Effects of baicalein on leukotriene biosynthesis and degranulation in human polymorphonuclear leukocytes

Studies were made on the effects of baicalein (5,6,7-trihydroxyflavone) on leukotrienes B4 and C4 biosyntheses and degranulation induced by calcium ionophore A23187 (A23187) in human polymorphonuclear leukocytes. Baicalein inhibited A23187-induced biosynthesis of leukotrienes B4 and C4 in human polymorphonuclear leukocytes. The concentration of baicalein required for 50% inhibition (IC50) of leukotrienes B4 and C4 formations was 1.46.10(-6) and 6.00.10(-7) M, respectively, using 1.0 microgram/ml of A23187. In addition, baicalein dose-dependently inhibited beta-glucuronidase and lysozyme releases induced by A23187, leukotriene B4 plus cytochalasin B and platelet-activating factor plus cytochalasin B. Furthermore, baicalein was found to inhibit dose-dependently Ca2+ uptake into the cells and Ca2+ mobilization from the intracellular stores.