Microtubule disruption suppresses allergic response through the inhibition of calcium influx in the mast cell degranulation pathway.

Mast cells are secretory cells that release their granules, which contain inflammatory mediators. Some recent data suggested that cytoskeletons play a role in this process. However, the role of microtubules in Ca2+ signaling has not yet been well defined. In this study, we demonstrate that the microtubule cytoskeleton is important to maintain Ca2+ influx in the degranulation pathway of mast cells, using the microtubule depolymerizers nocodazole and colchicine. The microtubule depolymerizers inhibited Ag-induced degranulation in RBL-2H3 cells and bone marrow-derived mast cells. When the cells were stimulated with Ag in the presence of the microtubule depolymerizers, the Ca2+ influx was decreased without affecting Ca2+ release from the endoplasmic reticulum (ER). Capacitative Ca2+ entry, which was induced by inhibitors of Ca(2+)-ATPase in the ER membrane, thapsigargin and cyclopiazonic acid, was also decreased by nocodazole. Fluorescent probe analysis demonstrated that nocodazole disrupted microtubule formation and changed the cytoplasmic distribution of the ER. The microtubule depolymerizers attenuated the passive cutaneous anaphylaxis reaction in back skin of Sprague Dawley rats. These results suggest that the microtubule cytoskeleton in mast cells is important to maintain Ag-induced capacitative Ca2+ entry, which is responsible for degranulation and the allergic response.