title: Alterations in Fc epsilon RI induced by protoporphyrin plus long-wavelength ultraviolet light in mouse bone marrow-derived mast cells.
abstract: As previously reported, protoporphyrin plus long-wavelength UV light (PP/UVA) inhibits IgE-mediated degranulation of mouse bone marrow-derived mast cells, as assessed by measurement of the release of beta-hexosaminidase. This inhibitory effect was seen with cells sensitized with IgE either before or after PP/UVA treatment (57.8 and 55.3% inhibition, respectively). PP/UVA did not dissociate IgE already bound to cells as assessed either by measuring release of bound 125I-IgE or by flow cytometric analysis. Results from immunoadsorption followed by SDS-PAGE analysis suggested that PP/UVA treatment may cause stable conjugation of IgE to its receptor. In unsensitized cells, PP/UVA did not cause conjugation of the unoccupied Fc epsilon RI to other proteins in the plasma membrane. Nevertheless, Scatchard analysis revealed that PP/UVA decreased the number of Fc epsilon RI per cell by 37% (0.95 x 10(5) vs 1.51 x 10(5)/cell), whereas affinity of the receptor for IgE was comparable between PP/UVA-treated and untreated cells (3.40 nM vs 3.27 nM). Flow cytometric analysis also confirmed the decrease in Fc epsilon RI number in PP/UVA-treated unsensitized mouse bone marrow-derived mast cells. Although 84% of PP/UVA-treated and 82% of untreated cells expressed positive fluorescence when stained with FITC-conjugated IgE, fluorescence intensity was reduced by 40% after PP/UVA treatment. We conclude that PP/UVA alters the conformational structure and/or number of Fc epsilon RI expressed on the mast cell surface. This effect could potentially explain the ability of PP/UVA to inhibit mast cell secretory function and may be related to an ability of PP/UVA to alter the properties of the plasma membrane.
authors.affiliation: Department of Medicine, University of California, San Diego, School of Medicine 92103.
authors.forename: A
authors.initials: A
authors.lastname: Yen
authors.forename: F T
authors.initials: FT
authors.lastname: Liu
authors.forename: K E
authors.initials: KE
authors.lastname: Barrett
authors.forename: I
authors.initials: I
authors.lastname: Gigli
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells; D015550:Cell Degranulation / Q000187:drug effects; D002478:Cells, Cultured; D007073:Immunoglobulin E / Q000378:metabolism; D008407:Mast Cells / Q000187:drug effects* / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D011701:PUVA Therapy; D017455:Receptors, IgE / Q000187:drug effects*
chemical_list: D017455:Receptors, IgE; D007073:Immunoglobulin E