 genes in cultured human elutriated monocytes comparred to vehicle (ethanol) treated control cells. Matched control versus treated cells
2011-09-20 | E-GEOD-24869 | biostudies-arrayexpress
Project description:BACKGROUND:Leukotriene B(4) (LTB(4)) and cysteinyl leukotrienes (cysLTs) are important immune mediators, often found concomitantly at sites of inflammation. Although some of the leukotriene-mediated actions are distinctive (e.g., bronchial constriction for cysLTs), many activities such as leukocyte recruitment to tissues and amplification of inflammatory responses are shared by both classes of leukotrienes. OBJECTIVE:We used human monocytes to characterize leukotriene-specific signaling, gene expression signatures, and functions and to identify interactions between LTB(4)- and cysLTs-induced pathways. METHODS:Responsiveness to leukotrienes was assessed using oligonucleotide microarrays, real-time PCR, calcium mobilization, kinase activation, and chemotaxis assays. RESULTS:Human monocytes were found to express mRNA for high- and low-affinity LTB(4) receptors, BLT(1) and BLT(2), but signal predominantly through BLT(1) in response to LTB(4) stimulation as shown using selective agonists, inhibitors, and gene knock down experiments. LTB(4) acting through BLT(1) coupled to G-protein ? inhibitory subunit activated calcium signaling, p44/42 mitogen-activated protein kinase, gene expression, and chemotaxis. Twenty-seven genes, including immediate early genes (IEG), transcription factors, cytokines, and membrane receptors were significantly up-regulated by LTB(4). LTB(4) and LTD(4) had similar effects on signaling, gene expression, and chemotaxis indicating redundant cell activation pathways but costimulation with both lipid mediators was additive for many monocyte functions. CONCLUSION:Leukotriene B(4) and LTD(4) display both redundant and cooperative effects on intracellular signaling, gene expression, and chemotaxis in human monocytes. These findings suggest that therapies targeting either leukotriene alone may be less effective than approaches directed at both.
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Project description:total RNA from mouse (male c57BL/6) spleen labeled with Cy3 vs total RNA from mouse (male c57BL/6) B cells treated with Leukotriene B4 (LTB4) labeled with Cy5- time course with repeats Keywords: ordered
2003-04-14 | GSE390 | GEO
Project description:Leukotriene B4 (LTB4) is a potent lipid mediator of inflammation, implicated in numerous diseases including atherosclerosis. We have used primary human monocytes, which express both receptors, to analyze transcriptional responses to LTB4. Comparisons were made between LTB4- and vehicle-treated samples at the same time point. The analysis showed that expression of 72 genes was upregulated at least two-fold at two time points. These genes include multiple chemokines as well as some genes with unknown function. Keywords: time course
2007-10-18 | GSE9332 | GEO
Project description:Timely inhibition of inflammation and initiation of resolution are important for the repair of injured tissues. Pharmacological inhibition of mammalian STE20-like protein kinase 1/2 (MST1/2) with XMU-MP-1 might augment tissue regeneration and repair by suppressing apoptosis and increasing cell proliferation. However, MST1 has anti-inflammatory activity, inhibition of which may result in therapy failure. Here, we identified an approach with the potential to overcome this limitation by protecting against cardiac inflammation resulting from inhibition of MST1 in macrophages. We found exacerbation of cardiac dysfunction in LysMCre-mediated Mst1/2-deficient mice after myocardial infarction (MI). This effect was attributed to a shift of macrophage subtypes from those expressing Cxcl2 and Cd163 toward those with Ccl2 and Ccl4 expression. Mass spectrometry identified leukotriene B4 (LTB4) as the lipid mediator that was upregulated in the absence of MST1. We found that MST1 phosphorylated 5-lipoxygenase (5-LOX) at its T218 residue, disrupting the interaction between 5-LOX and 5-LOX-activating protein, and resulting in reduction of LTB4 production. By contrast, a 5-LOXT218A variant showed no response to MST1. Moreover, treatment of peritoneal macrophages with LTB4 or with medium conditioned by Mst1-deficient macrophages resulted in high Ccl2 and Ccl4 expression and low Cxcl2 and Cd163 expression, except when the cells were co-treated with the LTB4 receptor 1 (BLT1) antagonist CP105696. Furthermore, CP105696 ameliorated cardiac dysfunction in LysMCre-mediated Mst1/2-deficient mice and enhanced cardiac repair in wild-type mice treated with XMU-MP-1 after MI. The combination of an MST1/2 inhibitor and a BLT1 antagonist represents a promising strategy for combatting the effects of MI.
2021-12-13 | GSE181935 | GEO
Project description:Human umbilical vein endothelial cells (HUVEC) or the human macrophage cell line, Mono-Mac-6, treated with Leukotriene D4 for 1 hour Keywords = Leukotriene-Transcriptome Keywords = Mono-Mac-6 Keywords = HUVEC Keywords: other
2004-08-20 | GSE1644 | GEO
Project description:Asthma is associated with the overproduction of leukotrienes (LTs), including LTB4. Patients with severe asthma can be highly responsive to 5-lipoxygenase (5-LO) inhibition, which blocks production of both the cysteinyl LTs and LTB4. Production of LTB4 has traditionally been ascribed to neutrophils, mononuclear phagocytes, and epithelial cells, and acts as a chemoattractant for inflammatory cells associated with asthma. The source of LTB4 is unclear, especially in eosinophilic asthma. We speculated that the benefit of 5-LO inhibition could be mediated in part by inhibition of eosinophil-derived LTB4. LTB4 concentrations were assayed in BAL fluid from patients with severe asthma characterized by isolated neutrophilic, eosinophilic, and paucigranulocytic inflammation. Expression of LTA4 hydrolase (LTA4H) by airway eosinophils was determined by immunohistochemistry (IHC). Subsequently, peripheral blood eosinophils were activated and secreted LTB4 was quantified by enzyme immunoassay. Blood eosinophil LTA4H expression was determined by flow cytometry, qPCR, and IHC. LTB4 concentrations were elevated in BAL fluid from patients with severe asthma, including those with isolated eosinophilic inflammation, and these eosinophils displayed LTA4H via IHC. LTA4H expression by blood eosinophils was confirmed by flow cytometry, IHC, and qPCR. Robust LTB4 production by blood eosinophils was observed in response to some, but not all, stimuli. We demonstrated that eosinophils express LTA4H transcripts and protein, and can be stimulated to secrete LTB4. We speculate that in many patients with asthma, eosinophil-derived LTB4 is increased, and this may contribute to the efficacy of 5-LO inhibition.
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Project description:Leukotriene B4 receptor 1 (BLT1) plays crucial roles in the acute inflammatory responses and is a valuable target for anti-inflammation treatment, however, the mechanism by which leukotriene B4 (LTB4) activates receptor remains unclear. Here, we report the cryo-electron microscopy (cryo-EM) structure of the LTB4 -bound human BLT1 in complex with a Gi protein in an active conformation at resolution of 2.91 Å. In combination of molecule dynamics (MD) simulation, docking and site-directed mutagenesis, our structure reveals that a hydrogen-bond network of water molecules and key polar residues is the key molecular determinant for LTB4 binding. We also find that the displacement of residues M1013.36 and I2717.39 to the center of receptor, which unlock the ion lock of the lower part of pocket, is the key mechanism of receptor activation. In addition, we reveal a binding site of phosphatidylinositol (PI) and discover that the widely open ligand binding pocket may contribute the lack of specificity and efficacy for current BLT1-targeting drug design. Taken together, our structural analysis provides a scaffold for understanding BLT1 activation and a rational basis for designing anti-leukotriene drugs.
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Project description:The cysteinyl leukotrienes (cys-LTs) are proinflammatory lipid mediators acting on the type 1 cys-LT receptor (CysLT(1)R) to mediate smooth muscle constriction and vascular permeability. GPR17, a G protein-coupled orphan receptor with homology to the P2Y and cys-LT receptors, failed to mediate calcium flux in response to leukotriene (LT) D(4) with stable transfectants. However, in stable cotransfections of 6xHis-tagged GPR17 with Myc-tagged CysLT(1)R, the robust CysLT(1)R-mediated calcium response to LTD(4) was abolished. The membrane expression of the CysLT(1)R analyzed by FACS with anti-Myc Ab was not reduced by the cotransfection, yet both LTD(4)-elicited ERK phosphorylation and the specific binding of [(3)H]LTD(4) to microsomal membranes were fully inhibited. CysLT(1)R and GPR17 expressed in transfected cells were coimmunoprecipitated and identified by Western blots, and confocal immunofluorescence microscopy revealed that GPR17 and CysLT(1)R colocalize on the cell surface of human peripheral blood monocytes. Lentiviral knockdown of GPR17 in mouse bone marrow-derived macrophages (BMMPhis) increased both the membrane expression of CysLT(1)R protein by FACS analysis and the LTD(4)-elicited calcium flux in a dose-dependent manner as compared with control BMMPhis, indicating a negative regulatory function of GPR17 for CysLT(1)R in a primary cell. In IgE-dependent passive cutaneous anaphylaxis, GPR17-deficient mice showed a marked and significant increase in vascular permeability as compared with WT littermates, and this vascular leak was significantly blocked by pretreatment of the mice with the CysLT(1)R antagonist, MK-571. Taken together, our findings suggest that GPR17 is a ligand-independent, constitutive negative regulator for the CysLT(1)R that suppresses CysLT(1)R-mediated function at the cell membrane.
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Project description:Neutrophils serve as a vanguard of the acute innate immune response to invading pathogens. Neutrophils are also abundant at sites of autoimmune inflammation, such as the rheumatoid joint, although their pathophysiologic role is incompletely defined and relevant effector functions remain obscure. Using genetic and pharmacologic approaches in the K/BxN serum transfer model of arthritis, we find that autoantibody-driven erosive synovitis is critically reliant on the generation of leukotrienes, and more specifically on leukotriene B4 (LTB4), for disease induction as well as perpetuation. Pursuing the cellular source for this mediator, we find via reconstitution experiments that mast cells are a dispensable source of leukotrienes, whereas arthritis susceptibility can be restored to leukotriene-deficient mice by intravenous administration of wild-type neutrophils. These experiments demonstrate a nonredundant role for LTB4 in inflammatory arthritis and define a neutrophil mediator involved in orchestrating the synovial eruption.
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