Biochemical and morphological modifications in dexamethasone-treated mouse bone marrow-derived mast cells

Addition of 1 microM dexamethasone (DM) to bone marrow-derived mast cells (BMMC) induced a time-dependent increase in cell histamine content. The latter reached a plateau of 2.5 micrograms/1 x 10(6) cells after 11 days in culture, compared with 100 ng/1 x 10(6) for untreated BMMC. Steroids, such as beta-estradiol, androsterone, and testosterone (1 microM), did not alter the histamine content of BMMC, whereas progesterone (1 microM) induced a moderate increase. Other glucocorticosteroids also enhanced histamine content, suggesting that the observed increase was specific for glucocorticosteroid. Treatment of BMMC with 1 microM DM for 14 days inhibited the Ag-induced, IgE-mediated release of histamine, beta-hexosaminidase, platelet-activating factor-acether, LTB4, and LTC4 by 65 +/- 3%, 66 +/- 1%, 93 +/- 3%, 66 +/- 2%, and 74 +/- 10%, respectively (mean +/- 1 SD, n = 3). In contrast with untreated cells which produce less than 2 ng/1 x 10(6) cells PGD2 after Ag challenge, DM-treated BMMC generated 16.8 +/- 0.3 ng/1 x 10(6) cells PGD2. Moreover, most of DM-treated BMMC became Alcian blue+/safranin+ and by ultrastructure, exhibited numerous cytoplasmic granules filled with abundant and uniform electron-dense matrix. The present results indicate that DM-treated BMMC exhibit biochemical and functional properties different from immature untreated cells, suggesting that a maturation-like process occurred in vitro during DM treatment.