Project description:Leukotriene E4 (LTE4) the most stable of the cysteinyl leukotrienes (cysLTs) binds poorly to classical type 1 (CysLT1) and 2 (CysLT2) receptors although it induces potent responses in human airways in vivo, such as bronchoconstriction, airway hyperresponsiveness and inflammatory cell influx suggesting the presence of a novel receptor that preferentially responds to LTE4. To identify such a receptor two human mast cell lines, LAD2 and LUVA, were selected that differentially responded to LTE4 when analysed by intracellular signalling and gene expression. Comparative transcriptome analysis and recombinant gene overexpression experiments revealed CysLT1 as a receptor responsible for potent LTE4-induced response in LAD2 but not in LUVA cells, an observation confirmed further by gene knockdown and selective inhibitors. Lentiviral overexpression of CysLT1 in LUVA cells augmented intracellular calcium signalling induced by LTE4 but did not restore full agonist responses at the gene expression level. Our data support a model where both an increased expression of Gαq-coupled CysLT1, and sustained intracellular calcium mobilisation and extracellular signal-regulated kinase (Erk) activation, are required for LTE4-mediated regulation of gene expression in human cells. Our study shows for the first time that CysLT1 expression is critically important for responsiveness to LTE4 within a human cell system.
Project description:Background: Cysteinyl leukotrienes (cysLTs) are important mediators of innate immune responsiveness and chronic inflammatory diseases. CysLTs acting through cysteinyl leukotriene receptors may influence the migration and activity of cells such as eosinophils, monocytes and dendritic cells. Objective: To determine the gene expression signature of human monocytes in response to cysLTs and to elucidate the signaling pathways involved in monocyte activation. Methods: Gene expression was analyzed using oligonucleotide microarrays. Responsiveness to cysLTs was assessed by real-time PCR, calcium flux, kinase activation and chemotaxis assays. Results: Cysteinyl leukotriene type I receptor (CysLTR1) transcript 1 is predominantly expressed in human monocytes and cysLTs signal through CysLTR1 in these cells. Several immediate-early genes, including early growth response (Egr) -2, 3, FosB, activating transcription factor 3 and nuclear receptor subfamily 4 were significantly induced by LTD4. This effect was mediated by CysLTR1 coupled to Gαi/o, activation of phospholipase C, and inositol-1,4,5-triphosphate (IP3) and store operated calcium channels. LTD4 induced p38 MAP kinase phosphorylation, a pathway also involved in the regulation of immediate-early genes expression in monocytes. LTD4 stimulated monocyte chemotactic activity that was fully blocked by a selective CysLTR1 inhibitor MK571 and pertussis toxin, suggesting that CysLTR1 coupled to Gαi/o is a dominant functional pathway in human monocytes. Conclusion: Our data show that cysLTs acting through CysLTR1 can significantly influence the activation and migration of human monocytes and that these effects can be fully inhibited by CysLTR1 antagonists. Clinical implications: Antileukotriene therapies are likely to significantly block the proinflammatory functions of human monocytes. Experiment Overall Design: 4 control sample, 4 LTD4 stimulated samples
Project description:Background: Cysteinyl leukotrienes (cysLTs) are important mediators of innate immune responsiveness and chronic inflammatory diseases. CysLTs acting through cysteinyl leukotriene receptors may influence the migration and activity of cells such as eosinophils, monocytes and dendritic cells. Objective: To determine the gene expression signature of human monocytes in response to cysLTs and to elucidate the signaling pathways involved in monocyte activation. Methods: Gene expression was analyzed using oligonucleotide microarrays. Responsiveness to cysLTs was assessed by real-time PCR, calcium flux, kinase activation and chemotaxis assays. Results: Cysteinyl leukotriene type I receptor (CysLTR1) transcript 1 is predominantly expressed in human monocytes and cysLTs signal through CysLTR1 in these cells. Several immediate-early genes, including early growth response (Egr) -2, 3, FosB, activating transcription factor 3 and nuclear receptor subfamily 4 were significantly induced by LTD4. This effect was mediated by CysLTR1 coupled to Gαi/o, activation of phospholipase C, and inositol-1,4,5-triphosphate (IP3) and store operated calcium channels. LTD4 induced p38 MAP kinase phosphorylation, a pathway also involved in the regulation of immediate-early genes expression in monocytes. LTD4 stimulated monocyte chemotactic activity that was fully blocked by a selective CysLTR1 inhibitor MK571 and pertussis toxin, suggesting that CysLTR1 coupled to Gαi/o is a dominant functional pathway in human monocytes. Conclusion: Our data show that cysLTs acting through CysLTR1 can significantly influence the activation and migration of human monocytes and that these effects can be fully inhibited by CysLTR1 antagonists. Clinical implications: Antileukotriene therapies are likely to significantly block the proinflammatory functions of human monocytes. Keywords: monocytes stimulated with LTD4
Project description:Uveal melanoma (UM) is an ocular cancer, with propensity for lethal liver metastases. When metastatic UM (MUM) occurs, as few as 8% of patients survive beyond two years. Efficacious treatments for MUM are urgently needed. 1,4-dihydroxy quininib, a cysteinyl leukotriene receptor 1 (CysLT1) antagonist, alters UM cancer hallmarks in vitro, ex vivo and in vivo. Here, we investigated the 1,4-dihydroxy quininib mechanism of action and its translational potential in MUM.
Project description:Cysteinyl leukotrienes (cysLT), i.e. LTC4, LTD4, and LTE4, are lipid mediators derived from the 5-lipoxygenase pathway. The cysLT receptors cysLT1-R and cysLT2-R are expressed on different target cells and mediate inflammatory reactions in tissue- and LT-R-specific ways. Though endothelial cells (ECs) predominantly express cysLT2-Rs, their role in vascular biology remains to be defined. To delineate cysLT2-R´s action, we stimulated human umbilical vein EC with 100 nM LTD4 for 60 min, determined gene signatures by microarrays, and characterized the resulting EC phenotypes. As controls, we compared LTD4-induced genes with those induced by 10 nM thrombin, a prototype vasoactive activator of EC that binds to protease-activated receptor 1 (PAR-1). Following application of stringent filters 37 LTD4-upregulated genes were identified (> 2.5fold stimulation). Surprisingly, most of the LTD4-regulated genes were also induced by thrombin and expression of cysLT2-R- and PAR-1-regulated genes strongly correlated (Pearson correlation coefficient: r = 0.90). Moreover, LTD4 + thrombin, when added together, augmented expression of LTD4- or thrombin-stimulated genes (Wilcoxon signed rank test: p < 0.01). Prominently induced genes that may play roles in vascular injury were studied in detail: Early growth response (EGR) and nuclear receptor subfamily 4 group A; E-selectin; CXC ligand 2; interleukin 8 (IL-8); a disintegrin-like and metalloprotease (reprolysin type) with thrombospondin type 1 motif 1 (ADAMTS-1); and tissue factor (TF). Transcripts of these genes peaked at approximately 60 min, were unaffected by the cysLT1-R antagonist montelukast, and were superinduced by cycloheximide. The EC phenotype was markedly altered: LTD4 induced de novo synthesis of EGR1 protein and EGR1 localized in the nucleus in LTD4-stimulated cells; LTD4 upregulated IL-8 formation and secretion; and LTD4 raised TF protein and TF-dependent EC pro-coagulant activity. These data show that cysLT2-R activation results in a pro-inflammatory EC phenotype through activation of immediate-early genes that resemble those induced by PAR-1. As LTD4 and thrombin are formed concomitantly during vascular injury and pro-thrombotic states, cysLT2-R and PAR-1 may collaborate in vivo to mediate vascular injury and repair. Keywords: Leukotriene Transcriptome, Thrombin Transcriptome, HUVEC, Immediate-Early Gene Expression, Cysteinyl Leukotriene 2 Receptor Gene Signature in HUVEC
Project description:Structural studies have recently shown that mechanism of selective AT1R activation by different classes of ligands is initiated by the ability of ligands to stabilize unique active conformations of the receptor. Active conformations enhance transducer coupling leading to effector mediated signaling, that has been proposed to be linked to differential phosphorylation of the c-terminal tail of the receptor. To determine how different classes of AT1R ligands effect receptor phosphorylation and activation of downstream signaling we used TMT-MS to identify the amino acid residues of the AT1R phosphorylated following treatment with the full balanced agonist Angiotensin II and a β-arrestin biased ligand, TRV023. Here we show that Ang and TRV 023 induce two distinct patterns of phosphorylation clusters a.a. residues along the entire c-tail with AngII inducing a greater magnitude than the β-arrestin biased ligand TRV 023, particularly in the proximal part of the tail. Selective mutagenesis of Ser and Thr residues, we found that of the 12 Ser/Thr residues within the c-tail, only the 4 proximal and 4 middle residues are all required for full β -arrestin functionality in response to either a balanced or β-arrestin-based ligand. Surprisingly, phosphorylation of 4 residues in the proximal c-tail is necessary for maximal G-protein activation to a full agonist. Taken together our data demonstrate that a AT1R ligands that stabilize different active confirmations of the receptor (full agonist vs. β-arrestin biased) induce distinct phosphorylation patterns on the c-tail of the receptor to evoke distinct receptor-transducer engagement and downstream receptor trafficking and signaling.