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Adriamycin induces exocytosis in rat and beige mouse peritoneal mast cells: an ultrastructural, morphometric and
E Crivellato1, L Candussio, G Decorti
1Department of Medical and Morphological Research, University of Udine, Italy. enrico.crivellato@kolbe.drmm.uniud.it
Abstract:
The process of exocytosis was studied in rat and beige mouse peritoneal mast cells stimulated by adriamycin (ADR) at 37 degrees C and 22 degrees C. ADR induces a non cytotoxic histamine release that is followed by a significant uptake of the drug. Examination was performed by transmission electron microscopy and, at the same time, histamine release and ADR uptake were measured by spectrofluorimetry. ADR accumulation in mast cells was investigated also by fluorescence microscopy. In rat mast cells stimulated at 37 degrees C, the secretory process developed abruptly and was virtually complete after 30 sec. Electron microscopy showed rapid intracytoplasmic channel formation and extrusion of secretory granules; spectrofluorimetry revealed a massive release of histamine and rapid uptake of ADR. In addition, fluorescence microscopy showed mast cells exhibiting an intense orange-yellow fluorescent signal localized at the secretory granules. At 22 degrees C, rat mast cells showed alteration of the granules, cavity formation by fusion of the perigranular membrane and granule discharge due to fusion of the cavity membrane with the cell membrane. Histamine release and ADR uptake proceeded less quickly than at 37 degrees C. Quantitative analysis of rat mast cell ultrastructure demonstrated that histamine release induced by ADR stimulation was achieved by sequential exocytosis. This process presents both morphological and biochemical affinities with the exocytosis induced by basic secretagogues such as compound 48/80. In beige mouse mast cells the process of exocytosis progressed more slowly and was completed after 20 min at 37 degrees C. By electron microscopy, the cytoplasm presented a rigid structure due to abundance of actin-like fibrils. Granule fusion was an uncommon feature and exocytosis was mostly the result of single granule opening to the cell exterior without extrusion of granule matrices.
Insights
Adriamycin (ADR) triggers non-cytotoxic histamine release and drug uptake in rat mast cells via sequential exocytosis, a process similar to compound 48/80. Beige mouse mast cells exhibit a slower exocytosis with distinct morphological features.
Area of Science:
- Cell Biology
- Pharmacology
Background:
- Mast cells are key players in allergic responses and immune modulation.
- Adriamycin (ADR) is an anticancer drug known to affect cellular processes.
Purpose of the Study:
- To investigate the mechanism of exocytosis induced by ADR in rat and beige mouse peritoneal mast cells.
- To characterize the morphological and biochemical aspects of ADR-induced histamine release and drug uptake.
Main Methods:
- Transmission electron microscopy for ultrastructural analysis.
- Spectrofluorimetry for quantifying histamine release and ADR uptake.
- Fluorescence microscopy for visualizing ADR accumulation.
Main Results:
- ADR induced rapid, sequential exocytosis in rat mast cells at 37°C, with massive histamine release and ADR uptake within 30 seconds.
- At 22°C, rat mast cell exocytosis was slower, involving granule alteration and cavity formation.
- Beige mouse mast cells showed a slower exocytosis (20 min at 37°C) with distinct cytoplasmic rigidity and less granule fusion.
Conclusions:
- ADR-induced exocytosis in rat mast cells shares similarities with basic secretagogue-induced exocytosis.
- Differences in exocytosis mechanisms were observed between rat and beige mouse mast cells, potentially due to variations in cytoplasmic structure.