Histamine modulates multiple functional activities of monocyte-derived dendritic cell subsets via histamine receptor 2.
ABSTRACT Expression of CD1a proteins in human monocyte-derived dendritic cells (DCs) specifies functionally distinct subsets with different inflammatory properties. Histamine is recognized as an inflammatory mediator released by various cell types including DCs. The diverse biological effects of histamine are mediated by G-protein-coupled histamine receptors (HRs), which are able to modulate the functional activities of DC subsets. The goal of the present study was to compare the expression and activity of HRs in the CD1a(-) and CD1a(+) monocyte-derived DC subsets and to test the effects of histamine on the differentiation, activation and functional activities of these subsets. We show that H2R is present at high levels in both DC subsets, whereas H1R and H4R are expressed in a subset-specific manner. Histamine shifts DC differentiation to the development of CD1a(-) DCs and modulates DC activation through its inhibitory effect on CD1a(+) DC differentiation. Histamine-induced reduction of CD1a(+) DCs is associated with increased secretion of IL-6 and IL-10, up-regulation of a typical combination of chemokines, expression C5aR1 by the CD1a(-) DC subset and enhanced migration of both activated DC subsets supported by the production of MMP-9 and MMP-12 enzymes. All these effects were shown to be mediated in a H2R-specific manner as revealed by the specific antagonist of the receptor. As H2R is expressed at high levels in both DC subsets, we propose that it may dominate the regulation of multiple DC functions. In contrast, H1R and H4R with opposing subset-related expression may have a regulatory or fine-tuning role in histamine-induced functional activities.
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ABSTRACT: G protein-coupled receptors (GPCRs) are among the most important targets in drug discovery. In this study, we used TaqMan Low Density Arrays to profile the full GPCR repertoire of primary human macrophages differentiated from monocytes using either colony stimulating factor-1 (CSF-1/M-CSF) (CSF-1 Mϕ) or granulocyte macrophage colony stimulating factor (GM-CSF) (GM-CSF Mϕ). The overall trend was a downregulation of GPCRs during monocyte to macrophage differentiation, but a core set of 10 genes (e.g. LGR4, MRGPRF and GPR143) encoding seven transmembrane proteins were upregulated, irrespective of the differentiating agent used. Several of these upregulated GPCRs have not previously been studied in the context of macrophage biology and/or inflammation. As expected, CSF-1 Mϕ and GM-CSF Mϕ exhibited differential inflammatory cytokine profiles in response to the Toll-like Receptor (TLR)4 agonist lipopolysaccharide (LPS). Moreover, 15 GPCRs were differentially expressed between these cell populations in the basal state. For example, EDG1 was expressed at elevated levels in CSF-1 Mϕ versus GM-CSF Mϕ, whereas the reverse was true for EDG6. 101 GPCRs showed differential regulation over an LPS time course, with 65 of these profiles being impacted by the basal differentiation state (e.g. GPRC5A, GPRC5B). Only 14 LPS-regulated GPCRs showed asynchronous behavior (divergent LPS regulation) with respect to differentiation status. Thus, the differentiation state primarily affects the magnitude of LPS-regulated expression, rather than causing major reprogramming of GPCR gene expression profiles. Several GPCRs showing differential profiles between CSF-1 Mϕ and GM-CSF Mϕ (e.g. P2RY8, GPR92, EMR3) have not been widely investigated in macrophage biology and inflammation. Strikingly, several closely related GPCRs displayed completely opposing patterns of regulation during differentiation and/or activation (e.g. EDG1 versus EDG6, LGR4 versus LGR7, GPRC5A versus GPRC5B). We propose that selective regulation of GPCR5A and GPCR5B in CSF-1 Mϕ contributes to skewing toward the M2 macrophage phenotype. Our analysis of the GPCR repertoire expressed during primary human monocyte to macrophage differentiation and TLR4-mediated activation provides a valuable new platform for conducting future functional analyses of individual GPCRs in human macrophage inflammatory pathways.Immunobiology 07/2013; · 2.81 Impact Factor
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ABSTRACT: Interleukin-10 (IL-10) is a negative regulator of immune responses and was previously shown to be expressed by human nasal endothelial cells, while the adhesion molecule MECA-79 plays a role in trans-endothelial migration of immune competent cells. In this study we investigate the relationship between endothelial IL-10 and MECA-79 expression to address the question whether immune competent cells could be affected at the mucosal entry site. Nasal turbinate biopsies were taken from house dust mite allergic patients, before and after nasal allergen provocation. Subsequent slides of biopsies were stained for IL10, MECA-79, CD34, and IL10-Receptor. Capillaries, arteries/veins, and sinusoids were evaluated separately. 90% of sinusoids are IL-10 positive and all sinusoids are negative for MECA-79, while 4.8% of capillaries are positive for IL-10, and 2.2% are positive for MECA-79. Although about 47% of arteries/veins are positive for IL-10 and 57.1% are positive for MECA-79, only about 20% are positive for both markers. Furthermore, we showed that the myo-fibroblasts surrounding all sinusoids stain positive for IL10R. IL10 expression on vascular structures is not related to MECA expression for sinusoids and capillaries and only partly related on arteries/veins, however sinusoidal endothelial IL10 expression is always seen in combination with IL-10R expression of sinusoidal myo-fibroblasts.Clinical and translational allergy. 01/2014; 4(1):2.
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ABSTRACT: Matrix metalloproteinases (MMPs) are endopeptidases with the potential to cleave extracellular matrix, support tissue renewal and regulate cell migration. Functional activities of MMPs are regulated by tissue inhibitors of MMPs (TIMPs) and disruption of the MMP-TIMP balance has pathological consequences. Here we studied the expression and secretion of MMPs and TIMPs in CD1a(-) and CD1a(+) monocyte-derived dendritic cell (DC) subpopulations. Our results showed that monocytes express TIMPs but lack MMPs, whereas upon differentiation to moDCs and in response to activation signals the expression of MMPs is increased and that of TIMPs is decreased. MMP-9 is expressed dominantly in the CD1a(-) subpopulation, while MMP-12 is preferentially expressed in CD1a(+) cells. Experiments performed with the synthetic MMP inhibitor GM6001 revealed that this drug efficiently inhibits the migration of moDCs through inactivation of MMPs. We conclude that modulation of MMP activity by GM6001 emerges as a novel approach to manipulate DC migration under inflammatory conditions.Immunobiology 07/2013; · 2.81 Impact Factor