Kohei Umezu

MY-1250, a major metabolite of the anti-allergic drug repirinast, induces phosphorylation of a 78-kDa protein in rat mast cells

Repirinast (MY-5116; isoamyl 5,6-dihydro-7,8-dimethyl-4,5-dioxo-4H-pyrano [3,2-c]quinoline-2-carboxylate) is an anti-allergic drug of demonstrated effectiveness for treating bronchial asthma in humans. MY-1250 (5,6-dihydro-7,8-dimethyl-4,5-dioxo-4H-pyrano [3,2-c]quinoline-2-carboxylic acid), the major active metabolite of repirinast, inhibits antigen-induced histamine release from sensitized rat peritoneal exudate cells (PEC). When purified rat mast cells were treated with MY-1250 (2.5 x 10(-5) M) for 1 min, phosphorylation of a specific mast cell protein of apparent molecular mass of 78 kDa was observed as previously reported for sodium cromoglycate (SCG). Phosphorylation of this protein induced by MY-1250 and SCG occurred in a concentration-dependent manner with IC50 values of 2.0 x 10(-7) and 1.4 x 10(-5) M, respectively. MY-1250 did not inhibit calcium ionophore A23187 (1 microgram/mL)-induced histamine release from rat PEC. In the presence of calcium ionophore A23187 (1 microgram/mL), phosphorylation of this protein induced by MY-1250 was not evident. In conclusion, MY-1250 induced phosphorylation of a 78-kDa protein in rat mast cells and MY-1250 may inhibit histamine release by regulating phosphorylation of this protein in rat mast cells.

An automated analysis of chemotaxis in vitro using a computer-assisted scanning densitometer

The quantitation of chemotaxis in vitro was developed with a computer-assisted scanning densitometer. The method of estimating the number of cells on a filter was based on the photo-reflection from the nuclei of stained cells. Samples obtained from a 48-well micro chemotaxis assembly were successfully analyzed by this method. This assay system could quantitate chemotaxis much faster and more accurately than by cell counting under the microscope. It was sensitive enough to determine the responsiveness of SMCs and fibroblasts to various chemoattractants. This system could be applied to medical and biological screening tests for drugs and clones in laboratories.

Inhibitory mechanism of tritoqualine on histamine release from mast cells

Tritoqualine (TRQ, (+)-(R*)-7-amino-4,5,6-triethoxy-3-[(R*)-5,6,7, 8-tetrahydro-4-methoxy-6-methyl-1,3-dioxolo[4,5-g]isoquinolin++ +-5-yl] phthalide) strongly inhibited the increased metabolism of [3H]arachidonic acid-labeled phospholipid and 45Ca2+ influx in mast cells stimulated by compound 48/80 (compd 48/80), Concanavalin A (Con A) plus phosphatidylserine (PS), or 2,4-dinitrophenyl-coupled-ascaris extracts (DNP-asc). However, TRQ did not disturb the binding of 14C-labeled compd 48/80 to the mast cell membrane. The activity of calmodulin purified from mastocytoma P-815 cells was inhibited by TRQ at IC50 1.0 microM. From these results, it is concluded that the inhibitory mechanism of TRQ on stimulus-induced histamine release from mast cells may be mediated at least partially by the inhibition of Ca2+ influx and calmodulin activity.