Abstract
Background: Although β-adrenergic receptor agonists inhibit antigen-induced release of histamine, leukotrienes and prostaglandin D2 from human lung fragments, dispersed human lung mast cells and human skin mast cells, subcellular mechanisms for the inhibition of histamine release by β-adrenergic receptor agonists are not well delineated. The aim of the present study was to investigate the inhibitory mechanisms of β-adrenergic receptor agonists for human mast cell histamine release using human cultured mast cells.
Methods: Human mast cells were obtained by culturing umbilical cord blood CD34+ cells in the presence of stem cell factor and interleukin-6. Cultured mast cells were sensitized with human myeloma IgE and stimulated with antihuman IgE.
Results: Stimulation of mast cells induced the elevation of intracellular cytosolic free Ca2+ concentrations ([Ca2+]i) and the translocation of protein kinase C (PKC) from the cytosol to the cell membrane, followed by the release of stored histamine. Isoproterenol, salbutamol and dibutyryl cAMP inhibited both the histamine release and PKC translocation, whereas they failed to affect the elevation of [Ca2+]i. H-89, a protein kinase A (PKA) inhibitor, abrogated the inhibition.
Conclusions: The present results suggest that PKA activation induced by β-adrenergic receptor agonists plays a crucial role in inhibiting IgE-mediated histamine release from human cultured mast cells through suppressing PKC translocation.
