ABSTRACT
BACKGROUND: Allergy and allergic asthma are significant health burdens in developed countries and are increasing in prevalence. Dendritic cells (DCs) initiate immune responses to common aeroallergens, and ADAM10 has been demonstrated to be important for the development of adaptive responses. This study's objective was to understand the role of ADAM10 on DCs in the development of allergic and anaphylactic responses. METHODS: In this study, we used mouse models of allergic airway inflammation (house dust mice and Alternaria alternata) and OVA-induced models of active anaphylaxis to determine the DC-specific function of ADAM10 and Notch signaling. To examine TH 1 and TH 17 immunity infection with Anaplasma phagocytophilum and Citrobacter rodentium respectively, were used. RESULTS: Mice, which have ADAM10 deleted from DCs, have dramatic reductions in IgE production and do not develop significant TH 2 immune responses. Further, ADAM10DC-/- mice are resistant to IgE-mediated anaphylaxis. This response is selective for TH 2 immunity as TH 1 and TH 17 immunity is largely unaffected. Notch1, a known ADAM10 substrate, when knocked out of DCs (Notch1DC-/- ) demonstrated a similar reduction in anaphylaxis and IgE. Without ADAM10 and Notch1 signaling, DCs were unable to make cytokines that stimulate TH 2 cells and cytokines. Anaphylaxis and allergic lung inflammation were restored in ADAM10DC-/- with the overexpression of the Notch1-intracellular domain, confirming the role of Notch signaling. CONCLUSIONS: Targeting ADAM10 and Notch1 on DCs represent a novel strategy for modulating TH 2 immune responses and IgE production.
Subject(s)
ADAM10 Protein/metabolism , Amyloid Precursor Protein Secretases/metabolism , Dendritic Cells/immunology , Dendritic Cells/metabolism , Immunoglobulin E/immunology , Membrane Proteins/metabolism , Receptor, Notch1/metabolism , ADAM10 Protein/genetics , Amyloid Precursor Protein Secretases/genetics , Anaphylaxis/immunology , Anaphylaxis/metabolism , Animals , Biomarkers , Disease Models, Animal , Gene Expression , Hypersensitivity/immunology , Hypersensitivity/metabolism , Immunoglobulin G/blood , Immunoglobulin G/immunology , Interleukin-6/genetics , Interleukin-6/metabolism , Kruppel-Like Factor 4 , Kruppel-Like Transcription Factors/genetics , Kruppel-Like Transcription Factors/metabolism , Membrane Proteins/genetics , Mice , Mice, Knockout , Pyroglyphidae/immunology , Receptor, Notch1/genetics , Signal Transduction , Th1 Cells/immunology , Th1 Cells/metabolism , Th17 Cells/immunology , Th17 Cells/metabolism , Th2 Cells/immunology , Th2 Cells/metabolismABSTRACT
Sodium valproate (VPA) is clinically employed as an anticonvulsant and, to a lesser extent, as a mood stabilizer. While the incidence of toxicity associated with the clinical use of valproate is low, serious hepatotoxicity makes up a significant percentage of these rare adverse effects, with fatalities occurring mainly in children receiving polypharmacy. Previous studies have highlighted the different pharmacological effects of acute valproate exposure, a combination of which are likely to underpin its observed broad-spectrum anticonvulsant efficacy. However, limited studies have been undertaken to investigate the subacute effects of this compound and how genomic effects may underlie the observed hepatotoxic effects. Investigation into the mild hepatoxicity observed in rats exposed to high doses of VPA may provide important information on the human situation. Male Sprague-Dawley rats were dosed with 500 mg/kg/day sodium valproate: after necropsy, mRNA was subjected to suppression PCR subtractive hybridization, identifying 8 up-regulated and 14 down-regulated mRNA species. The down-regulation of several mRNA species coding for enzymes involved in cellular energetics (e.g., succinate dehydrogenase, aldolase B) was of particular interest, as mitochondrial dysfunction is a key feature of valproate hepatotoxicity. In vitro studies were then undertaken to examine the dose and time dependence of these changes and also their effect on the overall energy levels within the cell. We demonstrate that, both in vivo and in vitro, valproate exposure in rats results in a significant decrease in pathways involved in cellular energy homeostasis. These changes may provide insight into the rare human hepatoxicity associated with this compound.