SHORT-TERM AND LONG-TERM CYTOKINE RELEASE BY MOUSE BONE-MARROW MAST-CELLS AND THE DIFFERENTIATED KU-812 CELL-LINE ARE INHIBITED BY BREFELDIN-A

Mast cells and basophils produce a wide range of cytokines, including large amounts of both IL-6 and granulocyte-macrophage CSF (GM-CSF), Ho wever, the route by which cytokines are secreted is poorly understood. In the current study, we used two inhibitors of vesicular transport, brefeldin A and monensin, to examine the routes of secretion of IL-6 a nd GM-CSF in the differentiated KU812 human cell line and cultured mou se bone marrow mast cells (mBMMC). Studies of cytokine production over 6 to 24 h demonstrated that IL-6 and GM-CSF release from both cell ty pes were inhibited by brefeldin A (BFA) following activation with calc ium ionophore, A23187, Monensin had similar inhibitory effects to that of BFA on the initial and ongoing IL-6 release from KU812 cells. In c ontrast, the amount of each cytokine remaining within the cells was si gnificantly enhanced. Similar results were obtained following IgE-medi ated activation of mBMMC. BFA significantly inhibited both the constit utive secretion of IL-6 and the immediate ionophore-induced increase i n IL-6 release from KU812 cells at 20 min postactivation, However, tre atment with these agents did not alter the release of histamine and be ta-hexaminidase from either mBMMC or KU812 cells. These studies sugges t that both the initial 20-min release of IL-6 and secretion of IL-6 a nd GM-CSF over up to 24 h by mBMMC and differentiated KU-812 cells occ ur predominately through a vesicular transport-dependent mechanism, an d that little, if any, IL-6 and GM-CSF is released through degranulati on.