pyrimidinones and Leukemia--Basophilic--Acute

An anti-allergic drug, permirolast potassium (TBX), inhibited antigen (Ag)-induced phospholipase D (PLD) activation in rat basophilic leukemia (RBL-2H3) cells. The concentration-dependent inhibitory profile for Ag-induced PLD activation was parallel to those for secretory response and inositol phosphate formation. In contrast, TBX had no effect on PLD activation caused by calcium ionophore A23187 or phorbol myristate acetate. These results suggest that TBX inhibits Ag-induced PLD activation by interfering with the signal transduction pathway upstream of Ca2+ mobilization and protein kinase C activation.

Topics: Animals; Antigens; Depression, Chemical; Enzyme Activation; Histamine Antagonists; Leukemia, Basophilic, Acute; Phospholipase D; Pyridines; Pyrimidinones; Rats; Tumor Cells, Cultured

Aggregation of high affinity IgE Fc receptors (Fc epsilon RI) on RBL-2H3 cells results in tyrosine phosphorylation of 33-, 42-, 44-, 72-, 80-, 90-, 125-kDa proteins. The 42 and 44 kDa proteins were identified as mitogen-activated protein (MAP) kinases with immunoblotting of anti-MAP kinase antibody. The effects of an antiallergic drug, pemirolast potassium (TBX) on Ag-induced protein tyrosine phosphorylation and MAP kinase activation were investigated. When RBL-2H3 cells were stimulated with Ag in the presence of TBX, tyrosine phosphorylation of three proteins (33, 42 and 44 kDa) was inhibited concentration-dependently (0.1-10 micrograms/ml). Inhibition of Ag-induced tyrosine phosphorylation of 33 kDa protein, which could be a beta subunit of Fc epsilon RI, suggests that TBX may prevent the activation of Fc epsilon RI. TBX suppressed activation of MAP kinases (42 and 44 kDa) in response to Ag as well as phorbol myristate acetate (100 nM) or calcium ionophore A23187 (500 nM), implying that the drug acts on signal transduction component(s) between the second messengers and MAP kinases. However, TBX had no effects on protein tyrosine phosphorylation and MAP kinase activation in MC3T3-E1 osteoblastic cells. These results indicate that TBX may affect Fc epsilon RI and also may act as a step distal of Ca2+ mobilization and protein kinase C activation leading to MAP kinase activation in RBL-2H3 cells.

Topics: Animals; Antigens; Calcium-Calmodulin-Dependent Protein Kinases; Enzyme Activation; Histamine Antagonists; Leukemia, Basophilic, Acute; Phosphorylation; Pyridines; Pyrimidinones; Rats; Tumor Cells, Cultured; Tyrosine

An antiallergic drug, pemirolast potassium (TBX) at concentrations between 0.01 and 10 micrograms/ml inhibited antigen (Ag)-stimulated degranulation in RBL-2H3 cells, which have the properties of mucosal mast cells. At the same concentrations, the drug suppressed both the formation of inositol 1,4,5-trisphosphate and the mobilization of Ca2+, indicating the prevention of phospholipase C activation. The production of 1,2-diacylglycerol and phosphatidic acid, which was mainly due to phosphatidylcholine hydrolysis, was also suppressed. Moreover, TBX reduced Ag-induced liberation of arachidonic acid, a precursor of eicosanoids, implying the inhibition of phospholipase A2. These data suggest that TBX inhibits the activation of phospholipase C, leading to decreased formation of the signal transducing molecules necessary for cell activation.

Topics: Animals; Antigens; Calcium; Histamine Antagonists; Inositol 1,4,5-Trisphosphate; Leukemia, Basophilic, Acute; Phospholipases; Pyridines; Pyrimidinones; Rats; Tumor Cells, Cultured