Flavones

inhibit proliferation and increase mediator content in human leukemic mast cells (HMC-1) Mast cells play an important role in early and late phase allergic reactions through allergen and IgE-dependent release of histamine, proteases, prosta-glandins, and several multifunctional cytokines (1). Mast cell proliferation has been well documented in the bone marrow and skin of systemic mastocytosis (2), as well as in urinary bladder of interstitial cystitis patients (3). Human leukemic mast cells (HMC-1) are useful for the study of growth characteristics, synthesis of mediators, and devel-opment of secretory granules because they secrete histamine, tryptase, and many cytokines (4), but only to prolonged stimulation with phorbol esters and the cation ionophore A23187 (5). Flavonoids are low molecular weight compounds found in many plants; they exhibit antioxidant, anti-allergic activity, and anti-inflammatory activity (6). Some flavonoids, like quercetin, inhibit histamine release from rat basophils and mast cells (7–10). Quercetin also induces histamine accumulation, expression of mRNA for RMCP-II and development of secretory granules in rat basophil leukemia (RBL) cells (11). Myricetin strongly inhibits histamine and leukotri-ene B4 (LTB4) release from rat peritoneal exudate cells (12) and down-regulates nuclear factor-kappa B (NF-jB) systems that are involved in immune and inflammatory responses (13). Flavonoids such as quercetin, baicalin, and luteolin have also been reported to inhibit leukotrienes, prostaglandins D2, and cytokines such as IL-6 and tumor necrosis factor-alpha (TNF-a) from human mast cells (10). Flavonoids have also been shown to have anti-proliferative effects on a number of transformed cells (6). In the present study, we investigated th