Project description:Mast cells are indispensable for LPS-induced septic hypothermia, in which TNF-α plays an essential role to initiate sepsis. Tec family non-receptor tyrosine kinases ITK and BTK regulate mast cell-derived TNF-α in response to allergic antigen, but their role in LPS-induced TNF-α production by mast cells and related pathology is unclear. We sought to investigate the role(s) of ITK and BTK in mast cell response in septic condition. We found that the absence of ITK and BTK leads to enhanced TNF-α production by bone marrow-derived mast cells (BMMC). Itk-/-Btk-/- mast cells exhibit hyperactive preformed and LPS-induced TNF-α production, along with enhanced expression of other related genes such as NF-κB targeted genes, compared to WT cells. Bone marrow cells from 8-week old WT, Itk-/-, Btk-/- and Itk-/-Btk-/- (double knockout: DKO) C57Bl/6 mice were cultured in murine Interleukin-3/Stem cell factor (IL-3/SCF) supplemented medium for 5 weeks to derive mast cells. WT, Itk-/-, Btk-/- and DKO bone marrow-derived mast cells (BMMC) were factor starved in medium without IL-3/SCF for 12 hours, followed by treatment with PBS (control) or 100 ng/ml LPS for 1 hour. Triplicates of each group were subjected to mouse whole genome genechip microarray analysis. Replicates were randomized on different chips to avoid systematic error.
Project description:Post-transcriptional regulation of immune-related transcripts by RNA-binding proteins (RBPs) impacts immune cell responses, including mast cell functionality. Despite their importance in immune regulation, the functional role of most RBPs remains to be understood. By manipulating the expression of specific RBPs in murine mast cells, coupled with mass spectrometry and transcriptomic analyses, we found that the Regnase family of proteins acts as a potent regulator of mast cell physiology. Specifically, Regnase-1 is required to maintain basic cell proliferation and survival, while both Regnase-1 and -3 cooperatively regulate the expression of inflammatory transcripts upon activation, with Tnf being a primary target in both human and mouse cells. Further, Regnase-3 directly interacts with Regnase-1 in mast cells and is necessary to restrain Regnase-1 expression through the destabilization of its transcript. Overall, our study identifies protein interactors of endogenously expressed Regnase factors, characterizes the regulatory interplay between Regnase family members in mast cells, and establishes their role in the control of mast cell homeostasis and inflammatory responses.
Project description:DNA methylation and specifically the DNA methyltransferase enzyme DNMT3A are involved in the pathogenesis of a variety of hematological diseases and in regulating the function of immune cells. Although altered DNA methylation patterns and mutations in DNMT3A correlate with mast cell proliferative disorders in humans, the role of DNA methylation in mast cell biology is not understood. By utilizing mast cells lacking Dnmt3a, we found that this enzyme is involved in restraining mast cell responses to acute and chronic stimuli, both in vitro and in vivo. The exacerbated mast cell responses observed in absence of Dnmt3a were recapitulated or enhanced by treatment with the demethylating agent 5-aza-2'-deoxycytidine, as well as by down-modulation of Dnmt1 expression, further supporting the role of DNA methylation in regulating mast cell activation. Mechanistically, these effects were in part mediated by the dysregulated expression of the scaffold protein IQGAP2, which is characterized by the ability to regulate a wide variety of biological processes. Altogether, our data demonstrate that DNMT3A and DNA methylation are key modulators of mast cell responsiveness to acute and chronic stimulation.
Project description:We used tyrosine phosphorylation profiling by anti-pTyr-antibody mediated enrichment and subsequent analysis by mass spectrometry in order to determine the changes in early signalling after mast cell activation. Mast cells were stimulated with varying concentrations of antigen for one minute and the differences between optimal (20 ng/ml) and supra-optimal (2000 ng/ml) antigen mast cell activation were analysed by nanoLC-MS/MS.
Project description:Mast cells, activated by antigen via the high affinity receptor for IgE (FcεRI), release an array of pro-inflammatory mediators that contribute to allergic disorders such as asthma and anaphylaxis. The KIT ligand, stem cell factor (SCF), is critical for mast cell expansion, differentiation and survival, and, under acute conditions, enhances mast cell activation. However, extended SCF exposure in vivo conversely protects against fatal antigen-mediated anaphylaxis. In investigating this dichotomy, we identified a novel mode of regulation of the mast cell activation phenotype through SCF-mediated programming. We found that mouse bone marrow-derived mast cells chronically exposed to SCF displayed a marked attenuation of FcεRI-mediated degranulation and cytokine production. The hypo-responsive phenotype was not a consequence of altered signals regulating calcium flux or protein kinase C, but of ineffective cytoskeletal reorganization, with evidence implicating a down-regulation of expression of the Src kinase Hck. Collectively, these findings demonstrate a major role for SCF in the homeostatic control of mast cell activation with potential relevance to mast cell-driven disease and the development of novel approaches for the treatment of allergic disorders. Mouse bone marrow-derived mast cells were treated with IL3, IL3+IL33, or IL3+SCF. Six replicates each.
Project description:Mast cells are hematopoietic cells that reside preferentially in tissues exposed to internal and external environments. Mast cells sense immunological, inflammatory and environmental stimuli, and can be activated to release granules and generate inflammatory mediators. Mast cell-derived products confer protection against snake venoms and some parasite infections. Aberrant activation of mast cells is a major contributor to human pathology, including allergy, asthma and adverse drug reactions. Their strict tissue location has largely impeded the isolation of large numbers of primary mast cell for further analysis. To better understand the biology of mast cells, we analyzed the proteome of primary human and mouse mast cells by quantitative mass spectrometry. We identified a mast cell-specific protein signature that was conserved from mouse to man. Compared to a comprehensive set of other immune cell lineages, proteome analysis identified a unique and distant mast cell cluster. The mast cell signature included proteins governing granule biosynthesis and secretion, as well as proteoglycan- and neurotransmitter metabolism. Proteome conservation across species suggests evolutionary maintenance of mast cell functions.
Project description:Interleukin-33 (IL-33) is elevated in afflicted tissues of patients with mast cell-dependent chronic allergic diseases. Based on its acute effects on mouse mast cells (MCs), IL-33 is thought to play a role in the pathogenesis of allergic disease through MC activation. However, the manifestations of chronic IL-33 exposure on human MC function, which best reflect the conditions associated with chronic allergic disease, are unknown. We now find that long-term exposure of human and mouse MCs to IL-33 results in a substantial reduction of MC activation in response to antigen. This reduction required >72 h exposure to IL-33 for onset and 1-2 wk for reversion following IL-33 removal. This hypo-responsive phenotype was determined to be a consequence of MyD88-dependent attenuation of signaling processes necessary for MC activation including antigen-mediated calcium mobilization and cytoskeletal reorganization; potentially as a consequence of down-regulation of the expression of PLCg1 and Hck. These findings suggest that IL-33 may play a protective, rather than a causative role in MC activation under chronic conditions and, furthermore, reveal regulated plasticity in the MC activation phenotype. The ability to down-regulate MC activation in this manner may provide alternative approaches for treatment of MC-driven disease. Mouse bone marrow-derived mast cells treated with IL3 or IL3+IL33. 6 replicates each.