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Prostaglandin D2 generation in mouse bone marrow-derived mast cells exposed to dexamethasone is associated with
1INSERM U312, Laboratoire de Dermatologie, Hôpital Henri Mondor, Creteil, France.
Abstract:
The appearance of fixative-sensitive peroxidase activity in the nuclear envelope and endoplasmic reticulum of bone marrow-derived mast cells (BMMC) cultured in the presence of 1 microM dexamethasone (DM) for up to 14 days and its relationship with immunologic release of prostaglandin D2 (PGD2) by these cells were studied. Endogenous peroxidase activity, previously shown as a marker of arachidonic acid metabolism in various cell types, was visualized by cell incubation in 3,3' diaminobenzidine-containing solution before glutaraldehyde fixation. PGD2 release was induced by passive sensitization of BMMC with an optimal dose of monoclonal IgE and subsequent challenge with specific a antigen. We found that 4-week-old BMMC, used as the starting population of the present study, exhibited immature morphologic features, did not present peroxidase activity when cytochemically processed, and released minute amounts of PGD2 in response to IgE-dependent stimulation. When such BMMC were exposed to DM during 24 hours, they showed aldehyde-inhibited peroxidase activity in the perinuclear envelope and a few endoplasmic reticulum segments. As compared with untreated cells, 24-hour DM-exposed BMMC released higher amounts of PGD2 upon immunologic stimulation. After an additional 14-day period of DM exposure, an intense peroxidase activity was detected in the perinuclear envelope and the endoplasmic reticulum of BMMC, which, under immunologic stimulation, released as much as 42.4 +/- 14.7 ng of PGD2/1 x 10(6) cells. Aminotriazole (20 and 50 mM) extinguished both peroxidase activity and PGD2 release from BMMC whereas indomethacin (1 microM) suppressed PGD2 production, but did not alter endogenous peroxidase activity. Previous cell fixation with glutaraldehyde totally inhibited endogenous peroxidase reaction in DM-exposed BMMC. Moreover, 14-day DM-exposed BMMC exhibited morphologic characteristics of mature mast cells and possessed alcian blue+/safranin+ granules. Therefore, the present data suggest that appearance of peroxidase activity in the nuclear envelope and the endoplasmic reticulum of DM-exposed BMMC is associated with the ability of the cells to synthetize PGD2 and appears as a cytochemical marker of the in vitro maturation of mouse bone marrow-derived mast cells.
Insights
Dexamethasone treatment promotes the maturation of bone marrow-derived mast cells (BMMC), indicated by increased peroxidase activity and enhanced prostaglandin D2 (PGD2) release. This peroxidase activity serves as a cytochemical marker for BMMC maturation in vitro.
Area of Science:
- Cell Biology
- Immunology
- Biochemistry
Background:
- Bone marrow-derived mast cells (BMMC) are crucial in allergic responses.
- Prostaglandin D2 (PGD2) is a key mediator released by mast cells.
- Endogenous peroxidase activity is linked to arachidonic acid metabolism.
Purpose of the Study:
- To investigate the effect of dexamethasone (DM) on BMMC maturation.
- To examine the relationship between peroxidase activity and PGD2 release in DM-treated BMMC.
- To establish peroxidase activity as a potential cytochemical marker for mast cell maturation.
Main Methods:
- Culturing BMMC with 1 microM dexamethasone for up to 14 days.
- Cytochemical staining for peroxidase activity using 3,3' diaminobenzidine.
- Inducing PGD2 release via IgE sensitization and antigen challenge.
- Inhibiting enzyme activity with aminotriazole and indomethacin.
Main Results:
- Dexamethasone exposure increased peroxidase activity in the nuclear envelope and endoplasmic reticulum of BMMC.
- DM-treated BMMC showed significantly higher PGD2 release upon immunologic stimulation compared to untreated cells.
- Peroxidase activity and PGD2 release were both inhibited by aminotriazole, while indomethacin only affected PGD2 production.
- Mature mast cell morphology and specific granule markers were observed in 14-day DM-exposed BMMC.
Conclusions:
- The appearance of fixative-sensitive peroxidase activity in BMMC is associated with dexamethasone-induced maturation.
- This peroxidase activity correlates with the cells' capacity to synthesize and release PGD2.
- Peroxidase activity can serve as a reliable cytochemical marker for in vitro maturation of mouse BMMC.