Gennaro de Crescenzo

Immunological characterization and functional importance of human heart mast cells

Mast cells are present in normal and even more abundant in diseased human heart tissue and their localization is of particular relevance to their function. Within heart tissue mast cells lie between myocytes and in close contact with blood vessels. They are also found in the coronary adventitia and in the shoulder regions of a coronary atheroma. The density of cardiac mast cells is markedly higher in some patients with myocarditis and dilated cardiomyopathy than in accident victims without cardiovascular diseases. More importantly, in some of these conditions there is in situ evidence of mast cell activation. We have described an original technique to isolate and purify HHMC for in vitro study. This procedure gives viable cells and after stimulation with immunological or non-immunological stimuli they release performed (histamine and tryptase) and newly generated mediators (PGD2 and LTC4). We have demonstrated that HHMC differ from those in other anatomical districts in that they are activated by specific immunological and non-immunological stimuli, and in their relation to the arachidonic acid metabolism, suggesting that the local microenvironment can influence their phenotypic and biochemical characteristics. Our own and other findings suggest that HHMC have complex and significant roles in different pathophysiological conditions involving the cardiovascular system. Direct activation of HHMC by therapeutic and diagnostic substances injected intravenously explains some of the anaphylactoid reactions caused by these agents. HHMC possess Fc epsilon RI and IgE bound to the surface and C5a receptors, which could explain how cardiac mast cells are involved in systemic and cardiac anaphylaxis. Cardiac mast cells and those in human coronary arteries also play a role in the early and late stages of atherogenesis and during ischemic myocardial injury. In conclusion, although studies of HHMC are in their infancy, their in vitro isolation may be useful in identifying additional mediators synthesized and released, stimuli relevant to human pathophysiology, and pharmacological agents selectively modulating the activation of these cells and their mediators. Drugs specifically acting on HHMC or on their mediators may eventually be useful in treating different cardiovascular diseases.

Human heart mast cells: a definitive case of mast cell heterogeneity.

Mast cells and their chemical mediators play a role in cardiac and systemic anaphilaxis. Perivascular and cardiac mast cells have been implicated in the pathogenesis of coronary artery spasm, atherosclerosis, myocardial ischemia, and cardiomyopathy. Despite this, nothing is known about the immunological and biochemical characteristics of the human heart mast cell (HHMC). We have isolated and partially purified HHMC and compared them with mast cells isolated from lung (HLMC) and skin (HSMC) tissues. Cross-linking of the high-affinity receptor for IgE (Fc epsilon RI) by a polyclonal anti-Fc epsilon antibody caused the release of preformed (histamine and tryptase) and de novo synthesized mediators [peptide leukotriene C4 (LTC4) and prostaglandin D2 (PGD2)]. The tryptase content of HHMC (19.4 +/- 1.5 micrograms/10(6) cells) was lower than HSMC (33.4 +/- 2.5 micrograms/10(6) cells) and higher than HLMC (10.6 +/- 1.9 micrograms/10(6) cells). Maximal stimulation of HHMC with anti-IgE led to the release of LTC4 (17.5 +/- 5.1 ng/10(6) mast cells) and PGD2 (17.8 +/- 5.0 ng/10(6) mast cells, whereas HSMC synthesized more PGD2 (65.0 +/- 6.8 ng/10(6) mast cells) and much less LTC4 (< 5 ng/10(6) cells). Recombinant human C5a anaphylatoxin and protamine induced histamine release from HHMC and HSMC, but not from HLMC. Substance P and morphine selectively induced the release of histamine from HSMC, but not from HHMC and HLMC. Compound 48/80 caused histamine release from HSMC and HHMC, but not from HLMC. The pattern of mediators synthesized and the responsiveness of HHMC to different secretagogues appear unique providing strong evidence of human mast cell heterogeneity.

Human basophil/mast cell releasability. XI. Heterogeneity of the effects of contrast media on mediator release†

BACKGROUND The activation of basophils and mast cells plays a role in the pathogenesis of anaphylactoid reactions occurring during the administration of iodinated radiocontrast media. METHODS We compared the effects of three contrast media (CM), Hexabrix (sodium and meglumine salts of ioxaglic acid), Telebrix (sodium and meglumine salts of ioxitalamic acid), and Optiray (ioversol) on the release of preformed (histamine and tryptase) and de novo synthesized (prostaglandin D2 and leukotriene C4) mediators from human basophils and mast cells isolated from lung, skin, and heart tissue. The commercial preparations were evaluated in parallel with the pure substances. Mannitol was used as a positive control inducing histamine release (HR) by hyperosmolar stimulation. RESULTS Hexabrix (0.1 to 0.3 mol/L), Telebrix (0.1 to 0.5 mol/L), Optiray (0.2 to 0.5 mol/L), and the corresponding pure substances concentration-dependently induced HR from basophils. A positive correlation was found between CM osmolality and HR from basophils. Mast cells isolated from different anatomic sites responded differently to the three CM. Hexabrix and Optiray induced histamine and tryptase release from human lung mast cells, but not from human skin mast cells. No correlation was found between the osmolality of CM and HR from human lung mast cells. There was a significant correlation between the percent of histamine and tryptase release induced by CM from human lung mast cells. Hexabrix, Telebrix, and Optiray also induced histamine and tryptase release from human heart mast cells. None of the CM induced the de novo synthesis of leukotriene C4 or prostaglandin D2 from basophils or mast cells. The kinetics of HR caused by CM differed according to the drug used and the cell (basophils or human lung mast cells) examined. CM-induced HR from basophils and human lung mast cells was temperature-dependent, partially influenced by extracellular Ca2+ concentrations, and not modified by preincubation of basophils with IL-2 or IL-3. CONCLUSIONS These results provide evidence of the heterogeneity of the effects of CM on mediator release from human basophils and mast cells from different anatomic sites. They also suggest that hyperosmolarity may be an important factor in the activation of basophils by CM, but less relevant for mast cells. CM induce only the release of preformed mediators. The measurement of plasma tryptase might be clinically useful for monitoring adverse reactions caused by CM.

Cyclosporin H is a potent and selective competitive antagonist of human basophil activation by N-formyl-methionyl-leucyl-phenylalanine

BACKGROUND Cyclosporin A (CsA) binds with high affinity to cyclophilin, a critical step in the molecular mechanism of action of cyclosporins, where cyclosporin H (CsH) has extremely low affinity for cyclophilin. CsH differs from CsA by the substitution of the L-methyl valine at position 11 with it D-isomer. METHODS We compared the effects of CsA and CsH on the release of performed (histamine) and de novo synthesized inflammatory mediators (peptide leukotriene C4) from peripheral blood basophils activated by N-formyl-methionyl-leucyl-phenylalanine (FMLP). RESULTS CsH (8 to 800 nmol/L) concentration-dependently inhibited histamine and leukotriene C4 release from purified and unpurified basophils activated by FMLP, whereas CsA (8 to 800 nmol/L) had little inhibitory effect on histamine release from basophils challenged with FMLP. Inhibition of histamine release from basophils challenged with FMLP was extremely rapid and was abolished by washing the cells (three times) before challenge. CsH (8 to 800 nmol/L) had no effect on the release of histamine caused by C5a, platelet activating factor, monocyte chemotactic activating factor, RANTES, IL-8, bryostatin 1, and phorbol myristate. Preincubation of basophils with granulocyte-macrophage colony-stimulating factor (30 and 100 pmol/L), but not IL-1 beta (30 and 100 ng/ml), concentration-dependently reversed the inhibitory effect of CsH on FMLP-induced histamine release. CsH competitively inhibited the effect of FMLP on histamine release from basophils. The dissociation constant (Kd) for the CsH-FMLP receptor complex was approximately 9 x 10(-8) mol/L, more than 10-fold lower than that (approximately equal to 1.3 x 10(-6) mol/L) of N-t-BOC-methionyl-L-leucyl-phenylalanine (BocMLP), a known formyl peptide receptor antagonist. CsH inhibited tritiated FMLP binding to human polymorphonuclear leukocytes with a concentration required to inhibit binding by 50% of approximately 5.4 x 10(-7) mol/L, whereas BocMLP was less potent with a concentration required to inhibit binding by 50% of approximately 9.1 x 10(-5) mol/L. Scatchard analysis revealed that the decreased tritiated FMLP binding caused by CsH was due to a decrease in the Bmax (0.22 +/- 0.04 nmol/L/5 x 10(6) cells vs 0.09 +/- 0.01 nmol/L/5 x 10(6) cells; p < 0.05), without a significant difference in the Kd (5.16 +/- 1.22 nmol/L vs 6.32 +/- 2.42 nmol/L; p = NS). CONCLUSION CsH is a potent and selective inhibitor of mediator release from basophils induced by activation of the formyl peptide receptor; it acts by interfering with agonist binding to FMLP receptors.

Human Heart Mast Cells in Anaphylaxis and Cardiovascular Disease

All sections of human heart tissue demonstrate tryptase- and chymase-containing mast cells (HHMCs) which have for the first time been isolated, partially purified and studied in vitro. HHMCs contain similar histamine levels as lung and skin mast cells, but tryptase levels are lower than in skin and higher than in lung mast cells. Complement C5a causes rapid dose-dependent release of histamine from HHMCs, but they are refractory to substance P and fMLP. Cross-linking IgE receptors on HHMCs leads to arachidonic acid metabolism through both the cyclooxygenase and 5-lipoxygenase pathways. HHMCs and their vasoactive mediators may be involved in anaphylactic/anaphylactoid reactions in humans and in the pathogenesis of some cardiovascular diseases.

Immunological modulation of human cardiac mast cells

Human mast cells, by elaborating various cytokines, chemokines and proinflammatory mediators play a complex role in several allergic and inflammatory disorders. Mast cells have been identified in human heart tissue in close proximity to the sarcolemma, in perivascular and adventitial locations and in the shoulder region of coronary atheroma. Human heart mast cells (HHMC) can be isolated from patients undergoing heart transplantation and can be immunologically activated in vitro to induce the release of tryptase, chymase, cysteinyl leukotriene C4 and prostaglandin D2. Several cytokines (e.g., stem cell factor and TNF-α) reside in secretory granules of HHMC. Mast cell density is increased in the hearts of patients with ischemic and idiopathic dilated cardiomyopathy. Cardiac mast cells might contribute to the evolution of atherosclerosis, dilated cardiomyopathy, cardiac and systemic anaphylaxis through the release of cytokines and vasoactive and proinflammatory mediators.

Eosinophil granule proteins are selective activators of human heart mast cells.

Eosinophilia in humans is associated with eosinophil infiltration and cardiac localization of eosinophil granule proteins. Eosinophil cationic proteins are responsible for cardiac disease in some patients with eosinophilia. We have investigated the in vitro effect of four eosinophil granule proteins: eosinophil cationic protein (ECP), major basic protein (MBP), eosinophil-derived neurotoxin (EDN) and eosinophil peroxidase (EPO), on mast cells isolated from human cardiac tissue (HHMC). ECP and, to a lesser extent MBP (0.3-3 microM), but not EDN and EPO, stimulated the release of histamine and tryptase from HHMC. This release reaction induced by ECP and MBP was Ca(2+)- and temperature-dependent and was abolished by preincubation with anti-ECP and anti-MBP, respectively. The activation of HHMC by ECP and MBP was abolished by preincubation with 2-deoxy-D-glucose and antimycin A. These data demonstrate that some eosinophil cationic proteins, ECP and MBP, are selective activators of HHMC, thus contributing to the cardiac lesions in patients with eosinophilia.

Biochemical Functions of a Pool of Arachidonic Acid Associated with Triglycerides in Human Inflammatory Cells

The distribution of arachidonic acid (AA) within intracellular lipid pools of inflammatory cells is thought to be an important factor regulating the production of eicosanoids. We have recently identified a pool of AA associated with triglycerides (TGs) in human lung macrophages. This pool is also present in other human inflammatory cells (mast cells, eosinophils, monocytes and platelets) and it contains a percentage of total cellular AA ranging from 10 to 45%. Kinetic studies of AA incorporation have shown that TG are the first acceptor pool for exogenous AA that is subsequently transferred to phospholipid pools. During cell activation, AA is released from phospholipids; however, a large amount of AA is rapidly reincorporated into TGs. The TG pool also supplies AA to the phospholipid pools once these have been depleted during cell activation. These data suggest that TGs are not only a storage site for AA but may also be important as regulators of AA metabolism and eicosanoid biosynthesis in human inflammatory cells.

Modulation of human lung mast cell function by the c-kit receptor ligand

The gene product of the steel locus is a growth factor for mast cells and a ligand for the c- kit proto-oncogene receptor, a member of the tyrosine kinase receptor class of oncogenes

Human Cardiac Mast Cells and Their Role in Severe Allergic Reactions

Publisher Summary Within human heart tissue, mast cells lie between myocytes and in close contact with blood vessels. Mast cells are also localized in the coronary adventitia and in the shoulder region of coronary atheroma. The density of cardiac mast cells is higher in patients with dilated and ischaemic cardiomyopathy than in subjects without cardiovascular diseases. Intriguingly, in some of these conditions there is in situ evidence of mast cell activation. Observations by different groups of investigators, suggest that HHMCs play complex and significant roles in various pathophysiological conditions that involve the cardiovascular system. Direct activation of HHMCs by circulating antigens, autoantibodies and therapeutic and diagnostic substances injected intravascularly can explain some of the anaphylactic/anaphylactoid reactions caused by these agents. HHMCs possess FcɛRI, C5a receptors and IgE on their surface, which could explain the direct involvement of cardiac mast cells in systemic and cardiac anaphylaxis. Of particular interest is the observation that the eosinophil cationic proteins ECP and MBP can activate HHMCs to release preformed and de novo synthesized mediators. This novel observation suggests that, in allergic patients with eosinophilia, eosinophilic infiltration and the deposition of eosinophil granule proteins might, through direct activation of HHMCs, contribute to the cardiac derangements observed in some of the patients.