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: Corticosteroids are standard treatment for patients with multiple sclerosis experiencing acute relapse. Because dyspeptic pain is a common side effect of this intervention, patients can be given a histamine receptor-2 antagonist, proton pump inhibitor or antacid to prevent or ameliorate this disturbance. Additionally, patients with multiple sclerosis may be taking these medications independent of corticosteroid treatment. Interventions for gastric disturbances can influence the activation state of the immune system, a principal mediator of pathology in multiple sclerosis. Although histamine release promotes inflammation, activation of the histamine receptor-2 can suppress a proinflammatory immune response, and blocking histamine receptor-2 with an antagonist could shift the balance more towards immune stimulation. Studies utilizing an animal model of multiple sclerosis indicate that histamine receptor-2 antagonists potentially augment disease activity in patients with multiple sclerosis. In contrast, proton pump inhibitors appear to favor immune suppression, but have not been studied in models of multiple sclerosis. Antacids, histamine receptor-2 antagonists and proton pump inhibitors also could alter the intestinal microflora, which may indirectly lead to immune stimulation. Additionally, elevated gastric pH can promote the vitamin B12 deficiency that patients with multiple sclerosis are at risk of developing. Here, we review possible roles of gastric acid inhibitors on immunopathogenic mechanisms associated with multiple sclerosis.BMC Medicine 06/2012; 10:57. DOI:10.1186/1741-7015-10-57 · 7.28 Impact Factor
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ABSTRACT: Alzheimer's disease (AD) is a neurodegenerative disorder characterized by beta-amyloid plaques accumulation and cognitive impairment. Both environmental factors and heritable predisposition have a role in AD. Histamine is a biogenic monoamine that plays a role in several physiological functions, including induction of inflammatory reactions, wound healing, and regeneration. The Histamine mediates its functions via its 4 G-protein-coupled Histamine H1 receptor (H1R) to histamine H1 receptor (H4R). The histaminergic system has a role in the treatment of brain disorders by the development of histamine receptor agonists, antagonists. The H1R and H4R are responsible for allergic inflammation. But recent studies show that histamine antagonists against H3R and regulation of H2R can be more efficient in AD therapy. In this review, we focus on the role of histamine and its receptors in the treatment of AD, and we hope that histamine could be an effective therapeutic factor in the treatment of AD.American Journal of Alzheimer s Disease and Other Dementias 05/2013; 28(4). DOI:10.1177/1533317513488925 · 1.43 Impact Factor
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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; DOI:10.1016/j.imbio.2013.06.012 · 3.18 Impact Factor