Background-We compared cardiac mast cell (HHMC) density and the immunological and nonimmunological release of mediators from mast cells isolated from heart tissue of patients with idiopathic dilated (DCM) (nϭ24) and ischemic cardiomyopathy (ICM) (nϭ10) undergoing heart transplantation and from control subjects (nϭ10) without cardiovascular disease. Methods and Results-HHMC density in DCM (18.4Ϯ1.6 cells/mm 2 ) and ICM (18.4Ϯ1.5 cells/mm 2 ) was higher than that in control hearts (5.3Ϯ0.7 cells/mm 2 ; PϽ.01). The histamine and tryptase contents of DCM and ICM hearts were higher than those of control hearts. The histamine content of the hearts was correlated with mast cell density (r s ϭ.91; PϽ.001). Protein A/gold staining of heart tissue revealed stem cell factor (SCF), the principal growth, differentiating, and activating factor of human mast cells, in HHMC secretory granules. Histamine release from cardiac mast cells caused by immunological (anti-IgE and rhSCF) and nonimmunological stimuli (Ca 2ϩ ionophore A23187) was higher in patients with DCM and ICM compared with control subjects. Immunological activation of HHMC induced a significantly greater release of tryptase and LTC 4 in patients with DCM and ICM compared with control subjects. Conclusions-Histamine and tryptase content and mast cell density are higher in failing hearts than in control hearts. SCF, present in secretory granules of HHMC, might represent an autocrine factor sustaining mast cell hyperplasia in heart tissue in these patients. The increased local release of fibrogenic factors (eg, histamine, tryptase, and leukotriene C 4 ) might contribute to collagen accumulation in the hearts of patients with cardiomyopathy. 1 Mast cells are present in human heart tissue 2,3 and in adventia and intima of coronary arteries of patients with coronary artery disease. [4][5][6] Moreover, the in vitro immunological activation of human heart tissue with anti-IgE induces the release of histamine and prostaglandin D 2 . 7,8 The concentration of histamine and the density of mast cells are increased in the arteries of cardiac patients, 4,5,9 and coronary arteries from cardiac patients are hyperresponsive in vitro to histamine. 4 Furthermore, in vivo administration of histamine and other mast cell-derived mediators (peptide LTC 4 ) in humans causes significant cardiovascular effects. 10 -12 Finally, serum IgE levels are increased in patients with coronary artery disease. 13,14 Taken together, these observations raise the possibility that local activation of cardiac mast cells might contribute, through the release of vasoactive mediators, to certain cardiovascular diseases. 15,16 Fibrosis is a hallmark of failing hearts in DCM and ICM. 17 The cells and the mediators responsible for fibroblast proliferation and collagen accumulation in failing hearts in DCM and ICM are largely unknown. Mast cells are involved in many types of inflammation and repair processes and are found in increased numbers in fibrotic tissues. For example, increased mast cell density has be...

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To investigate the mechanisms of anaphylactoid reactions to protamine, we have examined the in vitro effects of increasing concentrations of protamine (10(-6)-3 x 10(-4) mol litre-1) on the release of preformed (histamine and tryptase) and de novo synthesized (peptide leukotriene C4 (LTC4) or prostaglandin D2 (PGD2)) mediators from human basophils and mast cells isolated from lung parenchyma, heart, skin and synovial tissues. Protamine 10(-6)-3 x 10(-4) mol litre-1 induced release of histamine, but not de novo synthesis of LTC4 from basophils. At concentrations from 10(-5) to 3 x 10(-4) mol litre-1 it induced histamine release from human heart (mean 6.5 (SEM 1.5)%), skin (17.7 (4.1)%) and to a lesser extent from synovial mast cells, but not from lung mast cells. Protamine also caused the release of tryptase from heart mast cells (12.8 (3.2) micrograms/10(7) cells), but did not induce de novo synthesis of LTC4 and PGD2 from lung and skin mast cells. In these experiments cross-linking of IgE by anti-IgE caused release of LTC4 or PGD2 from human basophils or mast cells. These results demonstrate that protamine acted as an incomplete secretagogue, causing the release of preformed mediators from human basophils and mast cells.

To investigate the mechanisms of anaphylactoid reactions to radiocontrast media, in vitro mediator release induced by three iodinated contrast agents was examined using peripheral blood basophils and mast cells purified from human lung parenchyma, heart, and skin tissues. Three iodinated contrast agents, sodium and meglumine salts of ioxaglic acid, sodium and meglumine salts of ioxithalamic acid, and ioversol, were incubated with basophils purified from peripheral blood and human mast cells isolated and purified from different anatomical sites. Release of preformed (histamine and tryptase) and de novo synthesized mediators (prostaglandin D2 and leukotriene C4) into the supernatans was determined at various contrast medium concentrations after incubation for 60 min. Ioxaglate (0.2-0.3 M), ioxithalamate (0.3-0.5 M), and to a lesser extent ioversol (0.3-0.5 M) induced histamine release from basophils in a concentration-dependent manner. All three induced the release of preformed mediators (histamine and tryptase) from human lung, but not from skin mast cells. They also induced histamine and tryptase release from human heart mast cells. However, they did not induce the de novo synthesis of leukotriene C1 or prostaglandin D2 from human basophils or any type of mast cell examined. Cross-linking of IgE by anti-IgE induced the release of leukotriene C4 or prostaglandin D2 from human basophils or mast cells. Mannitol, an osmotic stimulus, induced the release of histamine from human basophils, but to a lesser extent from mast cells. These results show that different contrast media can differ in their ability to release mediators from enriched preparations of human basophils and mast cells. The three contrast agents examined act on basophils and mast cells as incomplete secretagogues, causing the release of preformed mediators, but not these novo synthesis of chemical mediators. It may be useful to measure plasma tryptase levels to detect adverse reactions caused by iodinated radiographic contrast materials.