PubMed Health⌕ Search

Biomedical subjects

Dean D Metcalfe

Publications and source records attributed to Dean D Metcalfe.

At least 19 recordsLinked to original sources
PubMed2006

5-hydroxytryptamine induces mast cell adhesion and migration.

The neurotransmitter serotonin (5-hydroxytryptamine (5-HT)) is implicated in enhancing inflammatory reactions of skin, lung, and gastrointestinal tract. To determine whether 5-HT acts, in part, through mast cells (MC), we first established that mouse bone marrow-derived MC (mBMMC) and human CD34(+)-derived MC (huMC) expressed mRNA for multiple 5-HT receptors. We next determined the effect of 5-HT on mouse and human MC degranulation, adhesion, and chemotaxis. We found no evidence that 5-HT degranulates MC or modulates IgE-dependent activation. 5-HT did induce mBMMC and huMC adherence to fibronectin; and immature and mature mBMMC and huMC migration. Chemotaxis was accompanied by actin polymerization. Using receptor antagonists and pertussis toxin, we identified 5-HT(1A) as the principal receptor mediating the effects of 5-HT on MC. mBMMC from the 5-HT(1A) receptor knockout mouse (5-HT(1A)R(-/-)) did not respond to 5-HT. 5-HT did induce accumulation of MC in the dermis of 5-HT(1A)R(+/+) mice, but not in 5-HT(1A)R(-/-) mice. These studies are the first to demonstrate an effect of 5-HT on MC. Furthermore, both mouse and human MC respond to 5-HT through the 5-HT(1A) receptor. Our data are consistent with the conclusion that 5-HT promotes inflammation by increasing MC at the site of tissue injury.

Actins↗
PubMed2006

Silica-directed mast cell activation is enhanced by scavenger receptors.

Inhalation of crystalline silica results in pulmonary fibrosis and silicosis. It has been suggested that mast cells play a role in these conditions. How mast cells would influence pathology is unknown. We thus explored mast cell interactions with silica in vitro and in B6.Cg-kit(W-sh) mast cell-deficient mice. B6.Cg-kit(W-sh) mice did not develop inflammation or significant collagen deposition after instillation of silica, while C57Bl/6 wild-type mice did have these findings. Given this supporting evidence of a role for mast cells in the development of silicosis, we examined the ability of silica to activate mouse bone marrow-derived mast cells (BMMC), including degranulation (beta-hexosaminidase release); production of reactive oxygen species (ROS) and inflammatory mediators; and the effects of silica on Fc epsilon RI-dependent activation. Silica did not induce mast cell degranulation. However, TNF-alpha, IL-13, monocyte chemotactic protein-1, protease activity, and production of ROS were dose-dependently increased after silica exposure, and production was enhanced after Fc epsilon RI stimulation. This mast cell activation was inhibited by anti-inflammatory compounds. As silica mediates some effects in macrophages through scavenger receptors (SRs), we first determined that mast cells express scavenger receptors; then explored the involvement of SR-A and macrophage receptor with colleagenous structure (MARCO). Silica-induced ROS formation, apoptosis, and TNF-alpha production were reduced in BMMC obtained from SR-A, MARCO, and SR-A/MARCO knockout mice. These findings demonstrate that silica directs mast cell production of inflammatory mediators, in part through SRs, providing insight into critical events in the pathogenesis and potential therapeutic targets in silicosis.

Animals↗
PubMed2006

Elevated tryptase levels are associated with greater bone density in a cohort of patients with mastocytosis.

BACKGROUND: Mastocytosis is associated with a pathological increase in tissue mast cells. Associated skeletal problems include a decrease in bone density and pathological fractures. METHODS: In order to explore the relationship between bone density and the severity of mastocytosis, 21 patients with mastocytosis who underwent dual-energy X-ray absorptiometry were entered into this study. Correlation coefficients were computed between Z-scores and demographic, clinical and laboratory data. Femoral neck Z-scores correlated with serum tryptase levels when all the patients were considered (p=0.029). RESULTS AND CONCLUSION: Patients with less severe disease had significantly lower values at the L1-L4 spine (p=0.046) and femoral neck (p=0.029) Z-scores compared to patients with more severe disease. Most patients who had low Z-scores (between -1 and -2.5) were under 50 years of age, had less severe disease and had lower serum tryptase levels. A history of gastroesophageal reflux disease and a history of hypotensive episodes correlated with lower L1-L4 spine Z-scores (p<0.05). Thus, patients with less severe disease and lower serum tryptase levels should in particular have their bone density determined with treatment appropriate to the findings.

Absorptiometry, Photon↗
PubMed2006

Second symposium on the definition and management of anaphylaxis: summary report--second National Institute of Allergy and Infectious Disease/Food Allergy and Anaphylaxis Network symposium.

There is no universal agreement on the definition of anaphylaxis or the criteria for diagnosis. In July 2005, the National Institute of Allergy and Infectious Disease and Food Allergy and Anaphylaxis Network convened a second meeting on anaphylaxis, which included representatives from 16 different organizations or government bodies, including representatives from North America, Europe, and Australia, to continue working toward a universally accepted definition of anaphylaxis, establish clinical criteria that would accurately identify cases of anaphylaxis with high precision, further review the evidence on the most appropriate management of anaphylaxis, and outline the research needs in this area.

Journal Article↗
PubMed2006

Treatment of systemic mastocytosis.

It is an exciting time in the treatment of systemic mastocytosis. Major advances in the past 2 decades have helped to define the molecular abnormalities associated with this disease and to delineate pathways involved in its pathogenesis. This has directly translated into the development of novel targeted therapies. These therapies hold great promise to patients and health care providers that a "cure" for systemic mastocytosis may someday be obtainable.

Antineoplastic Agents↗
PubMed2006

5. IgE, mast cells, basophils, and eosinophils.

IgE, mast cells, basophils, and eosinophils constitute essential elements in allergic inflammation. Allergen-specific IgE, synthesized in response to allergens in the environment, becomes fixed to FcepsilonRI on the membranes of mast cells and basophils. Aggregation of receptor-bound IgE molecules on re-exposure to specific allergen results in the production of mediators that produce the allergic response. Principal among the cells drawn to sites of mediator release is the eosinophil.

Animals↗
PubMed2006

Second symposium on the definition and management of anaphylaxis: summary report--Second National Institute of Allergy and Infectious Disease/Food Allergy and Anaphylaxis Network symposium.

There is no universal agreement on the definition of anaphylaxis or the criteria for diagnosis. In July 2005, the National Institute of Allergy and Infectious Disease and Food Allergy and Anaphylaxis Network convened a second meeting on anaphylaxis, which included representatives from 16 different organizations or government bodies, including representatives from North America, Europe, and Australia, to continue working toward a universally accepted definition of anaphylaxis, establish clinical criteria that would accurately identify cases of anaphylaxis with high precision, further review the evidence on the most appropriate management of anaphylaxis, and outline the research needs in this area.

Anaphylaxis↗
PubMed2006

Systemic mastocytosis.

Systemic mastocytosis is a fascinating disease with diverse clinical features. There have been numerous advances in understanding the basis of clinical manifestations of this disease and of its molecular pathogenesis in the last several decades. The development of methods to study mast cell biology using cell culture and murine models has proven invaluable in this regard. Clarification of the roles of mast cells in various biological processes has expanded our understanding of their importance in innate immunity, as well as allergy. New diagnostic methods have allowed the design of detailed criteria to assist in distinguishing reactive mast cell hyperplasia from systemic mastocytosis. Variants and subvariants of systemic mastocytosis have been defined to assist in determining prognosis and in management of the disease. Elucidation of the roles of the Kit receptor tyrosine kinase and signal transduction pathway activation has contributed to development of potential targeted therapeutic approaches that may prove useful in the future.

Animals↗
PubMed2006

Acoustic rhinometry in the practice of allergy.

OBJECTIVE: To provide a comprehensive practical overview of the use of acoustic rhinometry in the practice of allergy. DATA SOURCES: An all-inclusive PubMed search was conducted for articles on acoustic rhinometry that were published in peer-reviewed journals, between 1989 and 2006, using the keywords acoustic rhinometry, allergic rhinitis, and nasal provocation testing. STUDY SELECTION: The expert opinion of the authors was used to select studies for inclusion in this review. RESULTS: Acoustic rhinometry is a sound-based technique used to measure nasal cavity area and volume. It has been validated by comparison to measurements with computed tomography and magnetic resonance imaging. Acoustic rhinometry requires minimal patient cooperation and may be used in adults, children, and infants. It is used by medical practitioners to diagnose and evaluate therapeutic responses in conditions such as rhinitis and to measure nasal dimensions during allergen provocation testing. Acoustic rhinometry also provides a visual reflection of the nasal response to therapy, which may be useful in increasing compliance to prescribed medications. CONCLUSIONS: Acoustic rhinometry is a safe, noninvasive, objective, and validated measure of nasal obstruction that appears to be of practical use in the diagnosis and management of inflammatory diseases of the upper airways.

Hypersensitivity↗
PubMed2006

The high-affinity immunoglobulin-E receptor (FcepsilonRI) is endocytosed by an AP-2/clathrin-independent, dynamin-dependent mechanism.

Aggregation of the high-affinity immunoglobulin E (IgE) receptor (FcepsilonRI), expressed on mast cells and basophils, initiates the immediate hypersensitivity reaction. Aggregated FcepsilonRI has been reported to rapidly migrate to lipid rafts in RBL-2H3 cells. We confirmed that aggregated FcepsilonRI is found in the lipid raft fractions of cellular lysates. Furthermore, we show that the cross-linked FcepsilonRI remains associated with detergent-resistant structures upon internalization. Previous morphological studies have reported that aggregated FepsiloncRI is endocytosed via clathrin-coated pits, which in general are not lipid raft associated. To address this apparent discrepancy, we employed siRNA to suppress expression of components of the clathrin-mediated internalization machinery, namely, clathrin heavy chain, and the AP-2 (alpha-adaptin or mu2-subunit). Transferrin receptor (TfR) is endocytosed by a clathrin-mediated process and, as expected, each transfected siRNA caused a two to threefold elevation of TfR surface expression and almost completely inhibited its endocytosis. In contrast, there was no effect on surface expression levels of FcepsilonRI nor on the endocytosis of the dinitrophenyl-human serum albumin (DNP-HSA)/IgE/FcepsilonRI complex. On the contrary, internalization of DNP-HSA/IgE/FcepsilonRI was inhibited by overexpression of a dominant-negative dynamin mutant. We conclude that internalization of cross-linked FcRI does not require the AP-2/clathrin complex but is dynamin-dependent and may be lipid raft mediated.

Animals↗
PubMed2006

Growth of human mast cells from bone marrow and peripheral blood-derived CD34+ pluripotent progenitor cells.

Human mast cells (HMCs) are derived from a CD34+ pluripotent progenitor cell that is Kit (CD117+), CD13+, Fc epsilonRI- and lacks lineage-specific surface markers. Bone marrow and peripheral blood are two tissue sources available for obtaining CD34+ progenitor cells from which to culture HMCs. CD34+ cells can be isolated and enriched by magnetic separation columns and stored under specific conditions until ready for use. Alternatively, enriched CD34+ cells may be immediately cultured in serum-free culture media containing recombinant human stem cell factor (rhSCF), rhIL-6, and rhIL-3 (first week only). Weekly hemidepletions and the removal of adherent cells and/or debris enables the investigator to obtain HMC cultures, identified by Wright-Giemsa and acidic toluidine blue stains, by 8-10 wk.

Antigens, CD34↗
PubMed2006

Adrenomedullin is a cross-talk molecule that regulates tumor and mast cell function during human carcinogenesis.

We have previously demonstrated that adrenomedullin (AM) plays a critical role as an autocrine/paracrine tumor cell survival factor. We now present evidence that AM is an important regulator of mast cell (MC) function and that this modulation is potentially involved in tumor promotion. AM induced histamine or beta-hexosaminidase release from rat and human MCs through a receptor-independent pathway. AM was chemotactic for human MCs and stimulated mRNA expression of vascular endothelial growth factor, monocyte chemoattractant protein-1, and basic fibroblast growth factor in this cell type. Differentiated but not undifferentiated human MCs responded to hypoxic insult with elevated AM mRNA/protein expression. Using confocal microscopy, we identified AM-producing MCs in tumor infiltrates of human breast and lung cancer patients. In mixed culture assays the AM-producing human MC line HMC-1 augmented both anchorage-dependent and -independent growth of human lung cancer A549 cells, an effect that was suppressed by MC-targeted siRNA AM knockdown. Finally, HMC-1 cells induced in vivo angiogenesis as assessed by directed in vivo angiogenesis assay analysis; neutralizing anti-AM monoclonal antibody blocked this ability. Our collective data suggest a new role for AM as a cross-talk molecule that integrates tumor and MC communication, underlying a unique promotion mechanism of human cancers.

Adrenomedullin↗
PubMed2005

Mast cells, which interact with Escherichia coli, up-regulate genes associated with innate immunity and become less responsive to Fc(epsilon)RI-mediated activation.

Mast cells, which are associated with T helper cell type 2-dependent inflammation, have now been implicated in the innate immune response. To further characterize how mast cells are programmed to respond to infectious organisms, we used expression profiling using DNA microarray analysis of gene expression by human mast cells (huMC) during ingestion of Escherichia coli and examined immunoglobulin E (IgE)-mediated degranulation. Analysis of data revealed that specific groups of genes were modulated, including genes encoding transcription factors, cell signaling molecules, cell cycle regulators, enzymes, cytokines, novel chemokines of the CC family, adhesion molecules, and costimulatory molecules. Enzyme-linked immunosorbent assay analysis confirmed the production of tumor necrosis factor and the chemokines CC chemokine ligand (CCL)-1/I-309, CCL-19/macrophage-inflammatory protein-3beta (MIP-3beta), and CCL-18/MIP-4; flow cytometry confirmed the up-regulation of carcinoembryonic antigen-related cell adhesion molecule 1, the integrin CD49d, and CD80. Coincubation with E. coli down-regulated Fc receptor for IgE I (FcepsilonRI) expression and FcepsilonRI-mediated huMC degranulation. These data are consistent with the concept that bacterial exposure directs mast cell responses toward innate immunity and away from IgE-mediated effects.

Cell Adhesion Molecules↗
PubMed2005

Btk plays a crucial role in the amplification of Fc epsilonRI-mediated mast cell activation by kit.

Stem cell factor (SCF) acts in synergy with antigen to enhance the calcium signal, degranulation, activation of transcription factors, and cytokine production in human mast cells. However, the underlying mechanisms for this synergy remain unclear. Here we show, utilizing bone marrow-derived mast cells (BMMCs) from Btk and Lyn knock-out mice, that activation of Btk via Lyn plays a key role in promoting synergy. As in human mast cells, SCF enhanced degranulation and cytokine production in BMMCs. In Btk-/- BMMCs, in which there was a partial reduction in the capacity to degranulate in response to antigen, SCF was unable to enhance the residual antigen-mediated degranulation. Furthermore, as with antigen, the ability of SCF to promote cytokine production was abrogated in the Btk-/- BMMCs. The impairment of responses in Btk-/- cells correlated with an inability of SCF to augment phospholipase Cgamma1 activation and calcium mobilization, and to phosphorylate NFkappaB and NFAT for cytokine gene transcription in these cells. Similar studies with Lyn-/- and Btk-/-/Lyn-/- BMMCs indicated that Lyn was a regulator of Btk for these responses. These data demonstrate, for the first time, that Btk is a key regulator of a Kit-mediated amplification pathway that augments Fc epsilonRI-mediated mast cell activation.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed2005

IL-6 levels predict disease variant and extent of organ involvement in patients with mastocytosis.

Mastocytosis is often associated with organ involvement and hematological disorders. Patients may also exhibit elevated levels of plasma IL-6. To gain insight into the relevance of this observation, we correlated plasma levels of IL-6 and soluble IL-6 receptor (sIL-6R) with multiple disease parameters in 29 patients with mastocytosis. Mean plasma IL-6 levels were elevated in patients compared to healthy controls (P < 0.0001). Disease category significantly correlated with plasma IL-6 levels, as did severity of bone marrow pathology, organomegaly, and extent of skin involvement. In plasma, there was a positive correlation of IL-6 to total tryptase, alkaline phosphatase, IgM, white blood cell count, prothrombin time, partial thromboplastin time, and neutrophil numbers. There was an inverse correlation to hemoglobin. sIL-6R levels were not elevated. These observations demonstrate that IL-6 is a useful surrogate marker of severity of hematologic disease and suggest that IL-6 contributes to pathology.

Adult↗
PubMed2005

Thrombopoietin alone or in the presence of stem cell factor supports the growth of KIT(CD117)low/ MPL(CD110)+ human mast cells from hematopoietic progenitor cells.

OBJECTIVES: Thrombopoietin (TPO) is known to promote platelet number, have growth-promoting potential for human megakaryocytes (HuMKs), and increase erythrocyte, monocyte, mast cell, and granulocyte numbers in the presence of additional growth factors. We explored the ability of TPO alone or in the presence of stem cell factor (SCF) to support human mast cells (HuMCs). METHODS: CD34+ pluripotent and CD34+/CD117+/CD13+ HuMC progenitor cells were cultured in rhTPO and examined for HuMCs. Similarly, we added rhTPO to CD34(+) cells cultured in stem cell factor (SCF), which promotes HuMC development. RESULTS: When CD34+ cells were cultured in 10 ng/mL rhTPO and 10 ng/mL rhSCF, TPO enhanced HuMC numbers compared to rhSCF alone. Higher concentrations of rhTPO (50 ng/mL) in the presence of 100 ng/mL rhSCF inhibited the rhSCF-dependent subpopulation of CD117high HuMCs, while promoting CD117low HuMCs. Human CD34+/CD117+/CD13+ cells cultured in rhTPO alone for 1 to 2 weeks differentiated into CD41+/CD110+ HuMKs (85-90%) and FcepsilonRI+/CD117low/CD13+ HuMCs (5-10%). RhTPO-induced HuMCs expressed the TPO (CD110) receptor, tryptase, and chymase and survived when recultured in rhSCF. CONCLUSION: The effect of TPO on HuMCs in the presence of rhSCF varies, depending on the relative concentration of each growth factor, while TPO alone or in combination with rhSCF supports a unique population of CD117low/CD110+ HuMCs.

Cell Culture Techniques↗